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Schiggidyd

Vectrex Screen Centering... Help!

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Hello folks!

I've been recently blessed with a Vectrex and 15 CIB games for a fantastic price (190 dollars).

But I need your help!
I have an almost perfect vectrex, I just can't center the friggin' screen. It should be so easy but I can't figure it out.
I understand there should be a yoke magnet, but I don't understand the concept and when I loosen the clamp on the yoke, I only seem to be able to rotate the screen, there's no other magnet I can spin, it all spins in unison and rotates. What am I doing wrong?

 

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I have never seen a vectrex but with most other screens the centering of the screen has to do with pots on the analog portion of the boards, twisting of the magnetic yoke is not going to move the image to the Y or X axis, its going to twist it from the central gun position.

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As per Osgeld I have never take a vectrex apart but I would also expect there should be a couple of pots somewhere, as the problem is probably due to a lack of voltage on the appropriate deflection plates thus you do not get the correct amount of deflection in the required direction.

Try looking on the PCB for something labled along the lines of V-adj and H-adj either as silk screen on the component side or copper on the solder side. These may be on the main PCB or the one mounted on the back of the tube (if there is one).

 

I would not advise messing with the tube magenets unless you know exactly what you are doing as they are factory set to ensure beam alignment with the shadow mask/convergance and focus. Get it wrong and you may never get it right again, therfore before you start I would recommend you make sure you have a good guide, preferable from someone who knows a lot about either Vetrex repairs or CRTs and can ensure you only adjust the correct magnet if that proves necessary.

 

P.S.

Be careful, from what little I can recall on CTR theory CRT tubes will general have a couple of thousand volts at the cathode end and around 15000 volts EHT for a B/W screen at the front end.

If all else fails and you can find a TV repair store try taking it to them, they may not understand what the Vetrex is but they don't need to as I would expect the tube and associate circuit design should be similar to if not identical to that of a B/W TV set so they should be able to fix it.

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Thanks guys. I've asked a few others and the centering is indeed done with yoke magnets. I've found all the Potentiometers and adjusted them well, it's just off center by 2-3 millimeters. SO CLOSE to being what I want.

In the beginning it was too low, closer to the bottom left, I got that positioned better, perfect height, just slightly too far right.

 

I love this thing and want to enjoy it as it's meant to be!

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Also, thanks for the concern about safety, I've only been fiddling around with rubber gloves on, and a screwdriver which won't carry the electricity to my hand.

 

Any idea what might be wrong Manoau?

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No I don't know much about vectrex repair. There are a few articles online I have read about various vectrex repairs. I am away from my computer so i can't link them. You got a great deal even for just the games. Finding a vectrex that works 100% percent is rare. Mine has a minor sound issue.

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There are a lot of pots that affect the screen.

On the bottom computer board there is one at the back center of the Vectrex. It does move the screen around, but the manual says it should not be used to adjust centering.

On the power board there are 2 cloudy white plastic pots that you can adjust.

Then there are two or three tiny black plastic pots with white centers that you probably need a plastic TV adjustment tool (especially if you adjust it when it is running). They are deep inside between the tube neck and the power board. The one closest to the top adjusts the high voltage.

 

I always ground the metal under the center of the suction cup with ground.

If I do it right after I unplug it, I get a small spark. If I wait a minute there is no spark.

Somehow all the Vectrexes I have worked on discharge very quickly which is unusual - I thought they could hold a charge for years.

Adjusting with the Vectrex on, however, I would get some plastic adjustment tools, or make your own somehow.

Even a metal screwdriver can slip and touch some components shorting them, and you will have a non-working Vectrex!

I don't think I ever needed to adjust the yolk magnets...

To properly adjust the manual says to use an oscilloscope. I was able to get by without one, using the "test cart" program on my Flash Cart.

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Yeah, I've only found three adjustable pots, they move X and Y, and the other moves the screen diagonally from bottom-left to top-right. I used that one to get my height correct, now I just need to move the screen left a little bit, and I'll have a perfect vectrex.

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The DAC offset adjustment isn't really for centering, only the magnets are. If you move the DAC offset pot to far out of adjustment, vectors at the edge will become distorted. Unfortunately you'll need a scope to put it back 100%, but if its a bit off its usually OK

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Here are the 7 variable resistors you can adjust in the Vectrex.

They are marked in yellow.

post-29575-0-27668700-1385758672_thumb.jpg

post-29575-0-12262400-1385758673_thumb.jpg

 

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Thank you guys, I did solve the centering using the ring magents.

Hi Schiggidyd, can you explain how you did it by using the ring magnets? I've only ever fiddled with the pots on boards before.

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It is R525 & R526.

They adjust the high voltage (5,800 Volts).

Mentioned in the Service Manual when adjusting with an oscilloscope.

You had better use plastic TV adjustment tools if you get anywhere near there with the system powered on!

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I use a bic pen with a wire strap taped on it...

What do they actually adjust? something visible on screen like trembling or shaking?

Basically I have this (feeble) issue on my vectrex...

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I don't know what effect they have.

I don't have an oscilloscope.

It says, "Adjust R526 to minimum ringing in the displayed waveform (on a scope). Recheck High Voltage & adjust R525 to get proper reading of 5.8KV+/- 105VDC)."

 

The best I can do is measure a working Vectrex resistance of the two, while off, and make the one I am working on the same value.

 

As a challenge to myself, I did fix a white dot Taiwan-made Vectrex that had sound by doing a Cap Kit (probably unnecessary) and replacing IC401. It still is not 100% because after it warms up sometimes the vector ends that should meet, don't meet. Hard to describe. Probably with an oscilloscope proper adjustment, and replacement of the plug in cable between the logic and power board - meaning solder them on, not plug them in - I think it would be 100%.

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Hi Schiggidyd, can you explain how you did it by using the ring magnets? I've only ever fiddled with the pots on boards before.

the answer, better late than never ;) ..
see the picture below, the correct two centering magnets found at the rear of the deflection yoke, i have highlighted with red arrows..
you adjust (turn) those two tabs to change the position (placement) of the image on the vectrex screen:
mag84h748.jpg
notes from the vectrex service manual:
piccc8.png
Edited by vtek
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Hay all...so I am trying to center my Vectrex (if you are looking at the screen, it is too low and to far to the left).

 

I have tried to adjust the centering magnets but they will not budge. I'm a little worried about pushing to hard so before I went any where else I thought I would see if anyone here has suggestions on the best way to adjust them.

 

Thanks!

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i cannot remember if perhaps first you could loosen the 'key' (clamp) before attempting to move them, that might be worth trying

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I had to use the rings to center a couple Vectrex units that I have. If I recall right, the magnetic rings are held in place by either a glue or wax originally used to hold them in place. On both of mine, that stuff broke loose fairly easily. Now, one of mine also got to the point where the screen would sometimes either not come up, or would be rather weak. Turned out the problem was I had to remove the CRT socket, clean it with contact cleaner, and then re-seated it on the CRT. It had the same glue type stuff on it and was on crooked! Looked like it had left the factory like that and had finally lost contact!

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Hi everyone, Im working on getting the picture balanced on a Vectrex and I seem to be stuck. I have adjusted the two magnets on the CRT, and the two yellow pots that seem to stretch the image up and down or left and right, but I cannot get the picture to balance out correctly. At the start screen the two lines that form the box around the Vectrex name touch, and nothing I do seems to begin to fix this. Any ideas what is making this happen.post-43012-0-44393900-1522272752_thumb.jpeg

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I'd try pulling, cleaning and reseating the LF347N IC chip (IC 303) in the Integrator circuit (as well as the socket) and maybe replace the Integrator caps while you're at it, which can be bought at Console5.com

This may fix your vectors that aren't aligning and is good preventive maintenance either way.

 

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... I would not advise messing with the tube magenets unless you know exactly what you are doing as they are factory set to ensure beam alignment with the shadow mask/convergance and focus. ...

 

Generally surely a good point, but beeing a black/white crt the vectrex has no shadow mask and there is no convergance as there is only one electron gun present in the system. Thats why b/w crts where used in viewfinders, as no mask sets - and thus limits - a physical resolution.

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