Improper switching between pentnode and triode

[bfglp]

Marshall recommends being in standby mode for adjusting the 1/2 power switch on their amps, what would happen if frequently misused?

[Mars Amp Repair]

Hello bfglp,
Hmmm...I'm thinking of a couple of possibilities...1: The switch would be more likely to arc internally with B+ on it when the contacts are all momentarily all disconnected when the switch is thrown.
2: If there is a voltage spike created by throwing the switch, that could technically be some damage to any solid state devices in the amp.
Other than that, I have no suggestions as the tubes would be cut off with no screen voltage on them.

[mhuss]

If the switch changes PT windings, doing so while current is flowing is bad for arcing, etc. If it's a 'triode mode' thing, I don't think that switching the screen grid connection while live would be good for the tubes.

[bfglp]

If the switch changes PT windings, doing so while current is flowing is bad for arcing, etc. If it's a 'triode mode' thing, I don't think that switching the screen grid connection while live would be good for the tubes.

The switch on my dsl 40c is labeled pentnode - triode I believe other dsl’s are just marked as 1/2 power I’m really not sure how the switching works or if it’s controlled by the processor or not

[mhuss]

If it was under microprocessor control, it should be able to detect if it's in standby and refuse to switch if not. I suspect it's just a plain switch.

[Mars Amp Repair]

Guys,
Typically, the switch makes a triode out of the Pentode by connecting the screen grids of each pair (in 100watt versions) to the plates. I'm thinking, as I mentioned in a prev post, that the arcing might occur when the switch momentarily disconnects as it's switching from one set of contacts to the others.
Ultimately, why wouldn't you just put the amp in stby when switching the power modes. glen