Anyone familiar with the RCA KCS102 chassis?

[JohnCT]

In my long abandoned pile is a 1957 RCA 14" portable in very nice physical condition. I haven't looked inside yet but did download the schematic from Elektrotanya.

https://elektrotanya.com/rca_14-s-70.../download.html

Model is 14-S-7074

The first thing I checked was to see if it has a power transformer (it does.. nice for a small TV like this) but I am frankly surprised to see it has no AGC system (keyed or otherwise) nor any DC restoration.

I was thinking about restoring this TV at some point, but would only bother if it's a good performer. So my question is that, other things being equal, what kind of picture can I expect out of this little RCA?

John

EDIT: Unless the SAMS is wrong, this TV has no line fuse. IIRC, I plugged this TV in about 20 years ago for S&G and it was stone dead, including no filaments. At that time, I guessed it was just a series string TV with a bad tube. Seeing that it's a power transformer TV, this doesn't bode well unless it's just a bad switch (which feels OK at least). I guess I'll have to pull it apart and check that first. I can't ever recall seeing a TV without a line fuse.

.

[zeno]

RCA used to like using a fuse wire right at the interlock. Be something
like 1" of #24. Personally I would just put a GJV 4 in its place.

Being an RCA it should be a good running set. A GE would be another story !

73 Zeno
LFOD !

[JohnCT]

Originally Posted by zeno

RCA used to like using a fuse wire right at the interlock. Be something
like 1" of #24. Personally I would just put a GJV 4 in its place.

Being an RCA it should be a good running set. A GE would be another story !

73 Zeno
LFOD !

I remember many TVs in the old days used 24 gauge wire underneath but I can't remember seeing them on the interlock. Hopefully it's something like that. I can't imagine a TV being sold with no fuse. SAMS says there's one fuse, and there is one right on the damper, but that's all.

I guess I really should pull it apart.

BTW, how about the leather handles? This TV has the two loops on top but no sign of the leather handle. How does one go about replacing something like that? Thanks.

John

[Eric H]

I have a 7070 and it's a decent performer. Most low end B&W sets lacked DC restoration back then, and yes, it sucks, but that's the way it was. Every 7070 made is missing the Leather Handle, or it's so rotted as to be useless. You could have one made but it'll cost more than the set is worth.

I have quite a few of the RCA models from that time, hard to work on, fussy vertical circuits, but great looking sets with their gold trim, none of them come close to having a picture as good as my cheapo model, series string, 1957 17" Hotpoint (GE). Maybe the RCA's were better for DXing back in the day, but that's not important anymore.

[Electronic M]

DC restoration can be added if you want it...there were articles in 50s electronics magazines on how to do it.

[zeno]

Hint for hidden fuses.
This is more for the beginner. We used to get quite a few cheapo
Jap stereos & other smalls with open primary on power transformers.
After a few years I was working on one & saw a fuse INSIDE the transformer
on the schematic. We found many had one but was almost never in the
schematic or noted inside the rig anywhere. Dont remember any US
made stuff that way but keep it in mind.

BTW almost never changed a transformer after that.

73 Zeno
LFOD !

[dieseljeep]

Originally Posted by JohnCT

I remember many TVs in the old days used 24 gauge wire underneath but I can't remember seeing them on the interlock. Hopefully it's something like that. I can't imagine a TV being sold with no fuse. SAMS says there's one fuse, and there is one right on the damper, but that's all.

I guess I really should pull it apart.

BTW, how about the leather handles? This TV has the two loops on top but no sign of the leather handle. How does one go about replacing something like that? Thanks.

John

Regarding the leather handle, the set is so heavy, it's little wonder that a dried out handle would survive.
Maybe a thrift store belt would be suitable. Cut it to length and punch holes for the buckle.

[JohnCT]

Originally Posted by zeno

Hint for hidden fuses.
This is more for the beginner. We used to get quite a few cheapo
Jap stereos & other smalls with open primary on power transformers.
After a few years I was working on one & saw a fuse INSIDE the transformer
on the schematic. We found many had one but was almost never in the
schematic or noted inside the rig anywhere. Dont remember any US
made stuff that way but keep it in mind.

BTW almost never changed a transformer after that.

73 Zeno
LFOD !

Very common on the Japanese stereos. Here's a hint for those who haven't seen this: the primary will read open, and if you look at where the AC input is on the XFR, you will see a third terminal unoccupied. This is generally the tie point for the internal fuse, which is **thermal in nature. Jumping the center terminal to the appropriate AC terminal would restore operation.

For our personal stuff, we used to just jump them out. Never saw a single incident where a short in the stereo blew the fuse, and never saw a bad transformer either. My guess is that they would just fail from many thermal cycles over the years.

**Regarding the thermal fuse, it may have been a Japanese certification requirement. It's hard to imagine a scenario where a short or incorrect load in the stereo would cause overheating of the transformer to the point of being a fire hazard and yet not blowing either the secondary or AC input fuse. Maybe it was required in Japan for anything with a socketed fuse that might be intentionally jumped out (?).

John

[old_coot88]

Originally Posted by zeno

Hint for hidden fuses.
This is more for the beginner. We used to get quite a few cheapo
Jap stereos & other smalls with open primary on power transformers.
After a few years I was working on one & saw a fuse INSIDE the transformer
on the schematic. We found many had one but was almost never in the
schematic or noted inside the rig anywhere. Dont remember any US
made stuff that way but keep it in mind.

73 Zeno
LFOD !

I ran into this once in a Bose wave radio that had remote control, so it was 'on' in standby all the time. One day it was just stone dead. There was no line fuse at all, and the power transformer primary read open. I sed what the heck and opened up the xfmr. on the chance of maybe spotting the open. And the damn fuse was inside(!). Jumpered it, put everything back together and the radio was fine. Just installed a pigtail fuse was all.

[JohnCT]

Originally Posted by old_coot88

Jumpered it, put everything back together and the radio was fine. Just installed a pigtail fuse was all.

If you want to be a hero, you can install a 60C thermal fuse assuming you could get to it. Some are right below the outer plastic wrap and others are buried like potatoes.

If it were mine, I wouldn't have bothered either. A line fuse is a better solution. Must be some sort of underwriter's requirement.

John

[DavGoodlin]

I restored a 14S7072 (red) for a friend of mine. He got the correct stitched handle made for $25 by a local artisan. Those handles appeared to be paper and vinyl originally.

It is a good performer compared to most of the 14" metal sets. I restored a '58 14" Deluxe" - KCS-111 chassis, the series-heater version and it looked similarly good and sharp. Some models had only 2 IF tubes, "super" and "special" models, and were a tad less sharp as a result, still acceptable.

[JohnCT]

Originally Posted by DavGoodlin

Some models had only 2 IF tubes, "super" and "special" models, and were a tad less sharp as a result, still acceptable.

Sadly, this KCS 102 is a 2 IF chassis as well. Between the 2 IFs, no AGC, no DC restoration, I may pass on this one. It's not pretty enough to carry its weight. I may screw around with it at some point - maybe if the tube checks strong perhaps.

Thanks for the advice guys!

John

[DavGoodlin]

They are good projects for beginners. No PC boards and room to easily replace caps.

My 14S7074U has UHF, white cabinet in fine shape but the recap I did 40+ years ago, so it no longer makes HV. It was given by a friend of my Dad's from up State College, where there were few channels to begin with.

Another I got was that gray and missing the trim band, I gave to another collector who had none like this. Had to be one of the last 14" sets with a power transformer. I also have a 14" Hotpoint that is a GE inside. That worked once as well after a "recap"

[JohnCT]

Originally Posted by DavGoodlin

Had to be one of the last 14" sets with a power transformer.

Which is why this is so frustrating! Why would RCA put in a power transformer yet cheap out on the IF and other circuits?

I would prefer it be a series string with 3 IFs, keyed AGC, and DC restoration.

John