Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: billcreller on April 06, 2014, 12:58:04 pm

Title: schematic problem
Post by: billcreller on April 06, 2014, 12:58:04 pm

I stepped into replacing a chassis on an old Gretch amp, which is a Valco 510-54.  Don't know how to post it here, but the problem is the trem tube circuit, which shows a resistor that is shunted by a wire in the schematic, making the resistor null & void, so to speak.  Not sure how to use the resistor, like maybe chopping one leg in that circuit ??

This all started because the original chassis is rusted all to hell on one side, of the inside.   I clipped all the tube socket wires off, and drilled all the rivets out, to lift the terminal strips & their wiring out of the old chassis, mostly all wired together yet.  I'm gradually getting it wired to new tube sockets etc, until I got to the trem tube.
   Appreciate any ideas on how it's supposed to be wired on that resistor.....

Pila

Title: Re: schematic problem
Post by: sluckey on April 06, 2014, 01:29:08 pm

You mean the 2.2K connected to pin 7 of the trem oscillator? That resistor is not needed. You 'may' need a bypass cap on pin 8 though.

Title: Re: schematic problem
Post by: kagliostro on April 06, 2014, 01:33:40 pm

 Ciao Billcreller

I hope this can be of some help

K

Title: Re: schematic problem
Post by: billcreller on April 06, 2014, 04:37:16 pm

Thanks for posting it !
 The part in question is in the lower left corner....a resistor connected across a 90 degree wire intersection.....

That 2.2 K resistor can't do much when it's in parallel with a wire.. :dontknow:

Title: Re: schematic problem
Post by: PRR on April 06, 2014, 08:46:25 pm

Gibson may have been undecided.

It will work either way.

Title: Re: schematic problem
Post by: billcreller on April 06, 2014, 10:39:15 pm

OK PRR, I'll leave it in there for the ride.

Title: Re: schematic problem
Post by: kagliostro on April 07, 2014, 02:29:20 am

In some old RF apparatus sometime happen to find a resistor paralleled with a wire (some turns of wire wound on the resistor) with the purpose to form an impedance


but your didn't seem to be the same case


K