CDi 1000 Crown Amplifier

opacheco · Dec 16, 2014

Hi

I am in the repair process of a CDi Crown Power Amplifier, the problem is NO SOUND AT ALL but the amplifier turn on with the fan to the full velocity from the beginning (instantly).

I have searched the schematic or something like technical troobleshooting but found nothing about!. Has anyone had this problem before Here?, what can be the problem in this amp?, where I can find a schematic or service manual for this amp?

Thanks a lot anticipated,
opacheco.

joaquins · Dec 16, 2014

How does it sense the temperature? maybe the sensor is off and it's telling the amp it's overheated, protecting everything and spinning the fan AFAP. I wish it's just it, could make a simple fix, or not so simple, but no need to touch anything in the signal path...

JS

opacheco · Dec 17, 2014

joaquins said:
How does it sense the temperature? maybe the sensor is off and it's telling the amp it's overheated, protecting everything and spinning the fan AFAP. I wish it's just it, could make a simple fix, or not so simple, but no need to touch anything in the signal path...

JS

joaquins link,
Thanks for the comments!....I think so too, but how I can do in order to solve this false sense??
Do you have a Troubleshooting procedure for that or something like this in your experience??

Thanks a lot.
Opacheco

joaquins · Dec 17, 2014

Not so much, I would certainly start looking for visible damage, if it really got seriously overheated and caused the problem you will probably see where the fail started. Looking for shorted output transistors is a common practice in this case. It shouldn't be hard to bypass the protection but you have to be sure you won't burn anything, so limiting the current on it is a good idea to start the tests, once you have the power amp working is time to fix the protection.

If there isn't any visible burns maybe the sensor failed and you could just replaced it, if you are lucky you get the exact same part and only soldering is needed, if not you have to start thinking.

When it turns on, do you have any output? even if it's noise or DC, or before the output protection =.

JS

opacheco · Dec 17, 2014

joaquins said:
Not so much, I would certainly start looking for visible damage, if it really got seriously overheated and caused the problem you will probably see where the fail started. Looking for shorted output transistors is a common practice in this case. It shouldn't be hard to bypass the protection but you have to be sure you won't burn anything, so limiting the current on it is a good idea to start the tests, once you have the power amp working is time to fix the protection.

If there isn't any visible burns maybe the sensor failed and you could just replaced it, if you are lucky you get the exact same part and only soldering is needed, if not you have to start thinking.

When it turns on, do you have any output? even if it's noise or DC, or before the output protection =.

JS

JS,

Thanks a lot for your interesting advises!....This amp haven't any sound, when it turns on go without any sound at all!....The protection is instantly no chance to nothing!.....Follow your advise, I will check the temperature sensor first(if this have one!).

Do you know how I can do in order to Limit the Current in this amp?

Thanks again a lot!
Opacheco.

joaquins · Dec 17, 2014

A socket in series with a light bulb is a tool is very useful for this, you can swap the light bulbs to get higher currents but you'll never go higher than the current of the lamp in a dead short on the socket. This is used to avoid the smoke test, which you already did, but if you are playing around this may help you not to get to that point, if you bypass the protection to check if everything is working and only the protection is broken would be kind of a different smoke test, and there you should use it, once you see everything is going good you can take it out and plug directly. (BE SAFE!)

What I meant is to mesure the output with a multimeter, even if you don't hear nothing small DC could be present or maybe it has some relays at the output as part of the protection and you could measure the signal before those.

JS