Hello-

After realizing my CT-100 needs quite a bit of restoration of its own, I decided to work on my 8TS30 to get better experience with a full recap/test/alignment job first. When I first started collecting early TV sets about 1979-80, I was just beginning to learn TV repair (and knew nothing about doing a complete restoration), so I only did the repairs I learned or knew were needed on the sets I did work on, before essentially halting all of the work on my old TVs for 25 years as I followed my still-going career that includes video-display repairs itself. So, despite 30+ years of TV and electronics service work, this one will be my "first" real restoration. Besides plenty of useful experience, I have a good selection of test equipment (often chosen based on what works well at my job), as well as plenty of ideas learned from all of the great people here on Videokarma (and the Antique Radios forum).

I tested the RCA's CRT, and it started almost dead but went into the lower part of the Good scale on my B&K 467 after only a few minutes running in the Clean/Balance mode that boosts the filament voltage, so it is probably good enough to get going, if not plenty bright. It is an RCA 10BP4A from 1950, so it is already a replacement. The chassis also has two 5U4GBs from 1957-58, and a 6BG6GB horizontal output from 1960, so it was kept going at least that long. No obvious problems on the chassis, except a fuse that has had a piece of thick wire-type solder melted to both ends, and a 100 ohm 2 watt resistor that is cracked.

I checked all the tubes and resistors. Three weak tubes, and the 5V4 was replaced with a 5U4. A few resistors too high in value, and of course a chassis full of wax capacitors and bad electrolytics. I had most of the replacements for the wax caps in my kit from Just Radios, picked up the resistors and a few caps locally, and ordered the rest from Digi-Key tonight. I also picked up one tube locally and stole a couple of others from a beat-up 630TS I have as a some-day project here. The fuse is odd; it is in line between one filament connection and another, in this parallel-filament set. Who knows why it would have been added?

I will start the re-capping in the next few days. Here is the "before" picture:

keep posting, I've got one that I should probably get to pretty soon.

I will start the re-capping in the next few days. Here is the "before" picture:
Plenty of elbow room under there. Recapping should be straightforward.

Phil Nelson

I saw another picture of an 8TS30 chassis that had the same fuse, so it must be original. Now, I am going to trace that part of the circuit to figure out why it would be installed there. And, of course, I will replace it with a proper-value fuse.

Phil, I will use your Web site for inspiration! :)

I checked all the tubes and resistors. Three weak tubes, and the 5V4 was replaced with a 5U4. A few resistors too high in value, and of course a chassis full of wax capacitors and bad electrolytics. I had most of the replacements for the wax caps in my kit from Just Radios, picked up the resistors and a few caps locally, and ordered the rest from Digi-Key tonight. I also picked up one tube locally and stole a couple of others from a beat-up 630TS I have as a some-day project here. The fuse is odd; it is in line between one filament connection and another, in this parallel-filament set. Who knows why it would have been added?

I will start the re-capping in the next few days. Here is the "before" picture:

You cannot replace the 5V4 with a 5U4 in this set. The 5V4 is the damper diode and the indirectly heated 5V4 will have the appropriate characterisics for high frequency rectification. The directly heated 5U4 will not. In fact the 5U4 may help destroy your flyback transformer.

The fuse is odd; it is in line between one filament connection and another, in this parallel-filament set. Who knows why it would have been added?


Fuse? To which filaments is it connected?
I do not recall seeing a filament fuse on this set.

The 5U4 was in the socket when I got the set; I have a correct 5V4 that I will install after the chassis work.

The picture with the same fuse I have is from an 8TS30 that Steve Pielock restored and described on the Antique Radios forum. Here is the picture link:

http://i249.photobucket.com/albums/gg227/pielock373/CIMG6905-1.jpg

I hope the flyback has not already been damaged from having that 5U4 in there...

You may be able to extend the leads for the fuse topside so it would be easier to get to.

The fuse is odd; it is in line between one filament connection and another, in this parallel-filament set. Who knows why it would have been added?

I saw another picture of an 8TS30 chassis that had the same fuse, so it must be original. Now, I am going to trace that part of the circuit to figure out why it would be installed there. And, of course, I will replace it with a proper-value fuse.
Oops, a complete brain-fart on my part... The fuse is NOT in the filament wiring at all. It is in the boost circuit off pin 8 of the 5V4 damper. There is a part I have not yet identified nearby that is in the filament wiring, and I confused that part with the fuse.

I cannot believe it was six months ago that I last posted about this set. I did the recapping on and off as time was available, with the electrolytics only "restuffed" minus the can tops for now. Last night, I reinstalled the tubes. My Variac must be buried in my shed, so plan B was to plug the chassis into a Kill-A-Watt device and monitor the current. I fired it up without the rectifier tubes and it drew less than an amp, then I added the 5U4s and it read about 2.7 amps, and I got hiss from the speaker. A bit of adjustment and I had a raster on my 5AXP4! But... Then I saw smoke from near the transformer-oh, no! I saw there is a covered area behind the transformer, and I opened it up and see it has power resistors, covered with dust. I cleaned them and reapplied power, and no more smoke (whew!). Next, I connected a Channel 4 signal from a digital tuner, and I have good sound as well as video, but the horizontal is off-frequency and the hold pot does not change it. Still, I am 95% successful already. I posted some pictures below. First, the "after" recapped chassis, next is the dust-coated resistors, last is the raster on the 5AXP4.

The horizontal frequency problem got fixed simply by adjusting the "Synchrolok" horizontal discriminator control on the back panel, so this set basically came up working on the first try. I do still have a dirty contrast control, though, so maybe another few drips of Deoxit will help.

Way to go, put the 10" tube back in and see what it looks like!

Lookin' good! That cabinet is already in pretty good shape. Looks like you're just about done, apart from touching up the cabinet finish and reinstalling the CRT.

Phil Nelson

Thanks, guys. I found out the "dirty contrast control" is probably something more-I tested it and its action seems good but the IF/video gain fluctuates rapidly most of the time, sometimes showing a high-contrast picture even with the control all the way down, and even shorting its center terminal to the near-ground end does not affect the problem.

The plate voltages on the four video IF tubes are higher than what is on the schematic, and the last one especially changes along with the flickering picture. (I suspect that is a symptom of the problem though, not the cause, but I will need to do more tests.) Just putting the voltmeter probe on them calms the problem down a bit (and reduces the gain as well). This might be a good excuse to test and fire up the B&K 1077B I got a while back from a generous member.

Any suggestions are welcome as well, thanks.

I sure am jealous of youse guys who can do this type of stuff; it is QUITE beyond me.

Nice job on one of my favorite sets :thmbsp:

Thanks, Bob. Sandy, I bet if you were able to put in some time with a few books and then with some test equipment and a soldering iron, you could jump right in and make some sets work well too, especially with all of the great people here on Videokarma to help.

Regarding help... I did get the B&K 1077B hooked up and I verified the RCA's tuner works on every VHF channel the Analyst has (most but not all of the VHF ones). That also verifies that the B&K itself does still work, too. Next, I will try it on the IF and/or video circuits to try to track down this maddening flashing/gain changing problem.

Nice job getting this one going. I wouldn't mind having me one of these older RCA sets someday. They do tend to be a little scarce around here though.

Thanks, Kevin. Today, I got as far as confirming that the flicker/gain problem affects the first three IF stages, which are all connected to the contrast ("Picture") control circuit as is the tuner, and that removing the first and second IF tubes does not stop the problem from affecting the third IF. Then, a horizontal problem appeared that I found is in the B&K 1077B, so I will need to go ahead and recap/test it before further use.

I did some voltage tests and found the +135V line is too high, at +173 volts. That points to a problem with the high-power three-section resistor in the compartment by the power transformer; the 6750-ohm section may be bad. That will be my next check. The video was mostly behaving as I did the tests, and the one time I caught it, the +173V went down to +171, so it may be a separate problem from the voltage issue.

Maybe there is a mica that is intermitantly shorting.
Might be a good idea to check them with an eye type tester.

I don't know how similar this is to the 630TS, but the local oldtimer who aligned my 630TS advised me to replace a few mica coupling caps in the video IF, calling them notorious troublemakers.

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

Tom and Phil-
I will attempt to check those once I fix the 135V problem if the flashing is still there. The 8TS30 has the same chassis as a 630TS. I don't have a cap checker (other than an ESR meter for electrolytics), so I may just do a mass replacement job. The IF coupling caps are the "domino"-type ones. After all the other caps I replaced, a few more won't kill me.

Phil, I will use your Web site for inspiration! :)
If I had actually RE-READ Phil's description of his 630TS restoration, I would have seen references to both of my issues. Phil replaced all of the IF coupling caps right from the start, and he had a bad two-section bleeder resistor. I found out part of the same resistor has been replaced in my 8TS30 already as well. (The replacement can be seen in the second picture in Post #11 earlier in this discussion; it is the brown resistor on an angle between the two horizontal bleeders.) That replacement is 760 ohms, not the required 1360 ohms! Yep, I bet that could cause the 135V problem.

A discussion on the Antique Radio forum here (http://www.antiqueradios.com/forums/viewtopic.php?t=12334) mentions the coupling caps as well, and also the two caps on the AC input pins. So, I have my shopping list: Five 270pF 500V micas, a 1360 ohm 15-20 watt resistor, and two new AC line caps that I think I already have.

Five micas and a 25W resistor installed, and I have a solid, stable picture. Next, I used some Restor-A-Finish on the cabinet and it looks pretty good. The finish is "alligatored", though, and the Howard's did not fix that; maybe if I used 0000 steel wool rather than cheese cloth I could get the extra effect needed. I can see the light at the end of the tunnel, and it is not a fire truck with a burned-out headlight.

Here are some pictures of the 8TS30 reassembled. I had to reposition the focus coil and of course install the ion trap, and all of the controls behave just as they should. The only remaining work is to finish gutting and reattaching the cut-off electrolytic cans, and I need to find a correct channel-selector knob. (The one I am using is from an 8T241; it is similar but not exact.)

Looking good -- nice job! The finish doesn't look bad to me, at least in these photos. I have never minded a little alligatoring, if the color's reasonably even and the surface isn't flaking off.

An experienced refinisher could probably re-flow your alligatored finish smooth again. That goes beyond my skill level. My few attempts at re-flowing ended up looking more like half-hearted stripping.

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