SWTP Universal Tiger help: works, but very low power

kevinabb · 29th January 2007, 11:38 PM

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:

http://www.diyaudio.com/forums/attac...amp=1096758143

Thanks!

Original Burnedfingers · 30th January 2007, 01:26 AM

Replace C2 and re-check.

kevinabb · 30th January 2007, 10:02 PM

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.

peterdryan · 30th January 2008, 11:59 PM

Kevin -

Would your "SWTP preamp" be the model 211?

Thanks,

- Pete

kevinabb · 31st January 2008, 05:45 AM

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

29th January 2007, 11:38 PM	#1
kevinabb diyAudio Member Join Date: Jan 2007 Location: San Diego, CA	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: http://www.diyaudio.com/forums/attac...amp=1096758143 Thanks!

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30th January 2007, 01:26 AM	#2
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Replace C2 and re-check.

30th January 2007, 10:02 PM	#3
kevinabb diyAudio Member 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.

30th January 2008, 11:59 PM	#4
peterdryan diyAudio Member Join Date: Jan 2008	Kevin - Would your "SWTP preamp" be the model 211? Thanks, - Pete

31st January 2008, 05:45 AM	#5
kevinabb 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