PC2002M - Need help

Something on the pre-drive sheet may be whats holding the output at near rail temporarily when unit has been powered down for a while.
 
Replaced the all three TL072's, now there is no output from Channel A. After the replacements, initially the DC offset was about 4mV. Now its 0.5mV. When I connected a signal, no output. Something is amiss on the PDA board. I do have another working amp and swapped the PDA board. With the other board, everything works fine.

I did check very carefully for bad solder joints on the entire board and checked for solder bridges on the IC's. What should I look for next???
 
In reviewing the schematic, I noticed that the three IC's are not all TL072"s. that may be the problem. I will replace IC 101 and 102 with the original NE5443's and see what happens.

That was a dumb mistake!!!
 
Replaced the NE5534's and Channel A is again working, but still having the fluctuating DC offset. The TL072 is new. The off set ranges from -38mV to +8mV. After a few minutes it settles down to +-1mV.

Channel B is steady at 5mV.

Where should I look next on the PDA board???
 
Replaced the NE5534's and Channel A is again working, but still having the fluctuating DC offset. The TL072 is new. The off set ranges from -38mV to +8mV. After a few minutes it settles down to +-1mV.

Channel B is steady at 5mV.

Where should I look next on the PDA board???

I don't see any major problems.If it settles down to 1mv . Button it up,grab a cool one and crank up some tunes.
 
hey guys. reviving an ancient thread here. a friend has brought me a PC2002 in pretty bad condition. this glue is everywhere. also on power-on it just starts into both protection lights being on.
i examined the PDA and PDB board and found a completely disintegrated diode which i replaced, it was covered in the black solidified glue crust. completely corroded.
so im guessing i have a lot of glue picking to do...

i also started troubleshooting from the DC board, with both channels unplugged. all voltages seem to be good except the B+ and B- / Ba+ and Ba- ( im just paraphrasing the schemo here )
for B+ i get 87.8v
for B- i get -87.6v
for B alpha 's im getting + and - 94.6 volts...?

so is B /Ba the voltage for the driver board?

the DC board is completely covered in the gunk and a lot of terminals are reading 10 ohms between each other....is this the conductive mess?
 
Welcome aboard Blanca

the DC board is completely covered in the gunk and a lot of terminals are reading 10 ohms between each other....is this the conductive mess?
Need to see a photo of your " mess "
Clean it up the best you can....

Which terminals are you are reading 10Ω on ?
 
hey guys. reviving an ancient thread here. a friend has brought me a PC2002 in pretty bad condition. this glue is everywhere. also on power-on it just starts into both protection lights being on.
i examined the PDA and PDB board and found a completely disintegrated diode which i replaced, it was covered in the black solidified glue crust. completely corroded.
so im guessing i have a lot of glue picking to do...

i also started troubleshooting from the DC board, with both channels unplugged. all voltages seem to be good except the B+ and B- / Ba+ and Ba- ( im just paraphrasing the schemo here )
for B+ i get 87.8v
for B- i get -87.6v
for B alpha 's im getting + and - 94.6 volts...?

so is B /Ba the voltage for the driver board?

the DC board is completely covered in the gunk and a lot of terminals are reading 10 ohms between each other....is this the conductive mess?

Best to start a new thread on you 2002...:thumbsup:
 
What I ended up doing was to remove all of the glue and checked all of the components it touched. Several had to be replaced (diodes, jumpers, etc.) others needed the leads cleaned and I did replace the electrolytics, glue or not.
 
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