DPR-402 Fault-finding

[pvision]

Bought a DPR-402 recently but it turned up DOA.  On inspection I found the + 15 V rail fuse had blown and a little further investigation found two burnt resistors in the output stage of channel 1

There's an IC before a PNP / NPN transistor pair with two 22 Ohm resistors that feed the output via a 330 uF cap and a 1k8 resistor to ground.  I think it's the 22 Ohm resistors that have burnt

Looking at the schematic it seems the output is unbalanced -  a very odd choice, I'd have thought, for a piece of kit used so much in live sound - and wonder if this is related to the burnt resistors

Suggestions for how to proceed? Did the output get shorted and burn the resistors, taking the rail fuse out? Will the transistors be toast?

Assume that I can bluff my way round a schematic but have little experience of nailing down & fixing faults

Thanks

Nick Froome

 

[robomix]

why don't you starting with replacing the burnt resistors? then look what's happing; if was just overloading which i don't think your fine. otherwise start measuring transistor etc.

 

[gyraf]

Probably an upset transistor in output driver stage. I think Tanya (elektrotanya.com) has the schematic.

Jakob E.

 

[robomix]

if couldn't find the schematic drop me a mail or pm and i'll send it to you