Fender performer 1000 Hey Enzo

[Blastart]

Quite a while ago you helped me get this thing fixed by suggesting that I change out the 100 ohm resistors to the voltage rails. (the amp kept trying to channel switch when you strummed the instrument) It worked great after that. This last saturday night I had about a half hour to go when I lost sound. The amp shows the dirty drive lit (yellow led) the peddal shows the clean drive lit (red led). The pop I get when I fire off the amp tells me my outputs are still with me (thank goodness). I pulled the chassis out and tested the power transformer and it is fine. I have 30 volts AC at TP 22 and 25 which is good. I have -38.5 VDC at TP26 which is good. I have 0.73 VDC at TP23 which sucks. I checked the resistors R172 and 173. They measure 98 and 98.5 ohms respectively. The + rail at TP 24 is 0 VDC as well. I am useing service diagram ROC PRO 1000.
Can you help me out here? I can only guess it to be CR55 or maybe the sand resistor again. No where near as easy to figure out as a tube amp would be. For me that is. Thanks for your time. DB

[Enzo]

SO you have lost the B+? WHy on earth is this any more difficult to figure out than a tube amp? Transformer, rectifier, cap, resistor, how is this different from the same circuit in a tube amp? Pretend it is a 380 volt supply rather than a 38 volt supply, if it helps.

Are those resistors getting hot? That would point to a shorted CR56 zener, or a grounded B+.

Is this thing blowing fuses? Did you check the two large rectifiers ther for open?

CR52,53 serve that B+. Check them both. You have the AC right at their legs, right? Don't assume because it is elsewhere that it actually gets to the diodes. Flip the board over and look for solder failures in the area of these parts.

How about this scenario. R172 is OK and measures the 98 ohms or whatever, but the end of it at the test point either the solder has failed so it is not connected, OR the wire leg is broken off and the part is held in place by glue, with the leg remnant not touching.

[Blastart]

It was a bad trace from R172 to the cap. I hard wired it and the problem ended. As to the issue of circuit recocnition I do seem to have SS dislexia of sorts.I don't know if its because of all the extra components in a SS circuit or what. When I look at a tube circuit I can recognize any part of it with no problem. A SS circuit just throws me. I guess I need to spend a lot more time trying to read through different circuits. If you have any suggestions as to some references that may help me I would appreciate them. Thanks again for setting me on the right path. Respectfully; DB

[Enzo]

But here is my point. You detected right away that there was a loss of a power supply voltage. In the power supply it is the same stuff as in a tube amp. You have to get rid of that "I can;t even think about it because it is solid state" thinking. It doesn't matter where that power rail went, nor what it does once there, it wasn't happening in the first place. ANd like I said, whether 38 volts or 380 volts, the circuit is the same.

I am saying you CAN do this, just don't get in your own way telling yourself you can't befoer you start.