Replacement for QP1008 (HP9816 PSU)

Tony Duell ard at
Wed Apr 16 15:51:58 CDT 2008

> Update, the PSU works again.


> I used a BU208A witch seem to function fine.

I'll make a note of that. BU208As are pretty easy to find, and it'll be 
one to try if my 9816 ever has PSU prolems.

> As I supposed earlier C11 (220uF/16V) was leaking and destroyed the 2n222=
> 2=20
> witch blew the QP1008.

> On the secondery side there were some elco's going bad, after replacing t=
> hem=20
> the PSU is regulating ok=E9.

It's actually a fairly standard SMPSU design, I think. 

> Everybody thanks for the advise (and of cause Tony's cat for the schemati=
> cs)

Enjoy the mahcine. It's one of my favourite 68K boxes. I have a 256K RAM 
card in one slot of mine, and a GPIO (16 it parallel) interface in the 
other. RS232 and GPIB are of course built-in.

How much memory do you have on the provessor board? Most came with 256K 
(all loctaions filled with 4164s). You can increase it to 1M by replacing 
all the RAMs with 41256s, fitting a 74F158 in the spare location at one 
side of hte PCB, fitting a 33 Ohm (I think originally 31.6 Ohm, but it 
makes no difference) resistor in the ovious positon, and cutting a couple 
of jumpers (I can look up details). I've done this to my machine.

And which keyoard do you have? The 'compact' keyoard is odd in that it's 
not scanned. One side of each switch is grounded, the other sides feed 
banks of 4051 multiplexers. 


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