Speaking of RCA factory stunts........
 

Does anybody remember the RCA Victor tv I'm working on? The 6T74?
Original chassis. KCS 47A., oorrr, -1. whichever.
The vertical oscilator is a 6SN7, that doubles as a Sync amplifier.
Has a better video amp circuit, as well.
Well, here's a new one.

Someone recently sent me most of the gutts to the same model set, 6T74 that belonged in his family. He's turning his cabinet into a licquer cabinet. Ugghh....
Well, guess what?
This was his original chassis, and, the tube chart in the case shows that, but, it's different.
It is the cheaper chassis that used the 6J5 for vertical oscilator.
what goes on here?
The serial no , and, the painted picture tube cup point to a later production.
Did RCA get cheap????

Progress note. I believe I nearly have the problems licked on my set.
Bill Cahill

Glad to hear that you are reaching breakthrough! :thmbsp:

As for getting cheap, RCA in some of their models was a leader; they went downhill from 4 or 5 pix IF stages in the late '40s to a minimal 2 in some of their mid '50s B&W sets. I've even seen this pitiful minimum pix IF count in some of their COLOR sets in the mid '60s.

Further to mention here that very few of their FM Hi-Fi sets used the Foster Seeley discriminator, but rather the ratio detector design, which has always proved inferior in performance as regards distortion figures, etc....

I've restored in the past a number of sets that employ the cheap 2-stage pix IF chain--including RCA models, but was never really satisfied with their performance. I suppose that if I at the time was a trained TV technician that I might've done better, but I strongly doubt it. I think that they were generally crummy sets meant for urban use only, and I never had lived in an urban area.

Now I've got a question for you: Have you ever seen any model of Zenith television set with any fewer than 3 pix IF stages....?

Actually, yes. Early SS Zeniths some had 2 if's.
The chassis's I'm talking about in RCA still had 4 vid. I F's.
Bill Cahill

So where did the sync amp go? Is there another triode added somewhere? I'm missing something here....:scratch2:

That's my point. On the cheaper sets, thiere is a sync seperator, and, one sync amp. On the better chassis, there are two sync amps.
On the better chassis, also, the video amp has improvements over the other one.
All the way around, supposedly, the looks of the more expensive chassis was supposed to look neater. On many of the cheaper sets, for some reason, they copper plated the tuner, and, often, the brackets for the front controls, but, left the zync plating off.
They also obviously didn't examine every construction job, either...
Bill Cahill

My RCA is back up on the bench while moses' rp is awaiting parts.
I will be trying the set soon.
Just looking it over.
Hope to try it Sunday, but, definately Monday.
Wish me good luck, guys..
Bill Cahill

Bill,

You gotta go to bed! This business of being up at 4AM ain't gonna get that RCA done! You will b

Just pulln' your chain. I tried to call you today, you didn't answer...;)

I was at grocery store today. I'm home now.
Bill Cahill

Maybe I'm misinterpreting things, but that you're doing 3-4AM grocery runs means you must live somewhere that a Muntz TV might actually work. :D

Huh?? My grocery run was this afternoon. Muntz? I haven't worked on it yet.
Bill Cahill

The post you made saying the RCa was back on the bench has this for a timestamp:

03-01-2009, 04:41 AM

I can't explain that snafu.

I found out that the first vid. I F transformer, which was physically dammaged, but, at one time worked, now was open.
I ended up getting a friend to ship me one out of a junker KCS-47.
I finnished installing that yesterday, and, plan on trying set, again, today.
On last try, I had hv, vert., and, raster.
Hope this will now bring set back to life.
I'll post pics when I know more.
Bill Cahill

Well, some good news. I had tried set, and, no play. I had a raster, no sound.
Today, I found an open B+ resistor to I F stages, then, the reason. A tiny beed of solder shorting B+ terminal on Second video I F to chassis.
Solder gone... Now, I'll replace resistor.
I have a feeling that now it will work.
Bill Cahill :thmbsp:

Ladies, and, gentlemen, may we have a drum roll please?? ........... Thank you.....

I have an important announcement of great joy to make!!!!!
Picture speaks louder than words......

http://i18.photobucket.com/albums/b1...RCAplaying.jpg


I still have adjustments, and, tuning to do, and, am on my way on that.
But, after the last two long, hard years, It's finally playing!!!!!!
I've had it up to line voltage several times for several min. each, so far, and, it keeps a playing...... :banana::D:tresbon:
Bill Cahill

Ya made lemonade from the lemon!

It has no choice but to work now.

Congrats!!:banana:

looks similar to the chassis i am working on

Spent alot of time adjusting the audio I F, and, Det. stages. It's noticebly louder, but, still nothing to brag about.
Picture, however, looks quite good.
I will fool with it a bit more, then, put it together.... Then, I'll try it on original tube.
Bill Cahill :D:thmbsp::yes:

Cool, glad to hear you finally got that sucker working. I'm sure you felt good after seeing a workable stable picture on that set after all the effort you've put into it.

Well, last week on the bench tv was playing great, except for some slight horizintal fold over in the picture.

So, I put it in the cabinet, put everything together, hooked up my crummy hd converted box, and, brought it up on variac.
After much fiddling around, I had a nice, bright full picture with horiz. fold over.
I adjusted set. Got box to receive some stations.
I noted ch 3 oscilator on tv needs more tuning.
I decided to try a different horizontal output tube, of the correct no of course.
Started back up on variac.
Just as I was getting to operating voltage, I heard a very loud hum in the speaker, a grunt from power transformer, and, a loud pop out of chassis. I watched as dim video faded to a white dot. I shut it down.
Back to square one. :thumbsdn::nono::tears::sigh::no:
Bill Cahill

Well, heree it is. The tv is about finnished, and, back in it's cabinet.
Let me show you some pictures of it playing. Some picture adjustment issues yet, but, it's working reliably. It plays quite well, actually. What do you guys thinik?
I copied my photobucket links from ARF.
"Kelloggs, the best to you each morning, brings you Huckleberry Hound!"
http://i18.photobucket.com/albums/b1...oundonRCA5.jpg
http://i18.photobucket.com/albums/b1...oundonRCA6.jpg
http://i18.photobucket.com/albums/b1...oundonRCA3.jpg
http://i18.photobucket.com/albums/b1...oundonRCA2.jpg
http://i18.photobucket.com/albums/b1...oundonRCA4.jpg
http://i18.photobucket.com/albums/b1...oundonRCA7.jpg
http://i18.photobucket.com/albums/b1...oundonRCA8.jpg
http://i18.photobucket.com/albums/b1...oundonRCA9.jpg
http://i18.photobucket.com/albums/b1...undonRCA10.jpg
http://i18.photobucket.com/albums/b1...undonRCA11.jpg
http://i18.photobucket.com/albums/b1...undonRCA12.jpg

"...Don't let yourself forget. Tune up your tv set for Huckleberry Hound. That oh, so merry, chuckleberry, Huckleberry Hound.
......................................
Huckleberry Hound.............."
Bill Cahill :D

My similar RCA (TC-127) has always had a sound issue. Basically, I have to turn the volume wide open in order to hear the set across the room. When I did the recap a year or more ago I remember not being able to find any bad components, so I put it back together hoping that a different audio output tube or something would straighten things up. Since then I have replaced all of the audio tubes and nothing helps. Perhaps there is a resistor or something that I missed. I hate this because this TV playes PERFECTLY other than this one problem.

Any other ideas or pointers would be great!:thmbsp:

I'm afraid that problem has me stumped also.
I get fairly good volume all the way up, but, slight decrease in control, means major decrease in audio volume.
I've replaced micas, tubes, spkr., which had also been blown, resistors, and, checked voltages, which appear to be proper.
Vol. control appears good.
No shorts, just not performing well.
I'll look at that problem more when I get back on vertical, and, horiz. osc. issues.
Other than that, set has been completely stable.
Bill Cahill

I have an Admiral with low volume. I changed out the 6SQ7 1st audio for a 6SN7 and add another stage. Works great now. I think your RCA uses a 6AV6 1st audio you may want to try a 6J6.
Terry

No, thanks. The ampolifier isn't the problem. It's something in the i f 's.
Bill Cahill

It looks great. Nice work.