LSC - Help!! Fuse Blowing Only on Full Power (not tweed)

[lonestarlove]

Hi guys I'm new to the forum have have been playing boogies FOREVER (Mark IIc+ / Mark IV (2) and have always enjoyed the reliability and dependability of these little giants. My amp is running all 4 6L6's and runs fine on 50W Modes and Tweed Switch Engaged.

When I flip to Silicone Rectifieror Full Power (non tweed / variac setting) I blow a fuse?? I have done the isolation test ( removed all the tubes and powered up fine, but again as soon as I fire up the Full Power Switch My fuse dies.

Anyone have any experiences similar? Or might now what the issue could be?

Thanks!

 

[felix vampiro]

I can only suggest flipping when in standby mode and seeing if that makes a difference.
Certainly the LSC can blow fuses when flipping from tweed to full power but I have not had a problem when changing between silicon diode rectifier and tube rectifier tracking or from 50 to 100 W.

 

[lonestarlove]

I can only suggest flipping when in standby mode and seeing if that makes a difference.
Certainly the LSC can blow fuses when flipping from tweed to full power but I have not had a problem when changing between silicon diode rectifier and tube rectifier tracking or from 50 to 100 W.

Felix - Thanks! I may clean out the tube sockets with De-Oxit 5. I've pulled the chassis and everything "visually" looks good but I may have an arcing tube socket. I noticed a faint look of "black" on one of the power tube sockets.

 

[lonestarlove]

Anyone ever experienced blowing fuse dispute to arcing in a bad tube socket?

 

[roundaboutmusic]

Funny - I've just had my LSS repaired for a similar problem. Is yours oscillating at the 30W setiing before blowing a fuse (low frequency oscillation sounds like a motorboat)? That's what was going on with mine... so I took it in to the authorised repairer.

Turns out it was a manufacturing fault. Someone at the MESA factory had not only put in the wrong resistor in the power section, but they'd not grounded it either (as per the schematic). Cost me a fair bit to get fixed I'm out of warranty and hoping MESA/Boogie will help me out a bit, given that the problem was there right from the start.

 

[lonestarlove]

Actually, I retubed mine with all new 6V6 tubes / 5U4 Rectifier and it runs fine and sounds better than ever! I've tried 100W setting and Silicone Diodes and no more problems.