i do get the same voltage on one end of r600.should i replace all three opamps or just u11?I'm most likely going to add sockets when i replace them unless you think that might present some type of problem.What would cause an opamp to go bad?there was a blown trace that I replaced when i first got the amp that seemed to be connected to the ground shield.Could whatever damaged that have been responsible for destroying the opamp?
Yes, the voltage that burned the trace could have damaged the op-amp.
You can use sockets if you'd like.
I doubt that any other op-amps are damaged but it's possible. I'd begin with replacing U11 and then, if you still have DC, you can do further troubleshooting to determine which are defective.
The trace could have been opened by several things. The most likely would have been a shorted speaker wire (shorted to ground). An intermittently shorted transformer (shorted from primary to secondary) could also have caused it.
You can use sockets if you'd like.
I doubt that any other op-amps are damaged but it's possible. I'd begin with replacing U11 and then, if you still have DC, you can do further troubleshooting to determine which are defective.
The trace could have been opened by several things. The most likely would have been a shorted speaker wire (shorted to ground). An intermittently shorted transformer (shorted from primary to secondary) could also have caused it.
This amp is starting to become a nightmare.After replacing the bad op amp i went to power it up and when remote was applied the fuses blew.I checked all the outputs and found no shorts.I clipped one of the legs on all of the outputs and then applied remote again and the fuses did not blow but R1 burst into flames.This thing is turning into way more trouble than its worth.
The more I think about it the more it seems I must have made a mistake either reassembling it or maybe accidentally bridging two solder points together.Everything worked with the exception of having weak output before.The only thing that changed was the new opamp and I don't think it would have caused this issue.
If you didn't allow 12v to contact the shield ground, you may have a shorted transformer.
With the amp completely disconnected from the power supply and signal source...
Set your meter to ohms
Connect the black lead to the RCA shield
Connect the red lead to the B+ terminal of the amp.
Apply pressure to the transformer windings, twisting, pushing, pulling... if the meter shows a direct short while you're applying pressure to the transformer, the transformer is shorted.
Did this amp have an open ground trace?
With the amp completely disconnected from the power supply and signal source...
Set your meter to ohms
Connect the black lead to the RCA shield
Connect the red lead to the B+ terminal of the amp.
Apply pressure to the transformer windings, twisting, pushing, pulling... if the meter shows a direct short while you're applying pressure to the transformer, the transformer is shorted.
Did this amp have an open ground trace?
it had an open shield ground trace. I also had to replace the power input terminals on this amp.When dissassembled you can see where the B+ terminal had been pushed through the board and came into contact with the bottom plate of the amp and shorted.Would a shorted transformer still allow the amp to play though and make rail voltage?
If the transformer had windings shorted primary to primary or secondary to secondary, it would not power up. When the primary is shorted to the secondary, the amp will sometimes play. They generally destroy the head unit shield grounds or ground traces in the amp when they short P-S. The shorts are very often intermittant.
The excessive current draw may have been due to the 30k square wave getting into the audio chain. If th RCAs were connected, the current could have been going into the shield ground of the signal source (assuming the signal source was grounded to the power supply - as you'd have if you were using a head unit as the signal source).
The excessive current draw may have been due to the 30k square wave getting into the audio chain. If th RCAs were connected, the current could have been going into the shield ground of the signal source (assuming the signal source was grounded to the power supply - as you'd have if you were using a head unit as the signal source).
Do you have continuity between the secondary center tap and the RCA shields?
If so, it would appear that the transformer is OK.
When you power it up (have the transistors clamped to the sink), measure the DC voltage on the sheilds of the RCA jacks. It should never be more than a volt. Ideally, there would be no voltage on it. To double-check the transformer, you should try applying pressure to the transformer again while watching the voltmeter. If it suddenenly changes from 0v to something higher, you know there is a problem. You should also try it on AC volts. When measuring the voltage, you would connect the black lead to the chassis ground terminal of the amp.
If you cannot find a problem with the transformer and the outputs are not shorted, reconnect the cut legs and try it again. Remember to use a 10 amp fuse in the B+ line.
If so, it would appear that the transformer is OK.
When you power it up (have the transistors clamped to the sink), measure the DC voltage on the sheilds of the RCA jacks. It should never be more than a volt. Ideally, there would be no voltage on it. To double-check the transformer, you should try applying pressure to the transformer again while watching the voltmeter. If it suddenenly changes from 0v to something higher, you know there is a problem. You should also try it on AC volts. When measuring the voltage, you would connect the black lead to the chassis ground terminal of the amp.
If you cannot find a problem with the transformer and the outputs are not shorted, reconnect the cut legs and try it again. Remember to use a 10 amp fuse in the B+ line.
finally got back into this thing after a few weeks.I believe I've found the reason why it blew fuses and burnt that resistor.When I removed the board again I noticed that one of the rectifiers had a small burr on the back of it.Sure enough that burr poked through the kapton tape and shorted to the heatsink.I feel better after finding this but I think that it has killed the opamps again.What other components should I check?The rectifiers themselves appear to be ok I just fear maybe others have been damaged.
If the ground wire that connects to the sink is directly connected to chassis ground, that could have caused R1 to burn if the RCA cables were plugged in. It could have caused the fuses to blow also.
Before reassembling the amp, go over the area where the burr contacted the sink with 400 grit sandpaper to remove any rough spot or burr. Generally, when there is a short to the sink, there will be a tiny raised peak that will cause problems again.
Before reassembling the amp, go over the area where the burr contacted the sink with 400 grit sandpaper to remove any rough spot or burr. Generally, when there is a short to the sink, there will be a tiny raised peak that will cause problems again.
If it's in parallel with a ceramic capacitor (possibly labeled 224), it's probably a 1k ohm resistor.
Most manufacturers use values between 270 ohms and 1000 ohms.
Earlier, you stated that it was connected to the shields on one end and fhe FETs on the other end. I assumed that you meant that it was connected to the source leg of the FETs (chassis ground in this amp). If that's not the case, please clairfy.
Most manufacturers use values between 270 ohms and 1000 ohms.
Earlier, you stated that it was connected to the shields on one end and fhe FETs on the other end. I assumed that you meant that it was connected to the source leg of the FETs (chassis ground in this amp). If that's not the case, please clairfy.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.