Crate GX-140C Blowing Fuse

[Sloan]

I've got a Crate GX-140C here that is blowing it's fuse. I've checked power transistors, and resistors on main board and all is OK. If anyone has a schematic, that would be helpful.

[DrGonz78]

So have checked to see if any of the rectifier diodes are shorted? Was the amp just found in this state: meaning did you get it non working or did it suddenly have some trouble? Are all the power input cables in their right place? Just had some questions to get a bit more information thanks.

[Sloan]

No story on this amp, just got it blowing fuses. It's in really good shape (even inside), like new, so I don't expect any user error. Diodes seem OK.

[DrGonz78]

Well I think calling Loud to get the schematic would be a great idea here... I would first start to investigate that PT to make sure it's good then keep working backwards through the power stage of the amp. I say post some pics of the inside of that amp as a point of reference to see how the PT connects to the board.

[Sloan]

first is kinda blurry, need to find my tripod eh....

[Jazz P Bass]

Here is the 130C schematic.
It may get you going.
It is a different amp as far as the preamp controls are set up.
Contact Loud Tech, they will help with the correct one.

[DrGonz78]

Yeah exactly like a GX130c in many ways on the power board... I have some pics of all the power plug points of the GX130c on my phone but can't get them off the phone. I was hoping for a pic of all the exact plugins but they already look a tiny bit different where the B+/B- leads into the board. Most other cables look very similar to how transformer etc... plugs into the board. Very nice to see component names on the board since the GX130c did not have any on there at all.

My main concern is over heating of components solder joints on these wire wound resistors. Especially the ones that I pointed out in the cropped photo here... But look at all the wire wound resistors to make sure they are good, and check those solder joints too.



Not saying this is gonna fix the amp or not, but just that those are suspect places on these amps that need to be looked at anyways. This amp really cooks things and those two wire wounds looked really cooked. I think the far one on the left is 120 ohm 10 watt cement flame proof wire wound as I recall. I think those wire wounds eventually can just crap out. They either work or they don't but the one was still working even with cracking. I think it was cooking itself to death and it did not blow a fuse but it turned off the amp and then it would turn on again. (Edit:That was in regards to a GX130c that I had a while back...)

So you tested the output transistors on the amp? You also tested lots of other components... I hope you have a light bulb limiter for further testing?

Edit: BTW what is this on the one filter cap? Just can't see it that well... Probably nothing but just have to ask.

[J M Fahey]

If you do not have a tripod handy, 1) get *good* light on the amp.
Best is outside, but when a cloud covers the sun, to even illumination, or placing the amp by a white, sun illuminated wall (the Sun should be on your back).
2) if not possible, use some books or a chair to support your forearms, plus breath slowly and press the button also slowly, without shaking the camera.
I sometimes use the 10 second timer, so as to separate actual pushing from simple holding.

[Sloan]

I've checked the cement resistors, they all seem ok. I did a lookover for bad joints, but didn't notice any (they can be sneaky though!). On the cap, that's remnants from a sticker or something, nothing to worry about.

I do have a lightbulb limiter, thanks for reminding me!

I was hoping for a pic of all the exact plugins but they already look a tiny bit different where the B+/B- leads into the board. Most other cables look very similar to how transformer etc... plugs into the board.

This is good to note, as I am unsure if anyone has been in this amp or not. Doesn't look like it, but you NEVER KNOW.

[Sloan]

Wow, just called LOUD - 10 minutes later and I already have the schematics in my email. GREAT SERVICE!
You do have to fill out a disclaimer email stating that you are aware of the dangers and that you will not redistribute without written consent of LOUD.

Schematics are large format and easy to read as well.