It followed me home... Philco roundie - Videokarma.org TV - Video

RetroHacker · #1 02-20-2008, 09:25 PM

I bought this set from another AK'er. It kinda worked as it was, but had no color at all, just a purpleish tinted B&W picture. The previous owner tested the tube and said that the CRT is very strong, so it's definitely a problem with the chassis. I did a little work on it today - I removed the chassis and cleaned the considerable amount of dust off it, cleaned the controls, and vacuumed out the cabinet. I replaced a quite obviously bad small electrolytic on the board near the color oscillator circuit (there was a gooey leaked-electrolyte spot on the board, and it's leads were corroded a bit).

Testing again, I had some color. I get a weak red, and plenty of blue - but not even a hint of green. Rear controls don't have any effect on the lack of green. It will be a little while before I have time to go to the library and get a schematic, but at least now it's clean enough inside where I can see the boards.

I don't have a way of testing the tubes in this set, since my tester is too old to have settings for them (Heathkit TC-1). I've already tried swapping around 6GH8A's amongst the positions in the set, as well as the 6BL8's.

This set is really unusual. Not only is it a late Philco roundie, but it is a "backward" chassis - the flyback is on the left. Also, this set has a tuning eye - it's a side view tube, and it's mounted above the channel selector knob.

-Ian

jpdylon · #2 02-20-2008, 10:55 PM

cool set.

Look to the demod circuits you have to put R-Y and B-Y signals together and invert them to get the G-Y. However, if you can't get a white line in the service mode then You could also have an open screen pot or missing voltage. Are the voltages on the CRT all equal, or is the green lacking?

yagosaga · #3 02-21-2008, 02:35 AM

Quote:

Originally Posted by RetroHacker

Testing again, I had some color. I get a weak red, and plenty of blue - but not even a hint of green.

You should have an equal positive voltage (appr. 100 to 350v) at the cathodes of the picture tube, pins 4, 5, and 13.

Grid voltages should be also positive, but appr. 100v lower than the cathode voltages, pins 2, 6, and 12.

Screen grid voltages are between 300 and 800v, see pins 3, 7, and 11.

What are your actual readings?

- Eckhard

mr_fixer · #4 02-21-2008, 04:03 AM

Nice Roundie, I like the magic eye tube. EM84?

#5 02-21-2008, 08:16 AM

Maybe that was the last year before Philco became Philco-Ford.
I guess it's a '67 model?
That tuning tube does make it extra special.
Most of the Philco stuff I have seen has a nicely designed, impressive contol panel.

radiotvnut · #6 02-21-2008, 09:57 AM

I was thinking Ford bought Philco around '61; but, the Philco-Ford name did not appear on their products until the late '60's.

Don Lindsly · #7 02-21-2008, 10:49 AM

Philco formally became part of Ford in Dec 1961. Philco was marketed as a Ford subsidiary for some time and the Ford-Philco brand appeared somewhat later.

That chassis is a Philco design and not to be confused with the earlier RCA look alikes.

*zenithfan1* · #8 02-21-2008, 02:13 PM

Sweet!

oldtvman · #9 02-21-2008, 07:31 PM

That silvery look is classic low emission on the crt. Try adjusting screen cuts offs but if you have a crt tester you'll probably find bad crt.

AndyMack · #10 02-22-2008, 07:04 PM

great looking TV. Philco made some really cool stuff, and it's only the second televison I've seen with a tuning eye.

..and I'm a bit jealous too... since you live only about 20 minutes from me! I wish these sets would follow me home sometime

radiotvnut · #11 02-22-2008, 07:43 PM

Quote:

Originally Posted by oldtvman

That silvery look is classic low emission on the crt. Try adjusting screen cuts offs but if you have a crt tester you'll probably find bad crt.

And don't rejuvenate it with one of those "atomic blast" testers from the '60's! You'll probably do more harm than good. A B&K 467 or higher model number does a far better job than the older ones.

rcaman · #12 02-23-2008, 09:39 AM

i am also thinking a weak crt. steve

RetroHacker · #13 02-23-2008, 10:44 AM

The guy that sold it to me said that he tested the tube on his Sencore tube tester, and that it was strong on all guns. It looks pretty dim, but I'm pretty sure that once I replace the electrolytics and go over the chassis, it should play fine. I'm going to stop by the library to go pick up the schematic today. The chassis number is 17MT80B, Sam's # 885-2. I want to check to see what the screen voltages should be before I check them - my meter will only handle up to 600v, so I need to make sure that they're not going to be in the 800v range...

-Ian

RetroHacker · #14 02-23-2008, 01:42 PM

Well, I got the schematics and did some voltage checks. These are all measured from chassis ground:

Screens:
Pin 3 (Red) - 435v
Pin 7 (Green) - 433v
Pin 11 (Blue) - 435v

Grids:
Pin 2 (Red) - 72v
Pin 6 (Green) - 87v
Pin 12 (Blue) - 80v

Plates:
Pin 4 (Red) - 182v
Pin 5 (Green) - 191v
Pin 13 (Blue) - 181v

So... I'm getting voltage into the tube. All three filaments light. Why no green?

-Ian

Robert Grant · #15 02-23-2008, 01:45 PM

I briefly had a Philco color TV with a tuning eye.

I trashpicked it when I was a teenager. It was not a roundie - used the 25XP22. It had great sound, and presented a beautiful picture for a few seconds - after which the screen went black and a spark gap on a capacitor on the flyback board would spark.

I got the photofact for the set (954), and, after spending all my christmas money on a new flyback and two days installing it, turned on the set and STILL HAD EXACTLY THE SAME PROBLEM!

I haven't done significant work on a color set since. In retrospect, I'm guessing the 25XP22 probably had a short from the HV anode to something closer to ground potential.

I still have two radios that use this miniature horizontal tuning eye tube.

Rob