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Long story, feel free to skip to the problem...
I picked up one of the much maligned Crate Blue Voodoo BV212 combos with new EL34s for $80. It had a couple of funky pots and crackled if you leaned on the top. You could wiggle the pots and move the shafts in and out so I figured a couple of pots to solve that and the crackling was probably bad solder joints, cracked board, ground, etc. Probably something easily dealt with. For $80 it was a least a pair a speakers and some tubes if I couldn't fix it. When I took it apart I found that the pot caps were just about falling off the back so I re-bent the tabs on all the pots, re-flowed every solder joint and put it back together. All the problems were solved. I played through it a bunch of evenings and even used it at a recent band practice (3+ hours of constant playing). Recently I try a few different speakers I had laying around just to experiment. Still no problems.
Problem
I decided to use it at band practice last night and no sound. It powers up, all the lights come on and the power and stand by switches, which are illuminated, glow and all the tube heaters are glowing as they should. So I plugged the effects out of the BV to another amp's effects in and still nothing. I reversed the effects in and out, etc, nothing. So nothing from either the pre or power amp. At this point I'm thinking no B+.
The schematics are attached below if you want to follow along. The second link is the most pertinent.
So I take it apart and measure the voltage at C48+ and get 500V, should be 490V, close enough. I measure 500V on the left of R115 as I should, but get 0V on the right side of R115 where I should be seeing 480V. So I believe R115 is open. It's a 620/3W cement resistor.
Questions
Is my logic sound or am I missing something?
Why did it go and is there something else likely that I should replace as well?
Is R115 the problem or a symptom?
Any thoughts would be greatly appreciated.
5434d1242798066-296-11pl_pwa_sch_1.pdf
5433d1242798027-29601sch_2.pdf
29601PL_PWA_2.pdf
I picked up one of the much maligned Crate Blue Voodoo BV212 combos with new EL34s for $80. It had a couple of funky pots and crackled if you leaned on the top. You could wiggle the pots and move the shafts in and out so I figured a couple of pots to solve that and the crackling was probably bad solder joints, cracked board, ground, etc. Probably something easily dealt with. For $80 it was a least a pair a speakers and some tubes if I couldn't fix it. When I took it apart I found that the pot caps were just about falling off the back so I re-bent the tabs on all the pots, re-flowed every solder joint and put it back together. All the problems were solved. I played through it a bunch of evenings and even used it at a recent band practice (3+ hours of constant playing). Recently I try a few different speakers I had laying around just to experiment. Still no problems.
Problem
I decided to use it at band practice last night and no sound. It powers up, all the lights come on and the power and stand by switches, which are illuminated, glow and all the tube heaters are glowing as they should. So I plugged the effects out of the BV to another amp's effects in and still nothing. I reversed the effects in and out, etc, nothing. So nothing from either the pre or power amp. At this point I'm thinking no B+.
The schematics are attached below if you want to follow along. The second link is the most pertinent.
So I take it apart and measure the voltage at C48+ and get 500V, should be 490V, close enough. I measure 500V on the left of R115 as I should, but get 0V on the right side of R115 where I should be seeing 480V. So I believe R115 is open. It's a 620/3W cement resistor.
Questions
Is my logic sound or am I missing something?
Why did it go and is there something else likely that I should replace as well?
Is R115 the problem or a symptom?
Any thoughts would be greatly appreciated.
5434d1242798066-296-11pl_pwa_sch_1.pdf
5433d1242798027-29601sch_2.pdf
29601PL_PWA_2.pdf
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