Sanwa 29e31s help needed

[Trol]

This was working fine with a nice picture untill yesterday.. tried a TTX2 with probably a blown video card or a bad dvi to vga adapter.

It showed red dots an red flashes on the screen.
Fiddled wit the TTX a bit and the monitor died.

I can hear the startup noise from the psu, I think.
No static, no neckglow, no demag.
Checked the fuse and the 100v power, all ok.
What do I do next?
Checking the fusible resistor in a bit, but really don't know about fault finding in a a monitor.

 

[Trol]

Ok, the fusible resistor looks ok.
Also measured an ac to dc chip thing.
Ac side reads 100v, dc side reads about 134V.
Seems fine to me. I'm taking the chassis out and will test the HOT....

 

[Spunkworks]

You are using the wrong DVI to VGA adapter.

 

[Trol]

Yeah, found out today.
Got the TTX running fine.
The monitor dying is just bad luck, I think.

 

[Trol]

Well, the HOT is shorted.
I tested the fusible resistor again and it's really fine.
So I'll replace the HOT and wil see from there.

 

[Trol]

Replaced HOT, all fixed

 

[Trol]

Hot blew again..... damn.

 

[Trol]

Tried the next HOT.....got 5 from Aliexpress...lets hope this one lasts longer

 

[nem]

Likely something blowing the HOT.

 

[Trol]

Well, still running...lets hope for the best...
The original HOT was shorted, the ali HOT was open..I'm staying positive

 

[Trol]

Soak tested it this weekend.
Still running, so I consider it fixed.

 

[Trol]

Fuck me... Hot just blew again, I watched it go down
So definately something blowing the HOT.
Suspect nr. 1 is the flyback, right?

 

[dewmansnk]

The HOT is taking stored energy from the flyback and putting it into the deflection coil. I would suspect that the flyback is properly storing energy as you get it working for a short period of time. Across the HOT is a very important diode that I am thinking may have blown, although I think that might just result in instant HOT death, not the slow failure you have seen.

http://repairfaq.cis.upenn.edu/sam/deflfaq.htm#dshkb

In that repair FAQ, it lists the drive current into base of the HOT as a possible cause for increased HOT heating and the slower failure, so maybe start there. Should be fairly quick to also check the safety diode across the HOT and make sure that its still good as well.