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IBM PS/2 P70 Power Supply Outputs?

zombienerd

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Does anyone have a P70 that would be willing to disconnect the plasma power connector (6 pin) and take voltage readings? You have to cut a few zip ties and slide some heatshrink out of the way.

I can't find a reference anywhere for the plasma voltages. I have a "pinout" with colors listed (which are Red, Yellow, Black, White, Blue) - but no voltages listed! Gut is telling me somewhere between 100v and 600v DC, so please, if you attempt this, take proper safety precautions!

My P70 has a dead PSU, no schematics are available, and I can't find the culprit for the life of me, so I'm considering replacing the internals with a Meanwell supply (125W 5/12/-12), and custom design a buckboost or find another secondary psu that can do the voltages the plasma needs, but I need to know the required voltages.


Thanks!

Adam
(YesterGearPC)
 

oldpcguy

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I may be willing to do so. Can you post a picture of the specific connector?
 

zombienerd

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I may be willing to do so. Can you post a picture of the specific connector?

When you remove the backplate, the wire goes to the right hand side,and runs down. It has a piece of heatshrink over the connector, zip tied in place.

When disconnected, the plug looks like the attachment. I also understand there were two different PSU's used on the P70, so if you don't have this connector, the voltages will be different. The other style PSU's connector was a flat 6 pin.

IMG_20210921_015039197_HDR.png
 

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oldpcguy

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I'll see if I can get to it today or tomorrow. If not then possibly over the weekend.
 

oldpcguy

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Right now I'm a little hesitant to do this as I discovered neither of my floppy drives work. To pull the power supply might need me to disconnect the CMOS battery which will erase the systems configuration leaving me without a useable system. I need to get the floppy issue resolved before I can take on this work. Hopefully I can get one of the floppies working within the next day or so.
 

zombienerd

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Right now I'm a little hesitant to do this as I discovered neither of my floppy drives work. To pull the power supply might need me to disconnect the CMOS battery which will erase the systems configuration leaving me without a useable system. I need to get the floppy issue resolved before I can take on this work. Hopefully I can get one of the floppies working within the next day or so.

You don't need to pull the battery or remove the PSU, should be able to do it just by removing the back panel and lifting the cable up a bit on the right side.
 

oldpcguy

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I am confused. The only connector I see on the PSU is the following. Are you saying I can pull the power supply apart while it's in the system and check there?

Edit: Are you referring to the IBM PS/2 70 Portable system? If so that would explain the confusion.
 

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zombienerd

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I am confused. The only connector I see on the PSU is the following. Are you saying I can pull the power supply apart while it's in the system and check there?

Edit: Are you referring to the IBM PS/2 70 Portable system? If so that would explain the confusion.

Yes, the PS/2 P70 The P is for Portable :)
 

WBST

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Yes, I've been to that page, which includes the "pinout" for wire colors for the plasma connector, but not what voltages / signals might be present.


You need to consider the preceeding sections too:

BLACK = GND
RED = +5V
WHITE = ? (-5V at a guess)
ORANGE/YELLOW = +12V
BLUE = -12V
 

zombienerd

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You need to consider the preceeding sections too:

BLACK = GND
RED = +5V
WHITE = ? (-5V at a guess)
ORANGE/YELLOW = +12V
BLUE = -12V

The PSU outputs a High Voltage DC to drive the plasma screen (would need to be 100-600VDC) that goes down one of those lines. I'd love to take the standard colors as a guess, but it's not worth the risk damaging an unreplaceable display.
 
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