a real challange?

[Kevin Kuehn]

Originally Posted by Yamamaya42

I just have to wonder WTH was RCA thinking when they came up with this bleeder power design...
By routing main ground (-100) trough the focus coil and the adjustment for it, won't that cause the -18 & -2 to change when you adjust focus? Not to mention reference gnd with respect to the positive bias voltages?
It's hurting my head trying to understand what they ment to do...

It's a pretty common scheme to obtain negative bias voltages. Putting the focus coil in there actually saves some power vs wiring in to it's own separate voltage dropper off of B+. Don't think of it as ground going through those resistances, because chassis ground is still at 0 volts. What's happening is part of the B+ is shifted to the negative side of the rectifiers because the HV winding center tap is not connected directly to ground. The 5U4 diodes block the positive cycles from going that direction, so it has no choice other than to produce a negative voltage. You are correct that the bias voltages will change with adjustment of focus, but it's a very small amount because those resistances closer to ground are much smaller in proportion. And vacuum tubes are very tolerant to loosely regulated B+

[Yamamaya42]

https://imgur.com/dwrUtJr

same tube, pins cleaned

[Yamamaya42]

part of my voltage problem is /was that the focus control pot was so dirty that the center post was not making contact most of the time, and there was no easy way to clean it w/o taking it apart, could not get cleaner inside it :/

[Yamamaya42]

Originally Posted by Kevin Kuehn

Just for fun I looked up the RCA part number for the 630's 1st video IF coil and crossed it to a Meissner 17-1001. One of which is listed on ebay. Electrical specs look like a match. I'm not sure about the mounting, but there's a good chance it'll fit? Maybe you can message the seller and he'd be kind enough to measure the mounting bolt spacing. I agree your old one may work, but having this as a backup may let you sleep better at night.

https://www.ebay.com/itm/Meissner-17...5/291470458045

https://i.ebayimg.com/images/g/3e8AA...a3/s-l1600.jpg

https://live.staticflickr.com/65535/...a1bcddbf_b.jpg

Coil is installed and was a perfect fit, BTW.

[Kevin Kuehn]

Originally Posted by Yamamaya42

Coil is installed and was a perfect fit, BTW.

Good to know. I expect that you checked the winding's for continuity prior to installation. We generally don't know the storage environment that NOS coils have been exposed to over the years, so it's not entirely unlikely to find one open.

[Electronic M]

Originally Posted by Kevin Kuehn

Good to know. I expect that you checked the winding's for continuity prior to installation. We generally don't know the storage environment that NOS coils have been exposed to over the years, so it's not entirely unlikely to find one open.

I see that a lot with early to mid 30s Philco radio antenna and osc coils...they are often corroded open. Luckily they are single layer and easy to rewind by hand.

[Yamamaya42]

Originally Posted by Kevin Kuehn

Good to know. I expect that you checked the winding's for continuity prior to installation. We generally don't know the storage environment that NOS coils have been exposed to over the years, so it's not entirely unlikely to find one open.

yes, I did check it, I even popped the top off and took a peek inside, looks quite different

[Yamamaya42]

IT'A ALIVE!! HAHAHAHAHAHA!

https://imgur.com/Dn7mcf3

taken from the plate of the horz osc!

[Yamamaya42]

OK , here we go with the bad tubes
I have no tube checker...
I have NO HV and the HV rect tube has a violent purple glow to it :/
I CAN draw a decent AC arc from the AC line out of the flyback, meaning the 1B3GT is most likely bad,
have NOT turned up to full power yet, have variac at 90%, but at this point, should not matter, tube is bad :/
horz output seems to be decent, not sure at this point.

NOT a good sign :/
https://imgur.com/z7NnpHg

[Electronic M]

Your 1B3 is gassy...It happens. Good thing is it is a cheap plentiful tube (I've got a lifetime supply of used ones). It isn't a bad idea to buy 2-5 of them. They can only accurately be tested by a working TV (as repeated comparison of best in a lot tube tester VS TV has shown me).

[Yamamaya42]

new 1b3 on the way.
https://imgur.com/XymPhnp
trying a temp one!

[Yamamaya42]

Houston... we have raster!
https://imgur.com/VUa9QRs

for the first time in over 50+ years, raster!

I suspect the HOT is also a bit weak, as may be other tubes, have not tried to tune anything in yet, i suspect that I wont be able to.

And as I am using the test CRT 8YP4, the yoke does not fit quite right, ( expected this ) so wont get full screen, but this will do fine for working out the bugs.

[Yamamaya42]

and Video, although it be crappy...
https://imgur.com/lKzthZB
https://imgur.com/OrnQXum
https://imgur.com/lFGifq9

The yolk is obviously upside down, I REALLY don't like the short wires on it.
have the IF bypassed at the moment, feeding video into grid of pin 1 of 1st video, through a cap, not sure if that was the best pace or not for it, just took a guess. or perhaps would be what they have marked as POINT A, on the SAMS be a better place? 4th pix if removed.
As I mentioned before, I have no doubt that there are other flaky tubes, like i'm sure i have to get a new horz output, as it's weak, I'm sure and has a blue glow to it.

[Kevin Kuehn]

Looking very promising. All down hill from here.

[Yamamaya42]

I got the HV rect tube today, odd that the new one has a flashed getter and the old one does not, HV is still quite low, As i suspected, the HOT is also bad. has blue glow ( not as bright as the old HV rect was), will most likely also replace damper with solid state, only $10, and will never go bad. ( i hope ) https://tinyurl.com/ss5lv2b

very likely have other weak /bad tubes. for when i feed video into 1st vdo amp, by the time it gets to the final video output it looks like crap, noisy and distorted. and since in this set, the sync is taken from the final vdo amp, its very hard to get lock in this situation.

I should also go and check every resistor in the video line now, something I did not do yet, I was HOPING they would be OK enough, foolish i guess for a 70+ year old TV, i guess that it's working as well as it is now is a sign that they are SORT of OK, but that won't be good enough to get clean video through it.

I only worry about the filter coils that are wrapped on resistors, I have no way to test or replace them if bad.

on one up note, I WAS able to tune in something, but it was VERY unstable, and i could lock in on better sound,or better picture, and to see video i hooked up a ext color monitor to output of the video det (v8a SAMS) junc of L18&L19 through a .05 cap and was able to see a pic if i tuned it JUST RIGHT, ( very hard to get it ), i even got color through it, which i did NOT expect to see.