The Amp Garage

Hi all, Have a question on failsafe bias for a Fender. I am referencing https://www.valvewizard.co.uk/bias.html and find the following: "C2 is added to decouple the grid leak circuits from one another (when more than one valve share the same circuit) and simultaneously acts as an RC smoothing filter...

Update: I have a "bias range" resistor of 2k35 (two 4k7 in parallel) with a 10k pot and 15k resistor for the sweep. Proper GZ34. Got it to 402V @ 35mA for ~14W, which is nearly 50% of max dissipation. Stopped and listened to the amp and like what I hear, so I am leaving it there. Yes, the trem sound...

One more thing/FWIW... when I increased the "bias range" resistor and decreased the bias resistor, this brought the bias less cold. But then the amp started squealing. I flipped the OT primary leads on each power tube socket (pin 3) and the oscillation disappeared. So the trem works and sounds prett...

The mojo circuit is good, but you need to fine tune the 1K/3W bias range resistor. Wire the bias circuit exactly like the mojo circuit using the 10K pot and 15K tail resistor. Set the bias pot to half rotation. Now increase the value of the 1K (bias range) resistor on the bias board until you have ...

PT HT voltage (from your thread on the TGP) and B+ are considerably lower than original. So will be the screen voltage. The lower the screen voltage, the higher (i.e. less negative) the grid voltage needs to be for the same idle current. Hi Helmholtz. Apologies, I forgot to mention I am using a PT ...

The schematic has no bias adjustment pot. Do you want to sketch what you have now? I initially wired up the bias pot like this . Pulled that out and wired as stock but with a 10k in there (as my original post) in an attempt to increase the plate current (went from 4W to 7W - still too cold, it seem...

Hi all, Have a scratch build brown Vibroverb 6G16 I am having an issue with. Well, two issues. Firstly, schem/layout here . The first order problem is that I can't seem to get the 6L6GCs to bias up to anything over 7w dissipation. I have a 10k bias resistor in there now. Plate voltages around 394-39...

There is some information stamped on a transformer, two lines ... 0T - 215 682 531 682 is the EIA code for Electrical Windings, Inc. (Chicago). 531 *probably* indicates 31st week of 196 5 , though it could be 197 5 or even 198 5 if it's a replacement. If the solder connections/joints from/to that t...

ThePanda wrote: ↑Thu Jan 16, 2025 11:08 pm Have you found FM 11-66?

Nope, can't find that one. That one sounds like a good one too!

Cool:

https://www.dhtrob.com/overige/pdf/Elec ... _11-63.pdf

Yes!!! Thank you sluckey for the schem!

Thanks for your confirmation, patience and understanding sluckey. I appreciate it and respect your knowledge and input (pun intended ).

The downside is the NOR volume pot will also affect the TB channel. If that's OK with you then move the switch. My circuit allows you to set the NOR volume then set to TB volume independently. This way you can match the TB volume to the NOR volume, or maybe set the TB volume a bit higher than the N...

This may be closer to what you have in mind... Yes! Interesting. If you don't mind, could you help me to understand here... I would have suspected the DPDT to be located between the normal volume pot (R15 in the Thomas AC10 schematic) wiper and the 0.01 cap (C12). What's the downside to doing that ...

sluckey wrote: ↑Fri Jan 10, 2025 5:05 am You will have to add one dual triode if you want top boost. I guess you could put all the circuitry on one of those small add on chassis like Vox did. Should be fun.

Oh ya, fully aware. Yes, was thinking it could be accommodated via the top boost bracket put on the back panel.