Fender Bandmaster (clone) 5E7 problem

[abelljo]

short circuit somewhere in the amp

So if you use the bulb current limiter and plug your guitar in to the jack can you get a sound out of the speakers?

Have you tried a different power transformer?

That is to say use a wire with alligator clips to go from the rectifier diodes of one amp to the filter caps of the other amp.

The preamp tubes don't present much of a load for the power transformer, the output tubes do. The output tubes heater current alone is 1.8A or 11.34 watts. The preamp tubes use 1.8 watts in total.

If you think the problem is in the output stage try disconnecting the primary leads to the power tubes, tape the output transformer primary leads up so they are well insulated.

See what happens next.

Thanks for helping Mark.

Good idea about pluggin in a guitar and hooking up some speakers.
I will try that as soon as the amp is wired up again.

About "disconnecting the primary leads to the power tubes" I will try too.

I have not yet tried a different PT.
This one is a brand new one (from tubeampdoctor.com)

Probably somewhere this weekend. (busy week at work)

Thanks again, I'll keep you posted.

Jesse

Since all else is fine I would suspect the filter supply at this point. If you are sure your rectifier is good too. I did not read if your amp actually blows fuses or if you tried playing through it as is.

[jezzbo]

Ok Guys, finally I found what was wrong and it is so stupid of me.

I forgot to connect a wire between the 100uF elko to the diode in the bias.
I still can't get it how I missed that one.

First I resoldered the outputtube sockets.
Then disconnected the OT primary wires.
And still there was a short.
The only thing that was left as far as I know was the biasing.

Now no more shorts (bulb current limiter goes dim)
Tested without the bulb current limiter and everything meassures correct.
And no blown fuse.

All of you thank you very much for helping me.

Although it took long for me to find this error, I did learn a lot!

Next is testing through speakers.

[Structo]

Ha!

Don't worry, I'm sure we have all done something similar.

It is a face slapping moment for sure.

Glad you found the problem.

[Mark]

It is going which is the main thing. Did you check if bias was present on the grid of the output tube when you initially started fault finding?

The problem was it seems (after reading a few posts) you got into a mindset where you were looking for a faulty component and as you now know that wasn't the problem.

Of course everyone has done this at some stage, and often again and again.

Good work and it is good news the amp is working.

[jezzbo]

It is going which is the main thing. Did you check if bias was present on the grid of the output tube when you initially started fault finding?

Hi Mark,

Yes there was bias present on the grid. But way to low. Even when the biaspot was at maximum. I should have known then but I was searching at something wrong in the poweramp.

Sound test wil be in a few weeks since I won't have the time the next 3 weeks.