Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on March 31, 2017, 06:44:18 pm

Title: proper heater voltage
Post by: pbman1953 on March 31, 2017, 06:44:18 pm

Sunn 2000s-


I was thinking of installing KT-120's in my amp. I was talking to a tube re-seller I've dealt with and he said to check to see if I have 6.3 v on the heaters. To a quick measurement I pulled one tube to measure pins 2 & 7 which came to 3.2 ac volts each individually. Is that enough for the 6550's I have in there now? Should I think of a getting a filament transformer? Is my power transformer not putting out enough?
Would that effect my pre-amp tubes too?


I have KT-120's in my Traynor Yba3 Custom and have installed a new Hammond filament transformer. Before the Hammond I was at 4.5-5 volts and now a strong 6....


Thanks

Title: Re: proper heater voltage
Post by: sluckey on March 31, 2017, 07:16:34 pm

Connect one meter probe to pin 2. Connect the other meter probe to pin 7.

Title: Re: proper heater voltage
Post by: pbman1953 on March 31, 2017, 07:31:09 pm

6.45 volt


Guess I'm all set.


 :laugh:

Title: Re: proper heater voltage
Post by: Raybob on March 31, 2017, 09:06:38 pm

Quote from: pbman1953 on March 31, 2017, 07:31:09 pm

6.45 volt


Guess I'm all set.


 :laugh:

Only if your PT puts out enough current @ 6.3v to power all the tubes it needs to.

Title: Re: proper heater voltage
Post by: HotBluePlates on April 01, 2017, 07:09:56 am

Quote from: Raybob on March 31, 2017, 09:06:38 pm

Only if your PT puts out enough current @ 6.3v to power all the tubes it needs to.

Quote from: pbman1953 on March 31, 2017, 06:44:18 pm

I have KT-120's in my Traynor Yba3 Custom ...

Then why not just put in one KT120 to replace a 6550, measure heater volts, and if still above 6.3vac, put in the other & repeat.  The heater voltage drop (if any) should make it clear whether the amp can support them.