AudioVision 14” Restoration

[LaPorta]

Will do. Time to get some compressed air...

The design does not lend itself to getting underneath the board, but just firing the propellant at the actual component should suffice, yes?

 

[techknight]

Thats the only way you can do it, outside of resoldering bad solder joints. 

 

[LaPorta]

Alright...time to start the hunt this week! Thanks for the insight. Then I suppose try and resolder, and if that fails replace.

 

[LaPorta]

So I fired the propellant at every last capacitor I could find. There was one set that having fired it at made the issue all that much worse...but that was it. Nothing actually made it better or corrected it. I suppose that area is where I should concentrate my resoldering efforts.

 

[badCaps]

I've never heard of the upside down can method, that's neat.

Similarly when troubleshooting automotive vacuum leaks, you can spray brake parts cleaner around intake components and if the engine chokes you have found an area where a gasket or other component is leaking.  I had no idea there was a similar test for electronics.

So I think you have found the area to investigate!

 

[techknight]

So I fired the propellant at every last capacitor I could find. There was one set that having fired it at made the issue all that much worse...but that was it. Nothing actually made it better or corrected it. I suppose that area is where I should concentrate my resoldering efforts.

Yeap this is the area to investigate. Also, you can use the blowdryer/heatgun method if the freeze spray makes it worse. heat would make it better albeit temporarily. 

Regardless, now its time to try and narrow the field, hitting it component-by-component and watching for changes in between. 

 

[techknight]

also to note, I took a second look at that pic, the deflection section of that module looks almost identical to that of the Color Classic/LC5XX series. 

 

[LaPorta]

This regrettably got put on the back burner as I am trying to get the stereo fixed for my sister-in-law’s family

for Christmas. I’ll be back on the case once it is done.

 

[LaPorta]

Ok, updates to this now. I went through both the sound board and the video board. I found and repaired two issues: 1. - A cap and trace on the audio board had become severed from the rest of the trace. I patched that with a wire. 2. - The ground to the chassis cage on the underside of the video board had become cracked, so I re-soldered it. This corrected two issues: The sound is no longer crackling or distorted (no doubt due to the cap being re-connected), and the video is now sharp and clear with no further distortion or bouncing.

HOWEVER: after working well for five or so minutes, the brightness of the screen began to flicker, until it became a more consistent dark. You can see the image, and it is clear now, it just is quite dark. So, now I am left to try and figure out what is happening here. At least the audio issue is fixed, as is the flickering video. I tried cooling the video components to no avail. Does anyone know what circuitry could cause the darkening of the screen? One clue: there is less of a high-pitched squeal from the monitor when it is dim. The squeal is higher-pitched when it is brighter.

An additional note: DON'T forget to reconnect the video cable from the CRT to the video board! I did that by accident and saw a big whiff of smoke  so I shut it off immediately. I thought I somehow fried the whole thing, and saw the disconnected cable. I reconnected it, and then started it up, and the monitor worked fine, save for the problem that remains. Just a good warning for someone else doing this in the future.

 

[LaPorta]

Well, I found what I burned: RL34. I’ll replace it with a new one, but beware that that will happen if the CRT neck cable isn’t plugged into the video board.

 

[LaPorta]

Ok, some really good news: I pulled the video board again, and re-soldered everything in the video circuit area, and it seems to work. I left the screen on and hooked up to my PM 6100  for a good hour-plus, and fired up some Marathon to play. Everything seems to work well and is in good order. I also fixed the rotated CRT neck collar (fixing the geometric distortion that caused me to open it in the first place). I'll do a little more stress testing, but as of now it looks like it is good to go.

I'll post a recap here soon to review all I did, and to surmise the prudent steps to take and pitfalls to avoid on these monitors.

In addition, I want to give credit to @techknight here for his help and guidance on tracking down the issues, not to mention help on many other projects.

 

[techknight]

Nice. Glad you got it working