Replacement for QP1008 (HP9816 PSU)

[Roy J. Tellason]

On Monday 14 April 2008 18:18, Tony Duell wrote:
> > 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

You did those schematics?  I'm impressed.  It's been quite some time since 
I've been quite that ambitious...   :-)

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