Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BigE on December 02, 2011, 07:11:22 pm

Title: Silvertone Twin 12 with low output
Post by: BigE on December 02, 2011, 07:11:22 pm

On the bench is a Silvertone Twin Twelve 1484.  It's output volume is REALLY low on both channels.

I put a 3 prong cord on first.
Cleaned and tensioned all the tube sockets and cleaned the pots.
Replaced the 'litic caps.  C26 - 29 and C1 and C17. (except for the 3 in the can)
Tried other good tubes except for the 6cg7 (cause i don't have any extra to try, although I did swap them with no help)

Current Voltages:
   V7               v8          v3          v2               v1
3 - 450       3 - 450    1 - 216    1 - 76.3       1 - 92
4 - 330       4 - 330    2 - 60      2 - 0           2 - 0
5 - -31       5 - -31    3 - 115     3 - .9          3 - .87
                               6- 87.9     6 - 77         6 - 91
                              7 - 0         7 - 0           7 - 0
                              8 - 3        8 - .9           8 - .87


Haven't checked any coupling caps yet.  Figured I'd probe for some suggestions first before going there.
Ideas/suggestions anyone?

Schematic attached.

thanks in advance!!

Title: Re: Silvertone Twin 12 with low output
Post by: BigE on December 03, 2011, 11:17:27 am

Did some more work on this today.  I read that the OT's on these are notorious for going bad.
So I pulled the output tubes and measured the resistance from the CT to each leg.
One was 83 and the other 37.  Schematic notes should be 85.

So...  does this mean that indeed the OT is bad?

also, I put the listener box on it and listened to an ipod signal starting at the input through each stage.  Every one sounded good up until you got to pin 3 on the Output Tubes.

Anybody got any input/suggestions??

Title: Re: Silvertone Twin 12 with low output
Post by: sluckey on December 03, 2011, 11:35:28 am

Weber sells a drop in replacement for that oddball OT.

Title: Re: Silvertone Twin 12 with low output
Post by: BigE on December 03, 2011, 11:37:08 am

So it IS a bad OT?

Title: Re: Silvertone Twin 12 with low output
Post by: sluckey on December 03, 2011, 12:13:17 pm

Probably.

Title: Re: Silvertone Twin 12 with low output
Post by: LooseChange on December 03, 2011, 03:14:17 pm

I just finished installing a new OT in one of these. I used one from a Hot Rod Deluxe that I swapped out a while back.  Did a complete cap job too.  Sounds great.