Peavey Musician 400G

[nickbme07]

From left to right (I think): 180p, 47R, 4.7R, 4.7R.

No 4.7k, no L1.

When i test across L1 and R44 now i get the expected 2.5R. I believe they were 4.7R readings, it was the other conversation with Dude i mixed my letters, sorry! But does this answer why i dont see an inductor (100mH as in schematic) and see this resistor?

[nickbme07]

I follow you, Dude. I swapped out that U3 opamp to test and still showed bad voltage on the +15. This is the only opamp on the power board besides the U1 (this model doesn't have what I think is the compressor in the B version in position U2). This is the 400G

I just tried with opamp out (U3) and has same results, negative voltage on + of C40 is where I'm testing for +15

[The Dude]

See my post #59. I believe the blue one is an inductor- probably a 47mH. I don't think the schematic matches the circuit exactly.

[nickbme07]

See my post #59. I believe the blue one is an inductor- probably a 47mH. I don't think the schematic matches the circuit exactly.

The blue one is the R61 (47ohm) ive replaced twice now. It burns up if i variac over 50v with the power module molexes disconnected. R26 does same thing, it flip flops.

[Helmholtz]

I think what you are calling a 47R (blue) is probably a coil. The problem here is that I don't think the schematic exactly matches the circuit, which makes things difficult.

According to the layout it should be R61 and it looks like a 47R MF resistor, not like a 100µH inductor.
Wouldn't be the correct position for L1 either.

Of course the layout could be wrong.

[nickbme07]

So watching the voltage at the emitter of Q12, it follows the same up and down of the +15 rail (U3 removed)

[nickbme07]

According to the layout it should be R61 and it looks like a 47R MF resistor, not like a 100µH inductor.
Wouldn't be the correct position for L1 either.

Of course the layout could be wrong.

Can you look at post #58, I uploaded 2 pictures, one of my board and one of the schematic. The blue resistor is R61, it is a 47ohm. I've replaced it which is why it's blue. To its immediate right, the schematic shows L1, which should be the 100mH inductor,, No? My picture clearly shows its a resistor, as the same with the next position to its right, R44. I've circled L1 and R44 in the pictures.

Am I not reading this correctly?

[nickbme07]

Here I found a pic I took before any work. Here you can see the original R61 and R26 I've burned up and replaced with the blue ones you see in the new pics, as well as R44 flipped (guess it was R44, not L1 I flipped, but either way they are the same resistor...)

[g1]

If I recall, some versions of the circuit dropped the inductor and just used a resistor there. It may or may not have been shown on the schematic.

[g1]

That paper/cardboard thing looks to be the inductor anyway.

[nickbme07]

If I recall, some versions of the circuit dropped the inductor and just used a resistor there. It may or may not have been shown on the schematic.

Ok, good to know its even possible anyway. I most likely threw everyone off posting 4.7k and not the 4.7R. So theres two in parallel effectively making the 2.5ohm - if thats ok i suppose.

[nickbme07]

That paper/cardboard thing looks to be the inductor anyway.

Yes that is, in the L2 position, an additonal one on the schematic and layout. The L1 inductor would be for the "Y" side, whereas the L2 inductor is on the "X" side

[g1]

Yes, sorry, I was talking about the wrong inductor.

[nickbme07]

Yes, sorry, I was talking about the wrong inductor.
The blue part that looks like a resistor in one of the pics is an inductor. The green is a capacitor.

Not sure why everyone keeps saying that. That blue resistor is a 47ohm 1/4w resistor I installed to R61. The same is in R26 now.

[nickbme07]

Speaking of that C26 180pF.. I need to test that out of circuit, I'm getting a -1.5m resistance in circuit. It is directly related to the negative rail.