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WANTED: Compaq SLT 386s or 286 Power Supply

N

nztdm

Experienced Member
Joined
Mar 17, 2018
Messages
180
Location
New Zealand
Hello

I have a nice Compaq SLT 386s/20, but the power brick has died. (The power brick for the SLT 286 and 386s both look the same, but I am not sure if they are the same)
I have replaced the leaking caps, and tested most of the parts, but have had no luck fixing the power supply yet.
If anyone has a spare power supply, I would love to buy or trade for it.

Alternatively, the pinout to the power supply 6-pin cable (I can't reverse engineer it. Seems 'smart', and there is an unmarked IC in the 'smart' area of the power brick. I have some replacement UC80669 SMPS ICs coming, in case it's a primary side problem).
Or the pinout to the 4-pin battery, so I can power the machine from there temporarily.
 
I have opened the battery and worked out the pinout.
You can power the machine for testing purposes, with a lab power supply emulating the battery.

Compaq 2682 Battery Pinout.png
 
I would ALSO like to know the details of the power supply. I have one, but it's shot, and I don't have the cable either. The computers works fine off a 12v supply connected to the battery leads, but it's an ugly hack, and I need to take the modem out so the leads can exit the machine through the holes for the RJ11 jacks.
 
Nevets01 said:
I would ALSO like to know the details of the power supply. I have one, but it's shot, and I don't have the cable either. The computers works fine off a 12v supply connected to the battery leads, but it's an ugly hack, and I need to take the modem out so the leads can exit the machine through the holes for the RJ11 jacks.
Click to expand...

What happens to your power supply when you plug it in? How do you know it's shot?
If I could get my hands on it and try fix it, I could monitor the pins and see which is which (charging? Fault? Enable? +5V? +18.3V? GND?). Once we have this, a new PSU can be made.
My cable is also breaking around the strain relief. It's just a 6-pin header with a housing. Could be 3D printed perhaps.
 
Hello!

I've worked out enough of the pinout to get the laptop running with a third party power supply. I don't have a good battery, so I wasn't able to really determine what the battery sense terminals do, or see what things look like when charging. I can dig in a little later after I build a replacement battery; a project for another day.

IMG_2733.jpg

In the image you can see the pinout looking into the computer. These are the male pins.

1) Battery Sense - I don't really know what this signal does, other than it is related to the battery
2) Battery Sense - I don't really know what this signal does, other than it is related to the battery
3) PS_ON - Connect this signal to ground to turn on the power supply. The laptop doesn't care about this signal, only the power supply.
4) +18V - This is the main power feeding the laptop. This is at about +6v when PS_ON is disconnected.
5) Voltage Sense? - I believe this is to compensate for voltage drop across the wiring. When I disconnect this with the laptop powered, the voltage produced by the power supply increases slightly.
6) GND

I confirmed the computer will power with just 18V connected to pin 4, and 0V connected to pin 6, and all other pins open. This was tested with an SLT/386 and a bench supply.
 
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