Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bakerlite on July 10, 2012, 08:02:50 pm
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Just finishing off a blackface conversion (AA270 - AB763) and I am looking at the Dog house where the balancing resistors between the filter caps looks to have been stressed at some point
I hadn't planned on doing anything to the filter caps or said resistors as part of the conversion but now that I see the resistor damage I must.
The AA270 stock resistors are 10k and 2.2K between the 3 x 20uf caps - Ab763 schematic specifies 4.7k and 1k - this seems quite a difference in value from the silver face stock setup.
I am just double checking this will be ok.
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That should be fine.
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Thanks!
doh! Just after realizing my capacitor stock is a bit low :(
I am meant to have 2x 70uf caps to give 35uf capacitance at 700v rating before the standby switch.
All i have is 2 x 220uf - 6 x 16uf - 1 x 40uf - 1 x 8uf
I am torn between using the 2 220ufs which would give me the safe voltage rating but a massive 110uf of capaciance
or the single 40uf at 500v which is a bit tight considering it runs 450v
Am i out of luck?
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Pt the 220's on the hot side of the standby switch like you would see on a Super Reverb (which would have 70's there). Yes, the good book says no -- but it works perfectly well and it tightens bass response at high volume. You can use the 16mf caps in place of the 20's and likely not notice any difference.
Jim
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Which specific amp is it? Tube rectifier? If so, I might not want to step up to the 220's.
If it is a solid-state rectifier, yes go ahead. Make sure they fit under the cover first though.