Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on September 03, 2010, 09:28:04 pm
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For all pratical purposes i am finished rebuilding this amplifier. I have a real strange problem. (nothing new)
I built this using the Steve Luckey 2204/Plexi schematic using a 470k resistor to A/B the channels / I had to make changes from my original want
Both channels work but the treble pot is wacked. If i turn the treble all the way back the amp gets very loud in comparison to it's volume at full treble pot setting CW
It would seem i have something wired backwards in the EQ but this is a pretty elementary wire up
The blue cap next to the Sozo .68 is not hooked up yet (just laying there)
Anyway i had to put it away for tonight. This amp has kicked me but i got what i wanted done / Always something
This PT is the size of a small dog! The OT isnt far behind
(http://i356.photobucket.com/albums/oo5/plexijtm45/SDFTD.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/SDRFSIDE.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/SDRFFRONT.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/SDFBTOPDOWN.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/FILON.jpg)
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Is that 5U4? That one will get a workout. I think it's rated at 1000mA but It'll sag 40v at ~200mA.... I'd imagine it'll drop quite a bit in that unit.
Neat build anyway! :grin:
j.
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Well to be honest i think i am going to have to change the PT for a more sane voltage. It is on my variac at 107 VAC and the B+ is 485. I dont want an amp with a 575+ B+. I dont know that i want to try and tame this PT. I want a ballsy amp but not an AMPEG SVT if you know what i mean. Im using a 50uf/500V can cap for the standby and choke which is a 500 ohm resistor for now until the choke i ordered gets here. I have a SS rectifier plug i made to use in place of the tube but thats out of the question with this PT. If anyone has any ideas to tame this PT i will give it one more shot. Otherwise it would be less painful to just to get a JCM 800 PT. Using the 5U4GB sort of freaks me out thinking that it is holding up at all
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another possibility would be to do away with the tube recto, go SS recto and use a pair 6550's or KT88 tubes.
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Will using 6550/KT88 tubes draw the B+ down for me? The PT secondary HV is 415 VAC into the rectifier