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Hantarex MTC 9000 small points - Solved

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mjnman View Drop Down
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    Posted: 15 Nov 2021 at 10:46am
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




Edited by mjnman - 27 Dec 2021 at 7:59am
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gunblade View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 12:06pm
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?
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mjnman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 4:57pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 5:23pm
I rechecked and the issue is present without video cable...it's very very difficult to see but there is a tiny disturb. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 6:13pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 6:17pm
sub brightness pot is behind flyback but i think the issue earth related
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 9:43pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vamino Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 9:51pm
Are you connecting a PC or Jamma PCB to the monitor?
Insert Coin[s]
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mjnman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2021 at 10:26pm
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov 2021 at 6:52am
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 20 Nov 2021 at 10:36pm
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. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2021 at 9:08am
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 23 Nov 2021 at 4:45pm
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...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 23 Nov 2021 at 7:34pm
possibly a broken track or solder pad somewhere, is the picture affected by physical persuasion ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2021 at 10:10pm
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. Unhappy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2021 at 4:53pm
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?  Censored

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjnman Quote  Post ReplyReply Direct Link To This Post Posted: 27 Dec 2021 at 7:59am
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 27 Dec 2021 at 12:05pm
you went through a lot of work for something i mentioned in my first post
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