Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on February 21, 2020, 08:13:22 am

Title: Tubes gone bad
Post by: pbman1953 on February 21, 2020, 08:13:22 am

I'm trying to help a friend-


Fender Super Champ x2-   amp with 1-12ax7 and 2 - 6v6- all JJ's




While playing he noticed no power and distortion- The amp is 5-6 years but with light use and the amp was biased.


The 12ax7 was fine but the power tubes were cooked. Shouldn't they last longer? Plus, I know it would be hard, but any idea what would cause them to go.




Any tube suggestions?


Thanks

Title: Re: Tubes gone bad
Post by: shooter on February 21, 2020, 08:24:50 am

Quote

but any idea what would cause them to go.

typically current, either because of a fail in bias, B+, OT circuit.

Pull tubes, verify VDC, connections out to speaker, verify bias without tubes.  IoW, eliminate the good stuff n the problem is left  :icon_biggrin:

Title: Re: Tubes gone bad
Post by: pbman1953 on February 21, 2020, 08:29:18 am

Thanks, I'll tell him to have the amp looked at

Title: Re: Tubes gone bad
Post by: bmccowan on February 21, 2020, 02:29:10 pm

First thoughts when I saw

Quote

Tubes gone bad

Hangin' around with the wrong crowd (transistors); smoking; squealing; etc.

Title: Re: Tubes gone bad
Post by: shooter on February 21, 2020, 03:22:04 pm

Quote

Hangin' around with the wrong crowd (transistors); smoking; squealing; etc.

 :l2:
sound like the '90s kids that lived around here  :laugh:

Title: Re: Tubes gone bad
Post by: bmccowan on February 21, 2020, 05:41:14 pm

Hey you tubes - get off my lawn!

Title: Re: Tubes gone bad
Post by: shooter on February 21, 2020, 06:42:23 pm

Quote

Hey you tubes - get off my lawn!

there were still signs in Norfolk VA when I was a sailor "dogs and sailors stay OFF lawn".  we all wizzed on the signs  :icon_biggrin: