Variac power doesn't work

[scottcookmusic]

Hey guys,

Just a quick post to see if I can get any suggestions: I have a Mark V combo, and the variac power doesn't work. Full-power mode seems to work fine, but not the variac mode.

Anyone ever experience this?

Thanks in advance!!

 

[bandit2013]

That is interesting..... When you are on full power and switch down to Variac what happens?
Is the power light on in variac mode?
What power modes do you have on each channel? If they are all set to 90W dose this change anything?

When you switch on Variac mode from a cold start with the amp in standby, are the heaters active on the power tubes? If not, there may be a loose connection on the switch itself. If the heaters are glowing when in Variac mode on the power tubes, it may be component related on the 12 volt supply rail. What would give this away... no fan operation fan switch needs to be on. Also if you remove the cover on V5 and the tiny heaters are not glowing that would be the circuit with issues. Also if the LED's are not on for the channel selected that would also be related to the 5V supply which is fed from the 12 Volts supply.