View Single Post
Old 03-09-2015, 01:34 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 9,991
Originally Posted by Zenith6S321 View Post
Very promising indeed! Looks like it has a cloverleaf from a newer model. That's one less headache. Hope its an easy restore.

It don't look like any Zenith convergence clovers I've seen, and the integral purity rings are an interesting feature that I don't think I've seen before anywhere. There seem to be two adjusters per petal present, the black knob appears to be static convergence, but I wonder what the white lever is for....To lock the static convergence knob maybe? The electrical tape splices midway along the leads seem to typify the old repairs I've been finding so far....

Among those old shoddy repairs were replacing the dial light with the wrong type and leaving the metal shroud to bounce around inside the set, dealing with bad fuses by bypassing them, or replacing them with parts that are not of the correct speck.

I think I may have fixed the vertical problems (shrunken bottom, poor linearity, only synched at half frequency) it had by replacing all the bees in that circuit (the others tested fine on my heath C-3)....

....I say may have fixed because it did not let me get full confirmation. I popped the chassis back in, and powered it up to a blank raster that filled the screen and seemed to not be flickering at 30Hz as before so it is looking better. I think the tuner may not have been getting power. I found some bad warning signs elsewhere in the chassis while repairing the vertical, and as I was trying to fix the lack of signal those signs, and the slap shot repairs came home to roost....The PS section has submitted it's formal resignation.
While I was troubleshooting the no RF signal issue I was treated to a 3DG4 light show, and the line fuse blew a fraction of a second before I got to the power switch....The line fuse was supposed to be a 7Amp fuse, but low and behold a 10A was in there, and they even noted that by writing on the chassis.

It would appear this set has had a history of power supply problems. On top of the badly replaced horizontal and line fuses one of the heater fusible links opened and was crudely bypassed. The 10A line fuse modification, I'd guess, was the cause of the insulation melting off all the line wiring except the power xformer leads.
I don't know what to do about the wiring going to the power switch. the leads coming out of it's shielded jacket have melted, and I don't know if I should try to strip the jacket farther hoping the lead inside is okay, leave it as is (with most of the exposed damaged part replaced, and the ground shield lead clipped), or steal a similar (non-zip) cord off a newer VCR or DVD player...

The tube that arced had it's mica wafer knocked up and partially off the cage of the tube so I figured that might have caused the arcing, and tried another 3DG4 in it's place, put a new 7A fuse in, and powered it up again....The result: the heaters of all but the 3DG4s lit, and after a moment I wiggled the 3DG4s until one lit, and as soon as it was warmed up it arced and took out my only 7A fuse.

Since then I've started checking/replacing the lytics in hopes that a shorted one is the cause of the rectifier arcing, but frankly I don't know if that is even the right approach to troubleshooting the issue. The last time I had a similar problem (6X5 in an audio gen) over a decade ago it was solved by selling the unit with the problem (which is not a good solution to this)....Does anyone have any clue what would cause a 3DG4 to arc, have any solutions, or any experience with this kind of problem? I suppose I could try to convert it to silicone diodes as a last resort, but I want to at least try to make it work with tubes again.

The back damage I inflicted consists mostly of the mounts for the neck protector cup, and a small crack to the cup its self.

For more chassis pictures, rummaging around here will yield some.
Tom C.

What I want. -->

Reading between the scan lines since the mid 2000's.
Reply With Quote