Can someone tell me how to stop the CRT screen picture from shrinking to a 3inch strip in the centre of screen every now and then. It does this intermittently. Walk away from it and sometimes it regains the full screen picture. Turn it off for a few minutes and sometimes it regains the full screen picture. This shrinking of the screen picture does'nt effect recording to a VCR even when it regains the full picture. Is the tube on it's way out.? It's a 20" size screen. Model TC-51M75A. Can't tell you when it was made as the operating instruction booklet does'nt say and also it was given to us from my wife's Aunt a few years ago.

CRT fine.

If vertical drive failure, check the v-out ic and it's capacitors...could just be poor board soldering as well.

the strip can burn the phosphor permanently so turn the brite down or quit using til repaired.

Almost certainly dry joints on the vertical output IC. It's a very common fault in those Panasonic sets. I'd say 8 out of 10 of those sets (or the 68cm version) I find on the side of the road have it.

It's also a very easy fix. Resoldering the IC is often all that is needed, though sometimes the IC needs to be replaced. By this time some capacitors may also be marginal and need replacing. Worst case scenario it's about AU$20 in parts (about $8 of that is delivery fee, Dickless Smith/etc don't carry these). Generally I do it as a $20 job (not that I'm offering, I'm in Vic), though I use parts removed from scrap boards.

If you can solder open it up and resolder the IC (suck the old solder off first). If that doesn't fix it replace the IC. If the IC is bad it will usually take out the 2.2R resistor in it's supply rail.

I've seen many panasonics with loose connections on the vertical output IC. You'll need to fix that now because if you don't, you probably will end up having to change the vertical IC.

Thanks to all for your troubleshooting info. Much appeciated. Rob.

Can someone tell me how to stop the CRT screen picture from shrinking to a 3inch strip in the centre of screen every now and then. It does this intermittently. Walk away from it and sometimes it regains the full screen picture. Turn it off for a few minutes and sometimes it regains the full screen picture. This shrinking of the screen picture does'nt effect recording to a VCR even when it regains the full picture. Is the tube on it's way out.? It's a 20" size screen. Model TC-51M75A. Can't tell you when it was made as the operating instruction booklet does'nt say and also it was given to us from my wife's Aunt a few years ago.
I had the same problem with my Panny 31". It would start shrinking from the bottom up then would go blank with sound. Pushing up and down on the chassis would correct it for a while. Upon opening it up and doing some detective work, along with the tips on AK, found a bad solder joint on the 14 pin IC in the horizontal circuit. Happened to be a ground pin and had a .1mf 30v cap soldered accross to that pin on the solder side of the board. Getting a nice solder connection was a bitch but got it done. TV is like new again! :banana: