RCA "Deluxe" Portable KCS-111D
 

Hi Guys, I'm getting ready to recap the video board if my $15 portable RCA. I've recapped several radios and a few TVs (love the early B&Ws) but I've not seen this particular cap before. The 1958 documentation I can find describes the capacitors as "paper" so I think I need to replace them but because I don't want to put more into this TV than I have to, I thought I'd ask you guys.

So... what do you think? Rev up the soldering iron and weed out the bad boys?

Thanks in advance, Scott

The maroon drops are marginal. In some sets they are all still perfect, and in others something like 1/3 are failing. I tend to give them the "innocent till proven guilty" treatment.

The black tubes are paper dielectric junk, definitely change them.

Same with the obvious paper you plan to change.

Change them all, that set is too hard to take apart to do it over. Those are all replaceable with the modern Poly caps.

There are some odd values in the vertical circuit and they are somewhat critical, also check the resistors for out of spec. Vertical has always been the hardest thing to get right on these for me.

Thanks Tom C. & Eric H.,

I really appreciate your comments. You are right, that board is too hard to access so I'm only going to do it once and replace the lot. Oh, and any resistors that have drifted is a given.

Hey Eric, I am curious about your odd values comment. I re-reviewed the cap tolerances and found what I think are your devices of concern. There are some .027, .033 & .056 paper caps between the vert osc and vert out sections that are 5% devices. Are these the values of caps that fall into your thinking?

Thanks again guys, Scott

Success!
 

Well... I end up replacing all the caps because only three tested within tolerance. Only one resistor was out of spec and even thought it’s a pain in the you know what to get to the foil side of the circuit board, I’m glad I did because now the TV works really well.

Thanks again guys!

Yes, .033 is a common value, but the other two are not.

The vertical height & linearity is so critical on these sets to start with it's best to use exact values.

Oops!
 

Hello again,

I think I spoke too soon. I got so excited with a stable and clear picture that I didn't notice that the width was way too wide. I attempted to adjust it but then I noticed that the B+ voltage was higher than expected (330 vs 275V) which drove the picture tube horizontal voltage too high (550 vs 480V).

My line voltage is 124VAC. I know that is higher than the designers expected in 1958 (110-120 is spec). I also replaced the selenium rectifiers with silicon diodes which added to the increased output. There's not much I can do about those two things but I am considering adding a power resistor in series with the B+ output to lower the voltage. Is that a good idea?

I am assuming that lowering the B+ will work because when I use an autotransformer to lower line voltage, I can get B+ and picture tube drive into the normal range at 100-112 VAC. That seems a bit low for the parallel heater string so I was thinking I could add a series diode to the heater string which will lower that string voltage but I am uncertain about how to adjust the B+ voltage.

Once again I am asking you guys for your thoughts.

Thanks in advance, Scott

Ok. After replacing the selenium rectifiers with silicon diodes, I used a 33 ohm 25 watt resistor to get the B+ voltage right at 275VDC when line voltage is 124VAC. The resistor is added right after the rectifier diodes and before the filter caps. It drops 12 watts and it is chassis mounted to help heat dissipation. I used a 50 ohm, 20 watt ceramic resistor and replaced the existing 18 ohm dropping resistor in the heater string. It drops 9 watts of power making the heater string right at recommended value of 103VAC.

Now that I’ve got that sorted, I need to figure out why the horizontal is too wide and the high voltage is too low (~10k). I’m pretty sure the 17DQ6A horizontal output tube or the 17AX4GT damper tube (or both) are just tired so I’ll just do some swapping to see if I can improve it. If not, I’ve got a good picture and I’ve got a case to clean and paint.

What do you guys think?

These were inexpensive sets back in the day, some overscan was not uncommon and most did not have a way to adjust the horizontal width.

How wide is it? I don't mean to insult, but you are using a 4:3 source for the video?

Low HV will generally make the raster larger in all directions, the vertical can be adjusted to compensate but not the Horizontal.

Do you have a Variac? if so try cranking the line voltage up above normal and see if it improves.

Hi Eric,

Not insulted at all. Just trying to figure things out. Thanks for the suggestions.

It’s overshooting about 15%. There is a horizontal width adjustment but it’s all the way at one end. It’s an adjustable coil in parallel with a portion of the flyback. From what I can tell, it’s pretty standard stuff for the era. It’s tied into the 615v boost but it’s running low (~575V). My thinking is the coil de-tunes that portion of the flyback reducing the deflection thus controlling the width. I am not sure. What I do know is both the high voltage and the boost voltages are low and it seems that the 17DQ6A controls that part so getting the right values should be achievable. Maybe not. Like I said, I’m still learning.

Does any of that make sense? Am I delusional?

Oh, almost forgot. Yes, I’ve tried using my variac to simulate voltages. I am reluctant to increase much above 130VAC because the high voltage really does change all that much when I increase it. However, when I lower it to 110VAC, dropping B+ to about 230VDC, the width reduces to the point where I can properly adjust it. The filament string drops to around 80VAC and all tubes run about 25% low. I’m guessing that might improve tube life but then again, I’m not so sure.

Thanks again for your thoughts. I really appreciate it.

Sir, I would like to know why it is that if you are working on a vintage TV from about the same time period as mine, why you had to go into my thread and just randomly give me a whole "enviromental" shpeel about why its bad to use dim bulb testers and that I need to "keep up with the times"?

It seems to me you're working on your TV the same way I am.

Which by the way I was only using the advice given to be by others on here so don't go shooting the messenger.

So I would like to know why it is you're trying to cause trouble on here when no one was trying to cause trouble with you?

With all respect, what got me whipped up was the political aspect of your comment and the willful disregard of why the regulation was put in place. You brought in the comment that the President corrected this stupid law. I disagreed with you and voiced my opinion. Yes, We are working on similar things but just like using modern components in an old TV or radio to breath more life into these beautifully crafted machine, we should not long for this old technology to replace more efficient designs.

I work in the power industry and these small but important steps will help us all in the very near future insure that we all have the kind of power we want and desire. If we keep using incandescent lamps as our primary lighting, we will not be taking advantage of the knowledge we have to do it better. My comments were designed to suggest that the regulation was not stupid and we can still enjoy our hobby by being a bit more creative. If you think I was causing trouble then you missed my point and I apologize for not being a better writer.

I hope that helps but if you want to discuss this further, we should probably move this to a private session.

I kind of doubt a hand full of hobbyists utilizing dim bulb testers is going to create a national energy crisis. ;) Sometimes it doesn't make practical sense to utilize modern technology to replace something so simple that's been working reliably for decades, which is why most of us still utilize wheels to get from point a to b. Technology isn't bad in itself so much as are often the motivations behind marketing it to the masses.

I sent you a private message, complete with a video backing my views on this and if you wish to actually discuss this through private message, then I suggest you reply to my private message I sent you, otherwise I'm going to assume that you were just making that comment in my thread just to troll with no intentions to "correct misinformation".

+1 :thmbsp:

I agree I think he was overreacting when he posted his comment in my TV repair thread.