Peavey 300 combo bass amp, No signal

[FretWanker]

Hello, I recently re soldered the brown inductor coil back to the board, and replaced the resistor next to the coil (due to it burning up when the coil disconnected) after putting the amp back together, I have lost all signal. My power lights will not even come on anymore. Before I replaced the parts, the amp only performed at about half power, but there was still signal. Any Ideas on what I may have done to cause complete loss of power?

[Enzo]

Are all the cables connected back to the boards OK?

Did you forget to reconnect the four-wire cable between power amp board and preamp board?

Have you blown the main fuse?

The power tranny has two sets of secondary wires, the reds and the oranges. They use opposite gender pins, so you shouldn;t be able to swap pin sets. But do make sure they are on the pins properly.

[FretWanker]

I know its gonna be somethin small!

Yes I have re connected the wiring harnesses, some fit only one way, but there are two connections that can fit two ways. They are a three pin config, I'm not sure if I put them on backwards the first time and maybe damaged another part, however I have not blown any fuses, I have checked all three. I have continuity from the input of the amp, to the speaker output, but no power behind it. When I first tried turning it on, the comp light came on for a brief second then went out. I've had no lights since....Thanks for the response, can you think of any other issue that may cause this?

[Enzo]

There are two sets of three wires from the power transformer. Three are orange, and three are red. Each group ends in a three pin Molex connector. One set is male-female-male, and the other is female-male-female. So you can;r put them on the wrong places. They are AC center tapped windings, the center tap is the center pin of three. It doesn;t matter which wire is which on the ends - it is just AC feeding a bridge.

There are two three wire short cables between the powr transistor board and the main powr amp board. I think the colors are red, white, and blue? The wires are too short to reach the wrong pins, and the male-male-female arrangement means you can't plug it backwards. But those two must be connected for it to function.

The power amp in there is the 400BH board is it not?

Does the speaker thump at power on?

I don;t know what "continuity from the input of the amp to the speaker output" means, unless you are speaking metaphorically.

You may have continuity through the speaker from the connector on the 400HB board, but if the female pin has spread it might not be making contact. You did work on the inductor and resistor, L1 and R32. With the speaker connected, what resistance to ground from the inductor? Should be whatever the speaker is.

Play a signal through the amp. use a scope, and AC meter, or another speaker with clip wires to see if output exists

You get no power light?

Start from the start then. Look inside. VOltmeter. Got AC volts on those red wires and ornge wires? It won;t be wrong, it will just be present or absent.

Now DC volts, got +50 on the case of one half-row of power transistors? Got zero VDC on the cases of the other half-row? And on the ones with no DC on their cases, is there -50 on the 10 watt resistors next to them?

Yes? OK, CR20,CR21 are 15v zeners for the power amp itself. Got 15v across each? Now look at the 14 pin IC down the board a ways. Got +15 and -15 there? Pins 4, 11.

Then the power amp should make noise. The four wire (5 pin connetor) plug at the very corner of the PA board, opposite end from the big filter cap corner, connects to the preamp. Pull it off. Make sure speaker connected. The four pins now exposed in a row, the one closest to the small 8-leg IC, touch it with your finger. You should hear hum from the speaker. If not, the PA is not working. If so, it is, and we move to the preamp.

The power light is part of the preamp. The preamp has its own +/-15v supplies coming from the PA board. +15 and -15 are two of the pins on the four wire cable from the corner of the PA board. Are both present? Note the two separate sets of +/-15v on the PA board.

[FretWanker]

Thanks for the very descriptive information, I think that will help me zero in on this issue. I believe it is the 400BH board, but I will verify. Thanks again for the help!

[tubeswell]

..., can you think of any other issue that may cause this?

Um, maybe your frets have decided enough is enough and just are refusing to co-operate any more.

If anyone can help you Enzo can.

Welcome to the form BTW

[str1954]

kustom 200

i have a old kustom 200 head blue sparkle. i use it for bass guitar and realy like all of the great tone this amp gives me.i am haveing a problem with the amp. as i use the amp. even though it sounds good i get a static disturbence and then a slight pop then it is fine for a sort time and then does the same thing again and again. can anyone tell me what i should do to solve this ?

[Enzo]

Hi there 1954, welcome to the forum.

What you should do is start a new thread for your amp instead of asking at the end of a thread about a different amp.