I am at my wits end and its eating me. So I built a new version of my old amp, fancier chassis, better OPTs. And its working great. But I took the old amp (that has been working flawlessly for five years) in to my workspace and thought I wanted to play a little with it. Tube rolling for one. Put some 6n6p in place of e88cc AND somewhere along the way - moving from the living room to my working room (not calling it a workshop, cause it isnt) and putting new tubes in it something has happened. Only one channel is playing. Playing fine, no hum, no hiss and the other channel is just dead. Tubes light up fine on both sides. Anyway, its not that I need the amp anymore but I figured it could be some training to get it running so I have changed the entire PCB (I have several) newly populated, only thing I had to move from the old one was the coupling capacitors. Same thing. Changed the input RCAs. Changed to another set of OPTs. Changed back to the old ones. Same, same, same. One channel is dead AND I have 80v AC in/on? the chassis and I can not see where that is coming from. I just cant understand. Anybody get any ideas what I should check. BTW I do not have any fancy instruments. Only a universal meter.
First you must resolve the very dangerous AC voltage on the chassis.
Until this is fixed, do not attempt any other repairs.
Post some photos and the schematic.
Until this is fixed, do not attempt any other repairs.
Post some photos and the schematic.
Try to check (without mains) that in amp (mains switch ON) between mains Live and Neutral and protective Earth no continuity (the Ohm meter indicates infinite, or at least few MOhm).
Have you check your work room AC outlet to see if it is connected properly? Power to power, Neutral to Neutral and ground to ground.
AC inlet seems fine BUT I just, since I was measuring continuity found that one speakerjack has contact with the chassis. The insulating bushing LOOKS fine but Ill change it and see.
The schematic is not complete. There is no filament wiring, no transformer primary wiring,
and no indication of a connection between the audio ground and the chassis.
and no indication of a connection between the audio ground and the chassis.
Just check both speakers in your working room are OK. Swap left to right. I once experienced poor audio and it turned out the form of on of the bass speakers was completely loose.
Regards, Gerrit
Regards, Gerrit
Both speakers are OK, I have checked. But as I said the + side of the dead channel has contact with chassis. And filaments are sort of on the schematic. 3.15x2 center-tapped goes to the two e88cc and 6.3 w/ 0 grounded to the 4 el84. there is a star ground point on the PCB and that is the connected to the chassis. ( and a ground on the primary side. ) Im gonna change speaker jack in the morning and see what happends.
Hello from Greece! It is important to check your power transfomer! Maybe you have leak between bobbins of your power transformer,and lamination which is grounded! Your amplifier is grounded or not? Never use electric or electronic device with metal chassis with out properly ground! Safety first!!
OK, so this is spooky. I bypassed the speaker binding posts. I.e. I removed them and connected the cables directly. NOW the other channel is the only one working. ( and yes I know left from right and a did swap speakers back and forth ) Now I dont believe in the supernatural so there has to be an explanation but so far Im at loss for hypotheses. AND still 80VAC on the chassis.
So, it turns out one of the 6n6p is faulty. I figured Ill check by swapping the tubes from one channel to the other, but I figured maybe one of the output tubes. But it one of the others. I do have a couple of tubes more so Ill get it running and check the AC on the chassis again. The grounding should be fine and as I said no AC with the tubes out.