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B+ For Kaga KZ-20EN / Sega MC-2000-S


Grish

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Howdy All,

 

Picked up my first arcade cab a few days ago, It needs a little work :\

 

Starting with the monitor, I've got a few issues and questions, hoping you guys will be able to help me out...!

 

Ok so first of all, the Monitor is a Kaga KZ-20EN with the irreplaceable flyback :( I obviously had no idea this wasn't a serviceable monitor when I bought the unit, all well. It has been capped/serviced by Jomac, apparently just last October.. (it's got a Jomac sticker on it too) - Chassis is a little different (but basically identical apparently) to the Sega MC-2000-S which has a Video Bias pot and only two horizontal jumper options (no "middle" option) and a few other differences I've manually observed.

 

Whilst the picture overall is pretty good, there are various issues with Width, and jaggered / wavy edges that appear more evident depending on the picture. Here's a pic running WBML with the chassis width jump set to "middle" (there's only "middle" or "wide" options and wide is too "wide", middle is too narrow) I haven't dared attempt poking about at the H-Width Coil, plus Jomac (or someone) smothered it in hot snot... probably for a good reason!

 

The other thing is there doesn't appear to be anywhere to plug in the two socket Deguassing coil plug, according to the Sega's manual / schematic it should be along side the neck board, but mine appears to be non-existent. I've read they can be a little useless anyway, but I don't currently have a wand.

 

I have slightly adjusted the screen pot/dial (near flyback) to remove some horiz lines on dark backgrounds, and that's all good now. But I am completely lost in figuring out how to test/adjust the B+ DC voltage... I really want to check this as I've heard this can help with Horiz issues.

 

Hoping someone can help, I know the standard advise is to immediately ship it back to Jomac, but I bought this machine to tinker / learn / hobby more than actually to play games on, so I want to learn stuff too :)

 

Weird jaggered / wavy and "pulsating" edges / lines:

 

wbml_jaggered.jpg

 

No FG attached to switching PSU, should I add one?:

 

PSU_No_FG.jpg

 

The Nanao KB240331D Chassis, Is this the B+ pot?? and if so, where exactly do I put multimeter to measure the DC voltage?:

 

Nanao_KB240331D_Chassis.jpg

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Is the flyback for that model irreplaceable? I know the even older Nanao chassis with the flyback in it's own separate box is gone, but i hadn't heard that about the MC-2000S.

 

Would Jomac automatically have replaced the caps? I'm sure he wouldn't mind you asking about a monitor with his name/sticker on it, especially if it's that recent. You could maybe try measuring a few of the big electros in the power supply and deflection sections, though. And check the ground wire is connected from the neckboard to the aquadag coating on the outside of the tube.

 

These had a little separate, side-mounted PCB with the degaussing circuit on it, that plugged back into the main board. I think that circuit isn't reliable though. Mine is certainly dead. A degaussing wand is a better option to begin with.

 

Also, https://elektrotanya.com/sega_mc-2000s.pdf/download.html

Edited by buttersoft
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Plug another PCB into your cab and see what the picture is like, as your problem may be board related.

 

Joey would have re-built the monitor and tested the B+, so don't go messing with it.

 

You may have to adjust the Horizontal width, but you need the correct tool (not a metal allen key)

 

Regards,

 

Johns-Arcade.

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Is the flyback for that model irreplaceable? I know the even older Nanao chassis with the flyback in it's own separate box is gone, but i hadn't heard that about the MC-2000S.

 

I've seen various references to the Sega MC-2000-S being the same as the Kaga KZ-20EN and it having irreplaceable flyback (MSG1FAC02)

 

The Chassis: http://www.jomac.net.au/wp-content/uploads/2006/02/Kaga-Nanao-KZ-20EN-L.jpg

 

An Old Thread: https://www.aussiearcade.com/archive/index.php/t-39954.html

 

Jomac writes: ""these were one of the best 20" 15K monitors ever made"

 

"the correct model for the one you have is a KZ20-EN , when the flybacks were available for these 14 years ago they cost $165US so while it would be nice to keep it original I have had a replacement chassis specifically made to replace these that will produce a perfect picture and is cheaper for the entire chassis than the old flyback was. (Also these flybacks are not being made anymore)""

 

Would Jomac automatically have replaced the caps?
I'll see if I can chase that up with Jomac, but i would assume he did (red/pinkish coloured caps)

 

These had a little separate, side-mounted PCB with the degaussing circuit on it, that plugged back into the main board. I think that circuit isn't reliable though. Mine is certainly dead. A degaussing wand is a better option to begin with.
OK thanks, I'll stop looking for it, it's clearly been discarded at some point.

 

- - - Updated - - -

 

Plug another PCB into your cab and see what the picture is like, as your problem may be board related.

 

Joey would have re-built the monitor and tested the B+, so don't go messing with it.

 

You may have to adjust the Horizontal width, but you need the correct tool (not a metal allen key)

 

Regards,

 

Johns-Arcade.

 

Thanks John,

 

I've tried a few combos with 2 diff pcbs, I can get the MK pcb looking pretty good when the chassis jumper is set to "wide" however it's still too "wide".

 

I did make some progress with the weird "wavy/jaggered" lines, turns out if I reduce the brightness all the way down to almost black they straighten up and the speaker buzz/hum also goes away! Perfect!!! Apart from one minor detail.... I can barely see the game :( Any ideas whats going on here? So the brightness setting has a direct impact to the speaker interference AND the jaggered lines on the screen..!!?

 

Yes I was going to try and get hold of the proper plastic TV adjusting tool/s, I'll see what I can find online.

 

- - - Updated - - -

 

By the way, I tested the AC output from my transformer (It's a step down from 240v to 105v, and I'm not sure if it also provides isolation, but assume/hope it does!);

 

It outputs 2*60VAC on the Monitor side (weirdly it's 2*55VAC on the switching PSU side.. so NFI what that story is about either)...

 

So, I wonder if feeding 120VAC to this chassis is OK given it's only spec'd to grab 100VAC +/- 10% ?

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Weird jaggered / wavy and "pulsating" edges / lines....

 

 

Do they stay the same regardless of whats on the screen. Eg: title screen, playing through level one or two?

Are they less prominent if you turn the screen voltage down and or brightness?

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um ..how are you measuring?
Multimeter. This transformer appears outputs 2*105V lines, each line is then segmented as 2*55-60VAC lines.

 

I think they call that a "site transformer"?

 

- - - Updated - - -

 

Do they stay the same regardless of whats on the screen. Eg: title screen, playing through level one or two?

Are they less prominent if you turn the screen voltage down and or brightness?

 

As mentioned in previous post, the brightness seems to drastically impact the jaggered lines and also reduces the speaker buzz/hum...

 

Any ideas why? I need to turn it down to almost unplayable levels.

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Try turning all your R/G/B bias pots down (neck board) and turning the R/G/B gain pots up (chassis). Back off blue in particular as much as you can.

I'm going to guess that you get the "wavy" stuff where there is white... All guns on.

 

*take pics to put stuff back.

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I think, and this is just an I think, that if you show a static image and you're seeing static kinks following bright horizontal sections then the self-regulation in the horizontal deflection isn't responding fast enough to changes in brightness during the raster, so you get overshoot when the bright patch starts and undershoot when it stops. This has to be caused by the power going through the horizontal coils of the yoke, because that's what positions the image on screen horizotnally. The horizontal coils are often connected directly to the flyback on one side. I would guess that you're not looking at a shorted turn in the flyback, and that the flyback is ok, but that's only a guess.

 

The problem might be in the components on the other side of the horizontal coil (assuming that's what this chassis looks like) or it might be the supply to flyback. As you lower the brightness less power is required, so the problem becomes minimal. On cheap universal chassis this happens when they're new and you try to work them too hard. Which is not to say i have any idea what might be causing it on an old Nanao beyond caps, but when i recapped mine i did the polymers as well as the electrolytics, and i didn't regret that. I'd listen to people who actually know what they're doing before me, though :)

 

EDIT: Have you looked at the power supply going into the chassis? Regardless of measured voltages, if it's not delivering enough juice fast enough, i guess it might cause the problem you're seeing?

 

Updated description above.

Edited by buttersoft
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The problem might be in the components on the other side of the horizontal coil (assuming that's what this chassis looks like) or it might be the supply to flyback. As you lower the brightness less power is required, so the problem becomes minimal.

 

EDIT: Have you looked at the power supply going into the chassis?

 

Thanks mate, that does make sense, yesterday I also noticed a decent spark/arc at the neck board area when first turning the monitor on, if I turn off and back on again no spark.. this also has me worried!

 

In terms of checking the power supply to the chassis, can this be done simply with a multimeter? That's all I've got. There's two AC wires entering the chassis and I "think" they are both "live" lines ie. Not neutral or earth, is this correct?

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