NASA Apollo Launch Control Center PCB  - Page 1
Forum section: electronics / general

author: mikey12608
author_rank: Newbie
timestamp: November 17, 2014, 06:09:36 pm
content: I obtained this board from a estate sale a while back. The house use to belong to a retired NASA engineer from the Apollo Missions. He had a box written LCC (Launch Control Center) spare parts with these boards inside. I am no electronics expert but I am a space collector, so can anyone tell me what this board might be by looking at it?

author: LabSpokane
author_rank: Super Contributor
timestamp: November 17, 2014, 06:56:15 pm
content: Looks like a slew of diode transistor logic gates.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 17, 2014, 11:56:25 pm
content: It looks great, love the '60s front panel font and colors. Feels like you've unplugged HAL 9000.Could be a bunch of multi-input NOR gates or something. That's a lot of diodes!ICs were exhorbitant and transistors merely very expensive, this kind of board was the equivalent of 74 logic back then.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 18, 2014, 07:19:02 am
content: I think it is some sort of DTL (Diode transistor logic) NOR gates like Alex and LabSpokane suggest. Most things are in tens here; ten transistors, associated resistors and capacitors etc, but the input diodes are odd so we don'ty have ten identical gates.Looking at the lower left transistor and associated components, there are six input diodes leading into the transistor with some biasing through those brown resistors. What I find odd is that the signal seems to go through the black diode, which would be reversed biased (unless the current is flowing out of the base? PNP?). The signal (six inputs ORed together by the diodes) is amplified by the transistor and goes back out the connector.The lower right gate has only 3 input diodes, so it's probably a 3 input NOR gate.Thanks for sharing this! It's very interesting to me.

author: TheBay
author_rank: Unknown
timestamp: November 18, 2014, 07:25:17 am
content: Work of art. Love those early transistors and numbered resistors.

author: LabSpokane
author_rank: Super Contributor
timestamp: November 18, 2014, 04:51:12 pm
content: Each logic gate has one diode that appears to be opposite in polarity to the input diodes. That *could* make these NAND gates. That would make more sense to me than a 6 input NOR gate for the purpose of "if all these conditions are true, then we'll light a green status indicator."That said, these otherwise appear to be NOR gates like the other posters indicated.Thanks for the photos. The PCB is a work of art. Love the hand drawn traces.

author: AG6QR
author_rank: Frequent Contributor
timestamp: November 18, 2014, 05:21:23 pm
content: I like the way the leads are formed on those diodes. Looks like they had a constraint on the minimum bend radius of the leads, combined with a requirement that the diodes be flush against the surface. So the leads leave the diodes, curve up, and then down to the board. It is a thing of beauty, and a lot of care obviously went into its manufacture.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 18, 2014, 05:54:52 pm
content: Quote from: AG6QR on November 18, 2014, 05:21:23 pmWhat if they just wanted more space under the part for traces?

author: Seekonk
author_rank: Super Contributor
timestamp: November 18, 2014, 06:13:24 pm
content: More likely that diode bend up forms a clip point for test leads.

author: extide
author_rank: Regular Contributor
timestamp: November 18, 2014, 09:00:45 pm
content: Wow, that's quite a piece you've got there! I absolutely love the hand drawn traces on the backside, and it seems to be in excellent condition!

author: Kjelt
author_rank: Super Contributor
timestamp: November 19, 2014, 09:44:28 am
content: Christmass puzzle: where exactly in the picture does this pcb belong originallyLooking at the picture the computers did not have keyboards, the keys were integrated on the panels, so this pcb might be a keymatrix decoder, but just a guess.

author: ludzinc
author_rank: Unknown
timestamp: November 19, 2014, 09:54:59 am
content: Quote from: Seekonk on November 18, 2014, 06:13:24 pmActually they are thermal stress relief bends.

author: brabus
author_rank: Frequent Contributor
timestamp: November 19, 2014, 10:34:38 am
content: Infos on the diodes and other interesting stuff here:https://nepp.nasa.gov/index.cfm/5575

author: ConKbot
author_rank: Super Contributor
timestamp: November 19, 2014, 07:11:05 pm
content: Quote from: ludzinc on November 19, 2014, 09:54:59 am+1 not test points or for clearance. Stress relief. Glass packaged diodes need extra stress relief compared to the resistors which are ok with the leads being bent at least a specific distance from the end of the component. Same specs exist today for flight hardware and critical ground support hardware. Obviously there is standards for SMD components also now.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 19, 2014, 07:44:50 pm
content: Quote from: ConKbot on November 19, 2014, 07:11:05 pmThanks!

author: SNGLinks
author_rank: Regular Contributor
timestamp: November 19, 2014, 10:26:09 pm
content: Quote from: brabus on November 19, 2014, 10:34:38 amThat reminded me of my time at a NASA STADAN station. We used to get bulletins of the analysis of the failures of mission critical components.Interesting microscope photos of the insides of transistors etc.Ashley

author: TerraHertz
author_rank: Super Contributor
timestamp: November 21, 2014, 12:17:12 am
content: Quote from: mikey12608 on November 17, 2014, 06:09:36 pmI hesitate to ask, but did you buy just that one board, or the whole box of boards?If you have a box-full of them, I don't suppose you'd consider selling any?I'd really like to add a board like that, an actual Apollo relic, to my humble collection.

author: mikey12608
author_rank: Newbie
timestamp: November 21, 2014, 07:03:08 pm
content: Quote from: TerraHertz on November 21, 2014, 12:17:12 amI wish I bought the whole box. Sorry

author: Falcon69
author_rank: Super Contributor
timestamp: November 26, 2014, 04:53:30 am
content: I can't help but to comment on the picture in post #10.That security camera just seems out of place with the rest of the technology in there. I would have thought it to either be non-existent in that time, or BIGGER.If that is a board for a NOR gate, is that just one gate? If so, Man, I'd hate to see the size of the WOPR if it was made in the 60's.

author: LabSpokane
author_rank: Super Contributor
timestamp: November 26, 2014, 05:40:58 am
content: Quote from: Falcon69 on November 26, 2014, 04:53:30 amIt's likely 10 gates. DTL uses the transistor to correct the diode drop, which also inverts the output.

author: RJFreeman
author_rank: Regular Contributor
timestamp: November 26, 2014, 05:55:02 am
content: looks like a card from a computer made by a company called Computer Control Company, Inc aka 3C (logo in corner of board in IMG_0077.jpg)possibly a DDP-24 (or a DDP-116).The DDP-24 had 7 OD-30 cards, which were apparently an Octal/Decimal decoder as listed in table 1-8 found on page 1-12 of the DDP-24 instruction manual:https://archive.org/stream/ddp-24_instructionman_aug64/DDP-24_InstructionMan_Aug64#page/n23/mode/2up3C was later taken over by Honeywell so may be listed as Honeywell DDP-24

author: RJFreeman
author_rank: Regular Contributor
timestamp: November 28, 2014, 05:54:40 am
content: I have found you the schematics for that board (although it does look to be a slightly different revision).http://bitsavers.informatik.uni-stuttgart.de/pdf/honeywell/modules/130071184B_1MC_Series_S-PAC_Jan66.pdfstarting on page 3-123 (page 119 in the PDF).just in case you want to get the board working or something....

author: Kjelt
author_rank: Super Contributor
timestamp: November 28, 2014, 06:53:10 am
content: What a great finda true electro archive detective.Never bothered with old school electronics myself but what really is different from nowadays are the use of negative supply voltages in reference to ground, noadays it is all positive.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 28, 2014, 07:57:37 am
content: Great find, thanks!Perhaps the reason they went with negative voltage was to allow them to use PNP transistors, which I think were more easily made back then?Another question for whoever is interested in the architecture: is the purpose of the -18v supply to speed up the transitions?

author: nfmax
author_rank: Super Contributor
timestamp: November 28, 2014, 08:54:21 am
content: When I started at university in 1975, we got shown how to use a computer for circuit modelling. This was the first time I'd ever got to use a computer other than remotely: we were actually shown how to to switch it on from cold; set the switches to load the boot loader from paper tape (and respool the paper tape afterwards without slicing your hand open!); and load the operating system from disc. This was a Honeywell DDP-516. One of the circuit analysis examples was a DTL NAND gate just like the one here!

author: mikey12608
author_rank: Newbie
timestamp: December 04, 2014, 01:58:22 pm
content: Quote from: RJFreeman on November 28, 2014, 05:54:40 amGreat find! And thank you everyone!

author: mikey12608
author_rank: Newbie
timestamp: December 04, 2014, 02:31:43 pm
content: Quote from: RJFreeman on November 26, 2014, 05:55:02 amAfter this information I found this information on the AGC (Apollo Guidance Computer)http://dodlithr.blogspot.com/2011/10/apollo-guidance-computer-agc-and-its.htmlhttp://www.p3oriontopsecret.com/3c-computer-control-company-ddp-24-card-rack.html

author: RJFreeman
author_rank: Regular Contributor
timestamp: December 05, 2014, 12:10:36 am
content: If you feel seriously hardcore, there was a chap who built a replica AGC and documented his efforts:http://klabs.org/history/build_agc/and (at least) one other chap who duplicated his efforts:http://users.on.net/~pcschmidt/AGC/AGCRep.html

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 05, 2014, 01:26:33 pm
content: Quote from: RJFreeman on November 28, 2014, 05:54:40 amThanks for the detective work, BTW. I'm a huge fan of '60s electronics and reading about it.