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Author Topic: MTC 900 - orientation of C94 - repair anode-cap - color problem  (Read 1835 times)

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sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #40 on: March 20, 2018, 10:21:51 am »
Again you are right  :applaud:.  R131 read in the mega Ohms so I guess it went out. I bought a new one and there was somewhat picture again  :D. The same as before it went white. I desoldered R145 and C52 the both were good.
All the transistors on the interface board are replaced now. I also replaced all the BF871 transistors on the neckcard.

I connected the raspberryPi with Pi2Jamma and got a good picture. A bit dim, but a good stable picture (see picture). I don't think a Pi makes use of the -5V. So that is probably the problem with the gameboards. I remember giving the PSU a cap-kit and after measuring the molex-connector which gave -5V. So I am confident my other cabinet uses -5V. But I will verify that.

I was not totally satisfied with the colors so I connected the Streetfighterboard in Testmode. I got the same colored barrs again.
I started tweaking the neckboard and suddenly the screen became redder and the scanlines appeared. Just like before
Then the screen went white with scanlines and I was back where I started.
When I turned the cabinet off and on again the screen was still white with lines, but I heard crackling. I looked and saw spraks comming from R131 to the heatsheald next to it. Turned the cabinet off immediately.

I think something is overloading R131. I soldered everything with great care. The only thing that gives me doubts is the broken ceramic capacitor I replaced. It's 50V but it is so small I am not sure anymore if it's right. (see picture).

Could it be that connecting without the -5V could cause an overload?
Do you know where I can look to solve this?

« Last Edit: March 20, 2018, 10:40:52 am by sollima »

grantspain

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #41 on: March 20, 2018, 10:36:38 am »
maybe there is some short component on the neck board- did you change the red pots?

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #42 on: March 20, 2018, 10:38:55 am »
Yes I did. Should I replace them?

grantspain

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #43 on: March 20, 2018, 11:09:22 am »
be interesting to see what happens if you replace the resistor- see if the red is up high again
this of course could be the red gun in the crt itself, but they usually go super bright with flyback lines in one colour or no colour at all

a white screen with flyback lines is normally video b+ missing

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #44 on: March 20, 2018, 11:34:23 am »
I will buy several resistors and new pots tomorrow. I will not change the pots yet and film the effect of loosing the resistor. Then I will report back and see if I can detect a short on the neckboard.

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #45 on: March 21, 2018, 12:02:17 pm »
Bought new resistors today. Replaced the broken one.
I cleaned the neckboard and connected the -5V to the JAMMA-plug.

So when I booted up it looked good. But then I heared the crackling noise. I saw sparks flying from R131 to the heatsheald. But sometime they stayed away and the screen was 'giving picture' (see movie 100MB)
When scenes changed the picture went out of sync again.

I did capture a time when the resistor almost broke. On second 3 of the movie you can see the scan lines and reddish glow appear. Movie2 100MB. At the end of the movie you can see picture going out of sync. Sadly I was too late for the final burn through, but it looked like second 3 of movie but the screen went white with scanlines.

I think the spraks were getting worse when I tried to adjes RV17 Vert Lin.

I really hope you can help me.


grantspain

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #46 on: March 21, 2018, 12:58:24 pm »
its acting very strange, could be flyback- you did reconnect the crt earth to the neck card?

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #47 on: March 21, 2018, 02:07:47 pm »
I did reconnect the earth to the neckcard and to the clip connected to the metal wire that goes around the tube.

I hope it's not a broken flyback because that would mean a big finacial investment. Is it worth it? Is there a way to rule out if it is the flyback?

Could it be that IC2 is broken? Or that components on the interfaceboard probably got broken and cause an overload?

This thing is worrying and keeping me up. I would love for it to work properly.

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #48 on: March 21, 2018, 03:11:39 pm »
I read the repair guide from Ken Layton. Here It's for the 900E but the boards are very similar. Does this comment on the bottom of page 1 apply to me?

Quote from: Hantarex MTC 900/E repair guide
No vertical deflection problem: Check for an open or burned resistor R56 (6.8 ohm, 1 watt) on the deflection board. If the resistor is found to be bad then you must also replace the IC3 vertical output (TDA 2653A or NTE 1804).

Is this the same resistor as R87 1.5 Ohm 1W of my board? Or am I way off?


grantspain

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #49 on: March 21, 2018, 05:22:08 pm »
you have far too many odd faults, these chassis are fix after fix as they are old but is incredibly rare for the repairs to fail like yours
do you have a european 900e or usa 900e?

you may find you are throwing money at this, how do you know your tube is good btw? did you test that chassis on the mtc9000 tube(neck pinout allowing)

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #50 on: March 22, 2018, 02:22:58 am »
 :( that does not sound promessing. To be honest I do not know if the tube is good. It gives three colors and some picture, so I assumed it is good. Can I assume that you think the failing of the resistor should be the reason of the neckcard or up to the tube?

Sadly the crt-connector of the MTC900 is different from the MTC9000. My MTC900 has some kind of sleeve the MTC9000 has a female plug like connector. Is it possible to just switch the connectors and test?
The sticker to identify my monitor is missing so I can't say or sure.

The sticker on my chassis says MTC900. But searching the manual online it looks more like a MTC900/e. Although the manual I found online has a different silk numbering of the interface board. From discriptions I read I think I have a MTC900/e version2. But I don't know if it is a European or USA version. But because I live in the Netherlands, I assume it is the European version.
Is there a way to indentify it for certain?

Can I assume that testing the tube is the first priority before chasing IC or interfaceboard or flyback?

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #51 on: March 22, 2018, 04:13:31 am »
you can swap the crt socket but tbh you don't want to start messing with a working chassis- I would buy a replacement crt socket
euro 900e has 1 x 6 pin green connector for rgb and a 4 pin green connector for 120/230- usa version has same connectors you find on stuff like g07, there are some minor differences in the components and design of the chassis

sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #52 on: March 23, 2018, 10:29:53 am »
Thank you for your answer. Then I definitly have a european version. I will try searching for a crt socket.

I will report back when I know more.


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sollima

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Re: MTC 900 - orientation of C94 - repair anode-cap - color problem
« Reply #53 on: April 21, 2018, 08:08:55 am »
Yesterday I got around to switch the tubes of my MTC9000 (A51-427x) and my MTC900-e (unknown missing sticker).

I switched the CR23 plugs on the neckcards and placed both the chassis.

I think I have two issues.

1. The MTC900-e (with the failing of R131) failed again with the new tube. When booting up the picture was in sync, sharp, bright. I thought I deducted the problem as the monitor. But after a reboot the screen went white again with the scanlines. R131 was blown again. Dispite the tube change. --> my conclusion is that there is a build-up to a short in the neckcard. A component gives slowly which causes R131 to blow.
Does someone have a tip on which one it could be?

2. The working chassis of my MTC9000 was connected to the other tube (of the problematic MTC900e). I got the same results when connection the game. No way to correctly sync the game. Picture stays blurry, scrolling. The same as with the MTC900e.  (Strangely, when connecting a Pi with Pi2scart, the picture comes up nicely). Looking at the neckglow there is one filament glowing brighter than the others.
So I concluded that the tube is also faulty. (The same chassis MTC9000 together with the other tube gives a stable picture). Would one say that this is a fair conclusion?

Thank you for your help
« Last Edit: April 21, 2018, 08:14:20 am by sollima »

  
 

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