Marshall TSL mainboard material heating problem

[Rod]

Hello everyone!

I think that everyone knows the problem with this Marshall TSL.

My question is if the board turns conductive with temperature, can we have for example the B+ voltages enter in the ground,grid or cathode of the preamp tubes?

[Jon Snell]

It is highly unlikely that paxolin, which is an insulator, turns conductive unless there is something to carbonize the material like a flame or burnt component.
Cleaning the outer and leaving the discoloured material is not a problem unless it has caught fire.
When it gets hot, it gets discoloured but won't become conductive without burning.
I have tested a number of badly scorched boards to find they are all still good insulators, even with HT on them.
Ensure you replace the poorly crimped heater connectors with new soldered connectors or solder directly to the PCBoard.

[Rod]

Hello, Jon!

I bougth the bias drift mod of Dr. Tube, and im about to install it.

And if we have b+ voltages entering the - bias of the powertubes, with this board problem i tougth that this b+ voltages could enter also in other unwanted places of the main board.

[Rod]

Jon , what poorly crimped heater connectors are you talking about?

[J M Fahey]

It is highly unlikely that paxolin, which is an insulator, turns conductive unless there is something to carbonize the material like a flame or burnt component.......

Dear Jon, *there is* a well known Marshall TSL conductive board problem, probably due to contamination, so bad that Marshall itself offers assembled replacement boards asn the only solution.
They are not made out of Paxolin (phenolic paper) but epoxy-fiberglass.

Enjoy:
https://www.google.com/search Marshall+TSL+conductive+board+problem