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Post subject: Bassman transformers with cable burned
Posted: Mon Aug 01, 2016 9:20 pm
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Hi
Today i opened my bassman blackface 1965 and i found one cable burned and cut
I can't be sure if it was cut when i opened or before (it was very damaged) but until yesterday , the amp working without trouble.

I check the diagram and the cable is a digital ground.
What happens if i connect the amplifier without fix it ?
Here the pic ( the cable is the green with the yello cable ):
https://drive.google.com/file/d/0Bx_SS6jKtut8S0x1aEZrSHlYTTA/view
Thanks


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Post subject: Re: Bassman transformers with cable burned
Posted: Mon Aug 01, 2016 10:29 pm
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Do not use the amp. The burnt wire is the center tap of the main power transformer (secondary side). Your PT could have an internal short. Remove the fuse holder and see what amperage fuse you have. My bet, it's an automotive-type 15- or 20-amp fuse. Not the 2-amp slo-blow that is called for. I see this sort of thing ALL THE TIME.

Meantime, a tech will need to check the PT for shorts. Also, the main power supply filters, diodes, bias supply, and output stage (output tranny).

Do you know if the main filter caps (under the doghouse) were replaced? And when?

BTW... I think I know what you meant --- but, this amp has nothing digital in it. :)

Good luck!


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 1:57 am
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This green/ yellow wire is the heater center tap.
You may have a short on tubes heater circuit

This wire it is at secondary of the transformer .
A burned wire is mostly caused by the circuit which is fed by this wire, not not have results where the wire comes.
The transformer is probably not an issue.

Many solder look very bad, this amp need to see a qualified tech.

Be sure the amp use the right fuse, too many old amp use a wrong fuse wich can blow transformers in case of short.


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 7:17 am
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stratele52 wrote:
Be sure the amp use the right fuse, too many old amp use a wrong fuse wich can blow transformers in case of short.


I agree! If the fuse is the wrong amps, you may just get away with a fuse change and perhaps another PT ---- which needs to be checked for shorts in all internal lines.

I hope this is the reason. But, if the fuse is the correct one... may have internal PT or other problems.

In any event, off to a good amp tech! Good luck! :D


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 7:37 am
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BTW... OUCH!!! With respects to that lamp holder and the front faceplate. :(

Did your tech do that? NOS faceplates are getting as hard to find as good testing GZ34 rectifiers, these days.

https://drive.google.com/file/d/0Bx_SS6 ... ef=2&pli=1


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 7:46 am
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BMW2002Ti wrote:
BTW... OUCH!!! With respects to that lamp holder and the front faceplate. :(

Did your tech do that? NOS faceplates are getting as hard to find as good testing GZ34 rectifiers, these days.


+1000!

Guitar amps and jack hammers simply do not mix.

:shock:

Arjay

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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 8:29 am
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Bad looking pilot lamp installation could be the issue. This lamp use same wires as heater circuit.


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 8:58 am
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Kinda hard to tell, picture is a tad fuzzy... but may also have damage to main secondary line (in yellow).

Image


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 9:17 am
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BMW2002Ti wrote:
Kinda hard to tell, picture is a tad fuzzy... but may also have damage to main secondary line (in yellow).

]


Not in my opinion, look a normal blue line to me


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Post subject: Re: Bassman transformers with cable burned
Posted: Tue Aug 02, 2016 10:29 am
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From another amp board:

" A power tube has shorted, applying high voltage to the heater circuit. The center tap was the path to ground.

I had one that way a while back. I added the 100 Ohm resistors from the pilot lamp to ground, like later Silverface amps to create an artificial center tap."


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Post subject: Re: Bassman transformers with cable burned
Posted: Sun Aug 07, 2016 10:27 am
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[quote="BMW2000ti] NOS faceplates are getting as hard to find as good testing GZ34 rectifiers, these days.
[/quote]

So true, I just had a second JJ gz34 go up in smoke. I think I'm going to have to track down some vintage glass. 2 JJ's and one Sovteks in different amps within the past year is unacceptable.

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Post subject: Re: Bassman transformers with cable burned
Posted: Sun Aug 07, 2016 10:39 am
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socal323 wrote:
So true, I just had a second JJ gz34 go up in smoke. I think I'm going to have to track down some vintage glass.


When you find some, grab them and guard them like your daughter's virtue.

There simply aren't any durable GZ34's being manufactured anymore.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Bassman transformers with cable burned
Posted: Sun Aug 07, 2016 12:21 pm
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Retroverbial wrote:


There simply aren't any durable GZ34's being manufactured anymore.

Arjay


What do you mean by "no durable GZ34 " ?


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Post subject: Re: Bassman transformers with cable burned
Posted: Sun Aug 07, 2016 12:31 pm
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I mean, a bottle that will perform reliably for a decade or more.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Bassman transformers with cable burned
Posted: Sun Aug 07, 2016 12:42 pm
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I know for only $15 a JJ's GZ34 will last many many years. A decade I don't know .
Who care it is only $15


How much cost a NOS GZ34, $50, $100 and more.


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