Hantarex MTC 9000 small points - Solved

[mjnman]

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 a picture video issue link.

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

mjnman2021-12-27 07:59:56

 

[gunblade]

posted at byoac, disconnect video cable/obtain raster and see if issue is present

if it is then link fg/earth and ground/common on power supply

if not does sub brightness pot/circuit work?

 

[mjnman]

I disconnected the video cable and turn up the brightness and the image seems to be ok 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.

 

[mjnman]

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

 

[big10p]

If your chassis or monitor frame has an earth connection, try disconnecting it. I have a couple of mtc9000 monitors where the earth causes interference.

 

[gunblade]

sub brightness pot is behind flyback but i think the issue earth related

 

[mjnman]

I disconnecting the ground from neckboard and monitor frame but the problem it's same.

I tried to remarking the solderings in neck board and main board but nothing.

I thinking a bad component...next week i'll try to replace the BC639, BC548 and BC558. Next step l'll try to check all component connected with ground.

 

[Vamino]

Are you connecting a PC or Jamma PCB to the monitor?

 

[mjnman]

I'm connecting a PC with RadeonHD and linux 15khz kernel, no problem with other five chassis, 2 hantarex mtc 900e, CA&G VI2100, MTC 9000 clone and a Semio

 

[gunblade]

did you check the sub brightness pot works correctly as issues in that circuit can cause odd faults

also worth mentioning there are 2 earth tags on the chassis frame soldered to the circuit board

 

[mjnman]

Where are the two earth tags?

is it the RV7 the sub brightness? I already replaced.

I replaced all transistors BC558B, BC548B and vertical deflector TDA1670. Nothing to do, same issue.

 

[gunblade]

is does not look like a component failure as such

the earth tags are on the flyback heatshield, one is near the vertical ic and the other near r110

the sub brightness pot neeeds to be checked for function as faults in this circuit can cause real odd faults

 

[mjnman]

I replaced the transistor TR14 with new one, it's a BC639. When I powered on the tube there ware strange horizontal lines in movement.

I cameback to the old transistor and the image have the initial issue without horizontal lines.

The old transistor is good but also the new transistor is good.

I checked the voltage drop with tester and the old BC639 is 0.6v while the new BC639 is 0.7v.

The same issue with TR18, still BC639.

A checked a lot of time but it's the same type of transistor.

I cannot understand the reason!!!! Maybe a indication about the started issue...

 

[gunblade]

possibly a broken track or solder pad somewhere, is the picture affected by physical persuasion ?

 

[mjnman]

I checked all components with ground connection and look good. I going to check all ground points with GND in input video connector...component side where I can do.

 

[mjnman]

I checked all ground point with GND input video cable and it's OK. I didn't find bad GND point.

Plaese, what i can check?

 

[mjnman]

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.

f**k f**k f**k.

 

[gunblade]

you went through a lot of work for something i mentioned in my first post

 

[myazgan]

Herkese merhaba, yeni bir konu açmak istemedim ama aynı kasa ile aynı sorunu yaşıyorum. Raster testi temiz, ancak video sinyal kablosu bağlanır bağlanmaz beyaz atlamalar başlıyor. İki farklı video örneğini inceleyebilirseniz çok sevinirim. Bu atlamalar özellikle harflerde belirgin. Sorun nasıl çözüldü? Birisi güç kaynağından bahsetti ama tam olarak anlamadım. Herhangi bir öneriye minnettar olurum. Bu arada, RGBSGND kablolarımda ek yerleri var. Bunları yeniden bağlayamadım. Bu sorunun kaynağı olabilir mi? Eğer öyleyse, nasıl düzeltebilirim?