Moderators: pompeiisneaks, Colossal
martin manning wrote:Reservoir cap failure?
I am going to replace to see if it is the reservoir cap. Curious if I disconnect the cap and remeasure power supply voltage if it doesn't drop safe to assume the cap?martin manning wrote:Reservoir cap failure?
Ok strange phenomenon happening. I pull tubes no change in low voltage. I take a chop stick and start to move the ac primary off of on/off switch away from reservoir cap b+ and mechanical buzz of pt is 100 x lower and b+ came up? An hour later the output tube (older worn Mullard metal based EL34s) have internal melt down and take out opt protection fuse. Put new EL34s and protection fuse in voltage is back at the right spot and no issues???? Any possibility the ac being near the b+ reservoir off of standby could cause osc and voltage drop.martin manning wrote:Do you mean disconnecting the lead from the rectifiers? You would have pulsating DC, but you might get some indication that the transformer and rectifiers are ok. What happens if you monitor the voltage with the standby switch in standby? That isolates the PT, rectifiers, bleeders, and reservoir caps (2x 40u). There won't be much current draw (just the bleeders), but it might give you a clue.
I would suspect the switch contacts or the connection of the lead inside the PT.lpd wrote:I take a chop stick and start to move the ac primary off of on/off switch away from reservoir cap b+ and mechanical buzz of pt is 100 x lower and b+ came up?
The tube failure is probably unrelated. I don't think having the primary lead near the B+ would cause oscillation (it played fine previously, right?), but maybe it would add a little 60Hz hum.lpd wrote:An hour later the output tube (older worn Mullard metal based EL34s) have internal melt down and take out opt protection fuse. Put new EL34s and protection fuse in voltage is back at the right spot and no issues???? Any possibility the ac being near the b+ reservoir off of standby could cause osc and voltage drop.
