Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on May 27, 2023, 08:14:29 am
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Very little to no info on this amp other than compliments to it's sound. I want to slow down the tremelo a little and have found the trem oscillation section. I see (2) .01 caps and i believe those are the ones i want to change out to .022. But there are a few other disk caps like a .001 & 500pf. As well as a .05 coupling cap which i will change out for a new.047. Looks like i just have to tinker with the (2) .01 caps and take it from there. Any tips?
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Hi there is a Gretsch g6156 schematic so the 6156T might be the same only with a trem circuit added but I have no idea for sure. The amp was made by Valco. I would try changing the caps and see what results.
https://el34world.com/charts/Schematics/files/Gretsch/Gretsch_g6156.pdf (https://el34world.com/charts/Schematics/files/Gretsch/Gretsch_g6156.pdf)
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The 6151 is the same amp, but lower power, single ended output section. Tremolo circuit is the same. Try swapping out either (or both) of the .01's to .018-.022.
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It's been said that the amp is basically the same as a Supro 1624T. See if this tremolo circuit matches yours...
https://el34world.com/charts/Schematics/files/Supro/Supro_1624t_schematic_263.pdf
Most of those valco trem circuits are the same, or very close.
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Thanks so much for all your invaluable info. Well i changed out the disk caps to .022 and no change in trem speed. So i think i am looking at a cathode resistor value change now if i am not mistaken. Looking at the schematic now Steve.
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Changing the cathode resistor will not affect the speed. The 3 caps, 3 resistors, and speed pot that I circled are the only components that will affect the speed.
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Changing the cathode resistor will not affect the speed. The 3 caps, 3 resistors, and speed pot that I circled are the only components that will affect the speed.
Right. Thats where im looking now. A real tight compact work area. I found (2) 1Meg resistors and (1) 270Kr. Will parallel ing any of these resistor be what im after? There dug down deep.
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Right. Thats where im looking now. A real tight compact work area. I found (2) 1Meg resistors and (1) 270Kr. Will parallel ing any of these resistor be what im after? There dug down deep.
No. Paralleling resistors makes the resistance smaller and that will result in faster speed. I suggest you just work with the 3 caps. You can parallel a cap to decrease the speed. My Supro uses .047, .047, and .01 caps.
I suggest putting a .022 cap in parallel with either the .03 or .02. That should get you a nice slow speed.
EDIT: un-boogered quote -- HBP
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Ok got that nice slow speed. I was originally working on the intensity end of it until i said: (YOU DUMB ASS!) I found the speed section completely at and near the power supply section instead of near the 12AX7 tubes. Different. Thanks Much!
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Ok got that nice slow speed.
Exactly what did you do?
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Ok got that nice slow speed.
Exactly what did you do?
Well like i posted above i was actually working and changing caps in the intensity area and didn't figure it out until you posted the Supro schematic. In this amp the trem speed circuit was at the other end near the power tubes and i never expected that. It looked at first to me to be the circuit near the 12AX7 preamp tubes. NOT! So then i went to the far right near the power supply and found the speed caps (3).01 caps. Changed them out for .022 and then went back to the intensity area and replaced to original cap values. Crazy! But is is nice and slow now and thankyou much! Got an imbalance in heater filament voltage. Going to try (2) 100 ohm resistors from pilot light to ground now. By the way i just finished 2 other amps before working on this one this morning. I am wiped out and should just sit the hell down. Got to much go. Have a Mesa Express 5.50 next. I don't like Mesa amps. They are a PITA to work on. I promise to not get into it tonight. I promise. Ha!!!
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... i went to the far right near the power supply and found the speed caps (3).01 caps. ...
It might be a good thing if you drew out what you see of the amp's circuit, including the original trem speed cap values. Since there's no available schematic, you could contribute the schematic from what you have.
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... i went to the far right near the power supply and found the speed caps (3).01 caps. ...
It might be a good thing if you drew out what you see of the amp's circuit, including the original trem speed cap values. Since there's no available schematic, you could contribute the schematic from what you have.
Yes that is a good idea. I will get around to it. Thanks for the idea!