Attempting to Repair 1970 Incoterm SPD computer - Page 1
Forum section: electronics / repair

author: joeqsmith
author_rank: Super Contributor
timestamp: August 16, 2015, 02:11:18 am
content: This is my first electronic computer. It has been in storage and after I pulled out two IBMs, I thought I would try to get this system running. A little info on this computer can be found here:http://www.datormuseum.se/peripherals/terminals/incoterm-spd-20-20Currently I am checking the main power supply. This is a switching supply using a large 60Hz transformer for the first conversion followed by a smaller transformer for the switching stage.There are at least two bad caps so far. I suspect the one on the right is 35uF 35V Tant.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 16, 2015, 06:43:39 am
content: Replaced all of the output caps and several others. Put fresh grease on the sinks. Diodes were all fine but one transistor failed shorted. It also appears that three of the power transistors had failed.I had some better parts for the power transistors but I'll need to order the small one. For now I am testing it without the first stage transformer and just running it from my small bench supply to limit the power. Running at a lower voltage, I was able to use a different transistor and try it out. It seems to regulate with a small load just fine. It's a start....

author: joeqsmith
author_rank: Super Contributor
timestamp: August 16, 2015, 08:04:07 pm
content: Video showing the circuit boards and storage unit.https://www.youtube.com/watch?v=CDijWQ91JWQ&feature=youtu.be

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 16, 2015, 08:17:44 pm
content: I hope there's any data left on those disks...

author: joeqsmith
author_rank: Super Contributor
timestamp: August 17, 2015, 12:09:18 am
content: I'll cross that path when I get to it. In the mean time, here is part 2.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 18, 2015, 05:20:24 am
content: Stupid TO39 case was over $20/ea. 1970's vintage parts are expensive. It's getting a better part spec'ed in with a different case for 70 cents. Hope to get the power supply running this week.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 20, 2015, 01:16:18 am
content: New transistors made it in. Installed one and tried it out with a couple of back to back transformers. I'll check it on the auto transformer next and make sure it's fine under a higher load.With any luck there won't be too many more problems with it.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: August 20, 2015, 01:34:45 am
content: Wonderful piece of equipment! Hope you get it up and running!Those vintage parts can be a real pain to get. Have had a lot of fun trying to bring a 70's dumb terminal back alive..--Christoffer

author: codeboy2k
author_rank: Super Contributor
timestamp: August 20, 2015, 06:01:31 am
content: Awesome!I grew up with this tech.. not that Incoterm specifically... but hardware just like it, and sometimes even bigger still..And just think, now you can get 500 to 1000x the processing power in an Apple watchWaiting to see the blinking cursor and OS boot

author: joeqsmith
author_rank: Super Contributor
timestamp: August 23, 2015, 02:10:41 am
content: Red button is a sort of reset. Sets system to read the lower nibble of each key pressed and stores it into the core.

author: AF6LJ
author_rank: Unknown
timestamp: August 23, 2015, 02:39:05 am
content: That is so Cool.