admiral 24c15 with 20b1 chassis attempt at restore

[bandersen]

Couldn't say as I've never had one go bad. I've seen a few that had already been replaced though. Maybe I've just been lucky so far.

[fumplet]

I also need to replace the 35pf cap in 2nd I.F.can and i only have 34 and 36 pf...not sure those are close enough or do i need to go to mouser and order 35pf

[bandersen]

It really doesn't matter as you'll need to do an alignment regardless. They were not precsion parts back then. Would not be surprised if the actual value was anywhere from 30pF to 40pF or beyond.

[fumplet]

Ok cool if thats the case then for the 35 pf I could stuff in the 30pf I have now. Ok so if I have to align it because of vertical output transformer then maybe thats why it seems not as crisp for black and white as it did before the transformer was replaced. Id like to post up a picture of the video quality but my phone camera just makes the picture look like I have the brightness turned up all the way and washed out. I did notice the horizontal scan lines were closer together so maybe thats good.

[old_tv_nut]

Whoah there!
The vertical output transformer will have nothing to do with the IF alignment.

Regarding the capacitor in the 2nd IF, I would not sub 30 pf where 35 is specified. That's more than 10 percent off. Either the 34p or 36p you have should be good. What is wrong with the 35p that's in there now?

[fumplet]

The 35 as well as the 30 in the 1st I.F. can is a made in wafer mica sandwich cap that is failing. Wiggling the terminal made my sound come back fully or partially. Same with the 2nd I.F. can when I accidentially touched the can and bumped it, the sound got slightly louder so I will replace the cap.

[old_tv_nut]

Originally Posted by fumplet

The 35 as well as the 30 in the 1st I.F. can is a made in wafer mica sandwich cap that is failing. ...

Thanks

[bandersen]

These are the types of micas caps he's talking about hiding inside the sound IF cans.
They are not coated in anything so the silver tends to oxidize and develop "silver mica disease" from migrating silver causing intermittent crackles and degraded performance just like in a radio.

[fumplet]

Originally Posted by old_tv_nut

Whoah there!
The vertical output transformer will have nothing to do with the IF alignment.

Regarding the capacitor in the 2nd IF, I would not sub 30 pf where 35 is specified. That's more than 10 percent off. Either the 34p or 36p you have should be good. What is wrong with the 35p that's in there now?

My math was messed up so yes replace time.

[fumplet]

I have never done an I.f. alignment on a tv. Not even sure i have the equipment. Oscope with freq counter yes. Heathkit signal gen yes but tv signal generator no

[Electronic M]

Most TVs you can do the sound alignment with an AM radio alignment generator. I tend to do sound alignment by ear. If the sound alignment is decent now and you change the caps in a can you should be able to realign the can by ear then do the next can.

[bandersen]

What he said. Don't mess with the video IF but the sound is not so hard. Peak three of the coils for 21.5MHz. The last is for the FM detector "S" curve. Adjust that once so it sounds undistorted. You can get by doing it by ear.

[fumplet]

I have the 20b1 chassis I dont have 3 coils just two of them unless Im not seeing the 3rd one.

[bandersen]

Primary and secondary. The are adjustable slugs on both sides of the chassis. Four in total.

[fumplet]

Yes i discovered the secondary slug yesterday and not sure which to adjust first.as i didnt pay attention to which coil went to which terminals on the 1st I.F. can. I thought the adjustment was one continuious slug that was untill the bottom slug wasnt turning when i turned the top one. Going to guess by your picture bottom is primary