Ezg-50 circuit changes?

[M Fowler]

The pots are linear except for the Pre Volume pot which is A1M

Pre A1M
Post B1M
Treble B250K
Mid B10k
Bass B250K
Dwell B100K
Mix B250K

IMG_1192.JPG

[tubeswell]

Based on several bits of information from various sources, here is a revised schematic. Further corrections/suggestions welcomed

[M Fowler]

Thanks Pete I hope to continue building a EZG50 and continue to note resistor and cap values as I find them.

Mark

[Peeping tom]

Thanks for the schematic! On this schematic there are no 1.5k grid stopers befere the power tubes. Is that ok?
Maby because the Master Volume? Any thoughts?

[pompeiisneaks]

Those 220 go to ground and definitely aren't grid stopper resistors. They aren't mandatory, but tend to help with oscillations and abuse to the power tubes. You could experiment with them installed, or without and see what you prefer.

I'm not speaking of the Ez-50 itself, just general use case for grid stoppers.

~Phil

[M Fowler]

Thanks for the schematic! On this schematic there are no 1.5k grid stopers befere the power tubes. Is that ok?
Maby because the Master Volume? Any thoughts?

I have verified there are 1k5/2w grid resistors to the power tubes.

[Peeping tom]

Thanks for the schematic! On this schematic there are no 1.5k grid stopers befere the power tubes. Is that ok?
Maby because the Master Volume? Any thoughts?

I have verified there are 1k5/2w grid resistors to the power tubes.

Thanks a lot! That makes sense!

[Peeping tom]

Those 220 go to ground and definitely aren't grid stopper resistors. They aren't mandatory, but tend to help with oscillations and abuse to the power tubes. You could experiment with them installed, or without and see what you prefer.

I'm not speaking of the Ez-50 itself, just general use case for grid stoppers.

~Phil

Thanks Phil, it's good to experiment before you decide what suits the best for you.
Who's 220 do you mean that are going to ground? I can't see them..

Cheers!

[pompeiisneaks]

Those 220 go to ground and definitely aren't grid stopper resistors. They aren't mandatory, but tend to help with oscillations and abuse to the power tubes. You could experiment with them installed, or without and see what you prefer.

I'm not speaking of the Ez-50 itself, just general use case for grid stoppers.

~Phil

Thanks Phil, it's good to experiment before you decide what suits the best for you.
Who's 220 do you mean that are going to ground? I can't see them..

Cheers!

Sorry I misspoke I meant the two 220's that go to the bias circuit. then it goes to ground. You'd asked about the master volume, and I jumped to the conclusion it was the typical lar mar type without thinking. I'm looking now and see it's a pre PI type so my whole 220k thing was completely on the wrong path entirely. the 1.5k or so Grid stoppers to the power tubes are good as I mentioned, and that whole part was 'on topic' lol sorry for the confusion.

~Phil

[tubeswell]

Update with the 1k5 grid stoppers.

FWIW, 1k5 grid stoppers are a fairly traditional Fender amp value, but they don't actually do much to stop blocking distortion (where that is a problem). Going to 4k7 is a wee bit better, 10k or 22k is better still. In fact anything up to about 47k will be quite effective (while not losing guitar frequency bandwidth)

[M Fowler]

Thanks Pete appreciate your schematic.

Mark

[hywelg]

Apologies to those who asked for a copy of my pre-amp schematic, I'm not often visiting here. I've attached it now. I wish I had more free time to build amps, there are three or four I'd like to do.

I missed the 10k on the grid of V3b and I no longer have the amp to check it.
I also did not have a switched cathode bypass cap on v1b, not sure if that was added as wishful thinking! or as a mod on later models.

Would dearly love to have the opportunity to play one of these again, loud, they are fantastic amps.