6505+

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Pstroupe1975
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Joined: Sat Mar 20, 2021 7:02 am

6505+

Post by Pstroupe1975 » Sat Mar 20, 2021 10:05 am

I have issues with a 6505+ head. The vol controls never turn all the way down and on the lead channel it's worse. The controls start to increase under 3. The post vol around 3 sounds right and everything seems to work right above 3 but under 3 it increases said control but it's not gradual. It's like it jumps up loud and muddy. All pots test right both in and out of circuit. I was wondering if anyone else has seen this

Pstroupe1975
New Member
Posts: 4
Joined: Sat Mar 20, 2021 7:02 am

Re: 6505+

Post by Pstroupe1975 » Fri Mar 26, 2021 3:50 pm

Update, went through again checking all the pots, grounds and checked for DC on the pots. All checked out. Not even any kind of noise when you turn the controls. I'll go through some more to see if I can pin point it. Anyone ever run into this

asabbagh
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Joined: Tue Mar 23, 2021 9:41 pm

Re: 6505+

Post by asabbagh » Thu Apr 01, 2021 9:13 am

If your concerned that some signal is passing even when knobs are at zero? this is a normal situation as there is so signal leaking between the circuit. I dont remember exactly where. My combo did it and my head as well

Pstroupe1975
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Joined: Sat Mar 20, 2021 7:02 am

Re: 6505+

Post by Pstroupe1975 » Sat Apr 03, 2021 3:06 pm

I'm not so much concerned about the signal bleeding through when everything is turned down. I'm more concerned with the lead channel. With the pre up just a little and everything else at 0 it sounds loud. As you increase the post vol it goes up some until you get it to around 3 then it drops and seems like all the kids are sucked out. Cranking it up from there does odd things as well. The whole tone stack is that way also. When they hit around 3 it falls apart even more. Coupling caps are good, no dc leaking by. Pots and grounds are all good. Tube swapping ( all 12ax7s) does nothing. I haven't checked for any issues with the grid leak resistors or cathode caps because ive never seen them cause this. I've seen bad coupling caps cause it. Not bad enough to cause static but a few MV but there isn't any

Pstroupe1975
New Member
Posts: 4
Joined: Sat Mar 20, 2021 7:02 am

Re: 6505+

Post by Pstroupe1975 » Sun Apr 04, 2021 11:47 am

Going back through the amp I found the issue. Even though I replaced all the filter caps apparently one from my stash was bad. It didn't test bad and was new but once it was in circuit it broke down and didn't decoupler the gain stages as it should. Replaced it and its working perfectly. Goes to show sometimes you can't trust new caps. Now all the controls work as they should

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