Vertical collapse on Sankyo CRT - Let's fix this pictures and video

[judremy]

I will be posting pictures and video for this later today, but I just got this machine and after hearing some sounds like Rice Krispies, the monitor suffered full vertical collapse. Originally, it would be jumping while the picture started to shrink vertically and now, it is completly collapsed. My guess is that the vertical IC is toast and needs replacement.

I took a ton of pictures of the CRT boards as I opened the housing and laid them all out. I can test it outside the machine with the setup I laid out. So what pictures are needed and will help the most?

I'm hoping someone like DaveRob or someone else can chime in and help me out.

[daverob]

Post pictures of the board that the scan coils are connected to (both sides of the board) and the numbers of the chips on this board (if they're not clear from the photos) and we'll take a look...

When encountering frame collapse, this are my usual 'power off' steps of the fault finding procedure...

Measure the resistance of the scan coils (from the PCB end of the cable), and wiggle the cable, and gently tap around the coils themselves to see if the resistance changes.

Look for data sheets for the chips to find which one is the frame output. Data sheet should have an example circuit, which should help to identify the components for the frame drive circuit on the board.

Then examine carefully for dry or cracked solder joints or any signs of arcing around the area these components are in.

If there are electrolytic capacitors in the frame output circuit, replace them. They are likely to be old enough that they may cause problems, which will make further fault finding more complicated.

If you get this far and you haven't found the fault, then the next steps are tests and measurements with the power on. As CRT monitors require very high voltages to operate, and by necessity these voltages will be exposed during testing, working on a powered up CRT monitor can be lethal. Because of this I am reluctant to post further details on a public forum, where people without the experience required to do this safely may be encouraged to 'have a poke around'.

[judremy]

This album on my Google Photos drive has the images I have taken thus far and a video:

https://photos.app.goo.gl/7QDY6vKT9bWhMKxN6

[judremy]

I have these in higher quality that I can upload if needed.

Top of board: https://photos.app.goo.gl/LbTprVyTiwb6HnRp7
Bottom of board: https://photos.app.goo.gl/2Yecxj9MgGH9H1rj6

[judremy]

Another piece of information that may be helpful...

When we had it on and the picture was full, but jumpy and shrinking, you could hear a sound like "rice krispies" cereal with crackling sounds.

After it shrank down to a line, that sound stopped, but a buzzing sound can now be heard from the boards.

[daverob]

It's difficult to tell from a photo, but there appears to be quite a few solder joints on that board that look suspect. Look for any that appear to have cracking around the component lead, or a dark / dull ring around the lead, and resolder. If the new solder joint doesn't flow well around the lead, you may need to remove the solder and scrape any dirt or pitting from the lead.

CRTs often have crackling sounds due to the high voltages inducing static charges, though it could tiny sparks jumping across a cracked solder joint. The buzzing is likely to be from coils or transformer cores while the vertical oscillator is trying to start up (and failing).

[judremy]

OK. I will try that later today and see if I can find the culprit.

[judremy]

If the machine says 106VA, then it needs a better transformer than the original which was 43VA or the new one I tested with that is 96VA, right?

[Drunkenclam]

Well I know some people in the USA are using 120va (5A) on 150va rated machines. It is not recommended as it puts strain on the transformer, causing them to get rather hot and voltage drop. some don't seem to find it an issue. The first thing that stops is the screen as thats taking the most power.

However the machine is rated at 106VA then you really should be using a transfomer of that rating or slighly higher.

[judremy]

Well I know some people in the USA are using 120va (5A) on 150va rated machines. It is not recommended as it puts strain on the transformer, causing them to get rather hot and voltage drop. some don't seem to find it an issue. The first thing that stops is the screen as thats taking the most power.

However the machine is rated at 106VA then you really should be using a transfomer of that rating or slighly higher.

Best I have available right now is a 96VA, which is better than using the 43VA one. I have ordered a couple 150VA ones that should work nicely and they are only about $35 ea.