Attachment J.2 Drawings.pdf

PROJECT COMM-2014-000817-A

E n g i n e e r i n g R e p o r t C o v e r

OK Communications Engineering Team

Engineering Study Report

COMM-ES-NEXCOM SEG2 PS FAILURES

COMM-2014-000817-A

05/11/2017

Engineering Report

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1. Background.

In early 2014, OKCET AJW-1731 became aware, through shared emails from AML-8050, of CAVU-2100 Multimode Digital Radio (MDR) Power Regulator boards with catastrophic failures. This was making the boards unrepairable and sometimes melting surrounding cables and connectors. AJW-1731 COMM engineers performed initial fact finding through questions asked of AML-8050. The catastrophic failures were associated with the MDR transmitter (TX) only. The receivers have not had the catastrophic failure mode, as reported by AML. In April of 2014, Wesley Boyd (AJW- 1731 Manager) directed Bill Fields (Senior Circuit Design and Radio Control Equipment (RCE) Support Engineer) to look at failed power regulator boards and provide an initial assessment.

1.1. Initial examination of a power regulator board that had experienced catastrophic failure and review of associated printed circuit board (PCB) drawings revealed a serious layout issue related to trace spacing between the signal called VUNREG and circuit common (Gnd). The VUNREG voltage level is normally at about 34 VDC when commercial power line voltage is at 120 Vrms. 10 mils was the trace spacing on the visible top and bottom layers. As per IPC-9529B, 12 mils is the minimum spacing.

VUNREG surges of about 60 VDC would require a minimum spacing of 28 mils.

1.1.1. IPC-9592B is widely accepted throughout the world as a generic PCB design standard used by commercial and industrial applications for providing minimum PCB trace spacing requirements to ensure a flashover event is not experienced.

Depending on the voltage level of a trace with respect to another trace, a flashover event can result when traces are too close to each other. A flashover event can result in an electric arc between the traces. The electric arc is essentially a short circuit that may release intense energy resulting in vaporization of involved materials. Based on IPC-9592B, the power regulator boards’ VUNREG to Gnd traces were in violation of minimum spacing. Attached to this report is Power Supply Flashover Background (Attachment 3), which provides more detail.

1.2. Management decided to redesign the power regulator board and opened this engineering study to accomplish:

Project - COMM-2014-000817-A COMM-ES-NEXCOM SEG2 PS FAILURES.

The associated HDRs follow:

1.2.1. H-AJW-091411-0265 A/G - NEXCOM MDR POWER SUPPLY

REDESIGN

1.2.2. H-AJW-060214-0191 COMM--CAVU-2100 MDR POWER SUPPLY

FAILURES

1.3. Provided to Maverick Technologies were five catastrophic failed power supplies. Maverick was tasked by AJW-1731 to perform a failure analysis of these power supplies. Attached to this report is CAVU-2100 Failure Analysis Report (Attachment 4), which provides in-depth detail and corroborates the trace spacing violation between VUNREG and Gnd.

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1.4. The Program Office (AJM-313) provided $51k, tied to a FY-17 program directive, for initial AML stock of a final power supply design.

1.5. Below is identifying information related to the OEM (ITT) version of the MDR radio power supply and the OKCET Rev1 version.

1.5.1. The OEM is green. The OKCET Rev1 is red.

1.5.2. The OEM (ITT) part number (PN) for the power supply board is

PWB8199132-1.

1.5.3. The FAA part PN for the OKCET Rev1 power supply assembly is

PWB8199132-FAA-1.

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2. Objective.

2.1. Due to the high rate of CAVU-2100 power supply failures, this project will redesign the board. Prototyping will be fully tested prior to committing replacement power supplies to AML stock.

3. Findings.

3.1. During the power supply design, debug, and testing efforts, a requirement’s document was generated and maintained. Attached to this report is CAVU-2100 Power Supply Re-Design Requirements (Attachment 5). This document contains the high level functional and hardware requirements of the final power supply assembly product.

3.2. The original ITT design used a 4-layer PCB and 100% through-hole components. The redesign effort resulted in a 2-layer printed circuit board (PCB) with about 60% of the components changed to surface mount (SMT) devices. This result provides reduced manufacturing cost and increased reliability.

3.3. The ITT power supply utilized multipoint ground topology that split the ground plane layer (2nd layer) into two distinct ground planes, one for VUNREG and the other for the +5V and ± 15V regulators. Using a short (@ ¼”) piece of 28 AWG wire, the two ground planes were connected. That implementation-forced regulators’ current to actually use the board standoffs and chassis to obtain needed VUNREG current for the other radio’s boards being excited by the regulators. The OKCET power supply design did not use this approach. The OKCET Rev1 PCB has dedicated the bottom layer for signal ground (Gnd). The Rev1 power supply implemented a single point ground (SPG) solution with respect to chassis ground. The SPG minimizes ESD susceptibility and chassis ground leakage currents.

3.4. The Power Regulator board design addressed removal of unneeded circuitry and added circuitry to provide requested features listed in the requirement’s document.

3.4.1. Highlights include the following:

3.4.1.1. Removed ITT circuitry used for controlling selection of AC or DC as the radio’s primary power source.

3.4.1.2. Kept the original regulator circuits and components, as they have proven themselves over the years of radio usage.

3.4.1.3. Kept original connectors and descriptors, as much as possible.

3.4.1.4. Designed a new way to switch between AC and DC power sources.

3.4.1.4.1. Implemented power steering diodes configured as a wired-or circuit to control switching between AC and DC power sources. They provide automatic current flow from whichever diode is more forward biased. If both are equally biased, then current passes equally through each diode.

3.4.1.5. Designed new circuitry for controlling the AC and DC power steering relays. These circuits respond to diminished commercial voltage levels for the AC power relay and the external DC voltage level for the DC power relay. The design

P a g e | 5 ensured appropriate hysteresis to eliminate nuisance activations. These circuits resulted in the following designs:

3.4.1.5.1. A commercial AC voltage level monitoring circuit with single pole (-20 dB attenuation per decade) 33 Hz filter for the 120 Hz ripple voltage was incorporated. This ensures a smooth DC signal representative of the commercial AC level.

3.4.1.5.2. An adjustable AC level trip for control of AC power steering relay (K1). The monitor circuit’s AC voltage level sensing transformer is part of the monitor cable assembly. For potential tolerance changes between each transformer, the trip level adjustment allows a given cable assembly and power supply board to be matched to each other.

3.4.1.5.3. A comparator circuit for controlling the AC power steering relay (K1). The comparator circuit responds to the AC monitor circuit output.

3.4.1.5.4. An external DC excitation level monitor and comparator circuit for controlling the DC power steering relay (K2).

3.4.1.5.5. Protection components for K1 and K2 power steering relays.

3.4.1.6. Commitment to a 2-layer PCB.

3.4.1.7. Maximized conversion of PCB components from through-hole to surface mount devices. This resulted in 60% conversion to surface mount devices.

3.4.1.8. Ensured PCB layout allows for total circuit integrity, equipment installation, and service.

3.5. The process used for the new power supply assembly design, generated and maintained the following:

3.5.1. The schematic includes the alignment procedure for the AC voltage trip level, which determines when to open the AC power relay (K1). The new design opens K1 when commercial AC voltage falls to 108Vrms or below. Attached to this report is AJW-173 OKCET CAVU-2100 MDR Power Supply (Attachment 6) schematic.

3.5.1.1. The alignment procedure includes a trip level set at 85Vrms.

However, per Comm Program Office request, this trip level is not accessible to the end user.

3.5.1.2. Hysteresis of the 108 Vrms trip voltage required to re-enable (close) the AC power steering relay (K1) is 3 to 4 Vrms or 111 to 112 Vrms.

3.5.2. A cable assembly, connected between the power supply and the TX’s rear panel commercial power entry module, gives a direct interface for monitoring of the commercial AC voltage level. Attached to this report is drawing CAVU-2100 MDR TX/RX AC LINE VOLTAGE MONITOR CABLE ASSEMBLY DWG (Attachment 7). Also attached to this report is drawing CAVU-2100 AC MONITOR CABLE CONNECTION SCHEMA TO POWER ENTRY MODULE REAR TABS DWG (Attachment 8), which shows how the cable assembly is connected to the rear panel AC power module.

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3.5.3. A BILL OF MATERIALS (BOM) spreadsheet: AJW-173 OKCET CAVU- 2100 MDR POWER SUPPLY (Attachment 9), which includes the AC PWR Monitor Cable Assembly parts, is attached to this report.

3.6. The printed circuit board (PCB) fabrication drawings, documents, and artifacts were generated and maintained by Maverick Technologies, and provided to the FAA.

The files are stored at G:\PROJECT FOLDERS - ACTIVE\Air-to-Ground Comm\012317 MDR Rev1 PS Rel 1-3 Fabrication Files.

3.6.1. Attachment 10 is the Maverick Technologies CAVU-2100 MDR Power Supply Schematic.

3.6.2. Attachment 11 is the Maverick Technologies CAVU-2100 MDR Power Supply BOM.

3.6.3. Attachment 12 is the Maverick Technologies Listing of all CAD and Altium (Schematic and Layout) Files required to fabricate the power supply assembly.

3.7. The OKCET lab facilities and test equipment was used to perform debug testing. Results show both the OKCET Rev1 power supply versus the original ITT power supply. Compared to the ITT version, the Rev1 power supply provided consistent slight performance improvements. Attached to this report is the test results’ spreadsheet (Attachment 13).

3.7.1. Test efforts for the Rev0 power supply surfaced design related issues.

Rev1 efforts resolved all known Rev0 issues and provides support improvements. Rev1 is the final design.

3.8. Temperature chamber testing was performed with the Rev0 power supply assembly installed into a MDR transmitter (TX) and receiver (RX). Testing of the two radios occurred at operating parameter settings design limits, which is beyond operational limits. The temperature chamber was set to cycle between operational temperature limits every twelve hours. Testing duration was one week. No observed issues were associated with the new power supply assembly. Attached to this report are the test results (Attachment 14). Rev1 boards were not temperature chamber tested because the tested Rev0 boards included modifications that are on the Rev1 boards.

3.9. Performed exhaustive radio testing with the MDR TX and RX with both the ITT power supply versus the Rev1 power supply versus the Rev1 power supply with Stabilant 22A applied to all accessible connectors. The Rev1 power supply showed slight radio performance improvements to some radio parameters. The application of Stabilant 22A provided additional slight improvements to some radio performance parameters. The testing results are an attachment to this report (Attachment 15).

3.9.1. Stabilant 22 is a product that provides long term improved connectivity performance between mechanical connector surfaces. Attached to this report is a detailed description of Stabilant 22 (Attachment 16).

3.10. Two Rev1 power supply assemblies and Stabilant 22A were provided to the Tech Center for in-depth spectral testing. They committed in December 2016 to

P a g e | 7 commence by February 2017 the spectral testing of a MDR TX and RX using the original ITT power supply, the Rev1 assembly and then test again with the Rev1 assembly adding the Stabilant 22A to all accessible internal radio connectors, especially the RF connector. The FAA William J Hughes Technical Center, Atlantic City, NJ ANG- E62 Air/Ground Communications Branch (31 JULY 2017) 96-page report was received in August 2017. They decided not to apply the Stabilant 22A product to any internal radio connectors, because they indicated it would have required a great deal of disassembly. They did apply the Stabilant 22A to external connectors. This nullifies any Stabilant 22A testing data from them. Their testing results indicate that the OKCET Rev1 power supply assembly has no appreciable difference in performance, as compared with the OEM Power Supply. The Technical Center report may be seen within the OKCET project folder at G:\PROJECT FOLDERS - ACTIVE\Air-to-Ground Comm\COMM-2014-000817-A COMM-ES-NEXCOM SEG2 PS FAILURES\Misc\TechCenterTesting.

3.11. Four F&E radios were upgraded with the Rev1 assembly and installed at MHT RTR for long term testing. Attached to this report is the MHT test plan (Attachment

17) and the trip report (Attachment 18).

3.12. The trip report (Attachment 18) presents questions from Jennifer Levine (Coordinator; was acting supervisor). In addition, the trip report shows the initial test results where no incident(s) or issues were experienced. Air Traffic (AT) indicated proper operation. To date there have been no issues communicated.

3.13. AML (Perry Gering: Supervisor Communication Equipment Support Branch;

and Alan Maschino: Assistant Division Manager – AML-8000) requested a meeting to discuss implementation plans associated with the OKCET Rev1 MDR power supply assembly. On Wednesday, May 10, 2017 Perry Gering called Bill Fields and expressed some of what AML wants to discuss:

3.13.1.1. He expressed concern about National Airspace System (NAS) technicians working inside the MDR TX, and potentially causing other issues. Gering stated that AML technicians have many years of experience working inside the MDR radio. They know how to perform the maintenance and how to test the radio.

3.13.1.2. AML wants to establish a material product stream to support the Exchange & Repair (E&R) process for the MDR TX power supply.

3.13.1.3. AML desires to know who will finance the production of the Rev1 assemblies.

3.13.1.4. AML desires to know if a general bid process will be required.

4. Conclusions.

4.1. The location of the fabrication files for manufacturing the Rev1 power supply assemblies is G:\PROJECT FOLDERS - ACTIVE\Air-to-Ground Comm\012317 MDR Rev1 PS Rel 1-3 Fabrication Files\. These files were ‘put’ at this location due to the depth of the G:\ drive project folders’ construct and Window’s path name limitations. It

P a g e | 8 was not possible to put the fabrication/manufacturing folders and files under the project folder.

4.2. Initial AJW-173 stocking of Rev1 assemblies to AML is set to use Maverick Technologies to fabricate / package the assemblies, and perform first-level testing and alignment. Seed money in the amount of $51K is committed by the program office (Dieter Thigpen).

4.3. Large-scale quantities and long-term acquisition of the assemblies requires a general bid process for acquisition.

4.4. The design process utilized design-for-manufacturing (DFM) methods. The power supply assembly has demonstrated compliance to the redesign requirements and has passed vigorous testing.

4.5. The OKCET MDR Rev1 assembly testing and performance measurements show superiority to the original ITT power supply.

4.6. Flashover will no longer be an issue with the Rev1 assembly. This means flashover influenced failures and consequential attrition of other MDR radio circuit boards will be diminished.

4.7. The MDR TX recovery-mode-failure, that is a result of uncontrolled shutdown of the power supply regulators, will not occur with the OKCET Rev1 assembly. This is due to the Rev1 circuitry that monitors the radio’s AC and DC power excitation inputs and opens the respective power relay when either voltage level is too low. If both the AC and DC power relays are open, unregulated power is removed from all regulators’ input simultaneously.

4.8. Based on the Maverick failure mode analysis, it is clear ITT knew of the power supply’s Vunreg trace layout spacing issue with respect to circuit common (Gnd).

4.8.1. The final design (Rev1) resulted in implementing 25 mils spacing minimum for VUNREG only. The remainder of the board layout provided above minimum spacing for all other traces.

4.9. The Stabilant 22 product testing showed slight radio performance improvements.

4.10. As shown in attachment 16, pages 12 and 13, the Stabilant 22 product has been in operational use by Air Transportation System Specialist (ATSS) of Mason Service Support Center, WET26-CSG, to correct bridge-clip contact resistance issues.

Mr. Charles Angley started using the Stabilant product in July of 2014. He has shared the product with other workmates and expressed satisfaction of no further problems with all treated connections (bridge-clips-to-66-block).

4.11. Per attachment 17, paragraph 4.1.3, the MDR TX and RX meet requirements outlined in Order 6580.5B.

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5. Recommendations.

5.1. Schedule a meeting with AML (Perry Gering: Supervisor Communication Equipment Support Branch; and Alan Maschino: Assistant Division Manager – AML- 8000), Dieter Thigpen, and designated AJW-1731 personnel. The topic is to address ‘what is the best process going forward with the OKCET Rev1 MDR power supply assembly’ (reference paragraph 3.13 for background information). Work with AML to develop a repair plan for MDR TX. AML is running out of repair stock. Jointly determine the most efficient way to expend the remaining $51K for rev1 power supply assemblies.

5.2. The short term approach to provide AML stocking of the OKCET Rev1 Power Supply Assembly for MDR TX E&R activity follows:

5.2.1. Upon acceptance of this report and SCCC approval, process a PRISM purchase request (P.R.) for the next lot of 34 Rev1 assemblies from Maverick.

Additional near term lots will be acquired using PRISM to continue utilization of the $51,000 provided by the Program Office. These power supply assemblies will be distributed to AML for power supply E&R of failed MDR TX radios. Project COMM- 2018-000062-A SDR-COMM-XXX New Power Supply for Nexcom Seg 1 TX is planned to accompany the updated MDR TX.

5.2.2. Prior to delivery of the Rev1 product to AML, perform a minimum 10% random performance check (includes radio testing and trip level verification) of assemblies received. If issues are found, then test all assemblies and return assemblies that do not pass performance checks back to the vendor. Take appropriate action to correct the first level checkout and alignment processes.

5.3. Contingent on receipt of 3-year funding, the long term approach to provide NAS field-level support of the MDR TX follows:

5.3.1. Perform the System Support Modification (SSM) process. As part of the SSM process, ensure the following are also addressed:

5.3.1.1. Generate a packaging list of all items included within the Rev1 assembly packaging. Attachment 1 is a good starting point for the packaging list.

Provide the complete packaging list to winning bidder for inclusion within each assembly-packing box.

5.3.1.2. Address how to schedule product delivery via a waterfall schedule.

The schedule will be tied directly to the fabrication vendor’s capacity capability.

5.3.1.3. Address the disposition of the original ITT power supply when removed from the MDR TX. It is not trustworthy for TX usage. However, AML has indicated there have been no catastrophic power supply failures (flashover) in the MDR RX. The disposition plan should accumulate the ITT power supplies for potential usage in replacing failed RX power supplies.

5.4. Establish a life cycle project to monitor results of MHT RTR testing. Attachment 18 is a good starting point for who is involved at MHT.

5.5. For the MDR TX radio and as part of the installation procedure of the Rev1 power supply assembly: as a minimum application, use the Stabilant product to treat the

P a g e | 10 accessible radio frequency (rf) connector and DSP board’s ribbon cable connector that is farthest from the front of the radio.

5.6. For any/all connector contact resistance issues within the NAS, authorize and support the use of Stabilant 22 by ATSS.

List of Attachments

Attachment 1. Cost Estimate Attachment 2. Draft SSM Paragraphs Attachment 3. Power Supply Flashover Background Attachment 4. CAVU-2100 Failure Analysis Report by Maverick Technologies Attachment 5. CAVU-2100 Power Supply Re-Design Requirements

Attachment 6. AJW-173 OKCET CAVU-2100 MDR Power Supply Schematic Attachment 7. CAVU-2100 MDR TX/RX AC LINE VOLTAGE MONITOR CABLE

ASSEMBLY DWG

Attachment 8. CAVU-2100 AC MONITOR CABLE CONNECTION SCHEMA TO

POWER ENTRY MODULE REAR TABS DWG

Attachment 9. BILL OF MATERIALS: CAVU-2100 MDR POWER SUPPLY by AJW-

173 OKCET

Attachment 10. CAVU-2100 MDR Power Supply Schematic by Maverick

Technologies Attachment 11. BILL OF MATERIALS: CAVU-2100 MDR Power Supply by

Maverick Technologies Attachment 12. CAVU-2100 MDR Power Supply Listing of CAD and Altium

(Schematic and Layout) Files by Maverick Technologies Attachment 13. CAVU-2100 MDR Power Supply Debug Test Results (OKCET Rev1 versus ITT) Attachment 14. CAVU-2100 MDR Radio with Rev0 Power Supply Assembly

Temperature Chamber Testing Results.

Attachment 15. CAVU-2100 MDR TX / RX Critical Performance Parameter Testing:

ITT Power Supply versus Rev1 versus Rev1 with Stabilant 22A Attachment 16. Stabilant 22 Explained Attachment 17. MHT Test Plan Attachment 18. MHT Trip Report Attachment 19. Acquisition of OKCET Rev1 Power Supply Assembly High Level

Explanation Attachment 20. Single Source Justification to use Maverick Technologies Attachment 21. Some Design Equations of the OKCET Rev1 Power Supply

Assembly

Attachment 5_ Power Supply Redesign Requirements

Cover

Attachment 5

CAVU-2100 Power Supply Re-Design Requirements

Attachment 5_Power Supply Redesign Requirements

<This Page Intentionally Left Blank>

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CAVU-2100 Power Supply

Re-Design Rev1 Requirements Below is a list of known requirements. Contents are updated during the design and debug phases.

Functional Requirement Specification (FRS)

1. Listing of all Inputs and Outputs.

a. Associated connectors.

i. Initially use the present connectors’ nomenclature associated with ITT pdf schematic files.

1. Status: Done - reference schematics and connector spread sheets.

ii. Present connectors’ mfg. pn. with specification sheets.

1. Status: Done – reference BOM.

iii. Connector definitions.

1. Status: Done –

a. One new connector added to support line voltage monitoring.

Reference BOM and drawing AC Line Voltage Monitor Cable

Assembly.

b. Connector designations comply with 1 st generation of CAVU-

2100 power supply PCB connectors.

c. P8 (PRIMARY POWER SELECT) function has been redefined. It may be used to select either low (85VAC) or high (108VAC) as the level to automatically open the AC power relay and remove

AC power from the radio. Also, if it is decided to abandon P8, the power supply design provides a shunt selected circuit (P11) on the PCB to control which level is used.

d. TP6 (DC_FAIL) and TP7 (AC_FAIL) have been removed from PCB due to removed circuitry.

e. P10 has been added to allow forcing the AC power relay ON when the PCB is not installed in a radio.

iv. Connector pins’ definition.

1. Voltage levels and associated truth table(s).

a. Status: Done. Data gathered will be used to compare against new power supply during debug phase.

2. Amperage requirements.

a. Status: Done. Data gathered and will be used to compare against new power supply during debug phase.

3. Timing requirements (if any).

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a. Status: This item will address both the AC and DC power relays switching time (ON to OFF and OFF to ON), which may be measured and changed during debug phase.

2. Listing of other functions to improve radio operation that requires power supply access.

a. AC-to-DC and DC-to-AC switchover improvements. Voltage Trip Low (VTL) and Voltage

Trip High (VTH) are used below:

i. Removal of original product implementation via P8 to support making either AC or DC as the primary power source.

ii. Utilize front panel switch via P8 to allow user selection of AC voltage removal level as either 85VAC or 108VAC.

1. Status: part of Rev1 effort.

iii. Utilize via 2-ckt shunt the on-the-pcb manual selection of the AC voltage level removal. This is not a product requirement and no other NAS radio has this feature. This change leaves a nonfunctional front panel switch.

Status: Done.

1. Two trip levels are selectable via a 2-ckt shunt.

a. LO: VTL = 85 VAC.

b. HI: VTL = 108 VAC.

2. VAC Trip Hysteresis = @5 VAC.

a. LO => VTH = 90 VAC

b. HI => VTH = 113 VAC.

b. Improve AC filtering.

i. Nothing was done to change the power supply filter caps.

ii. External to the radio will be a filter for Electrically Fast Transients.

c. MOV upgrade to comply with USA usage.

i. Status: This was done via modification by ITT.

d. Grounding schema (single point or multi point).

i. Status: Single point ground implemented for the new power supply PCB.

e. AC and DC Switching circuitry made more robust.

i. Status: Done. This has been made seamless using steering diodes. Associated power relays’ contacts have also been protected against high current surges encountered when being turned ON or OFF.

f. Possible inrush current Vunreg power relay circuit improvement.

i. Status: Will not be done.

ii. This was a modification performed by ITT.

Hardware Requirements Specification (HRS)

1. Three assemblies are required.

a. Heat sink assembly.

i. Status: ITT data provided to Maverick Technologies and will part of a turn-key solution. This line item has been successfully done with Rev0 efforts.

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b. Power supply PCB assembly.

i. Status: Anticipating funding to commence Rev1 PCB layout and debug exercise.

c. Line voltage monitoring cable assembly.

i. Status: Rev0 cable assembly fabrication and testing has been done.

2. Dimensional limits related to LxWxH.

a. Make power supply assembly easier to install/remove, if possible.

i. Status: There was nothing to improve on this desire, so it was not done.

Rev0 to Rev1 PCB Changes

Rev0

Most of the following items are modifications performed to the Rev0 pcb. Implementation of all items is required to the Rev1 pcb:

1. Wrong footprint discovered on R7, R19 & R37. The device is a Wide 1206 3/4W device.

2. R37, will use a standard 1206, .25W package, CRCW12062K20FEA � change to

CRCW12062K20KEA due to typo.

3. R19 & R7 we will use a high power resistor in 1210 package, 3/4W, CRCW12102K20JNEAHP

4. C1 & C2 descriptions in BOM not correct. This applies to Maverick version only.

5. D2 & R24 can move away from K1 for more clearance to relay housing.

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6. Heat sink will need a modification to support traces under the heat sink or move the traces.

Not on drawing, but now see that it is present on the current heat sink. Since the pwb is going through a respin, we will adjust the traces.

7. Relay K2 needs to move away from screw mount between itself and heat sink to provide more clearance for installing/removing the mounting screw.

8. DC comparator circuit is prone to cause its associated relay to chatter when high current is pulled through the relay and Unreg adjusted at the turn-on voltage level. This is due to the

Unreg voltage being lowered, at the instant of the high current, across the associated resistors connected to both Unreg and the non-inverting comparator input. The resolution is to put 0.47uF caps from both R30 to Sgnd and R32 to Sgnd. These caps should be low DA type. 0805, 0.47 X7R ceramic

• http://www.digikey.com/product-search/en?keywords=490-3328-2-nd

9. External DC Control, other resistors in circuit affected the input DC source. Will need to cut the trace between R28 and Q3 to add another resistor.

• Add resistor on Base of Q3, 6.1K, 1/4w � 11122015 changed to 6.2K, New R44.

• Change R28 from 20K to 3.3K, 3/4w min � 11122015 changed to 0.5W

• change R29 from 4.64K to 9.3K, 1/4w � 11122015 changed to 9.31K

10. AC Control, other resistors in circuit affected the input AC Level. Will need to cut the trace between R14/R13 and Q1 to add another resistor.

• Add resistor on Base of Q1, 10K, 1/4w � New R5: made same as other 0.4W 10K resistors.

• change R14 from 20K to 5K, 1/2w � 11122015 changed to 4.99K

11. AC monitor circuit front end causes excessive leakage current.

• Remove rev 0’s R1, R5 and R44 from the design. Will reuse component designators as needed.

• Implement transformer for connection and isolation to line voltage. � New T1.

• Changing AC-Level related resistors

• Was: R3=1.4k, R4=2k pot, R6=5.1k

• IS: R3, R4=2.2K ohm pot, R6=3K ohm

• Remove connections of R3 to P10.

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• Add P8 back to provide front panel selection of AC trip voltage: 85Vrms or

108Vrms.

• PN: 22-04-0541.

• Pin 1 NC and is physically cutoff.

• Routing is P8-2 and P8-4 across R3.

• P8-3 is NC.

12. New P11 (like old P10) is used to provide product internal selection of AC OFF: 85Vrms or

108Vrms. This part provides internal manual selection in case the front panel switch is not to be used.

13. Support of AML power supply testing.

• New routes for P10:

• P10-1 to VR1 cathode pin 1.

• P10-2 to R15/R6/R4 node as close to R15 as possible.

• P10-3 is NC.

• New 2-ckt (P12?) to force +15V regulator to conduct and force -15V regulator on.

This item may become moot, if the reg status LEDs can force all regulators ON.

14. Distributed ground connections through the standoffs to chassis ground perhaps provides less regulators’ output noise. The Original board is around 60mV and the new board is seeing around 200mv.

• As of 10/21/2015

• Via measurements, it is concluded the addition of distributing ground via standoffs (multipoint ground or MPG) offers no improvement to measured noise levels of regulators’ outputs. Therefore, single point ground (SPG) will be maintained.

• The accumulation of shielding improvements has resulted in noise measurements that have improved over the ITT board for SGND and all regulators’ outputs. Expect additional noise level improvements when layout changes are made to regulator outputs to comply with the following:

1. Do not route any regulator output on top layer and underneath shield cans.

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2. As possible, keep all regulators’ output traces routed on the bottom layer. Maintain minimum clearance between regulator output traces and SGND plane of 0.15mm (6 mils). Attempt to maintain 6 mils.

3. For any regulators’ output traces forced to the top layer, ensure both sides of the trace are bordered with a SGND trace.

a. Use and maintain 0.15mm (6 mils) as clearance between regulator trace and SGND trace.

4. Any top layer trace(s) crossing any bottom layer regulator Vout trace will cross at 90 degrees to minimize any noise coupling.

15. The DC connector P2 was pinned wrong: need to change back to the old layout. Re-orient the connector.

WAS: old board

P2-1 DC_Source

P2-2 SGND

Is: New board

P2-1 SGND

P2-2 DC_Source

• Move P2 connector downward, so it may be removed using fingers only. Presently the top tab requires using a tool to actuate the unlock lever.

16. Although the LED power lines for both the AC-LED and DC_LED complies with the original power supply, these control lines both need to be connected after their respective power control relays, so that being ON actually means their respective power relay has engaged, rather than presently indicating simply that either/both AC Power and/or External DC is connected to the rear of the radio.

17. Reduce the shield pads around L7 & L4, they are a little too wide. Ensure shield pads completely surround the can shields and are connected between the can shields. Ensure an increased number of via connections to bottom layer ground plane.

18. Adjust either location or height of Test points, cannot get to some on the assembled board.

TBD.

19. Add green status LEDs down by the +15, -15, +5v test points.

20. Adjust the tall Elec caps to allow screw access for the regulators into the heat sink.

21. Test Points

• Eliminate TP14

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• Move TP2 over toward board edge around TP1. Can not get to it in-between the tall caps. � Due to difficulty connecting alligator clip associated with scope probe, changed TP1 and TP2 to Kobicon 151-100 series. Ref BOM. Ensure adequate length through PCB. If not long enough, change to 151-300 series.

• TP3, TP4 and TP5 are difficult to connect to due to being too small.

• Change TP3/TP4/TP5 to use Kobicon 151- series. Ref BOM. Ensure adequate length through PCB. If not long enough, change to 151-300 series.

• Change TP13 to a SMT threaded standoff. PN: 9774070151R

• http://www.digikey.com/product-detail/en/9774070151R/732-7106-1-

ND/5320711

22. Move Fiducial to gain some space down around TP12 area.

• Move TP12, TP13 & TP9 away from screw hole as much as possible

23. Adjust neck down on high current traces to allow more width, see marked up drawing.

24. Apply note in schematic and BOM about P7. " Cut Pin4 before installing P7" Only 3 pins are required, but a 4 pin cable has been used in all applications.

25. Apply note in schematic and BOM about P8. “Cut Pin1 before installing P8”. Only 3 pins are required, but a 4 pin cable has been used in all applications

26. Bevel corners associated with DC/AC lands to allow more current efficiency. See Bill

Bennett.

27. LEDs added for regulator status.

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Attachment 3_Power Supply Flashover Background

Attachment 3

Power Supply Flashover Background

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Attachment 3

Power Supply Flashover Background

What is an Arc Flash?

An arc flash is a rapid, explosive discharge of electrical energy that usually results from a short circuit fault. Metal vaporized by the 5,000+ degree temperatures of an arc flash produces a high-temperature plasma. A shock-wave blast can propel metal shrapnel at high velocities in many directions. An arc flash can occur in very little time. Explosions have been known to occur in as little as 1/1000 of a second. The event is unexpected, violent, and deadly.

Causes of Electric Arcs ( MDR Power Supply)

Over-voltages across narrow gaps: When air gap between conductors of different phases is very narrow (due to poor workmanship or damage of insulating materials), arcs may strike across during over-voltages.

The Nature of Electrical Arcs

• Electric arcs produce some of the highest temperatures known to occur on earth – up to 35,000 degrees Fahrenheit . This is four times the surface temperature of the sun.

• The intense heat from arc causes the sudden expansion of air. This results in a blast with very strong air pressure (Lightning is a natural arc).

• All known materials are vaporized at this temperature. When materials vaporize they expand in volume (Copper – 67,000 times, Water–1670 times ). The air blast can spread molten metal to great distances with force.

• For a low voltage system, a 3 to 4-inch arc can become “stabilized” and persist for an extended period of time.

• Energy released is a function of system voltage, fault current magnitude and fault duration.

CALCULATING SPACING BETWEEN PCB TRACES FOR VARIOUS

VOLTAGE LEVELS

CIRCUIT BOARD LAYOUT GUIDELINES

Proper distances between PCB traces are critical to avoid flashover or tracking between electrical conductors. Flashover is similar arc flash, but not as severe. Various industry and safety standards prescribe different spacing requirements depending on the voltage, application and other factors. Along with using UL60950-1 safety standard, to determine the electrical clearances, designers also consult with IPC-2221. It is widely accepted throughout the world as a generic PCB design standard for commercial and industrial applications. Of course, it is

P a g e | 4 always desirable to maximize whenever possible the distance between tracks (traces) on individual layers to minimize the possibility of electric breakdown and reduce parasitic capacitance. A recent IPC-9592 standard for power conversion circuits originally provided linear functional spacing requirements: SPACING (mm) = 0.6+Vpeak×0.005. In general, a linear relationship makes more sense. However, these requirements were also too conservative and at low voltages were not even practically doable. The latest IPC-9592B document left the above equation only for V≥100V. At other voltages the limits are as following:

• 0.13mm (0.005”) for V<15V

• 0.25mm (0.010”) for 15V≤V<30V

• [[[0.1+Vpeak×0.01]mm] / 25]mils for 30V≤V<100V.

The last equation is relevant for the MDR transmitter, as it normally idles with Vunreg at 33VDc. Surges associated with line power will result in an increase to Vunreg, but should not result in Vunreg increasing beyond 100V. As an example, using the last equation for Vunreg = Vpeak = 60VDC will result in spacing of 28 mils.

Based on the second above equation, the MDR power supply PCB layout was designed for Vunreg < 30VDc, as the spacing is measured at 10 mils. This is not okay and requires Vunreg keep-away spacing to be increased.

Original thinking was the MDR power supply was being subjected to Electrically Fast Transient (EFT) energy at sites employing an Engine Generator (EG), and likely occurring when the EG is tested monthly or commercial power is actually lost temporarily. The EFT source was suspected to be the EG contactors when switching the site load back to commercial power without the EG 60 cycle being synchronized with the commercial power’s 60 cycle. The EFT amplitude and frequencies is dependent on actual loading of the site equipment. It is perceived to be inductive in nature and accentuated by mechanical pitting of the EG contactors as they wear out. Site testing could not corroborate. Subsequent thinking was the commercial power voltage surges were a by-product of lightning events. As of April 2017, testing is being conducted at MHT RTR to attempt to capture lightning based transients.

Attachment 4_Power Supply Failure Analysis And Test Report

Attachment 4

CAVU-2100 Failure Analysis Report by

Maverick Technologies

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Attachment 4

CAVU-2100 Failure Analysis Report by

Maverick Technologies

CAVU 2100TM

Multi-Mode Digital Radio (MDR)

Power Supply Failure Analysis And Test Report

Maverick Technologies L.L.C.

PCA Manufacturing Technologies and Engineering Services

2800 S. Purdue

Oklahoma City, Oklahoma 73128

Ph. (405) 680-0100 CC: 3GA37

Federal Aviation

Administration

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General

This proposal and quotation covers the FMA work associated with reviewing the Power Supply failures on the CAVU 2100 system.

The general scope of work was to review the power supplies and attempt to make a best determination as to the failure mechanism and root cause of the failure.

In specific, we can review and examine the system/device failures to see if load, external influence, ie, surge or spike, could be involved. We can review to determine if any solder related, joint related, material finish or specific plating could be involved with the failure mode.

A final summary report will be generated which will detail any and all findings and any further work which may be determined to be beneficial in additional analysis.

Initial Review and History

A high rate of failure has been occurring on the CAVU 2100 power supply board, to an alarming rate that an investigation was started in an attempt to determine the root cause and both short and long-term solutions. At the time of the report 400+ units have failed since the product release.

The predominate failure is associated with the MDR Transmitter, with a much lower rate associated with the MDR Receiver module. In terms of power, the Transmitter has a magnitude higher requirement than the Receiver module, thus subjecting the Power Supply module to much greater load, which is indicated by the number of failures seen between the two modules.

The general power specs on the TX system are below:

Primary Power

• AC Voltage 120 V (±10%), 60 Hz (±3 Hz)

• AC Current

• 15W RF Power Output 4.0 Amps maximum

• 50W RF Power Output 8.0 Amps maximum allowed

• DC Voltage 24 V (-10/+20%)

• DC Current

• 15W RF Power Output 10.0 Amps maximum

• 50W RF Power Output 20.0 Amps maximum allowed

Real Time measured values during operation were seen to be as follows:

The 24v UNREG supply input was measured at 1.3A min/9.1A max.

No current protection exists on this power supply to limit input current, shunt inrush surges or output current limiting. This board will provide as much as it can, based on output load current draw.

The basic function of this board is:

• To provide DC voltage ( +5, +15 and -15V dc) to the DSP board in the system.

• It also serves to monitor the AC source and determine if there is need to switch over to an external 24v DC power supply. ( Dual 24vdc supplies, one internal & one external)

• Provide pass through connection for the unregulated 24VDC supply which is supplied to the PA.

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The below image, Fig 1 was viewed as some of the worst case condition failures, where the internal DC-

DC power supply was having a thermal distress condition, which would result in system failure, smoke and potential fire.

Fig 1.

Investigation

We obtained 5 of the MDR Power Supply boards, 4 which had failed and 1 known good board. An intial review was made to get a general feel of what had failed on each, the level of failure and some general information about each board.

The 4 boards that had some level of failure, were all labeled as PWB 8199132-1 MP-2107 Rev A, and the

PWB was manufactured by TTM Technologies. Date codes ranged from 0543 (43wk of 2005) up to 0832

(32wk of 2008). The known good board had a date code of 4302, ( assuming 43wk of 2002), and the

PWB was from a different vendor, PCB Acquistion.

Based on the electronic data that we were given, we reviewed the Gerber and Schematic files and determined that the board was fabricated as follows:

• 4 layer ( no stackup info available)

• Bare copper under soldermask, HASL finish

• 0.062 thick

• Green solder mask & white silkscreen

The design technology is 100% through hole, DC to DC Power Supply. 24vdc un-regulated input is ran through a series of step down switchers to provide the DSP with the +15/-15 and 5vdc power rails. The

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AC input signal is supplied to a logic circuit to determine if AC is present and then through some switch controls enabling either the system 24V un-regulated DC source, or an external 24vdc regulated supply as the primary input.

Based on FAA measured values on an operational system, the following is a summation of the Output power budget for the board:

• P5 Output connector ( +15/-15 & 5vdc supplies) = 1300mA

• P4 Output connector (+15/-15 & 5vdc supplies, 24vdc unreg) 2200mA

• P3 Output connector( 24vdc unreg) 8600mA

• P1 & P2 Input sources ( Unreg 24, & external 24vdc)

Fig 2

Fig 2 shows the general area around the input Connector P1 where thermal discoloration can be seen on all 4 boards that were obtained as failures. The FAA personnel commented that almost all failures were similar to the 4 boards that we were reviewing. The Fig 2 board is one that exhibited less burn conditions than of the others.

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Fig 3

Fig 3 shows a blow up of the area of concern, with the P1 connector inputs labeled. Under normal operating conditions, the system would be powered based on the facility AC source, which drives and feeds the AC-DC unregulated filtered in the system. This provides the 24v unreg source to either Pin 2 or Pin 4. If no AC is present, then the supply switches the input to the external 24v source, and that input comes in through Header P2. The above area is the general area on all boards where thermal breakdown has occurred.

In looking at all 4 sample power supplies which had failed, one had major damage to the point where the area around the failure was burnt beyond recognition. Fig 4 shows that board looking at the same area as compaired to the previous board in Fig 3 from a top view. Fig 5 shows the same board from a bottom view. From this board one can determine that temperatures were reached to the point that the board achieved self ignition, where unit system failure occurred and the system either was shut down or some overall breaker was tripped due to excessive current draw.

Power Supply

P1 Header Input

P

4 3 2

GND TX-AC RX-

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Fig 4.

Fig 5

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Fig 6

Fig 6 shows a few more pictures of the areas of concern on the other failed boards. From the 4 failed boards we are able to determine that there is a pattern of failure, only the magnitude of damage on each board is different.

From this initial review we were able to determine that all the failed boards had similar type damage in the same area, which leads to an early conclusion that on all the boards, we were dealing with the same issue, same defect and same events.

Device level review

The next phase of review involved reviewing all associated parts on the failed boards in an attempt to determine if a device failure was associated with this meltdown event.

All the damage on each board was in the same general area, and in some cases the PWB had burnt all the way through the board and in the most severely damaged board, all the parts in that general area were burnt beyond any test capability. Fig 7 shows the area of concern and where damage had occurred.

Fig 7

We started by reviewing the boards that had the least amount of damage and had determined that we had a direct short on relay K2 between Pin 3 and Pin 5. This is supposed to be the Normally Open side of the relay for switching the 24v Unreg input voltage. This should be Open in an off state.

Fig 8

We opened up and reviewed the device, verifying that the contacts were open and not damaged. See

Fig 8. We removed the device and verified that K2 was still operational and worked fine. This led us to the condition that the short had to be internal in the PWB in order to cross and short the input to the output. We confirmed that this was also the condition on the other boards, and each had the same shorted condition between the input 24v Unreg and the output leg of K2 Pin 5.

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All associated diodes, resistors, caps and Vreg on the boards were all verified according to specification.

The only devices that could not be confirmed were those on the board that had excessive burning to the point that the parts were damaged beyond examination. Based on this finding, this led us to a further direction that a device failure was not the failure initiation point and that we were probably looking at either PWB or Assembly as a failure mode.

The next item to review was associated with the PWB in the area of the burned and charred devices. In each case the area of investigation was between header P1 and Relay K2. This led us to review the schematic in this area to get an understanding of what was going on with the circuit. From the schematic and from the FAA measured operational currents, we can determine that the input 24V Unreg source comes in on Header P1-2 and goes over an inner power layer over to relay K2-3. At that point, power is switched and provided to the Power supply circuits, including the on board switchers through

Q1, the on board logic and 24v common. The top of the PWB in the area where all the burned material is located, is where the top copper trace is leading out of K2-5. This is also the area of highest current density for the circuit. All load passes between P1-2 and top copper trace heading toward Q1. Fig 9 shows the area of circuit that matches the physical area on the board where damage is occurring. Note the 3 arrows coming off Relay K2 Pin 5. These 3 arrows show the 3 pathways for current. The Green

Arrow is the highest current pathway leading off the board with the 24v Unreg supplying the PA module and also supplying the on board switching regulators. The Blue Arrow is the supply the logic circuit.

The Yellow Arrow is the 24 common rail. At the Pin 5 point, the Max current is seen up to the point on the trace where CR11 provides some pathway for current.

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Fig 9

Fig 10

Fig 10 shows close up of the area where thermal damage has been occurring. During this review we were also looking through the PWB Gerber layers to verify pathways and connections. During that review we noticed some Gerber layer differences from the actual Gerber data that we had and the actual PWB that is used on all the boards.

Circuit and PWB area of

K2

Top copper area

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Fig 11.

Fig 11 shows a comparison between the Gerber layer and the actual PWB top copper view. We found that the data that was provided to us for review did not match the data that was used to create and fabricate the actual pwbs that are used in all the boards that we examined. The data that was sent and associated drawings are listed as MP-3254 PWB Gerber, but has no revision, no date, and no owner listed on the drawings. Those fields are left blank.

In doing additional reviews between the Gerber data and the actual real boards we found no other areas of difference.

Finding this difference made us concerned about this area, as this is also the area where damage, failure and issues are occurring on all the failed boards. We found that the Top copper 24v Unreg trace coming off the relay K2, was thickened up on the real boards vs. the Gerber data. This meant that there must have been a concern and someone had taken steps to widen the trace pathway on the real Gerber data prior to production boards being built. What this led us to believe is that someone, having seen issues, knew of a current problem or of a potential problem and wanted to add additional copper in this pathway before final PWBs were fabricated. In adding the additional trace width, it meant that vias

K2 Pin 5

Top Copper Layer

24v unreg trace

K2 Pin 5

The actual PWB has had gerber changes to thicken up

The area marked up.

P a g e | 14 that tied R1 and R2 Caps/GND were now encompassed and went down through that trace. Prior to that their vias were outside that top 24v unreg trace.

We continued to focus our investigation into this general area, where we have now found to be the highest current density for the circuit and have also found that this was an area that had been changed to add additional copper surface area, which meant someone was trying to improve the current carrying capacity of the circuit in this general area.

Going back to the initial…