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Old 29th January 2007, 11:38 PM   #1
diyAudio Member
Join Date: Jan 2007
Location: San Diego, CA
Default SWTP Universal Tiger help: works, but very low power

After 25 years, finally dragged out my old SWTP preamp and Universal Tiger mono power amps. They still sound great!

One amp works perfectly. The other sounds great, but has only 25% (or less) of normal output. These two amps always spec'd out nearly identical, so something is wrong.

No pots/output controls on the amps. Anyone had this situation before? What should I be looking for? All suggestions welcome. I've been out of the analog world for 25 years, my chops are as rusty as these amps!

The schematic is at this link, posted previously to the forum by another member:


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Old 30th January 2007, 01:26 AM   #2
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Join Date: Nov 2002
Replace C2 and re-check.
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Old 30th January 2007, 10:02 PM   #3
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Join Date: Jan 2007
Location: San Diego, CA
Thanks, burnedfingers. Had both amps fired up last night, high signal levels, ready to measure at/around C2. My 20-pound cat, Lurch, jumped onto the test bench to inspect my work. Before I could get to him, he stepped onto the "suspicious" amp and scored a direct hit across the fuse terminal. Must have pushed fuseholder's output lug onto the metal chassis. One-in-a-million shot.

I saw the arc from across the room, then Lurch flying off the table. Didn't seem to damage him, but the fuseholder and fuse glass literally melted.

So I'll let you know about the C2 suggestion once I replace the fuseholder and whatever else was cooked along with it.
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Old 30th January 2008, 11:59 PM   #4
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Kevin -

Would your "SWTP preamp" be the model 211?


- Pete
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Old 31st January 2008, 05:45 AM   #5
diyAudio Member
Join Date: Jan 2007
Location: San Diego, CA
I believe my preamp is a model 198A. It has push-button tone controls - six buttons for bass, six for treble. A slide control across the top for balance, and one bing knob in the center for voulme.

It sounds great to my ears, even after 30 years and about 15 moves all around the USA.

- Kevin
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