ASTEC 8151 PSU (TRS80, Osborne etc)

Adrian Graham witchy at
Sun Oct 23 19:00:30 CDT 2016

On 24/10/2016 00:30, "Jules Richardson" <jules.richardson99 at>

> On 10/23/2016 08:02 AM, Adrian Graham wrote:
>> Hi folks,
>> Now that the bouncing has calmed down I've got a question about this here
>> triple output pretty ubiquitous power supply. This one had some burst caps
>> so naturally wasn't working and was probably why the machine it came out of
>> was taken out of use.
>> I've replaced all of them because why not, along with the .1uF mains
>> filtering cap that would also burst at some point and I still get low output
>> on all rails.
> Low output in-circuit? If not, are you using a large enough dummy load
> (probably just necessary on whichever output rail is deemed to be the main
> one)?
> Without enough load the regulation on switchers often doesn't work, and low
> outputs are a typical result...

Yep, and I hear this all the time about Apple ][s, but the PSUs from the
last few machines I've done have worked without a load, and these PSUs also
normally work without load also. Maybe it's a US/UK thing. I'm learning as I
go on....

Binary Dinosaurs creator/curator - the UK's biggest private home computer

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