Members edthecat Posted October 12, 2012 Members Share Posted October 12, 2012 I have an "Evil Twin", 94 Fender Twin, NOT the red knob amp that is often incorrectly called the same. I haven't played it in a while, and when I fired it up it had a loud hum, even when all of the knobs were turned all the way down. It hums on the 25 watt and the 100 watt setting. It's still playable... but when nothing is being played it has the loud hum. I've changed all the tubes, rebiased, disconnected the reverb, tried a ground lift plug adaptor (connects to power cord, removes the ground plug), checked to see if any of the capacitors looked swollen or leaking, and I can't figure out what is wrong. Anybody got any ideas what could be wrong? Anything else I can try to trouble shoot other than licking the power tubes to see if my tongue smells like bacon? Link to comment Share on other sites More sharing options...
Members Zozobra Posted October 12, 2012 Members Share Posted October 12, 2012 Remove just the PI tube. Does it still hum then? Link to comment Share on other sites More sharing options...
Members davebols Posted October 12, 2012 Members Share Posted October 12, 2012 does this only happen at home? try different circits. could be a bed outlet that you're plugged into. check grounding. Link to comment Share on other sites More sharing options...
Members SnowStorm Posted October 12, 2012 Members Share Posted October 12, 2012 Did you check your cables? Link to comment Share on other sites More sharing options...
Members Miter Gauge Posted October 12, 2012 Members Share Posted October 12, 2012 It really does sound like you need to replace your filter caps. Link to comment Share on other sites More sharing options...
Members edthecat Posted October 13, 2012 Author Members Share Posted October 13, 2012 OK. I removed the PI tube (the one closest to the power tubes) and no more hum. If I'm not mistaken, this should eliminate the problem being in the "power" section of the amp... any other suggestions, and, how can I test the filter caps to see if they need replacing? Link to comment Share on other sites More sharing options...
Members guitarbilly74 Posted October 13, 2012 Members Share Posted October 13, 2012 yeah if you remove the PI and the hum went away, that means the issue is in the preamp section, probably power supply or the heater...and this is stuff you don't want to {censored} with if you don't know what you're doing. Take it to a tech.. Link to comment Share on other sites More sharing options...
Members Kardula Posted October 13, 2012 Members Share Posted October 13, 2012 Originally Posted by Mr.Grumpy Just because a cap isn't swollen or burst open doesn't mean it's not bad. I've been told this as well. One of the local techs says caps need replaced every 5-7 years. Of course, if you crack open an amp and see that there are busted caps then you can see that there's at least one thing amiss. Link to comment Share on other sites More sharing options...
Members Miter Gauge Posted October 13, 2012 Members Share Posted October 13, 2012 Originally Posted by Kardula I've been told this as well. One of the local techs says caps need replaced every 5-7 years. Of course, if you crack open an amp and see that there are busted caps then you can see that there's at least one thing amiss. If you play the amp regularly you should get way more than 5-7 years out of them. I've had some last longer than 20 years but I understand the key is regular use (something about the dielectric in the capacitor IIRC) Link to comment Share on other sites More sharing options...
Members edthecat Posted October 17, 2012 Author Members Share Posted October 17, 2012 Upon closer inspection of a few caps, it seems that two might have a small leak. I've all ready drained the caps, and I am not scared to mess around in the amp... my only problem is that I don't know where to buy these caps, and which ones I should change other than the obvious ones. I know the larger ones need to be replaced, but what of the smaller ones? Any other help here would be appreciated. I do have the service manual for the amp which lists all of the capacitors and part numbers, but jeebus, there are like 40 caps listed. I was under the impression only the big guys needed swapping.*edit* WOW, pretty lame post for my 1000th post.... so... boobs and beer. Link to comment Share on other sites More sharing options...
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