One reason never to run a tube amp without a load. I'm not saying that was the reason in this case, but HV can punch through the insulation and ruin an "unobtainium" part.
If all else fails, there's a specialty transformer fabrication guy near Wilmington, DE, whom I've used a few times for modulation enhancement circuitry on public service UHF (Lo) repeater system repairs. Two year warranty, no problems since '82.
Hammond might make one that would work but not mount without drilling more holes in the chassis. And you'd need to do both channels to match. So maybe finding one off a parts unit would be the way to go
When you go back into this unit could you go into detail with the schematic and oscilloscope setup on doing the phase inverters for the push-pull output? Thanks!!
@@JordanPier Thanks for the reply. I've got my OT torn apart but I'm doubtful I'll be able to repair it. If you find it and want to sell I would be grateful. I thought there was a way to DM here but I'm not seeing it now.
hi john..were you testing chan ( L ) then chan ( R ) the latter being the good 1/2 of the primary winding?. i have dlx rev reissue that *seems to play fine till I up the vol/ hit chord hard /and aft it is on for a few minutes . looking for insight on how to spot a "going bad" OT.
Try taking the end bells off and boiling the trans in wax for a few hours. The Wax wil penetrate the windings and insulate against shorts, at least on the first few layers.
That was a fun diagnosis, well done! When it comes to replacing output trans in hi fi gear, I'll only use an exact replacement, or in lieu of that, a new matched pair. Hi fi has enough bandwidth that you can hear the difference in sound between channels that mismatched transformers can cause
Like a zenith vertical output Transformer
One reason never to run a tube amp without a load. I'm not saying that was the reason in this case, but HV can punch through the insulation and ruin an "unobtainium" part.
And the search begins! Tough one for sure , would be nice to see the amp up and running again
If all else fails, there's a specialty transformer fabrication guy near Wilmington, DE, whom I've used a few times for modulation enhancement circuitry on public service UHF (Lo) repeater system repairs. Two year warranty, no problems since '82.
Did you consider removing the electrolytic caps next to the transformers and placing axials down below in their place to make room?
Hammond might make one that would work but not mount without drilling more holes in the chassis. And you'd need to do both channels to match. So maybe finding one off a parts unit would be the way to go
When you go back into this unit could you go into detail with the schematic and oscilloscope setup on doing the phase inverters for the push-pull output? Thanks!!
Did you manage to score an exact replacement, or did you end up re-spacing/drilling some holes to accommodate something else?
Got the right thing,will do a video when I get time to put it in
Nice video. You don’t still have that OT for 500-c do you? Mine failed and looking to buy one.
I may still have it.
@@JordanPier Thanks for the reply. I've got my OT torn apart but I'm doubtful I'll be able to repair it. If you find it and want to sell I would be grateful. I thought there was a way to DM here but I'm not seeing it now.
Maybe you can find a transformer in a junk low cost jukebox amp. AMI /Rowe used 7868s in quite a few of their products. Good luck finding one, Jordan.
Is that possible to make a new winding for that old transformer? Why is not feasible be refurbishing it?
Doesn't Blueglow Electronics have a line on this xformer?
This amp/receiver is a classic and has value if put back into service - IMO . . .
hi john..were you testing chan ( L ) then chan ( R ) the latter being the good 1/2 of the primary winding?. i have dlx rev reissue that *seems to play fine till I up the vol/ hit chord hard /and aft it is on for a few minutes . looking for insight on how to spot a "going bad" OT.
Try taking the end bells off and boiling the trans in wax for a few hours. The Wax wil penetrate the windings and insulate against shorts, at least on the first few layers.
That was a fun diagnosis, well done! When it comes to replacing output trans in hi fi gear, I'll only use an exact replacement, or in lieu of that, a new matched pair. Hi fi has enough bandwidth that you can hear the difference in sound between channels that mismatched transformers can cause
Several 400 output transformers on eBay now.
Thanks! I bought one. Will make a video when I do the swap
@@JordanPier Glad to help. I'm a huge Fisher tube gear fan. Can't wait to see it.
Sad story. I have a KX200 with same outputs. You seem to be an OK cat BUT you will have to
pry that xformer out of my cold dead hands......
LFOD !
FISHER MC 4050 output transformer. CAN U HELP
Doesn't have an output transformer
HAY JORDAN DOO U HAVE ANY IDEAL ON THE MC 4050 STELPS ON THE POWER TRANSFORMER THANKS HOPE YOU AND FAMILY ARE WAIL
@@tntreviews3602 if lights out check for blown fuse inside. Likely overload from shorted part or amplifier STK module.
@@JordanPier Thanks. The transformer tested bad on one output.
thanks i tested the windings and one was no out put who rewinds transformer.