Avionics teardown: looking at some mystery Rocketdyne boards - Page 1
Forum section: electronics / projects

author: D Straney
author_rank: Frequent Contributor
timestamp: December 29, 2023, 07:35:58 pm
content: Index:Intro & CPU board (below)Hybrid boardI/O boardCPU board #2 & bare die photosOpening packages: resistor arrays on hybrid board & I/O board, crystal oscillator on CPU boardI found these unusual-looking aerospace-style boards at a surplus industrial seller (search "02602" athttps://teamequip.com/, but be warned they're obnoxiously expensive even with a decent discount) and couldn't resist getting a few: these were marked with the CAGE code 02602, which is for Rocketdyne (now part of Aerojet). As Rocketdyne has, as far as I can tell with some searching, never made anything outside of rocket engines, I think there's a good chance these were from some kind of rocket engine controller. I have no idea what kind of engine these would've been from (commercial launch vehicle, NASA space activities, military missile, etc.), but the date codes are all 1995-ish.You can see the full album of photos here:https://www.flickr.com/photos/147639706@N02/albums/72177720313550068/First of the 3 boards is the...CPU BoardI'm calling this the CPU board because it has what looks like a processor & memory in the bottom-left corner:The part numbers on this board are almost all custom, starting with "RM" (Rocketdyne Microelectronics?), but we can see this chip is made by UTMC (United Technologies' silicon fab & packaging division). The 12 Mhz oscillator next to the CPU(?) is almost definitely the main clock. I'd be curious to see under the lid: it could be a single microcontroller die, or a processor co-packaged with memory. You can see a multi-die package example with a Pyramid Semiconductor MIL-STD-1750 processor from CPU Shack here, so it's not a wild idea:https://www.cpushack.com/CPU_Photos2/pyramid/MIL-STD-1750A-Pyramid.jpg...however, it looks too nice intact for me to want to do anything to this copy. I'd chip in a bit if anyone wants to get another one of these boards and decap all the chips.There's also a communications section at the bottom-right, with a couple pulse transformers that are usually used for isolating MIL-STD-1553 interfaces. There's also 3 separate dual-cavity chips - the CPU Shack guy (who has seen a lot more chips than me) says they're dual MIL-STD-1553 transceivers, and it looks a lot like the UTMC UT63M1XX-series dual-transceiver versions:an RM2466-001 next to the transformers: the placement suggests this is the transceiver for 2 external interfaces through the transformersan F015690 just above this section: non-isolated internal interface to somewhere else?an RM2466-001 at the left edge: non-isolated internal interface to somewhere else?The 3 DIP packages next to the CPU(?) are JM38510R75705 = M38510/75705 = 74AC244 8x buffer w/3-state outputs. Together with the 19x 10-ohm resistors, this suggests these might be series-limiting resistors on either 19x discrete inputs or outputs that go elsewhere:The top-right section is more of a mystery:The JM38510/11201 surrounded by passives is an LM139 quad comparator, and so together with the "F015856" Linear Technology metal can (voltage reference?) this might form some kind of power-up reset and/or power rail monitor and/or watchdog timer circuit.The SP720AP is a 14-input ESD/over-voltage protection clamp: this might be responsible for protecting the external I/O for the serial buses.The 2 ceramic-and-gold Harris F015689 (also appears on another board) and Harris F0158040 are complete mysteries.Custom part numberingThere seem to be 2 different custom part numbering schemes here: the "RM..." on the larger ICs, and "F015..." on the smaller ICs, and even the resistor arrays:It seems very unlikely (and wildly unnecessary) to have this many custom parts, and especially custom IC designs from scratch - this applies even more on the other 2 boards. The more likely scenarios are:An HP-type situation, where internal part numbers are assigned to everything "just because": this can be helpful to explicitly keep track of manufacturing process changes from vendors, but high-reliability parts vendors already have ways to handle that type of thingSlight modifications to existing COTS designsUp-screened commercial parts: high-reliability electronics manufacturers, when they want to use a normal "commercial-grade" part in their design, will usually take the bare dies (in the case of ICs) and have them put through a separate, more rigorous set of tests: performance checks at extended temperature extremes, longer burn-in, etc. ...and then package the dies that pass the additional tests in a more robust package as well.

author: peter-h
author_rank: Super Contributor
timestamp: December 30, 2023, 12:23:33 pm
content: Date codes from 1994 latest, dry film solder resist, the usual stuff from 30 years ago.Mil stuff seems to exist in a time warp of its own, with designers using specially qualified parts regardless of whether they are necessary or not.Nice stuff

author: xrunner
author_rank: Super Contributor
timestamp: December 30, 2023, 12:45:28 pm
content: There looks to be a lot of internal structural bracing across the board and components, is that what I see? Would that lend itself to your idea it's associated with a rocket engine?

author: D Straney
author_rank: Frequent Contributor
timestamp: December 30, 2023, 01:55:09 pm
content: Quote from: xrunner on December 30, 2023, 12:45:28 pmHmm that's a good point. Hadn't thought of that aspect, that kind of construction is normal in mil/aerospace stuff for conduction cooling: the metal sheet provides a thermal connection to the rails along the edge, and through those to the enclosure. But you're right in that the ribs are strictly a structural thing, maybe to help with vibration etc.?

author: peter-h
author_rank: Super Contributor
timestamp: December 30, 2023, 02:44:29 pm
content: The last pic showing the holes around the missing chips, and the metal passing under the white chips (look carefully), that is for heat transfer. But the large beams are for rigidity.I did something like that many years ago for a sonar product which emitted powerful pulses.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: December 30, 2023, 03:39:07 pm
content: Wish we could buy those MIL spec capacitors* (preferably at sensible prices). Would save us a lot of trouble in future....*saliva running (German: "sabber")

author: SeanB
author_rank: Super Contributor
timestamp: December 30, 2023, 04:18:16 pm
content: Those dual package DIP chips look a lot like the last generation PDP processors, with the integrated mask ROM providing the program storage. Wonder if they are actually complete PDP11 processors, each one dedicated to a task on the board, as the 12MHz clock seems about right for them. I have abused those CTS13 wet slug tants, they do have a really good low ESR, and I was running a 100uF 16V one as SMPS filtering on a PC power supply, 5 in parallel, as the original ones had gone open circuit. 5V at 15A, and they did not even run warm, unlike the Fong Kong originals, which were 2200uF 10V units.

author: peter-h
author_rank: Super Contributor
timestamp: December 30, 2023, 06:55:35 pm
content: You can find milspec parts on Ebay. Type Milspec into the search box.e.g.https://www.ebay.co.uk/itm/256232342118- a bit pricey though!https://www.ebay.co.uk/itm/293760642576etc

author: Haenk
author_rank: Super Contributor
timestamp: December 31, 2023, 09:06:29 am
content: https://teamequip.com/02602-r077450-3-circuit-board-t114762/shows socketed/installed EPROMs; you would not do that on hardware that goes into a rocket, right?Other than that, those PCBs are really a piece of art, no expenses left out

author: peter-h
author_rank: Super Contributor
timestamp: December 31, 2023, 10:10:55 am
content: WOW amazing!I like "THIS IS A USED ITEM, IN GOOD CONDITION AND INCLUDES A 30 DAY WARRANTY." given that nobody will be able to test itI am looking for Max Technologies IPM-429 and this site might well have it but their search finds nothing.The socketed chips are interesting. Indeed no way could it do a lot of G but maybe they are for code loading only. Or they may be glued in place. The turned-pin sockets are highly reliable in all other respects.

author: D Straney
author_rank: Frequent Contributor
timestamp: December 31, 2023, 09:49:47 pm
content: Quote from: peter-h on December 31, 2023, 10:10:55 amYeah good point. This is another copy of the board, which looks like has some kind of ROM in the sockets:https://teamequip.com/02602-r077450-3-circuit-board-t114762/There's also what seems like a different version of the same board, with a soldered ceramic DIP module:https://teamequip.com/02602-9r077450-3-mfr4f972-26-93-7r071691-1-mfr94756-29-94-circuit-board-t101753/

author: peter-h
author_rank: Super Contributor
timestamp: December 31, 2023, 11:09:34 pm
content: The ceramic chips with the labels are normal UV EPROMs, I am sure. The other stuff is just weird. Incredible money spent there.

author: D Straney
author_rank: Frequent Contributor
timestamp: January 02, 2024, 10:49:39 pm
content: Oops sorry Haenk, missed your earlier post which said basically the same thing as I repeated later.Quote from: SeanB on December 30, 2023, 04:18:16 pmNow that's an interesting point there too. Counted the pins and the two RM2446 DIPs have 40 pins, not the 36 that the standard MIL-STD-1553 transceivers (and the F015... chip) have. So along with the single pair of transformers, it would make the most sense that the "F015..." DIP above the transformers is the dual MIL-STD-1553 interface, and the two RM2446 DIPs are something else, like CPU + memory as you say. Bet it would be obvious if one half had memory in it, from looking at the diesHere's the second board:Hybrid BoardThis one has 6 surprisingly large hybrid modules, all made by Teledyne. The 4 across the top are identical to each other, and the 2 in the middle are identical to each other. I cut open one of each, as you can see in the photo above, to take a look at the contents:I don't have access (yet) to a microscope good enough to pick out any die markings, but here's my speculation based on what I can see.All of these handle relatively small-signal stuff only; there's no discrete power devices like in theaerospace DC-DC hybrid module.The top hybrid has 4 identical sections, each with two large resistors, a few caps, and two ICs. There's also three vertical common traces at the left, which look like V+/V-/ground judging by their ceramic cap connections, plus an individual connection to each section (output?). There's two connections on the right (inputs?) that go to the large resistors. The two ICs in each section look identical to each other, and have 5 bond wires each. Overall, this leads to me to believe that the ICs are op-amps, and this hybrid contains 4x differential-input amplifiers. The hybrid-module form factor here is particularly useful for laser-trimming each resistor to get a precise gain and optimize the CMRR of the differential inputs, as you needveryclose matching (better than you can get from off-the-shelf discrete resistors) to have "standard" 80 dB+ CMRR.The bottom hybrid has a lot of misc. analog stuff in the left half where the function isn't immediately obvious, including a lot of separate substrates with resistors or resistor arrays. At the right side are 5x different similar/identical-looking ICs, which each have 4 or 8 identical "channels", and a common section. I don't know whether these are digital registers/latches, analog switch arrays, or something else unrelated. Overall, my best guess given the differential-input amplifiers above and the precision analog parts here is that these are ADCs of some kind.So, my guess at the purpose of this whole board is that it receives and digitizes sensor inputs. There's 4 of the top hybrids, and 4 channels each, which means 16 total input channels. Each possibly-ADC hybrid then probably muxes between 8 input channels.To be honest, I'm not sure why a discrete ADC implementation in the form of a hybrid module would be used here: it shouldn't have to do anything too special (high speed, ultra high resolution, etc.) that a military-grade off-the-shelf chip couldn't do. Maybe the middle hybrids are actually something different like synchro-resolver receivers - it would also be a weird design choice to have the sensor receivers on a whole different board than where they're digitized, but I guess it could also make sense to put all the input signal conditioning circuitry together. So there's your alternate interpretation for the middle hybrids.There's also some ICs scattered around the hybrids...Custom part numbers and a quad op-amp, kind of strange that there's only a single resistor near the op-amps though (unless they're all just connected as buffers / non-inverting followers):JM38510/65705 = 74AC244 8x buffer w/3-state outputs; bus interface for digital stuff onboard? Plus an LT1021 voltage reference in the metal can, which is probably used for the middle hybrids, as either an ADC or a synchro/resolver decoder would need a precise voltage reference:Lots of (digital) differential transceivers in the standard 26x31/26x32 family: overall there's 16x channels of differential line drivers, and 4x channels of differential line receivers. There's also a custom-marked mystery chip, of the same type as one that appeared on the CPU board too. Not sure how this relates to the rest of the circuitry:You can also see the missing conformal coating on the bottom of the board in one place, where someone reworked this custom-marked chip:

author: D Straney
author_rank: Frequent Contributor
timestamp: January 15, 2024, 05:37:52 am
content: Third and final board:I/O BoardThis is the largest of the 3, and there's a lot of different things going on, so let's take a look section by section...Digital inputsThere's a repeated set of series/pull-down resistors, a clamping diode, and capacitor which shows up in one half of the board - you can see 16 of them total:These seem to be the first-stage protection for a set of digital inputs, which are then compared against thresholds by the 4x LM139 quad comparators (16 total comparators):There's 2x LT1029 5V voltage references, connected in the scheme shown on the first page of the datashet, to provide both +5V and -5V references. I'm guessing these are used by the comparators for the digital inputs but haven't confirmed with a continuity check:Digital outputs (low power)Power enters near the connector through a potted common-mode choke followed by an AVX capacitor array:This is then used by the 3 identical blocks in the other half of the section we looked at previously:The ICs are 5962-8981001PC, which turns out to be the mil-spec equivalent of the Avago HCPL-5700 Darlington-output optocoupler. These optocouplers are used to drive the bases of the 2N3743 transistors (300V, 200 mA) in the metal cans, to provide a high-side switched output.Analog(?) outputs (high power)The part where it gets more complicated is with these modules over in the corner:They definitely look like power transistors heatsinked to the metal stiffener plate. Despite the custom part numbers (I discussed the "RM..." part numbers in a previous post), the silkscreen on the bottom of the board labels the terminals as "G", "D", and "S", showing that each one is a power MOSFET:There's also an op-amp, some custom gold-lid DIP ICs, and another power MOSFET nearby though:When tracing out the circuit (which I have to say, was a huge pain to do by continuity checks only - at least there's no conformal coating on this one...), it turns out that the adjacent section is part of the gate drive circuitry for these power MOSFETs:Here's the schematic:It looks like these are either analog or digital high-side-switched power outputs, all 3 ganged together from the same control voltage ("Vsp") and acting as source-followers. The long tube at one edge on the board is the current sense resistor, with 4 leads for a Kelvin sense scheme, and this is used to monitor the total current draw.They must've had a lot of extra space driven by other factors when designing this board, because it's very sparse overall, but the gate drive wins for most space-inefficient overall. It seems to be controlling the transient response of each MOSFET gate (identically) to changes in the setpoint voltage:When Vsp increases, the power MOSFET gate is charged RC-style through D28 and R83.When Vsp decreases, the VR6-Q4-D27 circuit is active instead, and forms a constant-current sink (VR6's zener voltage is imposed across R82, minus Vbe, by Q4 acting as an emitter-follower), with VR5 as a "special-case bypass" which speeds up the turn-off when the difference between the setpoint and the gate voltage is too large.VR9 just protects the power MOSFET's gate against overvoltage.The custom ICs here (RM2496-904) and what they do are a complete mystery to me: the only connections I could find were to Vsp, the source terminal of the corresponding MOSFET, and two pins (different for each of the 3 channels) on the connector. The only thing I can think of is that they could be optoisolators meant for monitoring the voltage difference between the Vsp setpoint and the actual output voltage (at MOSFET source terminal) and reporting back to control circuitry on a different card if this goes over a certain threshold (meaning that the MOSFET has either failed open or the load is shorted) - but this seems like a weird way to go about it.The current sense circuit uses the classic high-side current sense method that's popular on fully-integrated high-side current sense chips these days. The op-amp drives Q10 as essentially a variable current sink, to create a voltage drop across R111 that's equal to the voltage drop across the current sense resistor. Because Ids(Q10) * 100Ω R111 = I(R105) * 0.05Ω R105, this means that the current coming out of Q10 is going to be a 2000:1 copy of the current flowing through R105. You can then put this current into a ground-referenced resistor to get an output voltage that's level-shifted for free, or use it in some purely current-mode manner. Here, it becomes a bit of a mystery after this output current exits D41: I'm not sure what's going on with the resistors (R108, R109, R106), or why it's summed with the setpoint voltage, or where other side of R106 goes (I checked pretty much every single component on the board as well as every connector pin).It's worth noting that the MOSFET used in the current sense circuit (Q10) is MASSIVE overkill: theFRF9250is a Serious Power Transistor with high-thermal-conductivity BeO inside, a case meant for heatsinking, etc. but here it only handles the tiny signal currents. I'm guessing it was used here because it was either the closest thing to a small-signal MOSFET in the limited in-house high-rel parts inventory, or because it was already being used in other places in the same larger design. Similarly, the 2N3743s in the gate drive circuit are also overkill here, but again, these were already being used in the low-power digital outputs described earlier, so easiest to just use the same part when you're not trying to squeeze every penny out of the cost.I also had the thought that high-side load switching might be preferred in critical applications like rocket engines: if the system chassis is grounded (or grounded-ish), then a loose wire from a low-side-referred load would do nothing except fail open. A loose wire from a high-side-referred load (with low-side load switching), on the other hand, if it becomes physically disconnected or the insulation breaks down could touch a grounded piece of metal easily and activate something that should not be activated (like a fuel valve or an igniter) - this would definitelynotbe "failing safe"!Other PartsThese are photos of some of the other boards, taken from the TeamEquip / OCO Industrial website:1x of the same ADC(?) or synchro/resolver-input(?) hybrid as before, with other mystery circuitry:Possibly more I/O; looks like load drivers in the bottom third, possibly opto-isolated digital inputs or outputs in the top third, and no idea about the middle third:Analog inputs or outputs, with SP720 I/O-protection-diode arrays, and LT1012 op-amps or LT1017 comparators:Some kind of power driver:maybe analog processing and/or a common ADC??Strange-looking antenna:Box (which may have originally held some or all of these boards):

author: onsokumaru
author_rank: Contributor
timestamp: January 15, 2024, 09:41:07 am
content: Awesome, I love these teardowns, there is so much to learn and discoverThanks for the post and the great pics!

author: D Straney
author_rank: Frequent Contributor
timestamp: May 20, 2024, 04:29:41 pm
content: CPU Board #2The un-answered questions on these still bothered me, plus the industrial surplus seller was nice enough to agree to a massive discount, so I got a couple more boards from this same set. One of them was a 2nd copy (different revision) of the CPU board, to decap the chips and sort out what everything was doing.Ken Shirriffkindly offered to take some die shots after I contacted him about a different project, and so I got to work with a knife and coping saw (he decapped the tricker ones himself like the ceramic DIP packages, and the MIL-STD-1553 transceiver).Before:One of the differences, as you can see in that last photo, is that what was an empty socket on the other CPU board has a little ceramic daughterboard here, with two EEPROMs (AT28HC64) and a 54FCT139 (dual 2-bit/1-of-4 decoder) to select between them.After:OscillatorIt should be no surprise to anyone that the package marked "12 Mhz" was in fact an oscillator:You can see the quartz disk here, with electrodes plated on both sides (I accidentally chipped it while opening, it's supposed to be round). There's some other electronics present in the form of a couple ICs and a couple passives. You can build very simple crystal oscillator circuits with only a single transistor, or a logic inverter used as an amplifier, but I'm guessing some of the extra circuitry here might be involved with temperature compensation or ensuring reliable startup.RAMThe 2x dual-cavity ICs marked with "RM..." custom part numbers turned out to have RAM in both cavities:I don't know much about different memory topologies at a transistor level, but from looking at the individual memory cells Ken guessed it was SRAM as they seemed too complex to be DRAM. This is consistent with the SRAM that I've seen in other 80's/90's high-reliability computers (such as these Honeywell commercial-aviation boards:1and2), and makes sense because if the extra density of DRAM isn't strictly required, the refresh cycle just adds a whole new set of failure modes and complexity.The RAM, like a lot of the other ICs onboard, is made by UTMC (United Technologies Microelectronics Center):CPUThe large quad-flatpack chip I'd assumed was the CPU before turned out to be a standard-cell custom gate array - you can see the very regular layout here, with the irregular interconnections on top:For digital ICs, this is a popular halfway point in between using only off-the-shelf parts, and going through the massive effort of making a fully-custom IC design. In the standard-cell-ASIC scheme, the manufacturer designs a large array of logic gates, and makes one set of photolithography masks for these. A customer who wants a digital ASIC will then decide how to connect together this fixed set of gates to fit their application, and the manufacturer will make a custom metal-interconnection layer on the chip to fit the custom design (like a hard-wired FPGA). This way, most of the IC fabrication steps and expensive tooling can be the same no matter what, and can be designed once and made in bulk: only the much smaller number of fabrication steps and masks involving the metal layers have to be different for each custom design.I'm not sure why exactly this uses an ASIC instead of an off-the-shelf processor. There is obviously a lot of I/O interfacing that needs to be done here, to connect the many digital inputs and outputs as well as two separate UARTs for the dual MIL-STD-1553 serial interfaces, so combining that with a simple processor as a single (relatively) miniaturized chip was probably the goal - this still seems like a lot of work though, compared to using off the shelf parts, as even for aerospace-qualified processors and peripherals there was a decent variety available. It's also possible there's some kind of redundancy here, such as two simple processorsoperating in lockstepor using voting logic.I also considered that this might not be a processor after all, but some kind of simple state machine asrocket engine control doesn't have to be very complex, depending on the engine(for example, theJ-2 engine seems like it's mostly just a series of timers, no feedback loops or complex controls). However, that wouldn't make sense with the EEPROM, which couldn't really be anything but program memory. It's also possible the digital ASIC is just a CPU-bus-to-I/O-and-memory interface, and the CPU itself lives on a different board somewhere, but that wouldn't make a whole lot of sense either: there's no way the CPU would take up an entire board by itself (especially not when as willing as this to use custom parts), and what else would be grouped with it besides the memory?MIL-STD-1553 transceiverThe slightly smaller dual-cavity DIP package, above the dual pulse transformers in the bottom-right corner, is a dual transceiver for the MIL-STD-1553 serial bus: each cavity has one transceiver. The MIL-STD-1553 bus uses high voltages (>20V, "high" by signaling standards) and differential signaling for noise immunity in military and aerospace applications (imagine a radar transmitting nearby and all the wiring picking up the stray sidelobe emissions), and was standard for a long time on aircraft and spacecraft. This one's a standard part, yet again made by UTMC:Ken did a great writeup about the circuitry and various functions on the die:https://oldbytes.space/@kenshirriff/112198313439124398You can see the power transistors used as transmit drivers, as well as the laser-trimmed resistors used for differential reception.Other diesThe 54FCT139 decoder which selects the EEPROM chips turns out to be more interesting than would be expected - it's implemented as a (very small) standard-cell gate array, rather than a purpose-built chip as is common with standard digital logic:SeeKen's writeup on thisfor more details.AT28HC64 EEPROM:HA720 diode array, used to protect some external I/O:54HC244 buffer, for either driving or receiving external discrete I/O signals:54HC14 Schmitt-trigger inverters, either for external inputs or as part of the reset/watchdog logic:

author: CaptDon
author_rank: Super Contributor
timestamp: May 21, 2024, 01:46:24 am
content: Since RocketDyne was mentioned in this thread I thought I would add something. I did some work in the Rocket Motor Lab at York Harley Davidson back in '93. We built the LR-64 Rocket Motor and shipped them to Cessna for use in target drones. The device would nearly burn itself up but it was a one way trip anyway. I believe RocketDyne continues to build the LR-64 to this day.

author: Testtech
author_rank: Regular Contributor
timestamp: May 22, 2024, 11:20:19 pm
content: WOW!Some of the large hybrid modules were made by Teledyne Microelectronics, as denoted by the stylized "T".That hybrid DC-DC power supply module would have been a nightmare to build, and I bet the yield wasn't great with all that mixed technology.Nice finds, and great pictures!

author: D Straney
author_rank: Frequent Contributor
timestamp: July 02, 2024, 02:23:41 pm
content: Huh, I'd never thought of that as a "T", just as upside-down flower petals. Yep the CAGE code matches too @16170And thanks, glad you enjoyed.I decided to pop the lid on a couple mystery packages, and found that the DIP packages with the long gold lids contain custom resistor arrays. For example, take a look at the resistor array next to the quad op-amp,on the "hybrid board":Zooming in shows that there's a few independent ceramic substrates, each with resistance traces on the surface hidden by a cover layer of polyimide or something similar.You can see the same type of construction in a hybrid module I opened:The reason to use these custom arrays instead of discrete resistors would be either compactness, which doesn't seem like an issue on the other boards, or for trimming / matching of the resistances. You can laser-trim the resistance value on each ceramic substrate for a much tighter initial tolerance than an off-the-shelf resistor would give. Also, having multiple resistors made from the same material right next to each other (thermally coupled) means that even as temperature changes, the multiple resistance values will track together much better than if they were all separate discrete resistors. This is particularly useful in voltage dividers, where you care most about the resistance ratio remaining stable.This particularly makes sense here, right next to the quad op-amp: these resistors are probably used for feedback voltage dividers on these op-amps to precisely set gain.A similar resistor arrays also appearson the I/O board. Remember these mystery devices near the power MOSFETs? Also resistor arrays.Again, compactness doesn't seem to be an issue on this board (look at how much empty space there is) so my best guess is that these form a trimmed voltage divider used to sense these MOSFETs' output voltages elsewhere on a monitoring & feedback board.As a bonus, here's a zoomed-in view of the crystal oscillator module from the 2nd CPU board:I'm not sure what the green die is, but the black die looks like maybe a classic "CMOS inverter used as linear amplifier": you can see how only one of a few sections is used, and two of the pins are connected across the quartz crystal along with a small resistor (top-right on ceramic substrate).

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 02, 2024, 03:42:20 pm
content: Your board collection reminds me of that analog-guru Jim Williams photo, which shows all the boards for the Minuteman missile, which he had hung on his living room.You could do similarly.

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 02, 2024, 08:02:05 pm
content: Exciting stuff!Just an idea - though the housing is looking like flight hardware, is it possible that some of the boards are from the ground station? For sure Rocketdyne has delivered its rocket with some accessoires...

author: D Straney
author_rank: Frequent Contributor
timestamp: July 07, 2024, 10:05:44 pm
content: Quote from: schmitt trigger on July 02, 2024, 03:42:20 pmHa, that would be fun, right now it's just a small shelf with cardboard boxes.Quote from: Phil1977 on July 02, 2024, 08:02:05 pmI'd wondered about that too, before. The construction style, particularly all the glue and the stiffening ribs, really looks like something meant for heavy vibration. Also the rest of the telemetry and electronic systems on a launch vehicle/missile/spacecraft/etc. usually come from the system integrator or a specialty manufacturer, rather than the maker of just the rocket engine. But it's still possible that this is part of some in-house-developed data acquisition system for Rocketdyne's ground test-firing stands, for example - or maybe it does fly, but only on small suborbital engine-test vehicles to collect engineering data, or something like that.

author: stj
author_rank: Super Contributor
timestamp: July 10, 2024, 02:23:40 am
content: rocketdyne was involved in more than rocket engines.think black aircraft.they also had a reactor-meltdown!!!but thats another story - you can research that one yourself - just stay away from the park they built on the old site!

author: D Straney
author_rank: Frequent Contributor
timestamp: July 10, 2024, 04:35:38 pm
content: Hmm, the only reference I could find to aircraft was them working with NASA to do an aerospike-engine test (for the X-33) on NASA's inherited SR-71. Any more details?And yeah hah wouldn't catch me anywhere near that "Energy Technology Engineering Center" test site outside LA, with all the stories of dumping barrels of waste and making ponds boil. Looks like all their nuclear R&D (as Atomics International) was long since wrapped up (decade or more ago) by the time these boards were made.Since your post re-ignited my curiosity on what exactly these are from, I did a quick search through the National Archives database of military contracts (https://aad.archives.gov/aad/series-description.jsp?s=503&cat=GS29,30&bc=,sl) for the CAGE code 02602. Turned up a few things about Peacekeeper Missile modifications (probably supplied the rocket engines), a few weird unspecified underwater things for the US Navy (), and a whole lot of mystery contracts where the system description was "not spec'ed, or classified". Saw their power systems division did some spacecraft power systems, so tried to find more details about this (none of the circuitry says "power system controller" or "battery management", but it's not impossible) - but couldn't find anything besides that they were responsible for some of the ISS power systems. Tried the National Archives general gov't contract database (https://aad.archives.gov/aad/series-description.jsp?s=594&cat=GS29,30&bc=,sl) to see if anything came up for NASA, but the entries I found there didn't have any details on what the contracts are actuallyfor, so that wasn't much use. So "rocket engine controller of some kind" is still my best guess, but who knows really.