Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: chocopower on January 22, 2016, 12:34:10 pm
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I got this 60´s amp.
http://www.doctsf.com/grandlivre/fiche.php?f_ref=29394&ori=ps (http://www.doctsf.com/grandlivre/fiche.php?f_ref=29394&ori=ps)
My amp has some different stuff on it.
One i dont understand is that it have a B+ node for screens but there are too, a 100k resistor (with a 4700pf in parallel) between plate and screen.
.- Is this a kind of mix between triode and pentode operation?
.- It´s safe to remove it?
Attached the schemo with the resistor.
Thanks in advance.
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> mix between triode and pentode
No, because C14 absorbs all audio signal at screen.
The 4,700pFd is in-effect across the OT primary. A cap across OT is VERY common to reduce high frequency ringing in low-price OTs and possible supersonic instability. In this case it probably cuts response above 8KHz. For guitar I would leave it there. It does no harm and may be unstable without it.
The 100K is a complete mystery to me.
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Ok, thanks.
I´ll try to find some informattion for the 100k resistor.
Both seems original.
So... "ain't broken, don't fix it"