Probably just be overly cautious, but . . .
 

Put my Admiral 21K1 chassis on the bench last night for a few little "nits" that I was waiting on parts for. I had a 8.2 meg resistor to replace and wanted to test the one 3Kohm candohm chassis-mounted resistor. The candohm tested fine, so left that in. 8.2 meg replaced. Found one .01 uf flat molded paper cap (thought it was a mica at first), so replaced that too.

So the set has been totally recapped (except micas) and all resistors replaced that needed it. Then I remembered the two resistors in the HV cage. In the base of the 1B3 socket. So looked at the SAMS and here is what SHOULD be in there:

R89 - 2.7 ohm, 1/2 watt (HV Rectifier Filament)
R90 - 470k ohm, 1 watt (HV Filter)

Popped the socket open and could tell immediately that someone had already been in there at some point. Socket popped open way too easy and the solder joints had all been un-soldered and re-soldered. So the 2.7 ohm resistor tested over 6 ohms. Should replace that. Now for the uncertain part . . .

Instead of a 470k ohm resistor, there was a 150k ohm resistor in there. :scratch2: Actually, had written on it "0.15 MEG, 1 WATT."

Does anyone know why this would be???? Now, I have the Admiral Tele-bar, which uses the 21L1 chassis. 21L1 uses the exact same SAMS and the TV chassis is almost identical to the 21K1 except for the plugs and circuitry for the combo phono/radio addition. So I brought that chassis out, popped open the 1B3 socket and whadda ya know???? That has the correct resistors in it. 2.7 ohm and 470k ohm. I see no service notes in the SAMS of any kind regarding this 470k ohm resistor indicating that it should be a different value. I also have the original service manual (which comes with a schematic) and that also indicates a 470k ohm resistor.

Any reason anyone can think of that I should NOT remove the 150k ohm resistor and replace it with a 470K one???

Thanks.

As a side note, the set has been a great performer for the past year. Have put many hours on it. Only issue really is a dark picture. If I try to turn up brightness, picture gets blurry - especially if there is white text on the screen. When I say a dark picture, it is not bad. Can watch in a room with lights on, just not as bright as I would like. Certainly watchable. Example with lights off . . .

https://www.youtube.com/watch?v=fgCbTkjPYIE

Hi Al , You mention a dim picture , and a lower than specified value resistor under the HV rectifier . Could this have been some previous service in attempt to address the low brightness , by jacking up the HV a bit ?

I was kinda thinking that. But not sure. That is why I mentioned the low brightness. Guess I really need to know what that 470K ohm resistor does on the HV filter circuit and how altering to a 150K resistor effects it? I am a good mechanic and still need to work on my theory!!!! :)

Below photo is a portion of the schematic with the 470K resistor circled in red. Can right-click on it - save it and then zoom in on it pretty good to see . . .

Actually when I loaded it it lost resolution - so too hard to read, sorry.

:thmbsp: You were thinking the same thing I was . It's likely that a previous service attempt had been the lowering of that resistor's value as that would raise the HV . Thing is , the lack of brightness would be far more likely to be the 2.5 ohm resistor that is now up over 6 ! If the HV rectifier's filament doesn't receive the power it needs no amount of lowering the resistance on the high side is going to get any more HV out of the tube . I'll bet you see a great improvement when you get an actual 2.5 on the filament and go back to the 470 K on the HV filter .

So you think that once I get that new 2.7 ohm resistor in there I should go back to the 470K? Good deal!!! I am sure others will chime in if they think we are way off base. ;)

:thmbsp: And yes , Thank You for the schematic , that resister is exactly the one that someone would lower if they were trying to raise the HV . Thing is , that is a mistaken , "Band Aid" type of repair likely because they were unable to locate the actual source of trouble . MANY things can cause a lack of brightness , but the somewhat inexperienced may quickly jump from a plug in brightener not fixing it to "lets just crank up the HV and see iffin THAT gets it brighter" when confronted with a tough repair . I really think the 2.5 being over 6 is the problem they mistakenly overlooked , and the 150 for 470 swap was the knee jerk reaction to that .

And hell yea , go back to the 470 when you get the 2.5 sorted . I really do think that is gonna produce great results

Somewhere I read that the series 470K is there for current limiting. 1 meg was also a real common value. It's value isn't that critical under normal operation, but without it the CRT can be damaged from excessive beam current if something goes wrong. Agree the 2.7 ohm drifted high on the HV rectifier filament is more likely to be holding back the HV.

That seems to make sense now and thanks so much for explaining it. So the 1B3 filament is not getting the power it needs b/c that 2.7 ohm resistor is way out of tolerance. Theory is someone thought they could fix that condition by dropping the resistance of the HV filter resistor (470k down to 150k) to increase HV? But that would not work b/c tube still not getting filament juice it needs. Do I have it?

I think so.

THANKS fellas!!! I will let you all know how it goes. Funny thing is, I was not actively trying to troubleshoot the dim pic. I just figured I wanted to check these last two resistors in the set out of thoroughness. Will be a nice bonus if the picture improves b/c of this. I was happy to watch a slightly dim picture on a 62 year old set. :D

:) Exactly what I was thinking , Thank you Kevin for confirming my thoughts on this .

And yea , pictures of properly working old TVs are always welcome !

Well, put in the 2.7 ohm HV filament resistor and the 470k HV filter resistor. Fired up the set and the picture was pretty bad. Out of focus, could not adjust it in, etc. So I switched to a 100k resistor on the HV filter. That yielded buzzing in sound and unstable, staticky picture. Shut down very quickly!!! Put the 150k HV filter resistor back in, which the set seems to like even though all literature calls for a 470k.

Been watching for over an hour now and all seems stable. So I am now calling this set done until something quits. I think it looks good . . .

http://youtu.be/7kg7lyJU8Xs

Just curious, have you tried a new 1B3 (or whatever it uses for a HV rectifier)

Hi this is an interesting fault I myself would want to get to the bottom of it. do you have an eht meter to check how much eht is actually being produced running tubes with low heater volts can damage them so might be worth a new 1b3 as the fault would indicate low eht or maybe the crt is drawing to much current. another thing you could try is to supply the set with eht from another working tv to prove the crt isn't faulty.Danny

My next purchase is going to be a HV meter. Any suggestions on which one to get?

I have swapped out the 1B3 several times just to be sure it was not the HV Rect. tube itself.

Noise in the audio sounds like your CRT dag coating may not be making good contact to the chassis.

After messing with the 21K1 Admiral console all afternoon yesterday, I really wanted to just watch it for a while. Performed "Admirably!" :D

I then looked across the room and figured, "WHY NOT. . . "

Started assembly of the Tele-bar jigsaw puzzle. Man a lot of unmarked baggies full of parts . . . this is gonna be fun! The cabinet was completely stripped down and taken apart for the cabinet refinishing. So all door hardware, backing, speaker, radio/phono rails - everything removed and boxed.

The chassis has already been recapped come to find out. Very nicely too. Electrolytics are terminal mounted underneath very neatly, and all bypass caps are done. I just need to check all work, see if the proper two prongs of the radio socket plug are shorted out, and I can go for a controlled power-up of the TV chassis.

The radio has been disassembled into 4 parts. Partially recapped, but there is a filter cap and two paper caps that need to be done.

The phono is a MESS! Everything is frozen up pretty good. Need to disassemble the entire set, clean and re-lube. The motor spins freely and I don't see signs of any major issues, other than some frayed wiring and a lot of dust and dirt. Should come back with a little TLC.

The best part of yesterday was getting the TV control door operating as it should. If anyone has had an Admiral with this type of control door, most of them are broken. This one was no exception. Both top and bottom pegs that hold the control door in place were broken off. One was there in a baggie. I did not even bother with it. Drilled two small holes in the door and epoxied metal rods in place of the stock plastic pegs. I was lucky the original springs were still there and the door operates as new now. :banana:

Few photos of the set cleaned, glassware put away for safe keeping and the front CRT face installed . . .

Have some really neat period "bar" items to dress the set with when it is complete . . .

Nice!