View Full Version : Seeking System/34 Expertise

May 1st, 2016, 04:48 PM
I'm deep into cleaning up a poor neglected System/34 and I'm going to be installing a 220v service to get it powered up. I'm slowly going though the Operators Guide I found on archive.org.

I'm concerned about the filter caps and other power supply components. They are in cosmetically good condition, no leaking electrolytic, etc. But still the concern lingers (there are a lot of large capacitors in this thing). I have the idea of leaving the disk drives disconnected during the first power up to reduce the load and allow the power supply to 'warm up' for the first time in 30 years.

Anyways, it's mainly a cleanup project right now. I have a twinax InfoWindow terminal that will hopefully work with the computer. I'm going to be pretty happy if I can see it successfully IPL. Which leads to my next question; what should I be seeing on the CE panel to indicate a successful or failed IPL?

Not surprisingly, there's little information on the web about operating one of these other than the original documentation from IBM. The documentation is a little daunting considering the terminology is from a completely different era of computing.

The last thing I'm researching, is matching the white paint. The top panel needs a lot of touching up.

Here are just a few photos of the unit. I'll post more as cleanup continues.

May 2nd, 2016, 08:03 PM
Dang! I thought my project restoring an old S-100 system that was water damaged was daunting. This project is way beyond that!

The last time I touched an S/34 was probably late 1985 before we upgraded to an S/38. And that was from the keyboard side - the IBM CEs got real pissy if you opened cabinet doors. :)

Sorry I can't be of any help other than to shout encouragement from afar. Good luck - and keep us posted.

<*> Jim

May 4th, 2016, 04:52 AM
Great project, I never worked on the 34 systems but did lots of work in low voltage high current power supplies before. Think what I would do although it will be a lot of work is to remove and check one by one all the big capacitors in the power supplies. Once removed you can check them for leakage with a small DC power supply and also if you have access to meter you can verify their value. I have seen many of those old caps decrease value quite a bit. They rarely short but it has been known to happen, you’re more likely to see shorting in the higher voltage caps in switching supplies. I have seen that before in the newer series IBM switching supplies. Also removing all those caps gives you opportunity to clean around them. As long as all the caps are good and the transformers are clean and dry I would have no issues myself bringing up everything at full power, some people think you should run things up slowly with but I sometimes think that’s a recipe for disaster with regulated supplies although with the old series regulated stuff not as big a problem as it would be with switching supplies.
looking at the tag on the system it looks like you require 230 volts at around 6 amperes so that would have the system sucking down a little less than 1,400 watts and not much worse than a large window air conditioner. One thing you may want to also check is the tag gives power ratings for 208 and 230 and 208 may be assuming a three phase connection. If that’s the case there would be four wires in the main power cable, 3 phase and ground where a signal phase power cable will have only three wires, 2 AC feed and a ground so check the primary AC side real close. Doubt that it’s a three phase box but if it was configured to be used in a commercial environment although it may be signal phase it may be strapped for 208 volt operation and you will want to change the transformer taps to 230 volt operation.