Recent content by alebeaum

mmm. I'll check this out this week. The original caps were rated 525volts too when I look to the shematic, I'll also check out the voltage rating on my caps. Do you think I would be able to see any issues only by checking the power supply voltages, or I'll have to check the caps one by one?

Ok, so I changed the resistors and what I notice is they were ok as soon as I take it out from the circuits, this is probably the transformer who false my reading at the time. I also changed the 6an8 tube, for a short time it was looking find but, no.. it oscillates again. Any other ideas?

My plan (for bass 'cause the 200s seems to sound great on guitar too) , when my 200s will be fully fonctionnal ( it's a new amp I barely tried it, just want to make sure everything is ok before) is to use my other cab, a vintage EV (yes again a EV) 2x15 with upgraded speakers : One 15'' goes...

::::Though much more accurate, amplifiers with negative feedback can become unstable if not designed correctly, causing them to oscillate.:::: wiki

I think i've found the problem.. on the shematic, top left corner. The 680ohm resistor and the 1Kohms resistor. They are connected to the yellow wire on the OT. Their resistance were much lower http://www.prowessamplifiers.com/schematics/post/sunn_200s.pdf

I use 15'' EV speaker in a vintage Peavey Cab for the moment

NO i dont use it on 10. This is only test I've made to give more information for the troubleshooting :) ...

The 1Mohm resistor is OK. Still waiting for the tube

yes for the tone stack... I'm gonna change the 6an8.. Maybe I have a friend with one, So I can check it asap. They are unusual tube, this is the first time I see this tube

the amp had a cap job in 2001 and the tube rectifier was replaced by SS rectifier. The tubes are old. The oscillation start when I put the volume on loud (8 or more) or when I run my tone stack at 10 with a little bit less volume (6,5), this is a new amp So I don't have any info about that...

yes, This is the thing that make most sense to me, Since volume is just in front of the 6AN8 stage. I ordered a tube on ebay. Just waiting for it... Any other ideas?

When I turn the volume up to 8, the amp start to oscillate, I think this is the right term. Weird noise same thing with the bass unpluged. Does anybody input to resolve the problem. I have good experience with high voltage and automatisation but, in audio electronic my knowledge is limited...