Low Voltage Regulator in Mark IVa

[swbo101]

My Mark IV recently started smoking after drops in volume. I was told my low voltage regulator went bad and needs to be replaced. I hear that this is tied to the V1 pre-amp tube. Is this correct? Also what is it's function and any ideas why something like this went bad..power surge?

Thanks

 

[swbo101]

Ok..so I got my amp back from the tech and it sounds great. He noted that the low voltage power supply was repaired and he replaced a burned rectifier doubler diode. Also repaired the burned traces on the board. Amp sounds a bit louded than before. I guess the electronics were starting the go and that is why I was having some volume issues.

Are there any techs here who can explain the purpose of the low voltage power supply and doubler diode. Also any reason why they went....age? Unfortunatly the tech who repaired my amp, while he did an excellent job, wasn't very talkative. I've had the amp for 20 years, this is the only issue I've ever had with it. I guess eventually something was bound to happen.

Any insight would be appreciated. Thanks

 

[Boogiebabies]

The 15V supply goes to the footswitch. Then you have a 7812 and 7805 Voltage regulators. The 12V supplies the LDR's
and the 5V supply if for the LED and switching transistor circuit. As you can see, if anything gets taken out of the 15V supply
from a blown tube or power surge you get no voltage to the VR12 or VR5.

 

[swbo101]

Wow...thanks so much for the detailed info. Very much appreciated.