Hantarex MTC 9000 - Missing colour red - advice or UK refurb/engineer?

chrisg78

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Hantarex MTC 9000 - Missing colour red - advice or UK refurb/engineer?

Hi All,

I've got a UK-edition Playchoice 10 cab. It's generally been reliable, but the other day it suddenly (mid game) lost the colour red. There seem to be no other effects - the image is still sharp and steady, just no red (or perhaps very very little red, hard to tell).

I've done some basic troubleshooting by checking voltage on the red, green and blue lines, all the way through to the points on the neck board (marked on 4th image below). I see about 10-12v, depending on the image. This seems roughly the same as the green and blue signals.

The red gain and red cutoff on the neck board do nothing. I've not yet tried metering these components, because I don't really know what I'm looking for.. But I'll post an update if I find something there.

I've also not tried removing the neck board and re-seating it yet, because I've never done that before! (Does it just pull off on these monitors?)

Pics:


wRl3c.jpg


GbhJp.jpg


ROwTZ.jpg


JteIl.jpg

(red circles a points where I metered approx 10-12v)

97DyG.jpg


KqG1x.jpg


Has anyone got any thoughts on what to try next? The only equipment I have is a multimeter! (and I only have a basic knowledge of electronics)

Any advice would be gratefully received.

Also - Is there anyone in the UK who offers a full refurb service for this monitor? It could probably benefit from a cap replacement and a refresh of the tube. (I really don't have the time to do this myself!)

Thanks everyone
 
Does your multimeter have a diode test? If so, set it on that, and check between the base and the collector, and the base and the emitter on one of the transistors. Then compare that to the other two transistors. Then, reverse your leads and do it all over again.

If your red transistor comes back telling you that the reading is higher than the other two, then that transistor is likely bad.

Since your pots both don't do anything, though, I fear that the tube might be bad, or at least have an 'open' gun that you'd need a rejuvenator to attempt to fix.

While you're at it, measure the 'like' resistors on the neckboard with the ohm meter on your meter. If you look closely you'll notice that all three colors have the same resistors in the circuit. If you set the pots all at about the same place, you can measure them in circuit, against each other... for instance if there's a red/blue/gold banded resistor attached to each color circuit, and two of them read 10Kohms, and the one on the red circuit reads 1.5meg Ohms, then that resistor's way out of spec and cutting your red signal off.
 
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Thanks - I had a quick go at this. Assuming I'm checking the right things.... this is what I found:

H8pju.jpg


I note that my multimeter reads 'open' above about 1400 or so.

If that is the 'red' transistor, and it's bad, would that be enough to kill the red signal?

I don't actually know how to remove the neck board to get a better look at the components (especially resistors). Does it just pull straight off, or is there a catch of some kind?

Thanks for your help!
 
Yes the neckboard should just pull straight off the back. When you're checking diodes, a number between .400 and .700 or so means it's doing it's job, a number higher than that means that it's open (which sometimes it should be). So your three transistors are actually measuring the same, try it with the leads reversed, too, though. So for instance if you had your black lead on the base, and then were using your red lead on the other two pins, reverse the leads and measure again, to see if they're all the same that way as well.
 
Ah, ok - so maybe that transistor is ok then. Is it odd that it's giving a higher reading, or does that make no difference to it's function?

I've metered them all the other way around (positive on base), and they are all open.

Is there a simple way of testing the signal at the socket going into the tube? I notice points marked KR, KG and KB. Are they any use?

Sorry for my noobishness..
 
Thought I would post an update to this, for anyone who is interested..

The transistor on the neckboard was the main problem.. but there were other faulty components too.

I sent the chassis off to Craig at http://www.giz10p.co.uk who did a great job of fixing it up (and replaced the capacitors at the same time). Reasonable price as well.

When I hooked it back up I had a new problem though - an overload of green. Turning the brightness (screen) up more than about 50% caused the screen to flood with green. Adjusting gain and cutoff did very little to correct it.

I'd previously bought a B&K 467 rejuvenator off of ebay, and hooked that up. It seems the green gun had picked up a short; possibly from originally wrestling the neckboard off (which required quite a lot of force). I ran the restore process and after some nerve-racking sparking and cracking, the shorts were removed.

After that, everything now seems to be working well!
 
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