Crate GX-130c hard to trouble shoot...

[DrGonz78]

I have a Crate GX-130c and there are two 120ohm 10 watt wire wounds that are building up a lot of heat. This amp is from 1992 and it actually has no labeling of internal components. So, I was gonna ask for a schematic but that seems pointless in some way now. I will try to study the traces and test components for their proper values to see what is causing the problem. With wire wound resistors can they be soldered in either direction in a circuit?

There is a trace that leads right to the negative lead on one of the four 50v capacitors.

Here is a file that show the mainboard

or inverted is a bit easier to read certain things

[Enzo]

Actually a schematic would be more help here. I think my buddy KB is still waiting for that schematic from me.


SO these two resistors, is there something like 40v at one end and 15v at the other? Like they are the dropping resistors for the +/-15v zeners? Normal for those to get hot. Does the amp work?

[DrGonz78]

The amp was working for about a minute then it would turn off and then back on again. I replaced two of the wire wound resistors R37 & R38 and fixed some cold solder joint near that area as it had been heating up. So now I am getting current but now the ribbon connector never passes voltage to the front control board. So that is where the power light is... and it is not turning on anymore.

[mozwell]

I hope these help
First some quick checks. plug a stereo guitar cord from the "send" socket to the "return" socket, does this fix it.
use a multimeter, measure DC volts from each end of R37 & R38 to 0V (cathode of D17, the end with the stripe). One end shoudl be + or - 40VDC, the other end shoudl be + or - 16VDC

Is the 6A slow blow fuse intact or is it blown.

[DrGonz78]

Great information! You guys really steered me straight to figuring out the problem and the amp is sounding great. Thank you Enzo & Mozwell.

It turned out to be... Pin 4 on the ribbon connector had just a tiny bit too much solder and made a connection to pin 3. I think those are the pins in reference? Or they are 8 and 9. Either way I was getting correct readings on R38, but R37 was not passing 16VDC. So, I did continuity tests and realized my error in soldering. Thanks again you guys are great.

[elbobar]

Hey
Having a problem with the Gx130Ch, really need to see these schematics. Do the link works? Only get a black screen with small white dot. Could you pm me mozwell?

[DrGonz78]

Check out this link....

Index of ./crate/GX130C/

[elbobar]

thanx!
so the xl has the same circuitry as the ch? sorry for noob questions.

[DrGonz78]

I thought on that website was the exact one but maybe not... Anyway for the sake of making sure you can get the exact one here is a direct link. Just not sure about adding attachments here lately so we'll see how this goes... I don't think the XL would be the same so here is the right one.

GX-130C Real DealSchematics.pdf

[elbobar]

ah, many thanks!