I rescued a CRT in a Tek 502 that was damaged in the same way by very carefully with needle files removing glass from right around the lead. I wrapped another lead around the stub revealed and soldered it. A generous dollop of 5 minute epoxy and then re-extend all the leads to thread through the cap pins and I had a working scope. I did that repair about 28 years ago and the scope has served me well since then.

Give it a try; at this point you really have nothing to lose.

I have a gold volume knob for you if you want it, then you only need one more and the fine tuning, correct?

Yes, I'd love to have that knob :yes: and I do still need the other two.

Thanks so much.

I'm missing some knobs for my other two as well. I'm considering trying to make some replicas using casting resins like these from HobbyCast

If I'm successful, I'd be happy to make some for others in need.

The knob is yours, PM sent.

Knobs
 

I've received zenithfan1's kindly donated volume knob (plus substitute fine tuning). Comparing it to my channel knob makes me think I was wrong about it. Although it looks good and fits fine, it's not quite the same. It's back painted rather than colored plastic.

Yeah, I know they're just knobs but I think the quest to get all originals ones is kinda fun :D

Here's my motley assortment.

Testing donated flyback
 

I recently picked up an Eico 944 flyback and yoke tester so I can finally check the donated flyback. It's good!

Gave myself a little shock too :yikes:

http://www.bobandersen.com/images/7V...%20flyback.jpg

Have you had any success with the lead on that 7JP4? I was giving it some thought, and would think that using a needle-shaped diamond bit in a Dremel might be a good way to whittle enough glass away to solder on a wire. Just thinking, y'know.

Damaged CRT base
 

I had some time while waiting for parts to arrive, so I decided to tackle that damaged 7JP4.

http://www.bobandersen.com/images/7V...01%20-ugly.jpg

I found one lead that was broken off at the glass :tears: It was for the vertical deflection so I can test it as is.
http://www.bobandersen.com/images/7V...eaned%20up.jpg

It's a runner :thmbsp:
http://www.bobandersen.com/images/7V...ary%20test.jpg

I had an old HP CRT from a logic analyzer with burns that's going to be sacrificed for the base. I wrapped it in a blanket and gave it a whack.
http://www.bobandersen.com/images/7V...0-%20donor.jpghttp://www.bobandersen.com/images/7V...0-%20whack.JPGhttp://www.bobandersen.com/images/7V...new socket.jpg

I filed down the glass around the broken lead enough so I could solder a new wire. I had it wrapped in a blanket and wore eye protection. Even so, I was very nervous while working on it.
I then attached long, thin wires to thread through the new base.
http://www.bobandersen.com/images/7V...%20dressed.jpg http://www.bobandersen.com/images/7V...20threaded.jpg

Here goes nothing!
http://www.bobandersen.com/images/7V...%20we%20go.jpg

Success :banana:
http://www.bobandersen.com/images/7V...%20success.JPG http://www.bobandersen.com/images/7V...%20success.JPG

Ha - good timing. It was nerve wracking enough with a needle file. I'd be a mess trying to use a dremel. The glass (flint?) files away pretty easily with just steel.

Excellent job Bob!

Thanks Mark.
BTW that is your 7JP4 on eBay- right? Can't be too many guys in Kenosha with a 7TV5A ;)

Hope you get a bundle for it.

Yep, that's mine. I often wonder how many people in Kenosha have cool tvs. I don't think too many either.

Looks like after over 20 years of service (that's right!) Twenty years, one of the 6KV (that's all I could get back then to replace the tubular) ceramic discs in my Motorola VT71M-A failed. I rescued this set from a pile of garbage around two years before that and the owner of the shop I worked in roared laughing when I told him I was going to get it going. I find once these sets are up and running, they are pretty reliable. I just ordered new 6KV caps for the five in the set. I guess it's about time. It's still fun to have this old set running when cable service is needed and thie rest are hidden away!

I'm finally tackling this TS-18 chassis which is a real mess. I already knew about the missing tubes, HV cage and flyback.

What I didn't expect was wire and component leads to be clipped throughout the set. Some components missing too, but most often just one end is clipped and the part is still hanging in there.

So, I'm starting at V1 and checking every single connection and component in the whole set!

http://www.bobandersen.com/images/7V...tion/08-03.jpg http://www.bobandersen.com/images/7V...tion/08-05.jpg http://www.bobandersen.com/images/7V...tion/08-06.jpg

While doing so, I discovered a 10 MFD capacitor that's not in the schematic. It seems to go from the cathode on V4 to the filament node of V8, V9 & V16 (the CRT).

Any idea what this is for? Does anyone out there with a TS-18 have this cap?

http://www.bobandersen.com/images/7V...tion/08-09.JPG


Thanks!

Argh! I just discovered that one deck of the channel selector switch is broken :pistols:

http://www.bobandersen.com/images/7V...tion/09-02.jpg http://www.bobandersen.com/images/7V...tion/09-03.jpg

I'm not one to give up easily so I stayed up late tonight and repaired that broken switch wafer.

Here's one of my reference photo so I can put it back in properly
http://www.bobandersen.com/images/7V...tion/10-01.jpg


It wasn't too hard to remove, but I'd hate to do it without the benefit of a digital camera.
Repairmen must have had great memories back in the day
http://www.bobandersen.com/images/7V...tion/10-02.jpg


The offending deck is on the right. The phenolic wafer snapped in two locations.
http://www.bobandersen.com/images/7V...tion/10-07.jpg


The tip of the fine-tuning shaft has also broken off :tears:
http://www.bobandersen.com/images/7V...tion/10-08.jpg


I used a couple drops of super-glue to hold the pieces together. Then, some quick set epoxy for strength. I used a toothpick to apply it to avoid getting any on the contacts.
http://www.bobandersen.com/images/7V...tion/10-09.jpg


Finally, I used a little contact cleaner on those silver contacts. Seems good as new. Time will tell.

I'll deal with that fine tuning shaft later. It can be removed fairly easily even when it's back in the set.
http://www.bobandersen.com/images/7V...tion/10-10.jpg

Thanks Mark. I've decided that I'm going to reuse, repair, refurbish parts whenever possible rather than cannibalize another set. I think I'll draw the line at attempting to rewinding a flyback or yoke :D

Did you see my earlier post about that odd 10mfd capacitor?
Does your TS-18 have it? Unless someone can confirm it does something useful, I'm going to follow the schematic and remove it.

Here's a better picture of the capacitor in question. The green wire on the + side is soldered to pins 2 and 7 of V4. The negative goes to the 0.005uF and the CRT filament wire (the yellow wire at the top).

I'll just leave it out for now. Once the set is operational, maybe I'll clip it in to see what effect, if any, it has.

http://www.bobandersen.com/images/7V...tion/11-01.jpg

Hey John and Mark :wave: I hate to bug ya, but I'm a little confused again!

One lead to my Brightness control is going nowhere :tears:
http://www.bobandersen.com/images/7V...tion/12-01.jpg

According to the schematic, one end goes to B++ and the other to the Contrast control.

I don't think that's correct though. That end of my Contrast control is going to ground (pin 6 on the 6SL7GT Vert Sweep Output) and it looks original. From what I can make out from Mark's 7VT5 pictures, his Brightness control is going somewhere around the ballast tube. Maybe to ground as well ?

http://www.bobandersen.com/images/7V...tion/12-02.jpg http://www.bobandersen.com/images/7V...tion/12-03.jpg


I think that schematic might be missing a dot where the vertical line intersects the "ground" horizontal line. (see attachment)

I'm also wondering if that wire from the Video Amp to the Contrast control should be shielded. Isn't that what the dotted line around it means? My lead is just plain old wire.

Any ideas? Thanks!

Thanks for the quick reply and great photos! pin 3 is B++ and the other side looks like it's ground.

My scan came from a Wallace's Telaide 1946-1951 volume one. Who knows where they copied it from. Those dots sure make a difference :yes:

That's some cool looking vintage coax in your set. I'll see what I can scrounge up.

Look how simple that contrast control was in the earlier TS-4 chassis. I think the extra components in the TS-18 are an attempt to suppress the vertical retrace ?

Thanks for the help guys. I've got that control wired up properly now.
I used to not check lower value resistors all that often, but this set has changed my mind. Check out these.

This should be 82 ohms.
http://www.bobandersen.com/images/7V...tion/13-02.jpg

This should be 6.8K.
http://www.bobandersen.com/images/7V...tion/13-04.jpg

Ugh, more ooey, gooey capacitors :yuck: Did they really need to use that much tar?
http://www.bobandersen.com/images/7V...tion/13-01.jpg

Nah, it's not that bad. A little solvent (mineral spirits, lacquer thinner, etc.) will clean them right up :thmbsp:

http://www.bobandersen.com/images/7V...tion/14-01.jpg

The homestretch
 

I'm down to the sweep and HV sections and have a couple more questions for you guys.

The vertical sweep is missing two tubular ceramic capacitors. Here's what they look like from another set.
http://www.bobandersen.com/images/7V...tion/15-01.jpg

One of them had been replaced with a little disc cap and the other is missing entirely.
http://www.bobandersen.com/images/7V...tion/15-02.jpg

Working from the schematic, they don't appear to carry HV DC.
Is there anything special about those caps or can I use modern mica or disc ceramic replacements?





Finally, I need to rebuild the flyback.
http://www.bobandersen.com/images/7V...tion/15-04.jpg

Originally, it used a 1250pF mica cap like this photo from another set.
http://www.bobandersen.com/images/7V...tion/15-05.jpg

I dug up this more modern 1258pF mica cap. I'm not sure if that's close enough or the voltage rating is high enough.
http://www.bobandersen.com/images/7V...tion/15-06.jpg

Here's the schematic.
http://www.bobandersen.com/images/7V...tion/15-08.jpg

Interesting how the cage is now grounded whereas it's floating with a 470K to ground in the older TS-4 chassis.

Unless there's a known problem with the ceramic and Mica capacitors I wouldn't change them.

They are unlikely to go bad in most cases and the values are usually critical.

I agree, but they're missing from this set:(
I'd estimate about 20% of the components including the flyback and cage were missing overall. Seems someone was using this as a parts set :tears:

I dug up an old copy of the ARRL Handbook and determined that the flyback mica from another set is 10% tolerance @500V. So I think my replacement will be OK.

http://www.bobandersen.com/images/7V...-01%20mica.jpg http://www.bobandersen.com/images/7V...-02%20mica.jpg

Marathon session
 

I pulled a marathon session last night and finished replacing components and rebuilding the flyback. I went with 500V mica caps for both the missing flyback cap and the two ceramic tube-type missing from the vertical amp. Here's a little photo diary I made of my progress.

Just how I received it:
http://www.bobandersen.com/images/7V...tion/17-01.jpg

Rebuilt tuner, pulled electrolytics and fixed up RF amp.
http://www.bobandersen.com/images/7V...tion/17-03.jpg

Restored Vertical oscillator and Video amp
http://www.bobandersen.com/images/7V...tion/17-04.jpg

Started on Clipper and rear controls
http://www.bobandersen.com/images/7V...tion/17-05.jpg

Restored audio amp and restuffed and rewired electrolytics
http://www.bobandersen.com/images/7V...tion/17-06.jpg

Finished Clipper and rear controls
http://www.bobandersen.com/images/7V...tion/17-07.jpg

Restored Horizontal amp and started on Vertical amp
http://www.bobandersen.com/images/7V...tion/17-08.jpg

Cleared out HV caps and flyback area
http://www.bobandersen.com/images/7V...tion/17-09.jpg

Finished Vertical amp, replaced resistors and HV capacitors for vertical and horizontal output
http://www.bobandersen.com/images/7V...tion/17-10.jpg

And finally, the flyback. I used some nice 8KV HV wire from the same old HP logic analyzer I salvaged for the CRT socket earlier.
http://www.bobandersen.com/images/7V...tion/17-11.jpg http://www.bobandersen.com/images/7V...tion/17-12.jpg

Yummy vintage parts. Maybe I should put these on eBay :scratch2:
http://www.bobandersen.com/images/7V...tion/17-13.jpg

So does it work ?

Does it work???
 

I did some preliminary test for shorts cold joints etc. Then, I hooked up my variac and isolation transformer. I also plugged into a few test sockets. They make it a lot easier to check voltage without poking around under the chassis. I also stuck a dummy load across the 7JP4 filaments.
http://www.bobandersen.com/images/7V...tion/18-01.jpg http://www.bobandersen.com/images/7V...tion/18-05.jpg

I slowly powered it up and all seemed well. Voltages slowly increased and the tubes started glowing. At full AC input the voltages were in the right ballpark so I shut it down and hooked up a 7VP1 CRT.
A faint raster appears!
http://www.bobandersen.com/images/7V...tion/18-02.jpg

But it's short lived :tears: A friend noticed smoke rising from the set. I hit the power and started investigating. Argh. The main capacitor in the voltage doubler was smoking and bulging. :pity:
http://www.bobandersen.com/images/7V...tion/18-03.jpg

My first thought was the capacitor was in backwards, but it wasn't. It was the diodes. It seems that Motorola had reversed the capacitor and rectifier between the TS-4 and TS-18 chassis. I wired the capacitor by comparison to the original but the diodes by comparing to a TS-4 chassis.
Darn vintage symbols for a selenium rectifier!
http://www.bobandersen.com/images/7V...tion/18-04.jpg

Time to do a little repair!

Ah, that's better. Kinda interesting that a capacitor will work for a while when reversed.
Here it is with the 7VP1
http://www.bobandersen.com/images/7V...tion/19-01.jpg

And with a 7JP4.
http://www.bobandersen.com/images/7V...tion/19-02.jpg

There's a fade from from top to bottom (bottom to top?). Any ideas?

I'm also not getting any audio or video on either a local station on Ch. 6 or from my Blonder Tongue modulator on Ch. 5.

I'll fire up my B&K 1077B TV Analyst tomorrow and start investigating.

Considering how chewed up this set was, I'm quite happy.

Again a big thanks to Steve for the donated flyback and cage. It's working just fine so far :thmbsp:

I spent a few more hours troubleshooting and found an 82 ohm resistor measuring 200 and a bad connection from the audio output tube to B+. That helped a bit. B++ and B+ and right on the money, raster is very stable and bright. However, no video or audio - just a faint hum. Volume control has no effect.

I left all of the old mica and a few mica-mold caps in place. I'm going to start checking those.

Progress update
 

I discovered a missing capacitor in the audio amp. Now the volume control seems to be working. While working on the set, I got a nice jolt from the B++ cap http://www.bobandersen.com/images/smileys/shocking.gif. Always discharge those caps before poking around!

I also fired up my B&B 1077B and feed some RF into the antenna. Nothing on any channels whatsoever.

Next, I fed a composite video signal directly into the 6AU6 video amp. I detected some signs of life and audio. I made some adjustments to the hold and contrast controls. Here's the best I could get. I've got some major vertical linearity problems. Any suggestions?
I hope one of the HV caps hasn't failed. I'm out of them

http://www.bobandersen.com/images/7V...tion/20-01.jpg

So now I know there's something wrong in the RF amp, converter or IF amps. Or maybe my tuner repair wasn't so successful after all.

I'll dig into that later tonight. Gotta watch the Bears game first :D

Again, I have to salute your persistence in this type of project. With so many parts missing, etc., I would easily get discouraged.

Strange that a number of lower-value resistors are so far off spec. I usually don't check those, either, unless some clue points to one.

Phil

Thanks Phil! I think I'm getting close.
I hooked up a scope to the two vertical output plates. One is fine, but the other is clipped.

http://www.bobandersen.com/images/7V...tion/21-01.jpg http://www.bobandersen.com/images/7V...tion/21-02.jpg

I've already swapped out that tube with several other known good ones, so I think I can assume it's OK.

Time to double check all the components in the Vertical Sweep Output circuit.

All the components checked out in the vertical amp which got me thinking about Eric's comment to not replace the ceramic and mica caps.

Since the two ceramic tube capacitors were gone when I got this chassis, I didn't have much choice. I went with some 500V micas - maybe that wasn't right?

So I dug out my unrestored VT73 with a TS-4J chassis and pulled out these two capacitors.
http://www.bobandersen.com/images/7V...tion/22-01.jpg

Here's the resulting picture after some tweaking of the controls.
http://www.bobandersen.com/images/7V...tion/22-02.jpg

Surprising how much of a difference that made! The vertical isn't clipped anymore, but now I've got a "snake" and ghosting. Regardless, it's progress!

Does anyone know what's special about these caps? According to this great site, the 100pF is +/-10% and the 250pF is +/- 20% both with a temp coeff. of -330 ppm/C.

I would have though that 2% mica caps would be even better?

Unfortunately, I need to put these back where I got them, so I'll dig around my old parts and see if I can find something equivalent.

While taking that photo in total darkness, I noticed the 25L6 driving the flyback glowing blue. Should I be concerned?
http://www.bobandersen.com/images/7V...tion/22-03.jpg http://www.bobandersen.com/images/7V...tion/22-04.jpg

"While taking that photo in total darkness, I noticed the 25L6 driving the flyback glowing blue. Should I be concerned?"

To me, the blue glow looks like one would expect from electrons striking the glass of the tube...it is at the internal surface of the glass, right? and not inside the tube structure between the cathode and plate (that, I might take to be an indication of a gassy tube).

Have you tried swapping the caps back one at a time to determine if it is the 100 pf or the 250 pf That is causing the problem?

Incredible job, I would never have attempted to restore a set that is that far gone...Standing ovation from here!:thmbsp:

Thanks! Now that it's actually showing signs of life, it's a lot more fun to work on.

Yes, it's the internal surface of the glass that's glowing. It's the side facing the HV cage. It's a NOS tube, but I suppose it could still be gassy. I'm also wondering if the nearby HV or grounded surface could be affecting it. I'll try swapping it later tonight when it's nice and dark.

Very good point about those caps. I'll try swapping them one at a time. I've got some others to try as well. I did a little thinking while at work today and it occurred to me that the voltage on those caps might very well be exceeding 500v at the peak of the sweep voltage.

Maybe one of them was breaking down and conducting causing the clip with those 500v micas?

Sweet success!!!!
 

At long last, it's actually working http://www.jawaspot.com/smilies/greenwtfbanana.GIF

Here's a really poor quality clip. The battery in my good camera is dead and so am I - it's 4am :drool:

So what was the final problem? Well, I dusted off my B&K 1077 TV Analyst manual and put it to work. I already knew if I injected video at the grid of the video amp, I got a picture. So, I worked my way through the Rf and IF stages. That's one of the great things about the B&K - you can generate RF for most VHF channels and the right IF for older sets. Around 23MHZ in this case.

Here I'm poking around in a functioning set for a comparison.
http://www.bobandersen.com/images/7V...tion/23-01.jpg http://www.bobandersen.com/images/7V...tion/23-02.jpg

Well, no picture at any of those stages, but I could see on the scope that my signal was making it up to the grid of the 3rd IF amp, but no further. That tube was good and I swore I had check the voltages already so I figured the problem must like inside the demodulator box (dotted line).

Interesting to see (at least to me). I've never opened that box before.
http://www.bobandersen.com/images/7V...tion/23-04.jpg

I couldn't find any problems though so I rechecked the 3rf IF amp again. Finally, I discovered a bad 220 ohm resistor to B++. It was open! I replaced it with a cruddy used resistor (can't believe I'm out of decent 220s), powered the set back up and was treated to snow on the screen for the first time. http://www.jawaspot.com/smilies/spin.gif
http://www.bobandersen.com/images/7V...tion/23-03.jpg http://www.bobandersen.com/images/7V...tion/23-05.jpg

Hooked up the B&K and got a decent picture. It might not look like much, but keep in mind that's coming from the antenna input.
http://www.bobandersen.com/images/7V...tion/23-06.jpg

Hooked up a video modulator and got a decent picture. Finally, I tuned in the last OTA station in Chicago on CH. 6. That's what you see in my video.

I'll tackle the hum in the audio tomorrow. Time for bed :boring:

Great job my man! I knew you'd figure it out! Lookin' good!

Thanks Mark :wave:

I've swapped out that 25L6 and the blue glow is gone. I also replaced those ceramic tube caps with some higher rated mica ones.

The video is looking really good now :thmbsp:
http://www.bobandersen.com/images/7V...tion/24-01.jpg

Audio not so much :thumbsdn:

Here's a YouTube clip taken with my good camera. There's a brief clip from a Cubs game so I hope YouTube doesn't pull it!

There's a buzzing that gets really bad when these bright white on the screen. I've had this happen with other sets, but nowhere near this bad. The schematic indicates that shielded cable should be used for the contrast control, but my sets just has plain wire. I'll try putting in some coax and see if that helps tonight.