admiral 24c15 with 20b1 chassis attempt at restore

[fumplet]

Sometimes focus is good sorta in center and other times not. Not mounted correctly i dont know other than wires out of focus coil come out of coil at bottom of it. Going to post pictures of current picture quality when i get home. As for focus i dont know how it can be good then not good...the sand resistor has been replaced.

[bandersen]

I mean positioned correctly. Sorta good sometimes and not others is a big red flag. That means you have issues like an intermittent connection or short or tube that's going bad.

[Electronic M]

Originally Posted by fumplet

What qualifications do i need other than 250 and 150 uH. The schematic doesnt list the Q properties.

You need the inductance which is listed, and the resistance can be helpful. The RCA CT-100, 21CT55, and Motorola 21CT2 all use chalk peaking coils that rot open and I've had good luck using those 2 specs to obtain workable replacements off mouser.

Q might be helpful, but isn't essential. It's surprising how little effect shorting a good peaking coil has or how decent a picture can be with an original dead coil temporarily replaced with a jumper wire.

[fumplet]

almost seems as if focus changes when I set chassis on it side while changing/replacing something. might try checking that connector again under load

[old_coot88]

Originally Posted by Electronic M

..It's surprising how little effect shorting a good peaking coil has or how decent a picture can be with an original dead coil temporarily replaced with a jumper wire.

I've tried shorting a few just out of curiosity, and never seen it make the least bit of difference.

[fumplet]

Welll i have an assortment of peaking coils now. So if they dont make a difference then im sure i can find a use for them...very fascinating if they dont do anything.
If the picture tube has was is shorted gassey i would think it would go wonky alll the time we are watching it..just seems as if i mess with it and focus changes...could be just dirty tube sockets

[bandersen]

They do make a difference but you would need a good test pattern to see it. They improve the frequency response at the high end which results in finer image detail.

[fumplet]

sound still goes low and high but not totally off. I replaced the two 15k ohm resistors in the audio section since my replacement had measured 14k and also the 14k resistor measured 19 k. Focus is now back, will see how long it stays. the voltage drop across the 15k to ground was measuring 25 volts before now its 155 volts. 15k to ground I put in there is 5 watts and it does get hot. When I turn off the set it gives a louder audio buzz for a second, not sure thats normal, but doesnt do it all the time. Basically still has weird gremlins hiding here and there.
If I pull any of the video tubes other than the first video tube, the sound gets much louder. Just pulled the 2nd video tube then put it back in and sound went almost out, then adjusted sound I.F. cans and got sound back but different position of 1st I.F. can slug. Its as almost as if these I.F. cans are iffy in adjustment.
YAYYYYYY. I think I found it. The 1st I.F. CAN terminal that goes to ground and a 330 ohm resistor if you move the terminal you get loud or soft sound. I dont yet know if I have to remove the can, replace the 330 ohm.resistor or what. CAn I remove the square shield, or does the can need desoldered and removed.
Going to assume the capacitor inside this can is 30 pf, schematic does not say. but has to be pico farads. I have zero guesses as to how accurate the 30pf has to be. the 2nd I.F. can has a 35pf in that according to schematic.
I have disc caps at 10pf. 3 of those would be 30 but dont know if temperature would make them change value or not. If not then I will just have to settle for a trimmer cap till I get correct ones and I might as well replace that 35 pf cap too.
Well, stuck 3 of the 10pf caps inside the can. Works and no crackly junk when the terminal of the 1st I.F. can grounded/330 ohm resistor to the 2nd audio I.F. tube anymore is moved/wiggled and I bet nothing will disturb it.

[fumplet]

just blew the tv speaker trying to tighten d/a converter coax, the cone ripped away from voice coil form so I just reconed it. Had it sorta fixed with coffee filter and tacky glue but the cone itself was just tired and ready to expire so I just threw on a new cone.

[fumplet]

turned tv on this morning and sure enough not my imagination as I thought before that the vertical was stopping, well, the vertical went away for 2 seconds and nothing but a horizontal line then comes back so thats probably my jittery height issue. Seems rock solid for a while then vertical jittery shrinky a bit then clears up but now Ive seen this several times where the vertical just goes away, but this time it was long enough for me to catch it.
Im not even sure what exactly the vertical section is, the schematic just says sweep section but I do remember shango and others talking about integrators so sweep must be vertical??? Keeps losing vertical, tried cleaning the 6k6 socket and thought that was it so Im just not sure whats causing this, might just have to let it fail. and if yoke then its a parts set.
https://www.youtube.com/watch?v=v-eeTfhPrMk

[fumplet]

primary of vertical output transformer supposed to be 700 primary ohms and 12 ohms secondary is open....bummed now. Trying to figure out how to get a replacement since evilbay doesnt list them by ohms but by turns. turns ratio is weird 175/3. Not sure if I caused this or not.

[fumplet]

Just picked up a thordarson 26s75 universal transformer but not sure it will work, but it was only 15 miles away so I thought Id take a chance. Well, its working now soldered pins 2 and 3 together for primary and used 1 adn 4 measured was 1.1k ohms. and for secondary I used pins 5 and 12 for 12.9 ohms.........its working. Now is thee something I can check to make sure I did it right so I wont overload anything or....if its working leave it alone? Wife and daughter say its clearer now with no jumpyness. I cheated and found another post on videokarma looking for a vertical output transformer for an admiral 20z1 so assuming these are correct parts interchange and listed part numbers admiral 70b24-1 a This transformer is quieter dunno if thats normal can hardly hear it. Focus is still mostly to one end of the adjustment lets see if it will stay.
stancore a-8112
merit a-3036
chicago TS0-5
thordarson 26s51

[fumplet]

I still dont know the difference between vertical height and vertical linearity. Both seem to do the same thing....shrink or expand the vertical image top and bottom......watching mash with daughter...picture so far fingers crossed hasnt budged a bit. Just realized this was the first issue with this tv or any tv that I actually fixed myself kinda cool as I remember being handed a zenith 12 inch b & w by mom and dad and didnt know what to do as it had a vertial line down the center and of course I ended up wrecking the tv.

[bandersen]

Yes, both do affect the height but linearity will also stretch or smoosh the top or bottom. Put up a test pattern while you adjust them. Do the linearity so circle is not egg shaped or squares are uniform. Adjust the height to fill screen

[fumplet]

Ok will do another test pattern adjustment using usb test image....watched several episodes of tv programs aand rock solid...do vertical outpit transformers get noisy when going bad or is that just manufacture design differences becauseci can hardly hear the nos new one