Fuse trouble please help bv-60

[sellit18]

Hi i am new here. was using your search engine to find what i need but i cant seem to track it down.


anyways!!
I have a crate bv-60 the blue with gold crate emblem. have not used it for about 2 years. To get right to it i have tried every fuse that it calls for and blown every type more then once. hade a bad tube replaced it today still blows the fuses.

power on fuse holds up tubes warm up. flip standby pop goes the fuse. im pretty good with electronics took the whole thing apart and could not find a problem.

Ohhh the large capaciter makes a small hmmm right when i flip the standby and the fuse pop.

please give me some advice.

[mikeboone]

Maybe this will help. As you can see in the power supply schem, the SB switch is ahead of the bridge rect. and filter caps. I would start at the diodes and move forward to the filter caps looking for a low resistance or short to ground.

Since the fuse does not blow until you engage the SB switch, it would be reasonable that the problem lies there...

Hope this helps...

mike

[Enzo]

And i would add, the problem must be related to the high voltage, so either it is a tube - most common problem - or the high voltage power supply itself. Pull the power tubes out of hte amp and fire it up. If it still blows fuses, then the amp has trouble. If it holds the fuse with no power tubes, then one or more of them waas shorted.

Is this the head or the combo?

As suggested, look for shorted rectifier diodes or filter cap. but also look at the output transformer. Is either end shorted to ground? If so, check D23-26 for a shorted diode.

[sellit18]

Well thank you both for the advice i did check the cercuits they all seem fine i have not tried takeing out the tubes and turing it on. so i will try that when i get home tonight.

witch tubes am i removing the large power tubes or the small ones.

another thing, i took the large transfomer apart and there where no shorts. but befor i did that it was making a humming noise right befor the fuse would blow. i dont know if that has anything to do with it.


i dont have a lot of excperience troublshooting these kind of things but takeing it all apart and doing what needs to be done is not a problem.

So what do you guys think

[MWJB]

You are removing the large power tubes.

"another thing, i took the large transfomer apart and there where no shorts." What exactly do you mean by "took it apart"? The larger transformer is usually the power transformer, not the output transformer that Enzo mentioned. You should be checking the DC resistance from the power tube plate wires (from the "ends" of output transformer) to ground.

A short in a power tube is one of many things that could be causing your hum.

[sellit18]

transformers? large black metel box like hanging off the bottom of the amp head. correct?

i have the combo unit by the way.

That is what i took apart i took it off the unit and removed the side plates to see if any wires had rubbed raw on the metel cassing. that did not happin they seemed fine.

when i get home tonight i am gonna check to see if it is a power tube and if that does not work i will check ground fualts from the power tube circuit.

and i will let you guys know.
thank you so much.

[Enzo]

WHat you hear is the transformer vibrating before the fuse blows. This is because whatever is ashorted and causing the fuses to blow is draqgging a LARGE amount of current from the transformer. Its laminations will vibrate under these conditions. That is a symptom, not the problem.

Though they are similar, the schematic for this is the BV6212.

[sellit18]

Ok guys, again thank you for taking time to help me out.

I did all these things and still can not find a short. i took the tubes out fuse blows so i took the pre-amp tubes out fuse still blows.
the amp calls for three diffrent fuses 1.5a, 3a or 4a. i tried all 3 and they all blo-slo;-)

here what your sayin about the transformer hum telling a tail of a problem. but i can not find this problem.

i hadn't used the amp for about 4 years now could that have somthing to do with it.

what is the next step.

thank you.

[Enzo]

The next step is to start disconnecting things. Disconnect the center tap of the output transformer. Disconnect filter caps, disconnect things until it n o longer blows fuses, the we reconnect things one at a time to discover which part is responsible, unless of course we discovered the bad part while removing it.