Weird issue with an RCA 730TV2

[Kamakiri]

Well, got the replacement transformer in, and it ohmed out wildly out of spec, something like 50 ohms primary, 750 ohms secondary....so I didn't use it. I did, however, while I was in there, replace a few more out of tolerance resistors along with two other sections of the chassis mounted multi-value resistor (there were three, and only one tested bad....the one I just happened to have handy).

So, for the heck of it, powered the set up and this time only got retrace lines, and a very weak sync of some kind that I was able to lock in....no discernable video.

The weird thing is that when I was powering it up this time, I got what looked like an intermittent blue flashing short within the electron gun of the picture tube that came and went with the adjustment of the ion trap. Every time it shorted, I lost raster.

After the shorts stopped, I left it at a certain point where the picture was really bright and spent about 20 minutes fiddling with adjustments to try and get a picture back. No luck. During that 20 minutes though, the raster was nice and bright, sweep was fine, and the transformer ran cool.

Found a weak 12AX7 video amplifier tube, replaced that, powered the set up, and lost raster

My plan was to trace back the work I'd done on the chassis mounted resistor, but now I've lost raster, so I'm confused. Picture tube tests good still, and I tried a magnetic ion trap just for the heck of it to see if I'd get a picture. Nothing.

I do have good HV though. Hm. Kinda lost as to what might have happened.

[Kamakiri]

Originally Posted by Kamakiri

The weird thing is that when I was powering it up this time, I got what looked like an intermittent blue flashing short within the electron gun of the picture tube that came and went with the adjustment of the ion trap. Every time it shorted, I lost raster.

After the shorts stopped, I left it at a certain point where the picture was really bright and spent about 20 minutes fiddling with adjustments to try and get a picture back. No luck. During that 20 minutes though, the raster was nice and bright, sweep was fine, and the transformer ran cool.

Found a weak 12AX7 video amplifier tube, replaced that, powered the set up, and lost raster

My plan was to trace back the work I'd done on the chassis mounted resistor, but now I've lost raster, so I'm confused. Picture tube tests good still, and I tried a magnetic ion trap just for the heck of it to see if I'd get a picture. Nothing.

I do have good HV though. Hm. Kinda lost as to what might have happened.

Fired up the Eico 944 flyback and yoke tester. Confirmed bad yoke. Welp, at least I know what to do next!

[earlyfilm]

Originally Posted by Kamakiri

Fired up the Eico 944 flyback and yoke tester. Confirmed bad yoke. Welp, at least I know what to do next!

Tim, just double checking before you sink some cash on a new yoke . . .

I'm assuming by "confirmed bad" you mean that the vertical windings check shorted.

I'm not familiar with the Eico tester, but other yoke and flyback testers will read "bad" if one forgets to open the resistor paralleling the winding. The 730 uses a 560 ohms across each vertical winding.

[Kamakiri]

Right, but then I ran into this:

Originally Posted by Kamakiri

The weird thing is that when I was powering it up this time, I got what looked like an intermittent blue flashing short within the electron gun of the picture tube that came and went with the adjustment of the ion trap. Every time it shorted, I lost raster.

After the shorts stopped, I left it at a certain point where the picture was really bright and spent about 20 minutes fiddling with adjustments to try and get a picture back. No luck. During that 20 minutes though, the raster was nice and bright, sweep was fine, and the transformer ran cool.

Found a weak 12AX7 video amplifier tube, replaced that, powered the set up, and lost raster

My plan was to trace back the work I'd done on the chassis mounted resistor, but now I've lost raster, so I'm confused. Picture tube tests good still, and I tried a magnetic ion trap just for the heck of it to see if I'd get a picture. Nothing.

I do have good HV though. Hm. Kinda lost as to what might have happened.