Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fdesalvo on December 07, 2022, 03:01:46 pm

Title: AC30 clone outer tubes in quad redplating?
Post by: fdesalvo on December 07, 2022, 03:01:46 pm

Hello, all. Have any of you seen this before? Newish hayseed 30 build no leaky caps resistors test good. Very haphazardly assembled! Known good tubes redplate there as well.

Tia!

Title: Re: AC30 clone outer tubes in quad redplating?
Post by: sluckey on December 07, 2022, 05:41:00 pm

Sounds like a perfect breeding ground for gremlins.   :icon_biggrin:

Title: Re: AC30 clone outer tubes in quad redplating?
Post by: JPK on December 08, 2022, 11:56:34 am

Please see Slucky's signature.

Title: Re: AC30 clone outer tubes in quad redplating?
Post by: fdesalvo on December 08, 2022, 12:43:28 pm

I sorted it out gentleman. Dying battery in my meter was masking the nearly 400v on the plates lol.  I swapped in an old 5R4 rectifier tube and she’s down to 306 V. No issues. Thank you.

Title: Re: AC30 clone outer tubes in quad redplating?
Post by: tubeswell on December 08, 2022, 05:06:22 pm

If you have only replaced 2 tubes in an output tube quad, you can get problems with one of the pairs under heavy signal conditions in some amps (when the 'hotter' pair ends up drawing more current- particularly in amps like 1959 Super Lead 100 Marshalls with EL34 quads where the B+ is 500). Which is why you need to be careful with quads.

Title: Re: AC30 clone outer tubes in quad redplating?
Post by: fdesalvo on December 08, 2022, 05:07:44 pm

Quote from: tubeswell on December 08, 2022, 05:06:22 pm

If you have only replaced 2 tubes in an output tube quad, you can get problems with one of the pairs under heavy signal conditions in some amps (when the 'hotter' pair ends up drawing more current- particularly in amps like 1959 Super Lead 100 Marshalls with EL34 quads where the B+ is 500). Which is why you need to be careful with quads.

Truth. I tested four new ones.