Please say it is not so.......

jetusenet

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Hi,
Working on a Hantarex, complete rebuild including the HVT and fired it up - seemed to work great then got some "interesting" displays,,,,,,,,

https://youtu.be/kJZc0GlTzXQ

I am using a Wells Gardner pattern generator with the white grid pattern displayed.

It's about 6 min. long but you can see what I am talking about. Starts out great and then I get a background raster showing up, flashing and stuff. Around 2:30 it get interesting...... Eventually it settles down and goes back to normal. I think that it might be the CRT but I am not positive - looking for some insight.

I checked with my B&K and nothing bad shows up.

An interesting note, originally the colors were perfect but now, after some testing and such, the outside corners are off, like the yoke was moved but it is solid in place, with the white varnish that was applied at the factory intact, as is the varnish "line" over the ring set. Very weird......

Anyway, the point is that I am trying to figure out if the CRT is bad. Anybody else see this?

Thanks in advance

Jeff
 
complete rebuild including the HVT

Unless it was faulty I wouldn't replace it because the replacements you can get in the US are low quality Chinese knockoffs (OEM flybacks are still only available in Europe). Put back the old flyback and see. What chassis is that btw, Polo?
 
It was doing the exact same thing before I replaced the flyback.

I had rebuilt the chassis and could not locate a HVT so I had left the old one in. It then continued this "rasterizing" (new word?) so after searching for a bit, found a replacement and still has the same issue.

That was what I has though myself. I check for cracked traces and went through the solder joints as well....

Thanks for the suggestions.

Jeff
 
Replace all the big polypropylene and polyester capacitors in the deflection circuit (around the flyback).
 
Whatever was going has gone, no longer do I get a good display at all, just the rasterized version all the time:

https://youtu.be/BIXuL79HqXE

Video shows power applied while the screen control is full CCW then slowly turned up........ Always messed up now.

I took voltage readings of G2, which extinguished the display, is that normal?
The voltages ranged from 64vdc at screen full CCW to 142vdc at screen full CW. I do not if these are normal, just putting them out there.

HV ranged from 25.12kV to 25.39kV but basically remained steady at 25.28kV.

Regarding M L K 's suggestion, that would be all 10 film caps in the vicinity of the HVT: C43,48,49,64,69,70,73,75,99,118 - I can exclude C59 as that goes to SP25 which is not used.

As I have nothing to loose, I will give it a try and thank you for the suggestion.

Jeff
 
Waiting on delivery of a few caps to try this out but until then.......

Why does reading the voltage at G2 extinguish the display?

Just trying to learn.........

Thanks
Jeff
 
The G2 output (from the flyback) has a very high impedance and it cannot be measured with a standard multimeter. When the DMM probes are connected to the G2 the screen becomes dimmer because of the DMM's own impedance.

And the HV ceramic capacitor across GND and G2 can go bad with time causing the picture to become less bright.
 
Thank you for taking the time to explain that to me.....
And now I have another check point to look at if a display is dim!

Jeff
 
It's kinda embarrassing but I wanted to close this out for anyone else that might come across this,,,,,,,,,

See pic.....

Replaced socket and problem solved.

Thanks for the assistance.

Jeff
 

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