Plate Amp power cutout

[3KFX]

We (A friend and I) have a Kenwood Powered Subwoofer plate amp rated at 160 W power draw that goes into protection mode after the gain is set above ~1/4 total gain. Can anybody give us some guidance on how to find where the problem originates and what we could do to fix it?

If more information is needed, I'll try my best to get the info to you.

[XEAGLEKEEPER]

3KFX
Hello neighbor.Do you have a schematic or service manual?Have you replaced any parts(substituded) in the amp?
Dave

[zolthoff]

Hello, I am the friend that 3kfx talked about up there. None of the parts have been replaced in the plate amp. We suspect that the output transistors may have issues because there is a possibly that the outputs to the speaker(+ and -) touched. I will try to post a picture soon.

[XEAGLEKEEPER]

If the + and - touched,chances are the outputs are toast..

[3KFX]

would it be just the transisters... or could it be more?

[XEAGLEKEEPER]

Hard to tell without a schematic--possibly emitter resistors also The resistors would be the larger 1,2 or 5 watt wirewound low resistance variety.They are probably located close to the output transistors. Did it blow any fuses?
Dave

[zolthoff]

We carefully looked at all the components, 3kfx and I, and also we had another person, who has previously built simple amps and knows a decent amout about amps take a look at the components and couldn't find anything visibly burned. The resistors all looked fine. There was a tiny bulge on one of the two bigger caps. I'm not sure what that means, but he said it wasn't anything to worry about. Also, on a side note, the outputs consist of two orange (positive) wires coming from the board, and one black one. Its not related to the problem, but why the doubling up of the positive leads at the same gauge?

[XEAGLEKEEPER]

When I stated outputs I was referring to the output transistors. The wires you were referring to are probably the AC wires off of the transformer. As for the resistors and output transistors they are going to have to be checked with a DMM digital multimeter.They may look OK but still be bad they need to be ohmed out(checked)
The bulge on the capacitor is not good . This is another issue that needs to be addressed.

[XEAGLEKEEPER]

Just curious.Do either of you have a DMM? Do you know how to check a transistor or resistor?Can you post a couple close-up pictures or a schematic diagram of the amp?

Dave

[LightwaveDude]

Sorry guys for the confusing posts, but I was logged in on an old account (3KFX - I was at school and didn't remember my user name or password, but apparently guessed the old account)... I'll be using this one from now on...

I have access to a digital multimeter, and some other basic electronics tools. A resistor I assume you check by making sure it's the stated resistance. A transistor, I don't know how to check (though I haven't had time to search Google yet). Also, if the capacitor should be of concern, how would I check that.

Does anybody have a normal testing procedure they go through? Do we first test what voltage is put out by the amp before it cuts out? Check the transistors? resistors? capacitors? What should we be looking for?