The Amp Garage

The Bassman 10 is a silverface amp, but it's 50 watts, not 70 watts. And it is not a U/L amp.

CAUSE OF PROBLEM IDENTIFIED! As I postulated in my opening post it is caused by the proximity of the PT to the rectifier! Move it far out of the chassis and this hum is gone! I seem to remember that was suggested a long time ago. Glad to see you finally give it a try. :wink: https://ampgarage.com/f...

Stevem wrote: ↑Mon Mar 18, 2024 9:46 am Do it the way Fender mostly did it, levate and twist.

I suspect this means elevate the heater wires in the air above the sockets. Not talking about elevating the CT to some VDC level. Right?

I would completely remove the PT from the chassis. Then use some gator clip leads to connect the PT to the chassis. This should tell you if the location of the PT is the source of hum.

Slucky, Your schematic helped me in a practical sense with my current project. Your amp is first one that I’ve seen with the parallel preamps - I’ve had that same idea for years. Too much for me to pull off at this time…but with this schematic I’ll be very tempted. It seems like it would provide tr...

Look at the Princeton Reverb schematic. Or a Plexi schematic. Or this...

https://sluckeyamps.com/phoenix/phoenix.pdf

xtian wrote: ↑Fri Mar 15, 2024 9:19 pm Interesting thing going on with the screen grids in the power section. Screens are wired in series, with 100R resistor between the two:

They are not really wired in series. Just looks that way because of the tricky drawing.

I have never relied on email notifications for PMs. Anytime I send a PM I will be frequently checking on the forum.

A choke input filter should have a very small cap at the input to keep a small voltage on the inductor between cycles to avoid a complete collapse of the magnetic field, and the attendant noise from the current dump. This Hammond AO-63 amp does not have any cap before the choke. https://sluckeyamps...

Guy77 wrote: ↑Fri Mar 15, 2024 3:23 am The only change I would make is that I would have a 47uf electrolytic cap between the smaller .68uf cap and the choke.

If you do that you will no longer have a choke input filter. It becomes a cap input filter and the voltage will rise to 1.414 x RMS AC input.

You could do that. May be quicker/easier to just unscrew the nut and lift that lug with the single green wire from chassis. Fasten the other lug back to chassis.

The bias is connected to the oscilator circuit. Just trying to understand what is happening here and why. The bias holds the oscillator and driver tubes in cutoff whenever the footswitch is missing or the contacts are not connected. When you ground that point by stepping on the footswitch the sudde...

Disconnect the mains earth ground wire from the chassis. If the hum disappears you have a ground loop. There is a simple ground isolator circuit that works well and allows the earth ground to be connected to chassis.

Kee22 wrote: ↑Thu Mar 14, 2024 3:10 pm Can't get my head around this V1 seems like and odd solution. Pin 1 100k 0,022uf, pin 2 68k, pin 3 820 ohm 22uf.

Thousands of amps look exactly like that. Doesn't get any simpler. What don't you understand?

Phil_S wrote: ↑Thu Mar 14, 2024 1:48 pm

mike-p wrote: ↑Tue Feb 13, 2024 7:53 pm Tried to pm you but its stuck in my outbox?

For better or worse, it remains stuck until the recipient reads it. <shrug>

It's not really stuck. That's a feature that tells you the message has not been read. I like that feature.