Crescendo 6K

[caraudioguy2100]

Amp came in stuck in protection mode .

I pulled the output driverboard and the amp powered up .

Amp is producing +- 12 volts to all opamps .
Amp is also producing rail voltages .

Any ideas where to start checking ?

 

[Perry Babin]

Post the DC voltage on all pads for the driver board.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:

 

[caraudioguy2100]

Pin 1: -101.3
Pin 2: -164.4
Pin 3: -164.5
Pin 4: -152.6
Pin 5: 0.00
Pin 6: 0.00
Pin 7: 0.07
Pin 8:0.00
Pin 9: 0.00
Pin 10: -15.6
Pin 11:0.00
Pin 12: -12.01
Pin 13: 11.06

 

[Perry Babin]

Check the high and low output sections of the driver IC. Use the following guide but look at the pin function, not the number, for probe placement.

 

[caraudioguy2100]

Checked those with ic still on board and they all measure in the mega ohms

 

[Perry Babin]

Connect the driver board to the main board with wires. You may only need to connect those on the 5-pin connector. Drive signal into the amp. What signals do you see on pins 1 and 7 of the op-amp and pin 1 of the driver IC?

 

[caraudioguy2100]

Which one is the opamp on the driver board ?

 

[Perry Babin]

In the 3s driver boards, the LM211 (comparator, not op-amp) will always have pins 1 and 4 directly connected. That's how you determine which is an op-amp and which is the LM211 (LM311) comparator.

 

[caraudioguy2100]

I don’t get this I soldered the jumper wires in place and powered the amp up and it’s out of protection mode and has clean audio .

Any ideas ?

 

[Perry Babin]

While it's working, check the waveforms on the points from post #6 as well as pin 7 of the LM211.

To see if there are any intermittent problems, heat/cool/flex the driver board to see if anything changes.