Replacement for QP1008 (HP9816 PSU)

[Rik]

I'm replacing the elco C11 because it's expanding and I suspect it to leak , 
and yes I'm going to check the other components.
I didn't find any open pcb-traces yet but will check this too .
I'll keep you posted on this.


Thanks, Rik

----- Original Message ----- 
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
To: <cctalk at classiccmp.org>
Sent: Tuesday, April 15, 2008 12:03 AM
Subject: Re: Replacement for QP1008 (HP9816 PSU)


>>
>> I aquired a HP 9816 with a faulty power supply.

> I asusme this is the SMPSU board in the metal case at one side of the
> machine, and not the +/-12V regulators on the monitor PCB.

YES, your right.

>> Thanks to the diagrams of Tony I found out that the switching transistor
>> QP1008 is shorted and a 2n2222 but thats no problem.
>
> As you've probably noticed by now, this PSU was not made by HP. At least
> in my machine it was made byt 'Power/Mate'. Not that this helps very much.
>
>> I googled for it and searched my datbooks but can't find any replacement 
>> or
>> datasheet for it.
>
> Nor can I. My guess is that the it's a 'house number', and that the
> trnasistor was selected for some particular characteristic.
>
> My furst guess would be a 2SC1942, since that seems to work in many small
> SMPUS, but don't blame me if it shorts at switch-on. And of course if it
> doesn't you won;t know if that was becuase it was an unsuitale transistor
> or because the origianl fault is still there.

I won't,  I'm happy with every suggestion.

> I would certainly check all the secondary-side rectifiers and smoothing
> capacitors. And the snuber componets (R6, CR4, C12, C3, CR5)
>
> I assume that some of the low-value resistors in the Q2's emitter circuit
> have burnt out too. Any open PCB traces?
>
> -tony
>
>