ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

previous: Peter S Many amp designs had no screen grid... -- 5/20/2000 6:27 AM

Re: 100 ohm screengrid resitor???

5/20/2000 1:09 PM
T.B.	Re: 100 ohm screengrid resitor??? You're a good man Peter! And you're absolutely correct about there being another resistor in series. It's a 400 ohm 10 watt that is right after the plate supply (no choke in this amp) and right before the standby switch which feeds a second set of filter caps. Thus the first filter section (that feeds the plates) shows 500 volts (on schematics) and then reduces down to 490 volts to feed the screens. I'm about 10 volts less than that. Would that single 400 ohm resistor in series with all four screens actually equate to a larger value if the screens had each its own? Or smaller? Somehow or other I've got a slight mental block at the moment, (just woke up). Thanks again for your reply. Have a great weekend! T.B.

5/20/2000 1:09 PM

T.B.

Re: 100 ohm screengrid resitor???

You're a good man Peter! And you're absolutely correct about there being another resistor in series. It's a 400 ohm 10 watt that is right after the plate supply (no choke in this amp) and right before the standby switch which feeds a second set of filter caps. Thus the first filter section (that feeds the plates) shows 500 volts (on schematics) and then reduces down to 490 volts to feed the screens. I'm about 10 volts less than that.

Would that single 400 ohm resistor in series with all four screens actually equate to a larger value if the screens had each its own? Or smaller? Somehow or other I've got a slight mental block at the moment, (just woke up).

Thanks again for your reply. Have a great weekend! T.B.

Replies:

Peter S Yes the 400 ohm resistor on all fou... -- 5/20/2000 2:14 PM