Traynor YGM, sparks flying!

[J M Fahey]

Do NOT measure on plates, period.
Many schematics (not all) show various voltages at different points but state "do not measure" on power tube plates.

Maybe there's a reason for that

[Chuck H]

Do NOT measure on plates, period.
Many schematics (not all) show various voltages at different points but state "do not measure" on power tube plates.

Maybe there's a reason for that

Full disclosure I do it on preamp tubes all the time. But never power tubes. Not sure if this is a proper caveate or not but if it is I wanted to make the distinction.

[Helmholtz]

I spoke of power tube plates only. It requires the OT to generate that high voltages.
Not sure about the reverb driver. I've seen peak plate voltages around 800V there in normal operation.

[Dave H]

After passing a bulb limiter test, I went to check voltages and a big spark jumped from the filter node to my meter probe as it approached, and ruined the meter.
Totally freaked out by this I removed the whole affair on the CT and reverted back to stock.
Tried with another meter and different probes, same thing happened.

What on earth could be going on?

Are the dead meters auto ranging or manual? I've never liked auto ranging for measuring high voltage. I always use manual and set it to its high voltage range before connecting the probe. Auto ranging meters can draw a considerable current when connected to a high voltage/low impedance source like the B+ CT as the protection and ranging circuits operate.

[hylaphone]

Are the dead meters auto ranging or manual? I've never liked auto ranging for measuring high voltage. I always use manual and set it to its high voltage range before connecting the probe. Auto ranging meters can draw a considerable current when connected to a high voltage/low impedance source like the B+ CT as the protection and ranging circuits operate.

Both were manual, I don't care for auto ranging either. One was an old bench meter that lost a resistor in the input voltage divider. The other was a cheap handheld, SMD, that went in the bin.

Learned a valuable lesson with this one, so thanks all. I've been blissfully unaware of this hazard for many years and hundreds of amps, this is the first time it struck.