Philco 49-1240 horizontal (?) problem

[Phil Nelson]

I pulled the damper tube and repeated the flyback test (I also disconnected the HOT plate lead and HV rectifier plate lead as in the previous tests). Same result. It's possible my 1077B is not accurate. I haven't tried this feature before and I don't have any known-good flybacks lying around to check.

I looked again at the 320vdc supply line with the scope. Pulled the vertical output tube and turned brightness down. Same result. The jitters change when I turn the vertical hold control. I used 1x probe both times. The jittering is less pronounced with the vertical output tube absent, but still noticeable.

Capacitors C102 and C104 were previously replaced, along with all other electrolytics and paper caps. I suppose it's possible that one of those two is miswired or defective, although the supply voltages seem about right everywhere that I've checked. I'll keep poking around.

Phil Nelson

[Electronic M]

Phil, you need to pull the octal base(s) on the HV retifier(s) not the top lead. These testers can tell if the fillament is conected to it's single loose winding. To para phrase the manual on my 944....Disconnect the top leads on the HO tube and HV rect unplug and completely remove the HV rect tube form the set, and disconect all other wires going to the fly.....If the fly tests good you can then plug the HV rect into it's socket, and if the fly then tests bad with the HV rect in place then the fillament on the HV rect is good.

some testers (like mine) are sensitive enough to measure the short that the HV fillament causes on it's winding when connected!

[Phil Nelson]

I did pull all three tubes, but I didn't disconnect all wires from the flyback. The 1077B manual doesn't mention pulling tubes at all. It just says connect to the plate leads after pulling them off the HOT and rectifier tubes. Sometimes manuals don't tell the whole story, though.

I will disconnect it tomorrow and try again. Then I can take it apart and look for signs of arcing, maybe dab on some dope if that looks worthwhile.

Phil Nelson

[Phil Nelson]

I removed the flyback and got the same test result. Test lamp illuminated = fail.



This is the original flyback, part #32-8538, same as given in the Philco 49-1240 supplement. The supplement also includes this schematic for the HV output section, showing the two HV rectifiers.



I suddenly remembered that my restored RCA 721TCS chassis is sitting out, while waiting for its cabinet to be refinished. That flyback has no problems and it makes a wonderful picture. The 1077B test also said that flyback was bad (I removed the HOT, rectifier, and damper tubes for the test). Perhaps this tester simply isn't working right.

I cleaned the heck out of the flyback with isopropyl alcohol and examined it closely under strong light. No signs of arcing and I didn't observe any when running the set in total darkness, so corona dope doesn't seem appropriate. For all I know, this flyback is fine.

Phil Nelson

[Phil Nelson]

Tom was right, the funny squiggle disappeared when I cured the baffling horizontal problem.

I finally trekked to the regional library and photocopied all of the material in Rider's, which is quite thorough and encouraged me to investigate things more methodically. Checked voltages in the sweep sections, checked all resistors and replaced a few outliers, replaced a few micas just for fun, scoped all the sweep test points and recorded my waveforms in photos.

So many things looked right on the money, yet the picture was so messed up. Why??

I decided to gather all my scattered notes and mark up a clean copy of the Rider's schematic to show all of my replacements and voltage & resistance readings. Then it jumped out -- the stupid wiring mistake! I should have my soldering license revoked I didn't keep detailed notes, but I think I made the boo-boo early on, before I had realized how far wrong the Sams material is.

Anyhow, the 49-1240 looks and sounds great, and now I can get back on script. The CRT is strong & bright, and the lack of a fine tuner doesn't seem to matter. I honestly hadn't expected much from this E-waste refugee, and I grumbled about the cramped layout along the way, but it performs pretty well.

When I fired up Gone With the Wind to take the customary screen shot of Scarlett O'Hara, my son groaned and demanded that I play something different for a change, so he's responsible for this closeup.

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

P.S. I think teevee was also right in surmising that the ticking sound was the horizontal stopping and starting. It disappeared the minute I fixed the boo-boo.

[old_coot88]

Congrads, Phil. What was/were the details of the booboo?

[cbenham]

Originally Posted by miniman82

I have read that most ringers are so sensitive that the filament winding will cause a false 'bad' reading if the tube is left in, pulling the tubes seems logical.

I had not kept up with this thread until today when I read about the miswire and that the set now works properly.
I have experience in attempting to test these Philco flybacks. It can't be done with any "flyback" tester.

Looking at your photo of the flyback out of the set I see it is constructed with a laminated core rather than a powered iron core which makes all the difference in the world.

The Q is much lower for all flybacks built with laminated cores. I found this out when I had to replace the flyback in the Philco set pictured in my avatar.

Long story short, the Philco flyback was OK, but the HV 500 pf cap would short intermittently when the picture went to a dark scene because the HV would rise and arc inside the cap. Replaced the cap and all is well.

Glad you got your Philco working. It looks great.

Cliff

[bandersen]

Great job Harryhausen never looked so good

I wonder if an EICO 944 flyback tester would work ? They have a specific mode for iron core vs. powdered core.

[Phil Nelson]

Originally Posted by old_coot88

What was/were the details of the booboo?

Next-door terminal syndrome, where you have a bunch of components crammed onto terminal strips. You're replacing a few components in a tightly packed area and then the doorbell rings or the dog knocks over a lamp. When you return, you solder a loose lead to the next-door terminal instead of the correct one.

The chassis is in the cabinet right now, so I can't check, but it was one of the small .1 caps (C511 or C512, probably C512) on the grid of the vertical output tube. The wrong connection tied it to C517, the 560pf cap on a plate of the horizontal AFC/oscillator tube.

Groan. Small wonder the vertical & horizontal signals were tripping over each other.

In hindsight, I should have double-checked my work before looking for fancier causes, but it wasn't completely wasted time, as I always learn something from these debugging sessions. Anything that sends me back to my old TV books is helpful in the long run. And now I'm confident there are no marginal components left in this TV's sweep sections.

Regarding flybacks, it's good to know that different types won't all test the same. My 721TCS also has a laminated core, so my 1077B is probably working after all, as long as I use it for the purpose intended.

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

[old_coot88]

Originally Posted by Phil Nelson

...but it was one of the small .1 caps (C511 or C512, probably C512) on the grid of the vertical output tube. The wrong connection tied it to C517, the 560pf cap on a plate of the horizontal AFC/oscillator tube.

Groan. Small wonder the vertical & horizontal signals were tripping over each other.

Hah. So the horizontal was sorta squegging at the vertical rate, causing that squiggly retrace.

[cbenham]

Originally Posted by bandersen

Great job Harryhausen never looked so good

I wonder if an EICO 944 flyback tester would work ? They have a specific mode for iron core vs. powdered core.

The 944 is the first thing I tested it with. A Heathkit tester didn't test it well either. I removed the flyback from another same model 50T-14XX Philco set that was working and it tested the same as the original in question.
THEN I found the intermittent HV 500 pf cap. It was rated at 10KV so I replaced it with one rated at 15KV. No more troubles and both flybacks worked when put back in their respective sets. It's been three years but as I recall, both flybacks produced a very low reading on the 944.
Cliff

[Phil Nelson]

To complete the story, the cabinet needs a little more work, but the TV performs well and I want to get on to the next project. More details here:

http://antiqueradio.org/Philco49-1240Television.htm

Thanks to all who provided advice, and especially to Eric for providing an audio transformer.

Regards,

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

[compucat]

Wow that is a beautiful TV. Seeing the quality of restorations lately has inspired me to do better on my own projects. I love Philco radios so maybe I will have to get a Philco TV someday.

[kvflyer]

Seeing this thread, I had to check the set that I have. It is a 49-1040. I would guess very similar. I look forward to working on it soon and comparing the outcome. Thanks fore sharing Phil!

Update: I just checked the CRT and it tests good. It is a 10BP4 I believe. It is not on the tube layout.

[Phil Nelson]

Oops, I fixed the link in my previous post. Now it points to the article I wrote about restoring this TV.

Phil Nelson