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Main => Monitor/Video Forum => Topic started by: mjnman on November 15, 2021, 05:20:09 am

Title: Hantarex MTC 9000 small points maybe missing ground - Solved
Post by: mjnman on November 15, 2021, 05:20:09 am

I have a chassis with a first version of MTC 9000 with small white points in the screen, brilliant effect. (below a youtube video)

I tried to:
- replaced all electrolytic capacitors, total recap;
- replaced ceramic capacitor in the neck board C206;
- replaced flyback;
- tested with another tube;
- replaced transistor on the neckboard, TR201-202-203;
- checked all variable resistors on the neckboard;
- replaced RV7 on main board, brightness preset;
- removed fuse 2 then disabled degauss circuit and removed degauss cable;

I checked the main points and seems to be ok:
TP10 - 133.4
TP12 - 11.9
TP13 - 26.9
TP 1 - 24.8
SP11 - 202.9
G2   - 352.2 (ground on the NECK)

I tried to connect a direct ground cable between big heatsink and power socket and there is a little decreases of defect.
Maybe a bad component connected with ground side?
Please, what i can check? i don't know i can do.
In attachment the scheme of chassis and the video issue.

https://www.youtube.com/watch?v=cjd488gXUGw

Title: Re: Hantarex MTC 9000 small points maybe missing ground
Post by: grantspain on November 15, 2021, 06:05:03 am

if you disconnect video cable and obtain a raster by turning up screen volts a little do you still see this issus?

Title: Re: Hantarex MTC 9000 small points maybe missing ground
Post by: mjnman on November 15, 2021, 11:58:14 am

I disconnected the video cable and turn up the brightness and the image seems to be ok (white) but it's same thing with a single color, es. blue or red and connected cable.
Yes. The brightness on flyback work and the contrast switch work.

Title: Re: Hantarex MTC 9000 small points maybe missing ground
Post by: mjnman on November 15, 2021, 12:24:47 pm

I rechecked and the issue is present without video cable...it's very very difficult to see but there is a tiny disturb.

Title: Re: Hantarex MTC 9000 small points maybe missing ground - Solved
Post by: mjnman on December 27, 2021, 03:45:55 am

These are Jesus days...I found the problem.
From beginning I replaced:

- entire recap (solve flickering);
- replaced flyback (nothing);
- replaced ceramic capacitor in the neck board C206 (nothing);
- replaced transistor on the neckboard, TR201-202-203 (nothing);
- replaced ALL variable resistors (nothing);
- removed fuse 2 then disabled degauss circuit and removed degauss cable (nothing);
- replaced TDA1670A (nothing);
- replaced TDA2595 (nothing);
- replaced all transistors BC558B and BC548B (nothing);
- replaced transisitor BDX53A (TR17) (nothing);
- Checked all ground points (nothing);
- Checked all components near ground (nothing);

....at the end the problem was in the PSU!!!!...absurd.
---fudgesicle--- ---fudgesicle--- ---fudgesicle---.