Fender FM65R distorts after 1/2 hour

[booj]

FM_65R_schematic.pdf
The problem I think is in the power amp. I plug a guitar into the pwr amp in jack and it distorts, but only after it's been on for 1/2 hour or so. When I get a scope probe and start looking at stuff in the power amp section, the amp starts working normally. I'm not really hip on this circuit anyway so I'm left just guessing. Right now I'm thinking of a shotgun approach, but when I look up the transistors (namely the 2N4001 and 2N4003) in the Mouser or MCM catalog the parts are obsolete and require cross referencing to replace with a nearest type. This project looks to be more trouble than its worth to me, but I thought I'd get a hollar out to anyone who wants to put their 2 cents in.

[g1]

Maybe try a chopstick rather than the scope probe (wood or plastic please ).
It's possible you are flexing the board a bit and restoring the connection at an iffy solder joint.

[booj]

I've chopsticked it already. I've also re-flowed the solder on the entire board. Made no difference. I've freeze sprayed it and taken a heat gun to it with no change. It's only when I touch the circuit with a scope probe that it starts to work by itself. I was thinking it may be a transistor gone iffy, thus the shotgun idea.

[Enzo]

Or an open resistor, and the scope impedance completes a circuit enough to "discharge" it and it then works a while. Find out which components make it start working when probed and which do not, then find tehm on the schematic to see what circuits are sensitive.