Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 67polara on February 07, 2011, 05:57:34 pm

Title: Triode pentode switch
Post by: 67polara on February 07, 2011, 05:57:34 pm

I can not find a switch with a high enough rating (voltage) to do the triode pentode switch.  Will one with a 250 volt rating work?  Should it be a Plastic bat type or will a metal bat type work safely?

Tony

Title: Re: Triode pentode switch
Post by: Willabe on February 07, 2011, 06:14:49 pm

The old Fender power and standby switches were'nt raited for the full voltage either, they raised the current raiting to make up for it.
The standard carling power switch they used is raited at 3A @ 250 V. They held up well for many, many years. Fenders were metal bat type, but I guess plastic would add to your safty.

Doug has them in his store, metal bat anyway.


         Brad        :smiley:   

Title: Re: Triode pentode switch
Post by: PRR on February 07, 2011, 08:22:11 pm

The voltage _change_ is about zero, maybe 5V-10V drop in OT winding. That's what the contact specs cover.

The voltage from terminals to chassis (or you!) is a steady high voltage. Don't use a mini-tiny switch. Anything like the usual Standby switch (except DT) will be fine.

Title: Re: Triode pentode switch
Post by: 67polara on February 08, 2011, 12:21:39 am

Thank you.  Just didn't want to fry myself.  I think I will use a metal bat type switch but I think I will dip the bat in liquid tape or get a cover for it just in case the switch might fail.

Tony

Title: Re: Triode pentode switch
Post by: jeff on February 11, 2011, 09:41:38 am

 The screen voltage is close to the plate voltage. But what about at full swing in pentode mode?