Fender Roc Pro 1000 - Problem with channel distortion

[52 Bill]

There might be a slight language problem here. Anyone here willing to step in and translate?

[g1]

There might be a slight language problem here. Anyone here willing to step in and translate?

Ah! I didn't notice "brasil" before. Perhaps JM could help.

Please re-measure at TP31: black probe to chassis, red probe to IC8 pin2. clean,red,yellow. Do not use the dash symbol (-) unless you have measured a negative voltage.

[adiorgelis]

Ah! I didn't notice "brasil" before. Perhaps JM could help.

Please re-measure at TP31: black probe to chassis, red probe to IC8 pin2. clean,red,yellow. Do not use the dash symbol (-) unless you have measured a negative voltage.

""all with the symbol (-) are negative voltages.""

[52 Bill]

""all with the symbol (-) are negative voltages.""

I can't think of any failure mode that could happen where there could be negative voltages at CR47.

We need better data here to figure this one out.

[g1]

I can't think of any failure mode that could happen where there could be negative voltages at CR47.

I was thinking the same thing. How about if U8 itself was bad, could it put neg. voltage to it's input pin?
Also, this amp was purchased broken, so we can't assume someone else didn't try to repair previously and put in a diode backwards or something.

Edit: I see the voltages listed for U8 are different from CR47, so maybe he is measuring at CR47 anode.

[g1]

Please re-measure at TP31: black probe to chassis, red probe to IC8 pin2. clean,red,yellow.

[adiorgelis]

Please re-measure at TP31: black probe to chassis, red probe to IC8 pin2. clean,red,yellow.

position the multimeter DC voltage, black chassis and red pin on the second IC8, I got the following voltages
Clean= 0.5 volts
yellow = 13.90 volts
red = 6.85 Volts

[g1]

OK, all your TP31 voltages are correct.
So now check TP32: black to chassis, red to U8 pin7. clean, red, and yellow.

[adiorgelis]

OK, all your TP31 voltages are correct.
So now check TP32: black to chassis, red to U8 pin7. clean, red, and yellow.

multimeter in DC voltage, black chassis and red pin on the seventh IC8, I got the following voltages
Clean= 0.48 volts
yellow = 13.17 volts
red = 6.42 Volts

[g1]

So TP32 voltages are incorrect.
What is the voltage at the cathode (stripe end) of CR49?

[adiorgelis]

So TP32 voltages are incorrect.
What is the voltage at the cathode (stripe end) of CR49?

CR49 is an LM4040 measurement was place as follows:
black chassis and red in middle pin, multimeter in DC
the voltages obtained were:
Clean = 9.98 volts
yellow = 9.98 volts
red = 9.98 Volts

other pins are LM with voltages zeroed in all measurements

[g1]

Those measurements for CR49 are correct.
So U8 has the proper voltages going into it, but incorrect voltage at it's output. It is most likely defective and should be replaced (just like 52Bill suggested way back in post #10 ).

[J M Fahey]

Oi amigo, é preferível escrever em Inglês, mas qualquer problema de tradução ou de compreensão, você pode também escrever o original português.

Hi friend, it's better to post in English, but if any translation or misunderstanding problem appears, you *may* also include the Portuguese original.

Eu vou visitar a ExpoMusic em São Paulo entre o 18 e o 22 de Setembro, você também vai lá?.

[adiorgelis]

Oi amigo, é preferível escrever em Inglês, mas qualquer problema de tradução ou de compreensão, você pode também escrever o original português.

Hi friend, it's better to post in English, but if any translation or misunderstanding problem appears, you *may* also include the Portuguese original.

Eu vou visitar a ExpoMusic em São Paulo entre o 18 e o 22 de Setembro, você também vai lá?.

Ola JM Fahey tudo bem? eu ate estou compreendo muito bem eles... não sei se eles estão me compreendendo de forma correta... espero que sim.
sobre a expomusic eu queria muito ir mais nessa data estarei trabalhando e alem disso também a distancia e muito grande, acaba que não compensa muito o deslocamento.

JM Fahey, comprei esse amplificador ja com esse problema, e gostaria muito de resolver mais pelo que vi ai esse IC8 provavelmente esta defeituoso vou ver se consigo ele aqui mesmo na minha cidade e trocar pra ver se vai funcionar.
O amplificador funciona perfeito o canal limpo e canal amarelo, mais o canal vermelho não funciona de forma alguma.

[Jazz P Bass]

Bing Translate: "Ola JM Fahey. I'm even quite understand them ... I don't know if they're understanding me correctly ... I hope so.on expomusic I really wanted to go further on that date I will be working and in addition also the distance and too big, it turns out that doesn't pay much offset.JM Fahey, bought this amplifier already with this problem, and I would love to solve more from what I saw there that probably defective IC8 I'll see if I can it right here in my town and change to see if it will work.The amplifier works perfect the clear channel and yellow channel, plus the red channel does not work in any way: