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Author Topic: Hantarex MTC 9000 bridge coil worn off cant adjust but picture is just too large  (Read 2797 times)

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sollima

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there was something a lot of people used to do when the width circuit had a fault, they would adjust the core of the horizontal linearity coil as a quick fix- this may be what has happened previously to your chassis

I think you might be right. But the quick fix is now stuck and I canít reverse it. I hope that replacing C41 will help. Also ordered new MKP caps for C40 and C41 (same value as the originals). Maybe it helps.

From your answer I presume that the value I measured on the B+ is good and you donít have new leads at the moment?


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grantspain

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horizontal linearity coil is different to bridge coil, its the tall coil

sollima

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horizontal linearity coil is different to bridge coil, its the tall coil

OK, you mean adjusting the large coil (horizontal linearity coil) might turn the possible quick fix settings back. And maybe resolve my problem.
But I read somewhere never to touch the linearity coil. Save this for a last resort, or  it should be no problem to try.

grantspain

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horizontal linearity coil is different to bridge coil, its the tall coil

OK, you mean adjusting the large coil (horizontal linearity coil) might turn the possible quick fix settings back. And maybe resolve my problem.
But I read somewhere never to touch the linearity coil. Save this for a last resort, or  it should be no problem to try.
yes you are not really meant to adjust it but many people did as a quick fix, if your chassis has been messed with in the past this coil may have been adjusted

sollima

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It would work but it's too big and can't be installed in the proper spot. You could put it somehow on the bottom but if you can, get an axial one. Hantarex originally used a bipolar electrolytic and then switched to an axial poly cap:


My order arrived yesterday and I replaced the capacitor with the capacitor you suggested (and the way the picture shows). But sadly there were no differences in the picture width noticable.

But when I was adjusting/calibrating the picture I noticed something. When I turn the brightness knob of the LOPT (big black thing with the High Voltage suctioncup cable) my screen size expands. A bit like 'blooming', but stable. So I turned the brightness very low and my edges came back into picture. Downside was that the picture was so dim, you could barely see what was happening on the screen.
So I tried turning up the brightness with the potentiometer on the chassis. I could barely see any gain of brightness. So I replaced the brightness potentiometer on the chassis. But still no noticable difference in gain of brightness. If I turn the potentiometer completely counter clockwise the screen goes black, but when I turn it completely clockwise not much extra brightness.

Can this be something to persue? To regain some brightness from adjusting form the chassis instead of the LOPT?
Could it be that a poly-cap, resistor or transistor connected to the brightness is faulty? Or is the brightness gain by the chassis not very much and probably not faulty?



princess prin prin

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The brightness pot is known to decrease its value over time. Desolder it, measure it and if it's much less than 220k replace it.

sollima

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The brightness pot is known to decrease its value over time. Desolder it, measure it and if it's much less than 220k replace it.

Thank you, but the situation I mentioned was after I replaced it with a new one. Should I replace the polycaps connected to it?


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princess prin prin

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Have you done the white balance adjustment as shown in the manual?

grantspain

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not your exact issue but yesterday I worked on a 9000 chassis with a mass of faults, after doing the caps, flyback and usual brightness circuit faults I had the chassis running but with a strange width fault and a strange brightness issue- the width was too small but had adjustment, when you adjusted the width in the brightness would change and red cut off would increase. Not exactly your issue but similar

the brightness issue was down to c43(other known component failures are r90, r92,r93,r80 and c47)
the width issue was failing c36( other known component failures are tr16,tr17,c42,c41,c40,d12,d13), someone had also adjusted the h.lin coil at some point


sollima

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.....

the brightness issue was down to c43(other known component failures are r90, r92,r93,r80 and c47)

.....

Thank you for your answer and your experience.  I will replace the capacitor and the resistors you mentioned. In addition I will replace C37, C46 and C47 with new ones. Adding them to my order is not expensive.

I do have a couple of questions about the resitors:
- The manual states (besides the Ohms) 1/2 W and 1/4 W. Is it possible to replace the resistor with same or higher Watts? Or should it be te same Watts?
- The manual states carbon based resistors, but I the higher Watt resistors are sometimes 'Metal film' or 'Metal Oxide Layer' resistors. Can these resistors (Metal based) be used of will it give problems?

the width issue was failing c36( other known component failures are tr16,tr17,c42,c41,c40,d12,d13), someone had also adjusted the h.lin coil at some point

I replaced all the transistors and capacitors you mentioned and measured both of the diodes. That is why I think that maybe looking at another problem, like the brightness, will maybe help me come to a solution.

- I am a bit afraid of adjusting the horizontal lineairity coil because of the warnings I read. If I adjust the coil will the picture shink or expand? Or will the picture start rolling or become scrambled? And if the picture is scroling or scrambled do I adjust that with the adjusment board? Should I keep the adjusment as a last resort? Or just try it?

- How do I adust it? Do I turn the small cilinder with the square hole? Which direction for smaller image? Only with plastic tools and when the monitor is turned off?

Thank you for your help, it's much appreciated


grantspain

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i would always attempt to use same watt ratings on resistors but most are not critical, metal oxide are critical so if your schem says there is one there then make sure you replace it with the same. Replacing a carbon film with metal film is not an issue and replacing both types with a metal oxide is no issue- metal oxide are flame proof and tend to be used as a safety component.

the lin coil you can adjust with a flat blade screwdriver that fits snug into the core, I adjust it with the monitor powered on- it will adjust the final 1/4 of each side of the screen- to get it right you need a grid pattern so you can see if the grids are the same size

sollima

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Thank you for your explanation on resistors. I will order them shortly.

Just to be sure that I understand you correctly I added a picture of which coil we are talking about. Do I understand you correctly?
« Last Edit: February 25, 2018, 04:48:10 am by sollima »

grantspain

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yes absolutely correct

sollima

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I am happy to report that adjusting the H. Linearity coil as you suggested worked! You called it a few posts back. Somebody probably made a quick fix and adjustments to it.

I don't know if the geometry is totally correct, but I am very happy at the moment because it looks pretty good. I will probably replace some old polycaps with new ones I already ordered, but for now I will go on to the second part of my cabinet project. Repairing, cleaning and painting the cabinet, placing artwork, buttons and probably a Pi2Jamma configuration

I want to thank everybody who took the time to read my posts and contributed their time in helping me. I learned a lot about capacitors, soldering, reading schematics. I'm very grateful.
baritonomarchetto, princess prin prin and grantspain, Thank you!
« Last Edit: February 25, 2018, 07:03:56 am by sollima »

  
 

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