RCA CTC 187 is changing channels by itself.
 

It's a 32 inch RCA CTC 187 TV made in october of 1998. At first I thought this TV was a victim of the DTV switchover, but upon getting it home, I found that it goes through all its programmed channels, never stopping. It won't allow me to access the menu, or even turn the TV off.

I suspect that the EEPROM is corrupted. I do have another CTC 187 chassis that I could pull IC's off of... I'd like conformation before I dive into that though.

PS: this TV's been worked on before. The degaussing thermistor, well the 1/2 of it that's left was resoldered to the leads, and every solder connection in the tuner and power supply was touched up by someone who loves using an excess amount of solder. No bridged connections, but whoever had it before me *really* didn't like bad solder joints...

It could be defective front panel switches. You might try unsoldering them and see if the problem clears up.

Hmmmm, It came with a working remote, and not even the remote could access the menu. I know the remote works because of the RCA big screen TV in my living room.

Still, I guess its something to try before I start desoldering IC's. I'll look into it on Friday when I have some free time. Until then, I'd be grateful if you could list any other things it could be.

Try plugging it in, turning it on, then turn it off while it's scanning, then back on again... That should stop the scan, and you should be able to get the menu up. If not, you might have a mechanical problem, such as a banged-in button switch on the front of the PC board. Any of the buttons stuck "PUSHED" will jam the buss, and and none of the other buttons will work. But again, those RCAs scan for channels automatically on plug-in & first power-on, and it will scan til the cows come home if there aren't any analog channels to pick up.

Charles

Not familiar with this particular set, but a couple of observations:

Sets vary as to whether or not the front panel controls override the remote. For example if you hold down the volume up button on the front panel while holding down the volume down button on the remote. On some sets the volume will do up, others it will go down.

The little tact switches typically used for front panel controls can fail stuck on, especially if the previous owner was heavy handed with the controls or the set spent some time exposed to the weather before you got it.

Noise on the supply rail to the microcontroller (often 8V or 5V, 3.3V or even 2.5V in some recent sets) can cause some strange problems. I've had a couple of sets that would intermittently freeze up, get stuck in a loop, fail to respond to the controls, even activate functions/menus not present on that model. These faults caused by bad caps or bad regulators.

That said sometimes it is the microcontroller itself and sometimes similar faults have beaten me . I gave up on one Sony that would continuously go up through the channels like your set.

One final option to get some use out of the set especially if analog is dead in your area is to brute force the set onto AV. I've done this on a couple of sets with weird microcontroller/tuner faults that lived out the rest of their days as monitors. Check the datasheets for the microcontroller/jungle ICs for details.

I had some time today, so I removed the channel up and down buttons, and that seems to have fixed it! thanks radiotvnut!

Something I've noticed about CTC 187's. There's a fair bit of geometric distortion when the picture is bright. Is this due to marginal caps? All CRT TV's I've seen have some distortion when the picture is bright, but it's more noticable on CTC 187's. Part of a channel logo actually got cut off by the bezel when the image switched to a bright scene.