Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Nathan on May 09, 2025, 01:28:50 pm

Title: Add tube rectifier with separate 5VAC transformer
Post by: Nathan on May 09, 2025, 01:28:50 pm

My project amp PT does not have 5V tap but I want to add a 5U4GB.


I was looking at a Hammond 167M5 which is 3A: https://www.hammfg.com/part/167M5 (https://www.hammfg.com/part/167M5)


I figured this would be fairly safe or should I go with the next size up (6A)?   

 

Title: Re: Add tube rectifier with separate 5VAC transformer
Post by: tubeswell on May 09, 2025, 03:21:05 pm

Quote from: Nathan on May 09, 2025, 01:28:50 pm

should I go with the next size up (6A)?   

3A is sufficient for 1 and while 6A is more than sufficient, it might cost more (which you might be happy with).

Title: Re: Add tube rectifier with separate 5VAC transformer
Post by: kagliostro on May 10, 2025, 12:42:12 am

As the load will be constant (at 3A) my council is to install a bit higher power value transformer

This because depending on transformer quality it may become more or less hot at the labeled current

So I'lll prefer to stay a bit on safe zone using a 3.5A or 4A transformer

Franco

Title: Re: Add tube rectifier with separate 5VAC transformer
Post by: pdf64 on May 10, 2025, 02:23:14 am

What's the benefit of using a 6A transformer for a 3A load?  :dontknow:
At a 3A loading, a 6A transformer would have the downside of putting out more than 5V, thereby stressing the 5U4 heater.
If your mains transformer already had a 5V 3A winding, would there be similar qualms about using it?

Title: Re: Add tube rectifier with separate 5VAC transformer
Post by: kagliostro on May 10, 2025, 07:56:55 am

Exactly, my council is for a 3.5A or 4A one, I didn't say 6A

Franco

Title: Re: Add tube rectifier with separate 5VAC transformer
Post by: Brownie on May 11, 2025, 01:05:11 pm

I'd use the 3A model, because it's designed for using the 5U4. Perfect

Title: Re: Add tube rectifier with separate 5VAC transformer
Post by: Nathan on May 12, 2025, 07:41:39 am

Thanks guys, I suggested 3A or 6A because those are the only options for Hammond 167 series!
These are excellent quality so I would presume there should be some safety factor built in and how much does heater current really vary in use anyway?
I can go with a 5R4 which pulls 2A, but I already have some NOS 5U4GBs I can use (apparently 5Y3 no good for 6L6s).