Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: chocopower on January 19, 2021, 06:58:27 am

Title: Power transformer primary taps.
Post by: chocopower on January 19, 2021, 06:58:27 am

Hi.

I have a transformer with 110--125--185--220--250  primay taps.

My wall voltage is 230-234vac.
With  220 primary, heater voltage is 6.9vac
With  250 primary, heater voltage is 6.1vac.

I know it can work in both scenarios, maybe being the 250v the safest one.

I know too, that drop heater voltage is easy (diodes, resistors)

But looking at the transformer, a question grow up in my head, and knowing at 99% that my question is a silly one, i need to ask.

If i jump  the 110--125  taps, all the upper taps "loses" those 15volts?

This way, the 250v, becomes a "235" tap...

Picture attached.

Title: Re: Power transformer primary taps.
Post by: sluckey on January 19, 2021, 07:14:04 am

Something inside me screams DON'T DO THAT! Just use the 250V tap.

Title: Re: Power transformer primary taps.
Post by: chocopower on January 19, 2021, 08:41:07 am

Something inside me said the same.  And said too, "ASK FIRST!!!!"


Thanks, So you said is safer run heater voltages below specifications than over?

Title: Re: Power transformer primary taps.
Post by: sluckey on January 19, 2021, 08:49:18 am

Quote from: chocopower on January 19, 2021, 08:41:07 am

Thanks, So you said is safer run heater voltages below specifications than over?

Well no, I didn't say that. I think it's plenty safe to run at 6.1 or 6.9. But given the choice, I'd choose the 6.1V just because it's closer to 6.3. If my choices were 6.1 or 6.5, I'd just flip a coin.    :icon_biggrin: