1976 RCA picture problem

[Jon A.]

Originally Posted by Jeff-20

Making progress... Got the yoke twisted back in place per zeno's instructions (Thank you!). But not yet brave enough to take the tuner apart. All of the wires are soldered.

I took some pictures of the inside and discovered one of the corners that anchored the screen in place was completely broken! It must have gotten pushed in during shipping. I took pics of one of the normal corners and the broken one after some efforts to put in back in place. Would this kind of damage seem connected to the small image?

No surprise there, most sets I've opened have the RF input cable soldered in place. In my experience those things need really good grounds. If the 1st RF amp transistor is blown it'll be a real dog to replace if even possible, it's pretty tight in there. Unless you have a schematic that identifies the transistors don't bother trying. Any tuner that uses approximately the same B+ voltage should work even if it doesn't physically fit. Fortunately for me a blown tuner was very much the same internally as one from my parts stash, the most important feature being a removable shaft. The hardest part will be swapping the front of the housing so it will mount properly.

The damage to the CRT anchoring point has nothing to do with the image size issue.

[zeno]

Cabinet damage means the set took a good lickin. Thats why I said
to give the main PCB a look for cracks. Especially at the mounting
lugs & the flyback.

73 Zeno
LFOD !

[Electronic M]

Originally Posted by Jon A.

No surprise there, most sets I've opened have the RF input cable soldered in place. In my experience those things need really good grounds. If the 1st RF amp transistor is blown it'll be a real dog to replace if even possible, it's pretty tight in there. Unless you have a schematic that identifies the transistors don't bother trying. Any tuner that uses approximately the same B+ voltage should work even if it doesn't physically fit. Fortunately for me a blown tuner was very much the same internally as one from my parts stash, the most important feature being a removable shaft. The hardest part will be swapping the front of the housing so it will mount properly.

The damage to the CRT anchoring point has nothing to do with the image size issue.

His problem is probably a dirty tuner (easy fix) versus your transistor issue (not particularly easy).

First step on any noisy tuner issue should always be clean the contacts. You should not need to remove the whole tuner from the cabinet or any wires from the tuner. Most sets made it so that you could unclip and remove the tuner shield and clean the contacts with the tuner still mounted and connected. There is a front and back to the tuner that the shaft passes through and a "top" that the wires connect to(some tuners are mounted upside down or other wacky ways so "top" is not always pointing up)...The removable shield typically comprises the bottom and sides of the tuner. It usually clips into the top. To remove pinch the sides inwards near their centers at their upper edge where they meet the "top" and pull down after you've started to pinch while still pinching...The shield should slide off. After that identify the contacts and start spraying cleaner and spinning the knob...If there is lots of room around the contacts I like to stick a soft white pencil eraser in there and let the contacts brush against it...This alone will help but if you do it while they are wet with contact cleaner you will be impressed with how much tarnish it will remove.

[Jon A.]

Originally Posted by Electronic M

His problem is probably a dirty tuner (easy fix) versus your transistor issue (not particularly easy).

I guessed that this reply would contain an argument against what I said. You've done it to me many times, please try to refrain from it from now on. I know I'm not stupid but it still kind of stings.

It may be true that his tuner is dirty, but it wasn't I who initially suggested that the RF amplifier transistor may be blown.

[Electronic M]

Originally Posted by Jon A.

I guessed that this reply would contain an argument against what I said. You've done it to me many times, please try to refrain from it from now on. I know I'm not stupid but it still kind of stings.

It may be true that his tuner is dirty, but it wasn't I who initially suggested that the RF amplifier transistor may be blown.

Not trying to sting nor to imply any kind of stupidity. The topic has drifted away from what he needs to do into speculation into highly unlikely causes. Your Post seemed to suggest replacing that transistor was the way to go and that it is very difficult (and it was the most recent bit of talk on it). That will scare an amateur off of touching the tuner. I simply pointed things back in the right direction. (we should make sure the easy common issues have actually been dealt with before going off into the weeds should we not?)

If what I see as bad advice is given I will attempt to correct it (or improve the advice given) no matter who gives it, starts it, or contributes to it...If you happen to be caught up in the giving of bad advice that is not my fault. And you have no right to tell me where and how I can put my two cents in on an issue as long as I am abiding by the rules of VK. I will try to sound more respectful going forward...But bear in mind we ALL get correct by other VK'ers from time to time, and unless someone explicitly calls you a big dummy that is likely NOT even a tiny part of their goal in offering what they see as the correct information to those reading.