I have a pair of pdp8/L's here that I picked up years ago and it's about time I got around to restoring unit #2. Unit #1 is missing somewhere here, I got it to the point where it ran basic programs and I think it's in the closet underneath the pdp8/E.
Anyway, first step was cleaning up the key switches and replacing several broken toggle switches. I needed six of them, had three with broken pins and realized I could just print a couple of them on my Ender 3 pro. Hint: Do not use PLA, it's far too weak for the small pivots. PETG however works *very* well and now all of my switches are fixed and more importantly close reliably (no bounce or excess noise, cleaned the miscreants with Deoxit.)
This evening I checked out the power supply. Unplugging the it from the CPU and putting it on a very well insulated towel I powered up the supply and checked the voltages.
Color What is What should be Purpose
Blue/orange 10.21v Panel power Pretty unregulated
Grey/blue 0 -15 if locked Panel lock Would be -15 if unlocked, +5 locked
Orange 11.21 8v +5 input Unregulated, ok
Red 5.21 5 +5 regulated Regulated, ok
Blue -17.60 -15 Neg 15 power Unregulated, ok.
Green -35.17 -6 WAY OFF What is this? BAD!
Yellow -35.05 -30 Broken? Turns out ok ish.
Brown -.329 ? Mem reg base Unknown
So the only odd one is the -6 volt one. It is not tied to the power supply but goes to a pair of transistors as a regulator. Might get power from the regulator board next to it, not sure.
Anyway, any thoughts on the -6 line? Does the other card (G826) supply power to this?
I'm pretty certain at least one or two of the G220 register cards are sad, is there a troubleshooting guide to what components tend to fail and need replacement?
C
Anyway, first step was cleaning up the key switches and replacing several broken toggle switches. I needed six of them, had three with broken pins and realized I could just print a couple of them on my Ender 3 pro. Hint: Do not use PLA, it's far too weak for the small pivots. PETG however works *very* well and now all of my switches are fixed and more importantly close reliably (no bounce or excess noise, cleaned the miscreants with Deoxit.)
This evening I checked out the power supply. Unplugging the it from the CPU and putting it on a very well insulated towel I powered up the supply and checked the voltages.
Color What is What should be Purpose
Blue/orange 10.21v Panel power Pretty unregulated
Grey/blue 0 -15 if locked Panel lock Would be -15 if unlocked, +5 locked
Orange 11.21 8v +5 input Unregulated, ok
Red 5.21 5 +5 regulated Regulated, ok
Blue -17.60 -15 Neg 15 power Unregulated, ok.
Green -35.17 -6 WAY OFF What is this? BAD!
Yellow -35.05 -30 Broken? Turns out ok ish.
Brown -.329 ? Mem reg base Unknown
Wire color | What it is | What it should be | Notes |
Bl/Or | 10.21 | Unknown | Panel power |
Gr/Bl | -15 locked | 5 unlocked | Panel lock |
Orange | 11.21 | 8 | +5 input unregulated |
Red | 5.21 | 5 | +5 regulated output |
Blue | -17.60 | -15 | -15, unregulated |
Green | -35??? | -6 | Odd, not supplied by PS |
Yellow | -35 | -30 | -30 unregulated |
Brown | -3.29 | ? | Looks like from another card |
So the only odd one is the -6 volt one. It is not tied to the power supply but goes to a pair of transistors as a regulator. Might get power from the regulator board next to it, not sure.
Anyway, any thoughts on the -6 line? Does the other card (G826) supply power to this?
I'm pretty certain at least one or two of the G220 register cards are sad, is there a troubleshooting guide to what components tend to fail and need replacement?
C