1957 RCA 14" model 14-S-7070 TV set

This is not a TV forum, per se. Stereo Theaters, Home Theaters and other three-in-one combination console instruments contain a TV chassis. We can discuss them here, along with stand-alone TV set issues you may care to share.
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electra225
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1957 RCA 14" model 14-S-7070 TV set

Post: # 22007Post electra225 »

This was my parents' TV set. I remember watching Gunsmoke on this set. I remember it having a great picture, but also having really awful sound quality. I lived with my grandparents. Their RCA console TV had two 12" speakers and P-P audio and had really good sound. This new RCA TV was considered to have a huge screen, as my grandparent's RCA console only had a 10" screen. My parents got a new TV when the wife and I got married, and we inherited this old RCA. We used it until 1971 when we bought our first color RCA TV set. This old set went to the bedroom first, then the wife's sewing room, then the garage, then abandonment and storage after that. The wife thinks it may have been 40 years since it was in regular use. Like other items we still have, it just never got thrown away.

I am digging thru items I don't use much. I decided to see if this thing would be worth putting time into to get it running reliably again. The model number sticker is partially missing. I think it is a model 14-1075 with some letters in there someplace, but don't quote me on that even. The chassis is a KCS 102F. It has a 14" 14RP4-A picture tube, 14 tubes, transformer power supply and a chintzy "clock radio" 4" speaker. This set is one of those you have to pull the picture tube and chassis out the front of the cabinet. I'm told they are a pain to work on. This one is in fairly nice condition considering it has been largely abandoned for 40 years. I tested the picture tube. Cutoff and emission are both excellent, about like a new tube. It is date coded the 46th week of 1956, so that would make it a 1957 model, consistant with family memories. The story goes it was bought new from Cousin Calvin the RCA dealer right after my sister was born in January of 1957. The tubes I removed and tested were all white-letter RCA with the exception of the 6AX4 damper tube, which is a Raytheon. I don't remember whether red letter tubes or white letter tubes are the replacements. All the ones I removed had white letters some of which were pretty faint. The only date codes on tubes I could read was on the 6AQ5 vertical output tube which was the 43rd week of 1960, so there has been some service performed over the years. I'll need to remove the chassis to check for "fuzz" before I can make a determination of the approximate hours on this set. I'd say it got a lot of use, but there is little tungsten boil-off in the tubes. From what I can tell at this point, it should be worth rebuilding and maybe enjoying a bit going forward.
100_1025.JPG
100_1026.JPG
100_1027.JPG
100_1028.JPG
100_1030.JPG
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Re: 1957 RCA 14" unknown model TV set

Post: # 22034Post Hi-Fi-Mogul »

Do you need the schematic ?

It's in Sams 354-16, and production change 367-1.

Model:

https://www.radiomuseum.org/r/rca_14s7070g_kcs102f.html
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Re: 1957 RCA 14" unknown model TV set

Post: # 22044Post electra225 »

I do. Thank you so much, Mr. Mogul. That will be a big help. :D :D
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22096Post electra225 »

Now that I have a good schematic, and I have the little RCA 45 changer done, this task is next. Tomorrow is Western Red day, and it is supposed to be 118 in the shade here tomorrow, so this will make a good project for the day.

The service instructions say to remove the knobs, remove the trim around the front of the picture tube, then tip the whole thing up on its end with the picture tube down, take out some screws, then pull the cabinet up off the guts. We'll see how that works. I think I'll run the resistance chart, then shotgun the caps and resistors.
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22135Post electra225 »

I have the chassis out of the cabinet. Really not a bad procedure. You set the TV on the face of the picture tube, remove three screws, then pull the cabinet toward the back of the set, up and off the guts. The cover on the yoke is pretty "breakdownable", so I'll have to work on the chassis without removing it from the picture tube. The guys on ARF say this is impossible, so I am probably on the right track. I'll get a baseline, then dig into it. I'll try to post some pictures, then see if I can shut down the forum doing it like I did on Saturday.....
100_1041.JPG
100_1043.JPG
100_1045.JPG
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22148Post electra225 »

Good news and bad news with this TV. The good news is that I powered it up real slow, using the dimbulb and Kill-a-Watt. It took about an hour, but it seemed like the filter cap reformed okay. I had audio, the tuner worked, the vertical ran, the horizontal oscillator ran. It pulled 94 watts from the line at 118 volts input voltage. Now the bad news. One half of the high voltage winding in the power transformer is open. I have 275 volts on one plate on the rectifier, nothing on the other. B+ is 230 volts, which will let the front end of the set work. When I populate the vertical output tube, B+ drops to 204 volts. If I populate the damper and horizontal output tubes, B+ will be too low for the set to work right. This thing is officially a parts set. It has lots of known good parts and a strong CRT.
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22150Post William »

That is too bad. Is it possible to locate a PT for it?

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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22151Post electra225 »

I'm in that process now. I'll contact Moyers and see what they have to say. I also want to source a yoke just in case. This TV basically works. I have a raster, a bright "jug" (picture tube), horizontal and vertical deflection that is stable. I can have Don hot rod the case, paint it two colors maybe. The cover on the yoke is really delicate. I was going to can it until I remembered all you went thru with your Imperial. The TV guys seem to think I need a test picture tube to get this to work, I don't have that, so I'm going to have to improvise.

Initial start-up
100_1046.JPG
It's an image from the 1077B. Not much of an image, but it is there and it's stable at only 140 volts B+
100_1049.JPG
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22156Post electra225 »

Since I can't get a conversation started about this set on my own forum, the guys on ARF have advised that the power transformer may not be bad. The suggestion has been offered that I recap the power supply and the deflection circuits, then see what I have. The suggestion has been made that perhaps a poor connection to test equipment is the cause of no voltage on one plate, pin 6 of the rectifier. I have consulted the service documents, then made a list of all the resistors and capacitors in the vertical and horizontal deflection circuits, including the horizontal oscillator circuit. There are several 5% resistors in these circuits, so I think I'll hold everything to 5%.
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22157Post electra225 »

I got three or four hours in on this set today. I ran the resistance chart, checked all the resistors, recapped the sweep sections. I need three caps that I don't have the correct value for. I hesitate to substitute values particularly in the vertical sweep section. My next step is to power up and see what I've got. I need to figure out a way to get a bit more room to replace caps without removing the picture tube. Then I need to order parts and go from there.
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22158Post William »

You are making progress one step at a time and hopefully the PT will be just fine. Will you eventually recap the whole set?

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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22159Post electra225 »

Yes. The TV guys recommend, after you get a baseline, to start with recapping the power supply first, then recap the sweep section, the vertical and horizontal sweep sections. These are the areas that the capacitors are most likely to fail, and they are the areas that component value and condition are most critical. And they are the areas where component failure is most likely to lead to the breakdown of the major components, such as transformers and coils. It is recommended that you do one section at a time, then check performance. The theory is that this gives you a better chance at troubleshooting if you have made a mistake.
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Re: 1957 RCA 14" model 14-S-7070 TV set

Post: # 22160Post electra225 »

I don't care what the "experts" say, this thing needs a power transformer. Spec on B+ is 255 volts, I have 168 volts B+ after the high voltage comes up and the picture tube lights. I don't have the tuner cleaned yet, nor have I completed the recap, but the image on the screen is bizarre. This set will never work right with only half the power transformer working, only half the rectifier working. I'll continue with the recap and check after each section, but it's not going to work right with such low B+. It is almost 100 volts below spec....
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