Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Brownie on September 10, 2024, 12:21:07 pm

Title: Hammond 290CAX power iron for SuperChamp
Post by: Brownie on September 10, 2024, 12:21:07 pm
The filament winding of the Hammond 290CAX is spec'd for 6.3VAC @ 2A. The heaters on the 6V6s, 6C10& the two 12**7 total 1.95A. I think I'll still be alright? I know there are power transformers with 3A of 5VAC for the 5U4 that have been running happily for 50 years...   My reasoning is that if you had an understressed 6.3v@3-4A filament winding and 1.95A of tube heaters, then they would have 6.8VAC on those heaters...
Title: Re: Hammond 290CAX power iron for SuperChamp
Post by: Willabe on September 10, 2024, 12:36:38 pm
...  My reasoning is that if you had an understressed 6.3v@3-4A filament winding and 1.95A of tube heaters, then they would have 6.8VAC on those heaters...

No, it's not automatic that will happen. It might not run high at all. 

Depends on some things. Different transformers will behave differently. Depends on how their made. Different transformers have better self regulation, less sag from load, than others.   

And if you look in a tube manual, you'll see that the heaters for say, 12AX7 tubes, can be run +/- %. That would be; 5.67 to 6.93 ac/dc voltage.   
Title: Re: Hammond 290CAX power iron for SuperChamp
Post by: Willabe on September 10, 2024, 12:40:56 pm
The filament winding of the Hammond 290CAX is spec'd for 6.3VAC @ 2A. The heaters on the 6V6s, 6C10& the two 12**7 total 1.95A. I think I'll still be alright?

Yes, it'll be fine.

It's rated for 2A.
Title: Re: Hammond 290CAX power iron for SuperChamp
Post by: Brownie on September 10, 2024, 01:01:14 pm
Far out! Thanks for that! I'm ordering another one of these. I have a 290CAX I'm building a 6G2 with