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Roland Huisman
April 14th, 2013, 01:20 AM
Hello Everyone,

Does anyone have the schematics of the Astec 9251 power supply?
I need an Astec 9251 but it seems hard to find.

I found a quite similar power but it's configuration is slightly different.
The left one is the original Astec and the right one is an Klaasing.
(It seems the Klaasing is actually a re-branded Astec)

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I want to try to change the Klaasing power to the specs of the 9251.
But this is much easier done with a good original schematic.

Otherwise I have to draw the schematics of the 9251 first.

Thanks in advance!

Regards, Roland

Roland Huisman
April 14th, 2013, 02:05 PM
Hello Everyone,

Today I've drawn the part I needed myself. The hardest thing was to change the +15V into 12V.
This has to be done by changing the transformer. And today was my lucky day.
The wire which needed less windings was in the top layer of windings.

After some measurements it seems I had to remove 1,5 winding of the wire.
This was on the bottom of the transformer. The big problem with these
transformers is the very hard lacquer and the core which you can not disassemble.

It is also not possible to get the extra wire out of the transformer.
I've cut and shielded the top wire. At the bottom I've soldered a wire
to the two transformer wires (they are in parallel).

After I got the transformer on the right voltage it was quite easy
to modify the rest of the electronics. One negative voltage is missing
but this is not needed for the computer. (this winding is not on the transformer)

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I think its hard to find the original power supply. So I think this
is a nice original looking alternative... And this is all to fix a Holborn 6100.

http://www.vintage-computer.com/vcforum/showthread.php?35843-Holborn-6100-computer

Regards, Roland