Carvin Sx-200 blown switching power supply

[DGstrat]

I have a carvin sx-200 with a blown power supply. The viper100 has left a nice dark trail on the heatsink and the surface mount resistor next to it (R1) is cracked and open circuit. From the few other posts I have seen on this Amp, it looks like the optocoupler should also be replaced for good measure. I have checked the TIP142/147 power transistors in-circuit, nothing's a dead short, but I am seeing the diode check voltages of half a volt or so in both directions on one of them. I guess that I will have to remove them to get a final verdict.

R1 is not marked on the schematic. The part appears to be marked "5601", I assume that is 5.6K? Seems to be in the correct range, given the viper100 sample circuits on ST's website.

For reference, here's the schematic:

http://carvinimages.com/schematics/80-03201RevG-3.pdf

Does it sound like I've covered the bases? Something made this supply go poof, but I'm not seeing a guilty party. I suppose that it could have suffered a brownout on the mains...

thanks for reading.

Dave

[Enzo]

The schematic appears incomplete, the switching circuit is mossing, I assume the five VIPER references connect to something.

[DGstrat]

The schematic appears incomplete, the switching circuit is mossing, I assume the five VIPER references connect to something.

Yes, the VIPer100A-E switcher part:

http://www.st.com/web/en/resource/te...CD00070231.pdf

Same amp, similar situation as this post (you and Mr. Fahey were very helpful):

Rebuilding a Carvin SX-200

After I re-read it, I see that I missed checking the diodes, so I checked them and they look good.

[Enzo]

Remember, TIP142/147 are darlington transistors, which means two transistors inside, so the base to emitter will read as two drops.