Philco Predicta Pedestal

[Phil Nelson]

A clean chassis is a happy chassis!

You did the inside of the HV cage too, right? Rubbing alcohol is good for removing any sooty coating from there. Leaves no residue.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[Kevin Kuehn]

That cleaned up really nice!

[Radiotronman]

Thanks. My parts order came in today so I finished replacing all of th caps on the main board. Now the main board is complete and ready to be reinstalled. Time to finish the caps on the rest of the chassis and replace all of the electrolytics.

[Radiotronman]

I got the set completely recapped and have it a fsow power up on a variac. The horizontal has a high pitched whine, and when I adjust the horizontal controls it doesn't get better and you can hear brief arcing from below. What is going on here? I cannot get the whole screen to light up, just strips or opposite sides.

[WISCOJIM]

If you can hear arcing and can't get the whine to go away quickly, you could be destroying your flyback.

[bandersen]

Looks like your yoke may have slipped off the back of the CRT. It could be shorting out.

[Radiotronman]

Bob, good call on the yoke being loose. The clamp screw was very loose and it was sliding on the neck. I tightened up the yoke and got it straight, but my problem still persists. Any other thoughts on what to try next?

[Radiotronman]

I checked the yoke and took off the black cover, hoping to find a snapped off lead or something, but everything like old ok. There was a couple cold folder joints where the ceramic capacitor is, so I touched those up.

[DaveWM]

this is with just a raster, no signal correct?
I would scope the video lead to the CRT cathode/Grid look for a horz rate blanking signal.

next I would look a the boost voltage filter cap, make sure you have the right value and its not open, scope the boost voltage (use a 10x prob), see if its clean at the screen grid of the CRT. I don't have that model but my predicta show boost 400v at the CRT screen grid, and uses reduced boost voltage to control the brightness, if you don't have well filtered boost there perhaps that could be an issue.

something is blanking a the horz rate, it has to be the grid/cathode/screen of the CRT. should be easy to locate if you look there.

[Radiotronman]

Ok,

I'll give that a try. I've been busy at work and haven't had much time to get back to it.

[Radiotronman]

I haven't got s chance to dig out my oscilloscope, but I did take find voltage checks.

CRT
Pin 2-6 (420v) I get 470
Pin 7 (35v) I get 69v
Pin 4 (0) I get 0

6CG7 horiz mult
Pin 1 (175v) I get 190v
Pin 7 (-15v) I get -10v
Pin 6 (175v) I get 155v
Pin 8 (6.5v) I get 6-7v

My boost voltage is supposed to be 435v and is 460v

9BR7 horiz AFC/sync
Pin 8 (3.5v) I get 2v
Pin 7 (-0.5v) I get 0v
Pin 1 (55v) I get 59v
Pin 2 (-2v) I get -3v

I'm not trained in electronics but enjoy this hobby and know the basics. Do these readings throw up any flags to any of you guys? Maybe a couplate causing these issues? I've checked all of the resistors and caps I put in and do not see any errors.

Thanks
Scott

[Radiotronman]

The brightness and contrast also seem to have no effect. I also tried hooking up a DVD player to see if any video got through and it also had no effect.

[Radiotronman]

Bandersen suggested that maybe the CRT, which filters the hv, may not be grounded properly. That got me thinking, why not try the CRT that works in my holiday. It's a 6.3v CRT, but should work anyway. I hooked it and it has a full raster! So what's going on with my CRT that came with it? Anyway, I hooked up video and see some signs of life, but no images yet...

[Electronic M]

Was it JUST the CRT or the CRT and yoke you switched? If the yoke got swapped too I'd suspect that.

[Radiotronman]

Both got swapped, so I don't know what's wrong with it yet.