XL1201 Instability Next Steps

Wed, 06 Jul 2016 02:44:36 +0000

Well, the instability on the XL1201 has been disheartening. However, I have a few suggestions and plans to see if I can figure it out.

Kalman Reti would like to see backtraces to see if it’s a software problem. I will definitely get these for him; awesome to have a Symbolics expert offering to help - thank you.
I’ll put the Fluke 289 data logger on the 5V power supply rail and see if the voltage has any spikes or “events” when the computer reboots or acts strangely. If not, I’ll try the other three rails too (12V, -12V, -5.2V).
There are a number of tantalum bypass capacitors on the RAM, Merlin II and I/O boards. If any are going bad, they could short, heat up, “heal” and then work again for a little while.
- Test the tantalum caps for resistance (briefly, as the resistance will change as they charge) - anything under 6 ohms might be bad. This will be very difficult to do with the backplane caps, though; I may have to learn to disassemble the XL1201 chassis.
- After the problem happens, quickly power down and remove the boards to see if any components appear overly hot on the FLIR one IR camera.
Remove the cards again and push on all the socketed chips to make sure they’re all seated properly. Possibly apply contact cleaner to the socketed chips. Maybe the whole board - they seem dirty. Not sure if this “whole board” is safe or not.
Remove the cards and all socketed chips, clean the chip and socket, and reseat them. This would take a long time as there are a ton of chips and I haven’t pulled chips in literally decades. I would need to get a chip pulling tool and be super careful as this stuff is, as far as I’m concerned, irreplaceable.

Unfortunately, I don’t have a way to run the Merlin II without it being installed in the XL1201 chassis so I can’t test the caps directly or watch the heat signatures directly without doing a massive disassembly and hack job on the computer chassis, backplane, power supply, etc.

Status and Next Steps

Fri, 24 Jun 2016 14:13:13 +0000

Status

XL1201 running clean Genera 8.3 on X15 drive from DKS
MacIvory III running clean Genera 8.3
All physical drives ddpt’d for backup

Next Steps

Preparation
- Permanently mount X15 drive and SCSI2SD into XL1201 and close it up
- Install new 8MW RAM into XL1201
- Copy all ddpt backups to Google Nearline for offsite backup (using Arq)
Genera work
- Set up one computer as a namespace server (probably MacIvory)
- Set up both with Sites
- Set up both with TCP/IP
NFS and backup work
- Set up a NFS server
- Back up LMFS from XL1201 “original” SCSI2SD to NFS
Document all of the above in blog posts with pictures
- Make the HTML pre code blocks wider
Concurrently: review console hardware and document all electrolytic capacitors and order replacements when the computer isn’t running

Questions

Status on Symbolics LISP Engineering

XL1201 Instability Next Steps

Status and Next Steps