Starting work on the Sylvania 7140M
 

This is the set I won at a local auction a month or so ago.

First thing I wanted to do is see how well the CRT held up, it hasn't been tested for a month so after pulling the chassis I hooked it up to the B&K 466, it didn't shoot up immediately to good, it took maybe 10-15 seconds but it ultimately went up to the top of the scale in less than a minute so i'd say it's pretty good!

Next, after removing the CRT from the chassis I wanted to clean off the heavy Cadmium Oxide crud, this stuff is highly irritating and very toxic.
I put down paper towels and sprayed it with cleaner, most of it was so loose and dusty it just rinsed right off, a toothbrush took care of the rest.

I pulled all the tubes and put them in a box to clean and test later.

I had noticed from looking at the schematic that this set used a very unusual set of tubes to rectify the high voltage, something I've never seen before in a set this old, it uses a pair of 5642 rectifier tubes.

I had to look those up because I had no idea what they were, turns out they are very small tubes that are soldered in place on the back of what I think is the flyback, I didn't take it far enough apart to see what that looks like.

I'll take the chassis to work to clean the rest of it off, it's just regular dirt that's left and the chassis seems to be very nice underneath it all.

Wow....Those look like the little "Peanut/Pencil" tubes in a PRC-6 Korean War era walkie-talkie...

I have some 5642 tubes if yours turn out to be weak.

John

I had a Sony portable transistor set that used HV rectifiers like that, I think I still have the tubes somehwere if you need.

I had a Scott table top set using the Philips Protelgram system. Part of it was a hermetically sealed oil filled can containing the high voltage transformer, caps and three tubes in a tripler configuration that looked similar to those tubes although there was no marking on them. There was no HV from the system so I opened it up to find one tube bad. This system was driven by a 1KC oscillator and was noticeably noisy in operation. I used a modern SS tripler to get it working but eventually found an original replacement and got the set back to original form. Wish I still had it….

I believe I have a pair of those 5462 rectifiers as well, pulled from a Tektronix scope.

I finished cleaning the chassis today, the front section was Cadmium plated and severely oxidized, it's terribly toxic and it would come off on my hands every time i touched it, my throat got raw feeling whenever I got near it, (though that may have been mostly my imagination).

I took the entire front section off, it only involved unbolting the tuner and unsoldering a half dozen wires, cleaned it with Rust Remover and painted it with Silver paint. I cleaned the tuner contacts and lubed the tuner shaft.

This process also unavoidably removed the stamped inspection markings and a paper warning label but I took good clear pictures of those and will print them out and glue them on in the same locations.

Add just one more of those tubes and you could go back and buy a brand new CT-100

:thmbsp: So that's where Doc Brown got the idea.

Yeah, well, ya gotta do what ya gotta do...I DETEST a nasty dirty filthy chassis, it just offends my Germanic sense of order...

Ach! Ist nazty durty! Nicht gut!

It looks great and I don't thinks it's your imagination. That old metal oxide dust is very irritating.

Any clue what this does?
 

The tuner on this is odd too.

The smallest shaft seems to be the fine tuning, string driven inside the tuner.
The largest shaft is for the band switch and the middle shaft is for changing the channels, also string driven. It's really just a two speed setup with the fine tuning having a higher "gear" reduction than the channel changer.

My question is what does the lever with the spring do? It seems to just rock back and forth on the outside of the band switch shaft.

I suppose it might be obvious if I dug the knobs out of the inside of the cabinet and put them all on but I'm feeling pretty lazy so I'm just asking.

I'm guessing some kind of stop, but why the spring, which only operates in one direction by the way.

If my rectifier tubes light up like a Flux Capacitor I'd better replace them! :yes:
Anyway this set can only take me back as far as 1950.

1950's as far back as anyone need go!:D

Just don't alter the future for your own personal gain by buying a Grays sports almanac.:nono:

All the cans are re stuffed and about half or slightly more of the paper caps have been replaced.

There are still three small axial Lytics under the chassis to be replaced.
Perhaps later this evening I'll be ready for a test run. :yes:

I found the green corroded leads of a 150 ohm 3w resistor that had completely fallen off, I don't know where the rest of it went, I never saw it when I removed the chassis. :no: It went to one of the Filters so it's probably important, could explain why it was totally non functional.

I finished the recapping tonight and have been working on the set for the last 4 hours.

I complicated matters somewhat by leaving a capacitor unconnected at one end and forgetting to solder the ground wire on one of the stuffed cans but I did finally get a picture on it, not a very good one either.

The HV rectifiers must be weak, the HV drops like a stone when the brightness is turned up, either that or the .001@10k ceramic caps aren't a very good sub for the .0005@10k Sprague paper caps, I would think they should be fine since they are double the value and are just for the doubler circuit.

I went ahead and bought a couple NOS Sylvania 5642's to put in it, they were only $4 each.

The Flyback setup on this set is more than a little bit of a pain in the butt to work on, you have to unbolt the yoke to remove the cage since it's all one piece.

The other problem I noticed is the Phasing is off, I have a picture split right down the middle with the left half on the right side and the right side on the left, oh well, one step at a time.

All these difficulties makes me wonder how they were able to align/set up TVs at the factory. Imagine their having to do this accurately AND quickly. Yikes

I meant to take the Wallace's in to work to scan today but forgot.

I'll look at the schematic when I get home tonight. I think the circuit is similar to my Sylvania and I think it was the tube acting as a variable reactance that had a very small grid leak causing the same problem that you're observing.

Actually in mine there were two causes. I also had an open video IF transformer, but enough signal was leaking through it to give me a distorted picture that looked like only a horizontal problem.

John

Thanks John, the 6BF5 Video output tube is somewhat weak but I just checked it again and it's not all that bad, no shorts either.

I'm getting strong video but there is some horizontal ghosting that moves across the screen when I adjust the Horiz Hold coil, it never quite disappears before the picture loses sync, in either direction.

Otherwise I have a good stable picture, no rolling, no jitters, good sound, just split in two, it's dim though, I attribute that to the low HV which is about 10k with no load but drops as the brightness is brought up, I can see the picture well enough to see whats going on.

I'm poking around checking resistors and voltages today, so far everything looks really good.

I had the same problem on a Sonora I rebuilt, in that case it was the replacement Flyback had the polarity reversed on a winding that affected the pulse that affected the Phasing, I can't remember exactly how it worked but I had to reverse the connections to the winding to fix it.

Someone has replaced or tinkered with the Horiz Size Coil at some time, I could tell because of the spliced wires inside the HV cage.
I don't see how that would really affect it but I mention it just in case.

The .0005 cap C213 seems to be hooked to the wrong side of C211 according to the schematic,, it looked like that was factory wiring however, I tried it on both sides and it doesn't seem to matter much so I put it back like it was.

I'm having some difficulty understanding how the Phasing and Sync are related, i.e. what section should I be looking in to find the problem.

If anyone has any suggestions please chime in, here's a link to the schematic picture kindly provided by John.

http://vintagetvsets.com/schem/sylschem.jpg

I'll have to replace or cover the Yoke wires when I finally do get it working, they are so dry and brittle they kinked and cracked from all the moving around while removing the HV cover numerous times, it looks terrible, couldn't be avoided, just one of those things that happen on 60 year old sets.

Video posted
 

I posted a short video showing what's happening with this set. http://www.youtube.com/watch?v=C9HuJxELL6c

In other news, this set uses one of those integrated circuit type Vertical Integrator things, looks like a large flat Ceramic Disc cap, anyhow the center leg of it is broken completely off the component, I would expect this to only affect the Vertical section since the Sync for the Horiz is taken off immediately before this section.

I can poke the leg back into the hole and it makes a very slight difference in the Vertical but has no apparent affect at all on the Horizontal.
I suppose I'll have to build one of these out of individual parts, it seems to be a very typical Vertical circuit with the 8200 ohm resistors and some small value caps.

It makes so little difference Mad Man Muntz would just cut it out and leave it that way. :D

maybe some noise on the sync pulse out of the sync sep. Try scoping it and see if you get a nice clean series of sync pulses at 15kc.

I've attached the instructions for adjusting the phase and... It's from a different model, but the procedure is the same.

If V17 the 6AU6 has any grid leakage at all you won't be able to make the adjustment work. Most tube testers won't have enough sensitivity for this test and you need to use a leakage tester.

This set doesn't use feedback from the flyback to control the phasing.

John

Uhh, I just realized the numbers are different. Where it says R90 it should be R226, the ringing coil is L63. B1 should be sticking out the back of the set and B3 should be in the same transformer, but on this inside.

Looks like the horizontal oscilator never really locks onto anything, it's just drifting through it's range. Looks exactly like my CTC-7 when I couldn't get the chroma demods to work correctly, the colors would just float by and never settle into a stable picture like it should. I suggest you begin looking at your sync seperator section and if that's working as advetised, see if the sync signal is actually making it to the horizontal section.

You just can't trust a Tube Tester.
 

Good grief John, you nailed it on the first try.

I swapped out V17 with one of the Sound i.f. tubes and the set started working!

I retested that rube and it checks very good, however bumping up the heater a little made the Short light start to flicker a little, after that it stayed on dimly, testing it the first time it just didn't get hot enough to show up the problem.

The second tube was a even little jittery when tapped so I tried another, now it's really solid.
Those same tubes work fine in the Audio section but I'll replace them anyway.

It's been messed with so much I still need to run through that setup procedure but at least it's working, when I get the new HV rectifiers in I'll try it with the 17" tube.

I should have mentioned in my video that i was turning the Oscillator coil back and forth, it would lock, just not where it should.

Sweet :thmbsp: Glad you got it working.

I've been finding more and more that tube testers don't tell the whole story. That includes tubes that test weak but work just fine!

Well it's 4:45am and I couldn't sleep so I thought I'd post a little more on the progress.

Another tube that tube testers really can't tell you much about is the 5U4, both of the ones in this set checked good but weren't really.

They are wired in Parallel in this set so you can pull one out and the set keeps on working, I pulled the first one out and it kept working fine, a little picture shrinkage and the sound dropped a bit but nothing dramatic.

I put the first 5U4 back in and pulled the second, well, a huge difference, the picture shrank and dimmed almost to the point of disappearing!

I scrounged up another tube from another set and tried it, now the picture was stable on either 5U4 but a little better on the replacement tube so I scrounged another one, now it worked well on either tube by itself.

This also increased the High Voltage substantially, it's running 12k with the picture adjusted to normal brightness, it still drops if I crank the brightness way up but I believe it has enough oomph to try the 17" tube in it.

The Horizontal is working pretty well but it still drifts after a while so that it gets a ghosting or fold over creeping in from the left side of the screen after a while, I can adjust it out but it comes back. I still need to run the setup but there may be a resistor drifting a little after it gets hot, I'll poke around more tomorrow and see what I can find, I'll try the big CRT also, I'd like to see how it looks even though it checks good.

Have you verified that the 6AL5 phase detector (discriminator) is good and that it's lighting up? That would be the first thing to verify based on the symptoms you describe. Bill(oc)

The 4.3 ohm resistor in series with the heater for that tube might have shifted value also. But it might be more stable once you go through the setup.

This set is getting on my nerves.

I flipped it up and started checking resistors, nothing really far out so I moved on to heat stressing capacitors.

When I got to C197 on the 6AL5 V16 I could get the Horiz smearing to come and go across the screen as I heated or cooled the Cap, it was a Micamold and I am pretty sure it is Mica, anyhow I swapped it out with something close from a junk chassis, I let it play for a good half hour or more and the problem seemed fixed.

I decided to clean up the mess in the Flyback cage, solder in the 10KV caps correctly and fix the wiring on the width coil.

In the process of fixing the width coil I reversed the polarity on it, I didn't know if that would matter but it seems to matter a lot.

After I put the big CRT back in and fired it up I had several terrible drive lines on the right half of the screen, I was able to adjust them out except one bad one in the dead center of the screen.
I noted that I had to screw the slug nearly all the way out instead of nearly all the way in like it was before I switched the coil around.

Does it make sense that reversing the coil would have this effect? I'm not even 100% sure it's the correct coils ince it's been replaced but I didn't have any serious drive line problems before, there was a little ringing on the left side though.

This picture was taken before I did all that stuff, note the smearing through the picture. Not it doesn't smear but it had a bright lin down the center of the pic and faces distort when the pass through it.

I did a little more in the wee hours.

I took it back apart and reversed the Width coil, I don't think that's why I had the drive lines though.
I found a jumper wire between the lugs of the Flyback that had come loose when I soldered the HV cap in, it was nearly touching so I didn't notice it.

Put it all back together and all is nearly well, I'm still getting a little fold over creeping in on the left side after a while but at least it's not smearing across the entire face of the tube now, I need to rerun the Horiz setup again too.

I'll order some new Mica caps for the sweep section and just replace them all, there's not very many. Also I don't know if I even used the right value, I just clipped the only one that was easy to get from the parts chassis and it must have been close because the Horiz locked right in.

Oh, and i probably jumped the gun on buying some new HV rectifiers, 12kv and plenty bright, doesn't hurt to have some spares of those oddballs though.

Pictures, I'm sure your all familiar with these characters:

And one more thing, what was Sylvania thinking putting the Contrast control on the rear apron next to the Vert H and Vert L controls?

I mean sure it has AGC so the contrast is fairly constant but it would be nice if it was easily adjustable.

As it is the Contrast has little effect on the picture, the AGC on the other hand will go from blank to black.

Oh yeah, I found out that lever I was asking about is the switch for the dial light.

Nice job!

I like how you used "leave it to Beaver" for the screen shots,any minute now that '59 Desoto will be driving past Wally and Beaver as the closing credits roll.

I had a lot of bad micamold capacitors in my '49 set also. Even the ones that were really mica. The other brands were fine.

There's not a lot of difference between your 7140M and my 1-108. The video is DC coupled so the brightness should be quite stable. I would have thought that if anything, they'd put the brightness in the rear and the contrast in front.

I've attached the AGC adjustment for the 7130. I think it should work for your set too, but use pin 5 where it says pin 6.

John

I have a Sparton set at my folk's house with the contrast in back too, I agree it's not the best idea. It's a 21" set, and pretty cheap too. Maybe they were just trying to simplify the controls for users?

I got the Mica Caps from Mouser and installed them, I also went ahead and rewired the width coil circuit to match the schematic.

The set now comes on with the Horizontal locked and stable, no smearing, there's a very slight amount of ringing on the left side, a new damper helped and it's so slight it's not noticeable unless you really look for it on blank scenes.

I forgot to fix that vertical integrator thingy but the set works just fine without it so that can wait until the next time.

I cleaned the safety glass and the genuine simulated woodgrain screen surround and put the chassis back in.

I made and posted a quick video here:
http://vintagetvsets.com/videos/Video%2020%202.flv

I played that video through twice without a hiccup.

I just need to polish the brass covers that go on the small knobs for the Volume control and Channel Selector and glue them back on.

When I try to view the video it opens Adobe Flash Player 9 but does nothing.

John

Congrats :beerchug: It looks pretty darn good to me!


P.S. It played in Windows Media Player fine for me. Maybe you need a newer version of flash ?

It didn't open in any window for me, it just downloaded. When I opened the download it played fine in WMP.