Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Duncan on November 11, 2023, 09:37:11 am

Title: Dropping the 60v bias tap to create 5v to facilitate tube rectification?
Post by: Duncan on November 11, 2023, 09:37:11 am
Howdy.

I’ve got a gutted Traynor YBA-1 that I’m looking to build into a Matchless Chieftain type circuit.

The only components remaining from the Traynor are the transformers and pilot light. The only thing is that the power transformer (Hammond 291JX equivalent) doesn’t have a 5v tap. It DOES have a 60v tap however.

According to some numbers I crunched, I could pass this 60v through a pair of 2.7k 2w resistors (one for each side of the winding) to get me 5v.

Does this sound like it would work?
Title: Re: Dropping the 60v bias tap to create 5v to facilitate tube rectification?
Post by: sluckey on November 11, 2023, 10:48:42 am
No. That 60V winding is only rated for 20mA.
Title: Re: Dropping the 60v bias tap to create 5v to facilitate tube rectification?
Post by: Duncan on November 11, 2023, 12:24:49 pm
Quote from: sluckey on November 11, 2023, 10:48:42 am
No. That 60V winding is only rated for 20mA.

Well dang. You’re right. We’ll nevermind on that idea.

Looks like it’s the diode life for me!
Title: Re: Dropping the 60v bias tap to create 5v to facilitate tube rectification?
Post by: kagliostro on November 11, 2023, 12:29:02 pm
What Sluckey say

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You don't need a tube rectifier, use Solid State rectify and a SAG resistor

Franco
Title: Re: Dropping the 60v bias tap to create 5v to facilitate tube rectification?
Post by: PRR on November 11, 2023, 12:58:04 pm
A rectifier heater winding is not a TAP, it is an isolated winding. It sets 400 Volts away from circuit common.

Bias 'taps' usually ARE taps connected to HV common (actually just the first 500 turns on one side of the HV CT).
Title: Re: Dropping the 60v bias tap to create 5v to facilitate tube rectification?
Post by: sluckey on November 11, 2023, 01:01:15 pm
The 291JX has a real separate 60V winding, not a tap on the HT winding.