Zenith 5311U / 24MC32 restoration

[bandersen]

Thanks for the tips. It does have a 6BK4C/6EL4A installed

A friend stopped by over the weekend and we organized the basement a little. It's not much of a workbench, but this card table is a start


After getting his Farnsworth radio working, I figured why not take a whack at this Zenith?

Doug said he had tried powering it up and there was no B+. I hooked it up to a Sencore PR57 so we could monitor the current draw and turned it on.

The tubes lit up but no B+. I gave the circuit breaker a couple nudges and viola - power. A few moments later, the tell tale crackle of HV and a raster



That was quickly followed by a lighting show around the CRT anode lead. I moved some wires out of the way and that mostly tamed it.

Now we still have an analog OTA LP NTSC station on channel 6 and it's very handy for testing. Try as we might, we got nothing.
There was some noise and static as we changed channels, but no hint of reception. So I dug into the tuner to swap out the tubes.

While doing so I noticed some bits of wire dangling from what I think is a CRT grounding wire


Anyway, after some cursing I managed to get the two tuner tubes swapped out. The dial lamp is out too, but I'll save that for another day.
Is partially visible in the bottom-right. Is there any easy way to get at it ?


That did the trick! We had great sound, but a horribly out of focus picture. The focus control had no effect.


Seemed like the obvious thing to do was replace the 1V2 focus rectifier. Bam! We had a sharp, bright image, but no color.


A little control adjust took care of that Not bad for basement reception of a low power station using a scrap of wire for an antenna!


The HV arcing happened a few more times while swapping the tubes so I wedged in a gob of HV putty.
That helped a lot but there is still the occasional hiss and whiff of ozone.
Seems to me the HV cup and anode wire are a little on the skimpy side. I'll be replacing them eventually.


All in all not bad for a first power up. Don't recall ever having a set come back to life so well just by replacing a few tubes.