No DC differences but let me check if that voltage recovers back. I haven't thought about that.
The pin 5 voltage tells me that the tube sockets have become conductive. Voltage is leaking from 4 to 5 which causes current to flow through the 220 k resistors in a direction which is causing an opposition voltage to the negative bias voltage.
That's why I suggested the 56k resistors in place of the 220 k. You don't have to pull the resistors, you could tack on a couple of 82 k resistors in parallel with each if the 220 k resistors.
What this does is lower the voltage drop across the 220 k resistors caused by the leakage. The conductive path from pin 4 screens is shunted to ground via the bias supply with a reduction of 400 percent leakage voltage, which should be enough to tell you if it is the tube sockets. I just did this to a pair of JCM 2000's that same through the shop.
Don't worry about the screen voltage being over the handbook voltage ratings. This has been going on ever since they started making tubes. There are thousands of guitar amps out there running these voltages.
- Added 82k's on the 220K's but to no avail... The current is still rising.
- I rearranged some wires but no success neither.
- Pin 5 does bump back to its initial -49.6V.