CRATE GT-80 (Yes another transformer down)

[talmwilliams]

Hi all,

I'm new here, so please be kind !

I have already tried searching the web for any kind of advise I can find - it seems this is a very common problem, but there are not a lot of solutions out there.

So, this amp has died twice over the years and, was bought back to life by a simple transformer transplant both times. It has gone again, but the are no longer any available, and Crate, despite the excellent product, have crap service and will not give me any info to fix it.

What I wanted was a schematic, that shows the output voltages from the main transformer, and I will get one made locally. Or if anyone has a fix to stop this happening again?

Cheers,

Tim

[talmwilliams]

By the way, if someone could just let me know what the voltage values are, I wouldn't need the schematics.

Thanks,

Tim

[g1]

Looks like the schematics here:
http://music-electronics-forum.com/t14951/

[talmwilliams]

That one looks different, as from memory, I think mine has a 3 pair of outputs from the transformer, this only shows one.

Thanks anyway.

Tim

[km6xz]

How old is it? Is it a GT80DSP or an original Gt80?
What is wrong with the transformer, primary, secondary, open, shorted??
If the primary, carefully open the transformer, cutting the tapping gentally with an exacto knife and you will find where the primary wires enter the transformer windings, where the thicker vinyl wires conned to the small enameled wires, one has a small metal cased fuse or thermal cutout device, the size of a 1/2w carbon comp resistor. That is open about 80% of the time with bad Crate transformers. Replace it with a similar fuse or thermal cut out. The old ones had fuses and the newer series had the metal thermal cutout.

[Jazz P Bass]

I do not think what you are asking is feasable.
Besides the transformer voltages you need to know what current each winding is capable of sustaining.
What Exactly is wrong with the transformer?
Here is the GT50 schematic.
It should be close.

[talmwilliams]

Thanks for the replies.

KM6XZ ; It is a DSP, and it is not the thermal fuse. When I disconnect all of the outputs, it still blows the main fuse.

Jazz P Bass ; Thanks, the schematics look similar - although I can't tell what the output values should be on each winding, but I'm halfway there just having the drawings.

As this is the third time this has happened, I plan to over engineer the new transformer, once I can get the spec. Maybe I could stop thrashing it!!!

[oc disorder]

Crate GT80 DSP Schematic

[talmwilliams]

Perfect - Thank you oc disorder!

[Thiago Figueredo]

Hello!
I'm new here and I really need this Crate GT80 DSP Schematic but I can't open this PDF.
Could send it again?

[DrGonz78]

Here it is...

[DrGonz78]

oh yeah I had two versions of this one... Both schematic qualities are not that good but it was all I could find a while back when working on this amp.

[Thiago Figueredo]

Thank you so much, DrGonz78!

[audiopete]

Is it possible you have other issues that keep taking out the PT. Have you checked the power supply components to confirm its all good there? Are you running different tubes? Again, what exactly is failing with the PT? Never heard of an amp eating PTs like that under normal conditions.

Btw I've had excellent help in the past from Loud Tech for both Crate and Ampeg parts and schems. I could see them not giving service advice out though.

[Enzo]

Pete, the OP with two failed transformers posted over three years ago, and has only 5 posts total, he's long gone from here. The new guy didn't mention transformers. Transformers rarely kill themselves, as you imply.