Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: stantheman on September 18, 2010, 03:23:49 pm

Title: No preamp voltages on fender bassman 135 b
Post by: stantheman on September 18, 2010, 03:23:49 pm

Hello,  I am hitting my head against the wall on this repair project.  This is a bassman 135b head.  Lights up. no sound.  No shorts with current limiter. 530 dc on b+ rail nothing coming out of the power supply filters. OT all caps screen grid and socket resistors changed out.

I get voltage readings from the power tube pins but nothing on the preamp tubes.  I have fixed a lot of amps but this one has me beat. I resoldered all of my solder jobs and cannot find the culprit yet.   Here are my voltage readings (filament voltages ok)

sjbassman1.htm

Title: Re: No preamp voltages on fender bassman 135 b
Post by: stantheman on September 18, 2010, 03:59:45 pm

Holy crap.....

2.7 k 10 watt resistor totally open.... Sometimes I need an outside opinion to get my focus.

I will replace and thanks.

Title: Re: No preamp voltages on fender bassman 135 b
Post by: plexi50 on September 18, 2010, 06:27:11 pm

That 2.7K resistor must take a real beating. Probably would sound better as well with a real choke in that spot

Title: Re: No preamp voltages on fender bassman 135 b
Post by: stantheman on September 19, 2010, 01:11:28 am

noted:

will do.

My bass player played the amp at a gig. Worked well. 

Thanks again.