Crosley 9-403m Help Needed

[cdmarion]

Originally Posted by earlyfilm

If you or someone has a schematic of the video, vertical and CRT sections and could post it, it would help.

James

Here's a scan of the schematic, I had to do it in two files due to the size of the schematic.

[cdmarion]

I started checking resistance on the video amp tube pins and found pin 6 had no continuity so I traced back to the L23 peaking coil and it was open, so I replaced it with one out of an identical parts set and checked it again, it reads 17K and I'm supposed to have 8k but I figured it was better then the original. I turned the set on and now I get a wavy vertical line, see attached pic. It appears I've now lost my Horz sweep, so I disconnected one end of the coil, removed the 12au7 expecting to see a full raster as before but I still had the vertical line. I've got another bright / contrast pot from my parts set and will replace that tomorrow morning just to eliminate that as a probable cause.

[cdmarion]

I forgot to attach the pic.

[earlyfilm]

Originally Posted by cdmarion

I've got another bright / contrast pot from my parts set and will replace that tomorrow morning just to eliminate that as a probable cause.

Chris,

The good news is, now that I've seen your schematic, your set does not seem to have the high level FM switch some same period Crosley's used that can create difficult to pinpoint intermittent problems.

When you unsolder the Brightness control BEFORE YOU REMOVE THE SHAFT NUT, check for a slider to case short. Also check for continuity between the outside terminals and check the slider for continuity between both ends while rotating it. (It probably would not hurt to perform the same test on the contrast, before removing it.)

If no problem is found there, I'd suggest that before replacing any more parts, you take a couple of days off and then look at the set with new eyes, checking especially for correct wiring on items that you replaced after the mouse visit and using a bright light, for additional damage that was not noticed.

Your symptoms do not seem to point to a single failure and this causes me to suspect either a newly introduced wiring error, or unnoticed rodent damage.

If you have an oscilloscope, it might be a great help in this case as the design of this set causes many controls to interact unexpectedly.

James

[cdmarion]

Originally Posted by earlyfilm

Chris,

The good news is, now that I've seen your schematic, your set does not seem to have the high level FM switch some same period Crosley's used that can create difficult to pinpoint intermittent problems.

When you unsolder the Brightness control BEFORE YOU REMOVE THE SHAFT NUT, check for a slider to case short. Also check for continuity between the outside terminals and check the slider for continuity between both ends while rotating it. (It probably would not hurt to perform the same test on the contrast, before removing it.)
Checked this control yesterday morning and it tested good

If no problem is found there, I'd suggest that before replacing any more parts, you take a couple of days off and then look at the set with new eyes, checking especially for correct wiring on items that you replaced after the mouse visit and using a bright light, for additional damage that was not noticed.
I agree, I put the set up yesterday morning, I may get back on it later today or tomorrow morning. I've triple checked my wiring and it seems to be correct, I even compared it to my parts set and it matches, I'd almost bet that there is additional rodent damage that I'm just not seeing.

Your symptoms do not seem to point to a single failure and this causes me to suspect either a newly introduced wiring error, or unnoticed rodent damage.

If you have an oscilloscope, it might be a great help in this case as the design of this set causes many controls to interact unexpectedly.

James

One additional thing I noticed after replacing the L23 peaking coil I went back and checked pin voltages at the video amp tube and where I had 0 at pin 6 I now have 340VDC. Which is way high, it's supposed to be 185VDC. Pin 2 at the crt went from 0 to 250VDC, supposed to be 70 and Pin 11 went from 70 to 250 which is supposed to be 400VDC.

James, I really appreciate your advice, I wouldn't have gotten this far without your input.

[cdmarion]

Update 13-1-2012, So I took your advise James and tool a few days off, When I got back on it I decided to check resistance on the rest of the tubes in the video section. I found two resistors that were more than 50% out of spec and replaced them, fired up the set and with a few control adjustments had a good picture,. I've been watching the Burns and Allen show for nearly an hour now and it seems to be stable at this point. I'll run it for the rest of the day and if it's still good in the morning then I'll but it back in the cabinet.

Again thanks to everyone for your advice. James I appreciate your interest in this problem.

I have to say I'd rather bring a TV back to life that hasn't worked in 40 years then to try and fix one with rodent damage.