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 [TABLE="border: 1, cellpadding: 1, width: 500"]
[TR]
[TD]Wire color[/TD]
[TD]What it is[/TD]
[TD]What it should be[/TD]
[TD]Notes[/TD]
[/TR]
[TR]
[TD]Bl/Or[/TD]
[TD]10.21[/TD]
[TD]Unknown[/TD]
[TD]Panel power[/TD]
[/TR]
[TR]
[TD]Gr/Bl[/TD]
[TD]-15 locked[/TD]
[TD]5 unlocked[/TD]
[TD]Panel lock[/TD]
[/TR]
[TR]
[TD]Orange[/TD]
[TD]11.21[/TD]
[TD]8[/TD]
[TD]+5 input unregulated[/TD]
[/TR]
[TR]
[TD]Red[/TD]
[TD]5.21[/TD]
[TD]5[/TD]
[TD]+5 regulated output[/TD]
[/TR]
[TR]
[TD]Blue[/TD]
[TD]-17.60[/TD]
[TD]-15[/TD]
[TD]-15, unregulated[/TD]
[/TR]
[TR]
[TD]Green[/TD]
[TD]-35???[/TD]
[TD]-6[/TD]
[TD]Odd, not supplied by PS[/TD]
[/TR]
[TR]
[TD]Yellow[/TD]
[TD]-35[/TD]
[TD]-30[/TD]
[TD]-30 unregulated[/TD]
[/TR]
[TR]
[TD]Brown[/TD]
[TD]-3.29[/TD]
[TD]?[/TD]
[TD]Looks like from another card[/TD]
[/TR]
[TR]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[/TABLE]
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 [TABLE="border: 1, cellpadding: 1, width: 500"]
[TR]
[TD]Wire color[/TD]
[TD]What it is[/TD]
[TD]What it should be[/TD]
[TD]Notes[/TD]
[/TR]
[TR]
[TD]Bl/Or[/TD]
[TD]10.21[/TD]
[TD]Unknown[/TD]
[TD]Panel power[/TD]
[/TR]
[TR]
[TD]Gr/Bl[/TD]
[TD]-15 locked[/TD]
[TD]5 unlocked[/TD]
[TD]Panel lock[/TD]
[/TR]
[TR]
[TD]Orange[/TD]
[TD]11.21[/TD]
[TD]8[/TD]
[TD]+5 input unregulated[/TD]
[/TR]
[TR]
[TD]Red[/TD]
[TD]5.21[/TD]
[TD]5[/TD]
[TD]+5 regulated output[/TD]
[/TR]
[TR]
[TD]Blue[/TD]
[TD]-17.60[/TD]
[TD]-15[/TD]
[TD]-15, unregulated[/TD]
[/TR]
[TR]
[TD]Green[/TD]
[TD]-35???[/TD]
[TD]-6[/TD]
[TD]Odd, not supplied by PS[/TD]
[/TR]
[TR]
[TD]Yellow[/TD]
[TD]-35[/TD]
[TD]-30[/TD]
[TD]-30 unregulated[/TD]
[/TR]
[TR]
[TD]Brown[/TD]
[TD]-3.29[/TD]
[TD]?[/TD]
[TD]Looks like from another card[/TD]
[/TR]
[TR]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[/TABLE]
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