I got this amp 2nd hand and it has no output. Somebody has had the circuit out and cut off the ground prong and 2 screws were missing for mounting the pcb into the chassis. The power supply works. The power transformer is center tapped with a DC full wave rectified and filtered output of 32V. The unit uses 5 4558 opamps and a TDA2003 amp. I am suspecting that somebody may have installed the TDA2003 ic in replacement for something else because the TDA2003 operating voltage is 18V max and it is connected directly to the 32V. The board is laid out for a 5 pin power amp ic. I am not able to find a schematic for this but have spent hours making up my own. Any help with this from any of you with experience would be much appreciated.

 

I'd like to add: The TDA2003 VCC is connected directly to the Rectifier output of 32VDC. The -VCC of the TDA2003 is connected to Ground. The 4558's are all connected to the same ground as the TDA2003. There is no negative supply. The 32VDC is divided in approximately half with resistor voltage dividers to power the TDA2003. I'm thinking now, because this is the actual design of the PCB and 16V is less than the maximum supply voltage for the 4558's, I'm suspecting that someone put the wrong 5pin audio power amp ic in.

 

PROBLEM SOLVED! I couldn't hold my breath any longer for some help here but thank you all anyway just incase any of you did actually read this and begin some thinking. I installed a TDA2050 and it works awesome. The 2050 can use either a single supply or split supply, and it's operating voltage range goes up to 50VDC. I hope this thread will be useful for someone else.

 

Good job enj99, thanks for posting your progress and solution.

 

I read your post but couldn't find an online source of detailed service info., so I figured why reply. BTW, that model "was" all tubes.... has it been revamped to be all solid state now-a-days?

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