Roland DB-500 no sound

[pontiacpete]

This amp starts up on the light limiter, no shorts. Perhaps the output is still good. The pre amp works, getting sound out to another amp.
I start tracing a signal from the input. There is a signal thru up thru IC2 pin 1 and to pin 14 of IC4.
Does anyone know where it should go from there?

[pontiacpete]

Ok my mistake, since the pre amp is passing signal, then no need to sort out where the signal goes in IC4.

[MarkusBass]

This amp starts up on the light limiter, no shorts. Perhaps the output is still good. The pre amp works, getting sound out to another amp.

I'm not sure which output you are talking about. DI OUT, or LINE OUT (or both)?

I start tracing a signal from the input. There is a signal thru up thru IC2 pin 1 and to pin 14 of IC4.
Does anyone know where it should go from there?

Check the second input: pin 13 of IC4.
Then, I would check whether the signal is present on the MASTER pot. If it is, the amp is just muted.

Mark

[pontiacpete]

I'm getting signal out of the 'send' jack.
Still trying to find the mute circuit to post.

[pontiacpete]

here are rest of the schematics..

[MarkusBass]

I'm getting signal out of the 'send' jack.
Still trying to find the mute circuit to post.

This does not mean anything. The SEND jack is before IC4 so you cannot say that the preamp is working correctly. Check the LINE OUT output. And ,as I said, check the signal on the MASTER pot. The mute signal is on the power amp schematic.

Mark

[pontiacpete]

Oops,forgot to mention the master volume pot, there is a signal but a very shaky one.

Also, no signal on Pin 13 of IC4

EDIT: is the mute circuit Q16 and Q24?

[MarkusBass]

Also, no signal on Pin 13 of IC4

This is almost impossible. The signal from pin 1 of IC2 is sent to pins 12, 13, 14 and 15 of IC4 (through C31 and C39). If there is no signal on pin 13 of IC4, I'd say that C31 has failed (or one of the tracks/vias that lead to the cap). Can you check the signal before C31 and after C31 - directly on the cap leads?

Mark

[pontiacpete]

Again another mistake, there is a signal on pin 13. sorry. I'm having a hard time getting the prob on these small pins. Some of the pins have the hole thru connection that you can make contact with easier than the IC itself.

[MarkusBass]

In this case check outputs from IC4: namely pins 1 and 7 of IC3. Apart from this, I already suggested checking LINE OUT output. Have you had time to check it? To make life easier, you can check the signal on pins 1 and 7 of IC5.

Mark

[pontiacpete]

IC 3 has a signal on pins 1 and 7
IC 5 has a signal on pin 7 , no signal on pin 1

[MarkusBass]

IC 5 has a signal on pin 7 , no signal on pin 1

This is again not possible. It's because IC5B simply inverts the signal from IC5A. I think that you do not check it correctly which makes helping you very difficult. You should understand the signal flow in this amp. The input signal is provided to pins 12, 13, 14 and 15 of IC4. The outputs are pins 21, 22, 23, 24. The signal from pins 21 and 22 is provided to IC3A, IC5A and IC5B and finally the LINE OUT signal on CN9. The signal from pins 23 and 24 is provided to IC3B, then to CN10 connector. The pin is marked incorrectly as NASTER instead of MASTER. From CN10 the signal goes to CN8 connector on POWER board - to the MASTER pot. So, if the signal is bad on the MASTER pot, the question is whether it is correct on pin 7 of IC3B. Is it also bad? Between pin 7 and the MASTER pot there is only C11 and the wiring harness W15 so maybe you should take a look at them.

Mark

[pontiacpete]

Thanks for this,
BTW there is a signal coming out of Line out.

[MarkusBass]

BTW there is a signal coming out of Line out.

Devil is in the details. Is the signal on LINE OUT correct?
Please compare signals on pin 7 of IC3B with the signal on pin 1 of IC3A. They should be the same. If they are the same, I'd say that the preamp is working correctly and I'd move to the MASTER pot. This is under assumption that you checked C11 and W15 harness wire (to the power amp board).

Mark

[pontiacpete]

Thanks for your patience. I don't know why I was getting a shaky wave. Maybe the chorus was on ? Turned off now there is a close to normal wave on the master pot. THis wave is the same on IC3 1 and 7, and at the connector.
Here's picture.