Admiral T2301DR restoration

[bandersen]

Now to get everyone up to speed on where I'm at.

All the wires were very sticky. I saw EM post that this is due to the plasticizer oozing out over the years. Denatured alcohol does a good cleaning it up.


As for the tuner, it's only held on by two screws and floats on rubber grommets. The tuner chassis is grounded via a braided copper strap to the main chassis. I assume they did this to minimize vibration to the mixer / oscillator tube.
I tried using some reproduction grommets I had for vintage radio tuning caps but they were too soft.

A quick trip the hardware store for some harder grommets and washers did the trick.




I did some voltage checks to track down the blurry image and found the HV was about 11 kV instead of 15.5 and the 440 V boost was only 315.

I tried swapping 6DQ6 HO tubes, tweaking the drive control and double checked my work. Nothing helped. Voltages on the 6DQ6 are normal.

Working my way back I found the plate voltage on the horizontal osciallator about 50 low. It also appears the vertical integrator has been replaced and it's resistance is measuring about twice what it should be.

Got frustrated trying to work on that board so just unmounted the darn thing! I'd already clipped out a few mica caps hoping to find a leaky one but they all tested fine.


At least now I can really go to town. That will include replacing the dual selenium phase detector with schottky diodes and building a discrete vertical integrator.