Sync Problem
 

I was wondering if any one had any ideas about the problem in the video below. I have not yet performed the horizontal alignment procedure on this set. I'm not sure if that would account for the drifting horizontal or not.
http://www.youtube.com/watch?v=WGW0VQr36vA

Hi All;
VTS, Without more information, I can only give suggestions from my book.. In the Sync section, check is Video signal strong enough, or weak tube or check caps and resistors.. In Horizontal Sweep input to AFC, check tubes, caps and resistors.. Horizontal Deflection, check resistor values.. Without knowing what you have checked, and/or replaced.. and knowing what areas you have checked with a scope and compared them to the RCA 630 pictures.. As I have just got my Caps for my power supply, (Tonight) I cannot make any attempt to duplicate your problem on my set at the present.. Once I get the caps put in and have powered my 630 up, and find out what works and what doesn't.. Then I can try to be of more help...
THANK YOU marty

That's a huge ripple in the B+ supply to the sync and horiz. osc areas, caused by a bad filter cap (or caps). Have you replaced any of the electrolytics?
The sync loss appears to "come and go" due to the slight difference between the 60hz powerline frequency and the vertical sweep rate.

You might get more feedback by posting up in the "Early B&W and Projection" forum.

Hi All;
Old Coot, Thank You.. I am trying to be of some help, but as usual, I just don't know enough, nor had any experience.. I want to be able to help as well as ask.. I know that You Old Timers who have been doing this for Years, can spot the trouble a mile away.. That is something I wish I could do.. And I admire Your abilities..
THANK YOU Marty

VTS,

You are in no way ready to start a horizontal alignment on this set until you fix this problem.

You are seeing 60 cycle hum in the picture that is mostly effecting the horizontal sweep.

It maybe in the power, sync, or video sections, or in most any place in the system. If the hum also comes from the speaker, that might be a clue pointing towards the power supply.

If you have not replaced the electrolytics, they are is the most logical suspects, especially in the power supply. (If you suspect a bad electrolytic -- ie, open, not shorted -- jump it with another for test. If it improves the picture that is either part of or the problem.)

I would check all the tubes for heater cathode shorts, as that is also a very likely spot. All tubes should have been checked for shorts prior to the first power up.

A oscilloscope might be a help in narrowing the problem, especially if it is from a wiring error made while recapping.

Also, another possibility is this is that you are picking up a hum between the ground of the B&K and the set you are testing. If your tuner is working, feed the set by hanging 3 foot wire on the RF output of the B&K and picking up the signal "over the air".

Just in case this problem is originating with the B&W analyser, have you tested the set with another analog signal source?

By the way, what is this set? I can see that is an early small roundie, but can't see enough in the video to recognize it.

James.

Of course it is! :sigh: I feel like I should have recognized that :sigh:.

I figured that was the case. I knew enough to know this wasn't a normal state of affairs, just didn't put the puzzle together.

I'd like to use my scope on this one to learn more about how it functions. It sounds like the problem could be coming from a bad electrolytic, a wiring error, or an HK short in a tube. I test every tube in every set I work on as one of my first steps so I will say that is the least likely candidate (of course not impossible though). I have replaced every electrolytic in the set so that is the next possibility, but the most likely would be a wiring error. I can look for a wiring error manually, but if I wanted to use a scope to check wiring error or bad electrolytic how would I do that? Bear in mind I have no formal training in how to use a scope at all, but a great desire to learn.

Since you've replaced all the electrolytics (and verified they're all in correct polarity), i would tend to suspect wiring error at this point. Does the schematic show any of the electrolytics "floating" (ie., not connected directly to chassis ground)?
Is this set the RCA 630ts that was having the low B+ issue?

There are a number of good oscilloscope tutorials on Google. But the problem at hand should be easy enuff to resolve without a scope.

Hi All;
Since I have taken out all my Electrolytics on my 630, I can speak to this.. And the answer is that there are "two" caps that are Isolated from Ground, on top.. C220 and C222 and "two" that are underneath the cabinette.. C221 and C225.. All four of these are not connected to ground, but If I remember correctly there is a Ground connection to one of the caps, for a reverse polarity.. The can is positive (in comparison to the other caps).. I would recheck all wiring against schematic, make a copy of your schematic on another paper(s) and as each wire is checked, draw thru it with a marker, your choice of color.. I prefer yellow markers, but blue also works..
THANK YOU Marty

Hi All;
VTS, I have looked at your old postings, So, I have some questions .. In your Bleeder Resistor -- What did you use or replace the Bad Bleeder or Bleeders with ?? Check, to make sure that not only you have the correct value but also wattage.. and of course wiring.. Your next posting was asking about your power supply/ bleeder voltage.. What did you find there ?? And what did you do to correct that ?? Either one of these issues could possibly be the cause of your current problem.. Retrace your work against your schematic.. and get the Riders/RCA manual for the 630.. It may give you additional insight into something.. Once I get my Caps taken care of, I may be looking at some of the same issues.. As I have a couple of the bleeder resistors to replace as well, just not the same ones as you have.. And a Ton of wires to re-connect to the right/correct place.. Not that it will help, it may not, but I took alot of pictures, while taking each cap out, before and after I removed each wire, until the cap had no wires on them.. Starting with the cap fully wired.. I know I have some wires to replace, as the insulation came off.. Good Luck !!!!
THANK YOU Marty

I tend to think wiring error also, nobody's prefect least of all me :). There are four floating electrolytics and two which are at ground.
This is the 630 with the low B+. I went through section by section and found where it was bogging down and fixed that problem.
I did find some nice tutorials on youtube about scopes. I think I'll keep this set out of the cabinet for a bit after I'm through with her and get some practical experience.

Hi All;
What did you find that was bogging down the power supply ?? You said that you found it, but didn't say what it was..
I would also suggest (If you do not have it already) that you get the Riders/RCA Manual for the 630.. Phil Nelson has a link from his site.. The Riders show where and the path of each of the wires, (Sometimes its hard to follow) but it all seems to be there.. and by following that you can find where each end is connected to.. Check with an ohm meter and mark it on a seperate piece of paper, as done and as wired correctly.. That seperate piece of paper should be a schematic.. Please let us know of your progress and what you did and what you found that was wrong.. It may help the rest of us when we have to go and do the same kind of thing in our sets..
THANK YOU Marty

Um.. if they are at ground, they wouldn't be floating. :D
Just curious, what wuzzit?
Excellent idea. Become reasonably proficient with the scope first, then it can be a useful tool in troubleshooting (such as looking at the waveform of ripple on a B+ line and measuring its amplitude).

Hi All;
Old Coot, I think what He is trying to say, since I have the same set and the same schematics, is that out of the Six Electrolytics, Four are Floating and two are grounded.. Not that two are floating and grounded at the same time..
THANK YOU Marty

Aha! Makes perfect sense now.:yes:

:banana:

This capacitor was the problem. I thought I had gotten all of the caps the first shot around but this one snuck past me.

http://farm9.staticflickr.com/8497/8...1d616099ce.jpg

It was C169 in the schematic below. The picture is rock solid now. Time to move up the chain and improve the picture and sound.

http://farm9.staticflickr.com/8507/8...63d5f0a59f.jpg

I think it must have been a tin whisker. I went though the set section by section removing B+ to one area at a time until I found where it bogged down. The problem area was in the lead to the tuner, however when I re-soldered the lead back in the problem disappeared.

Well sunnuvugun. Was it shorted? Leaky? Congrads on nailing it.
I'm tryin' to figure the mechanism by which it caused the symptom in your vid.

It was not shorted, I don't have a capacitor tester so I don't know if it's leaky. If you figure out how a failure in that part would cause the symptom I had please let me know, I would really like to understand it more.

Hi All;
Congratulations on you Find.. It seems like its the little things that can mess things up.. My best guess, is since the Sync Discr Trans is coupled by this cap to the Horizontal Osc. Control, that this is where the Sync pulse comes in, and so it had trouble keeping the oscilator synced to the sync pulse.. Or maybe to the wrong pulse, like noise instead.. Its just a thought.. More than likely some one like Old Coot could speak better to this and tell you what is happening, alot better than I could.. Good find !!!
THANK YOU Marty

Dang, that's a puzzler for sure:headscrat. In the vid, there was definitely a 60hz component mimicking B+ ripple (hum) from a bad filter cap. But it wasn't that, obviously.
Lacking a cap tester, have you checked the old cap for leakage with an ohmeter? A good cap will show infinite resistance on the highest R range (after a brief charge-up blip).
Any leakage might be a clue to what was going on. If the old cap's good, maybe the problem was a tin whisker. :scratch2:
(This is not a good test for electrolytic caps though, as good ones will always show a small amount of leakage.)

Edit. .. Since one end of C169 goes to the cathode of the 6AC7, if something was allowing 6V AC heater voltage to get onto the cathode, it could certainly cause the problem

It's a mystery for sure. When I went through replacing the caps in the set there was a wiring error in this part of the set. C173 and C169 were reversed. What I hadn't noticed was this red tubular cap was also wired in C169's place. So in essence there were two capacitors in C169's position, I replaced the one I could see (and put them in the correct place) and didn't notice this one hiding until later. The junction of T108A, C172, C173, and C169 was hacked up pretty bad from a previous repair job, lots of leads just clipped off and left in the set waiting to short something else out. There was also a bumble bee cap hiding in that junction (mistake these for resistors sometimes) that tripped me up for a little while.
All part of the fun.
Can't wait to get this one finished and posted up in the B&W section.

Hi All;
VTS1134, I noticed that in my copy of the schematic, that it was slightly different than your copy, on the posting.. Yours showed the cap 169 at .015 all by it self.. Whereas, the one I have has two caps in parallel.. C169 at .015 and C164 at 1200.. It would be interesting to see what various versions of schematics that exists.. And what or in what way they differ.. And also look at the schematic for the 730 and the 8T30 and if there is a 9T30, and see what changes to the basic circuit they made, thru the years.. It may be that they had trouble with that part of the circuit and made more than one fix, since you say that there were numerous wires that had been cut.. and/or parts replaced in that area..
THANK YOU Marty

VTS1134, for the short time you've been doing this stuff starting from zero experience, you're certainly demonstrating an outstanding aptitude for it. Many kudos to you.

:thmbsp:

Thanks Bill. I can't believe how much I still don't know. In the beginning I didn't know how much I didn't know so it didn't seem all that daunting. Now that I have a small bit of knowledge it seems like such a bigger task to restore these gems. I only wish I had more time to devote to it, but sadly there aren't enough hours in the day. I'm even considering volunteering on a few Saturdays a month for a local repair shop just to learn as much as I can first hand, although it would would be radios (no one's silly enough to fix an old TV :)). In a few more years I want to be able to confidently handle every aspect of a television from adjusting a front panel hold control to IF alignment.

I just went back and looked at the Sams version and you're right there are two caps in parallel in that area. That solves the mystery as to why there were two in my set. I still wonder why removing the smaller cap solved my problem.

Hi All;
VTS1134, This Schematic came from my Riders/RCA Service Manual.. I have two different Riders/RCA Schematics.. and then also the Sams.. I have not minutely compared them, section by section..