problem fender roc pro 1000

[xf650xf]

Hi every one.
I ve a problem wit h my amps. during my session ( 3/10 volume) after 10 15 minutes it start to distort (not good way of course...) clean and warp channels..the cabinet become so hot...
Maybe some problem of transistors darlington tip147-142? I checked the input is everithing ok 38 V...It seems clipping but it never hapenned before.. what should I do? did anything have a similar problem?
sorry for my english

[xf650xf]

did anybody have fixed this amps?

[52 Bill]

It may be a broken off capacitor on the pc board. Carefully inspect the board for broken off parts or bad solder joints.

[Enzo]

This amp is very much like many other amps.

The TIP142-147 each have their own power supply voltage. Are BOTH positive AND negative voltages present? Are they both about the same voltage, other than polarity?

DO both sets of transistors seem to get hot together, or do the one one one end seem to get hotter than the other ones? There are the four 0.47 ohm 5w resistors connected to the TIPs, R112-115. When the amp starts to get hot, measure the voltage across each to see if they all have about the same or if one or two of them have more than the others.

There are four diodes in series after the op amp. CR25-28. When the amp is overheating, measure the voltage across each one. DO they all have about the same DC voltage across each, or does one or more have a higher voltage?