Replacement for QP1008 (HP9816 PSU)

[Tony Duell]

> 
> Rik wrote:
> > I aquired a HP 9816 with a faulty power supply.
> > Thanks to the diagrams of Tony I found out that the switching transistor
> > QP1008 is shorted and a 2n2222 but thats no problem.
> > I googled for it and searched my datbooks but can't find any replacement
> > or
> > datasheet for it.
> > So does somebody knows the specs or a replacement for this transistor ?
> 
> Maybe I don't understand what you're asking, but the replacement for a
> 2N2222 is a 2N2222.  They're still made, and not at all hard to find.

Err, no....

This PSU [1] has 2 transistors on the primary side. The chopper, 
component reference Q2, is a TO3 can marked 'QP1008'. There's also a 
current-sense transistor, Q1, a 2N2222

The latter is not a problem to replace. The 2N2222 is trivial to find, 
and it's not _that__ critical anyway.  But the chopper transistor is 
almost certainly selected for some parameter, but I have no idea what (so 
that, for example, taking the chopper out of a good 9816 PSU board and 
sticking it on a curver tracer won't help, you don't know what you're 
looking for)

[1] A Power/Mate EVD-6S-300S IIRC.

And before someody suggests replacing the complete PSU, I should point 
out hat this thing has strange outputs. +5V (normal), +15V and -15V (or 
+14.4V, -14.4V?). The latter 2 are regulated down by linear regulator 
circuits on the monitor PCB to give +/-12V.

[An aside for those who don't know the HP9816. It's a 68K computer with 
uilt-in monitor, although no built-in drives (those connect via an HPIB 
port). There are 6 PCBs in the case, and 2 expansion slots for HP DIO boards.

Flat in the bottom of the case is the processor board, which contains the 
CPU, RAM (normally 256K bytes, it's possible to get 1M on there), boot 
ROMs, HPIB port, RS232 port, keyboard port, etc.

THis plugs into a little backplane which carries the DIO slots

On top of that, also plugging into the backplane is the monitor PCB, 
which contaisn the CRT drive circuitry and the +/-12V regulators)

Plugged into that are 2 more boards of mostly digital ICs. The larger one 
is the text video circuitry, the smaller one the graphics video.

And finally there's a metal box down one side of hte mchine (LHS seen 
from the back IIRC) that contains the SMPSU we're discussing here. It 
connectes by 2 camels (mains in, DC out) to connectors on the monitor PCB]

> 
> If that's not what you're trying to replace, what is the part number
> you're replacing?  I could be wrong, but QP1008 looks like a component
> designator, not a part number.  Even if there's only an HP part number
> (e.g., 181x-xxxx), that's more useful for finding a replacement than
> a component designator.

There are no HP part numbers on the PSU board components.

-tony