It’s taken us longer than we would have liked, but this weekend we finally made our first steps to getting Edith, our System/38, back among the living. It was a big, long, 10 hour day but we made some exciting progress and we feel confident that we’ll at least have a diskette IPL by the end of the year – if not by the end of Summer.
Earlier in the month, we put power to Edith just to see what she would do. This weekend, we started the day the same way, and found that the same fault lights were still on – we initially thought that we were having a +5v Base overcurrent check and all other voltage supplies undercurrenting. This will come back to bite us later.
For now, we proceeded as if the +5v Base OC check was our problem. Here we get into the power supply of the System/38. The green board in the upper right of this image is the base supply protect card, which we removed and checked for shorted diodes and tantalum capacitors. We did not find anything, so at this point in the morning we set Edith aside and went to take care of some other business.
We needed to get the 3430 tape drive and the 9370 half-rack and 9332 DASD off their shipping pallets. This went easy with minimal fuss as they’re far, far lighter than a thousand-pound System/38. The 3430 tape drive is a vacuum column tape drive and as you’d expect after 40 years of existence, the vacuum lines have gone hard and brittle. We will need to replace the lines before we can spool tape on this drive.
The 9332 DASD was partially disassembled and the dust bunnies were blown out. After cleaning, we plugged the drive into power and hit the switch, and amazingly after 40 years and being bounced on a truck up to and back down from Canada, it just spun up and came ready with no fuss!
We broke for lunch and then came back to Edith where we attempted some more diagnostics. We are currently flying completely blind, as we do not have any of the Maintenance Analysis Procedures or Field Logic Diagrams to show us what to check for fault analysis. We dug through the power supplies and contactors looking for the source of the +5 Base OC fault, and we even disconnected some power rails from the backplanes to try and find the fault. We did find that some power connectors had popped loose over the years, but nothing solved the fault. That was, until one of our other club members just happened to ask…
“Hey, what’s this switch do and why’s it tilted like this?”
At this point, Joe remembered something from working on System/38s back in the day. The Maintenance Switch was a diagnostic aid for field engineers and when engaged, would allow the System/38 to IPL from diskette and would bypass several fault conditions that it would normally check on. Normally, the switch is straight up and down, and would be turned off when the chassis door was shut. In this case, our switch was so tilted so the machine could run in production with whatever fault the machine had that the FE couldn’t diagnose. And just what was our fault?
Turns out the fault code wasn’t actually 5v Base overcurrent. It was a cable check. Oops.
We flipped the switch back to the On position, and applied power to Edith again. Hey look, no power checks! Upon this revelation, we immediately booked it down to the hardware store and rented a generator so we could actually attempt to power Edith up.
Our first actual power on attempt yielded another Power Check fault. This time, the check code is actually for a 5v base overcurrent fault. We removed main storage boards trying to find the fault, and while we didn’t find any shorted tantalum capacitors, we did determine that this time the 5v base overcurrent fault is real and that we need to perform an overcurrent adjustment procedure on the base protect card. For now, we’ll just try to run the system with less main storage installed.
And run, she tried to! Our 72MD diskette drive appears to need some work as it chewed up our SLV1A diskette trying to IPL. Fortunately we made backup copies of all the diskettes beforehand. We saw the status lights count down stages of IPL, though, and other diskettes inserted into the drive did give us a “Wrong Diskette” error. At this point, we just decided to go for broke and attempt a disk IPL off the 62PC drive.
Unfortunately for us, the 62PC drive did not want to play ball with us. We managed to get the drive to spin up exactly once, and only for about 15 seconds, but every other IPL attempt before and after that the drive did not spin. We managed to trip the spindle motor’s thermal fuse a few times, and after checking the motor start relay and capacitor and finding them good, we believe our 62PC spindle motor is bad. The good news for us is that we have several other 62PCs with faulty cards or disk assemblies that we can pull motors from. This is where we left Edith for the day, and will likely leave her for the next few weeks as we get ready for Southern-Fried Gaming Expo and Vintage Computer Festival Southeast next month.
So, what else is there to do on Edith now? There’s quite a bit that needs to be done, but nothing that should take too long:
- Replace the 62PC motor
- Perform the overcurrent adjustment procedure
- Remake our SLV1A diskette
- Align the 72MD drive
- Attempt diskette IPL
We’ll be back soon with another update post once we recover from our exhibition events. In the meantime, why not support us on GoFundMe or one of our other donation methods?