Low Heater Voltages- Is It The Transformer?

[BCorbett]

The heater voltage is 2.9 on my DR. The tubes light up and make sound but it seems like it would be good to get them Nice and warm with the right voltage.

Is there anything I can check, or change to fix this ?

Thanks. Brendan

[ampgeek]

If that is from each terminal to ground....it is just about right!

Should be ~6.3 vac from terminal to terminal.

Cheers,
Dave O.

[BCorbett]

Thanks, I thought they needed 6.3 at each pin for a total of 12.6vac per tube.

[ampgeek]

No sweat mate!
Dave O.

[ampgeek]

I should have mentioned for clarity that 12A*7 type tubes can be operated with each triodes' filament in series or parallel.

If pins 4&5 are tied together at the socket and the filament power supply lines land on 9 & 4/5, they are in parallel and 6.3 vac will do the trick.

If the supply lines land on 4 and 5 separately and pin 9 is hanging out on its own, they are in series and 12 vac will be required.

Dave O.

[Jana]

Dave, you need another cup of coffee!

Pins 9 and 4/5 are the heaters.

[ampgeek]

Yikes.....! Probably more than a cup of coffee needed.

I will correct it in the post.

That'll teach me not to be spewing off after a handful of scotches.

Thank you Jana!

Dave O.

[BCorbett]

I a glad to know I don't need a new PT. I have an Gibson GA 15 RVT that I had been trying to make sound decent. The preamp tube had started adding a crackling sound. They were not that old.

I came up with the theory that the heaters were not Hot enough, ruining the tubes, it must be that the PT was failing. I got fed up stuffed it in the closet and declared it a lost cause.

Now I will have to dust it off and try to solve the mystery.