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Jomacs Universal Chassis


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I'm fixing up a 20" lowboy that needs a chassis so i ordered my uni chassis on the weekend. Just thought since this question about replacement tubes and chassis come up often I will sticky this thread for all to see.

To order one of these chassis suited for 13"-21" monitors and are $145, read in information in the Products / Parts section on what you have to do to order.

Click on Links where you can find Jomac's link to his site.

 

What you get.

Chassis

Degassing coil

Earth wire

RGB connector

http://members.iinet.net.au/~golga/IMG_0112.jpg

 

http://members.iinet.net.au/~golga/IMG_0114.jpg

 

I must say from a first look im impressed, I specially like the knob on the horizontal size coil so no special tool required to adjust.

I'll keep adding to this thread with chassis installed and running with picture quality etc (wont be till the weekend).

 

Please don't reply to this thread.

Edited by Arcade King
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Ok here she is all installed and set up, still need to make some colour adjustments etc but im VERY happy. Easy to install and adjust 10/10.

Considering repairs can cost more than this it is worth considering going new.

 

http://members.iinet.net.au/~golga/IMG_0117.jpg

 

http://members.iinet.net.au/~golga/IMG_0118.jpg

 

I'm hoping Joey will add some more information to this thread.

Now I go to rewire the rest of the cab :D

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Yes it is :)

I should point out what Joe told me yesterday that these chassis can run on 240 volts so it removes the need for a stepdown transformer, pretty damn sweet.

It says on the sticker on the side 90-260 volts.

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This is a perfect example of how easy this conversion is supposed to be ,

 

The tube that Trav is using in this Pic is probably one of the most common type we come across in Australia , for some reason rarely used outside of Australia though.

The main difference between this CRT and others used for Kortek , Sanwa etc is that this one uses a 12 pin neck and high impedance yoke , CRT manufactures call this a Low Bi CRT , meaning it needs a much lower focus voltage ( around 21 KV ) compared to ( 28 KV ) on all 8 and 10 pin CRT's .

While this chassis looks identical to some that others here have installed this one has a different flyback that has been specially made to suit this type of CRT , it has the lower focus voltage allowing for a sharp in focus picture. physically it looks the same except that this one has a white front on the flyback, the Hi Focus type has a Black Front .

There are also other parts used for this model to correct the geometry in the horizontal drive section , hense the reason why there appears to be less parts on the chassis used for 8 and 10 pin models.

 

Having said all the above , when I was in the development of these chassis I wanted these to be interchangable between all the common types of tubes we use , so basically by changing very few components they can be converted from say the one Trav is using here to fit a normal 10 pin CRT very easily .

 

Some other key features I considered are ones that will help users greatly .

 

The Horizontal Size adjustments was taken very much into consideration , so added was a 3 pin primary size selector , S=Small M=Medium L=Large which can all be fine tuned using the front H=Size control that has a built in adjuster .

 

The third way the overall size can be adjusted is by using the B+ pot in the power supply section , I have made this "clamped" meaning you can adjust this pot full scale in either direction without the chassis shutting down or emitting harmful Xrays.

 

Colour Drives are also clamped to protect screen burn on single colours , meaning that if you try to drive a single colour through these chassis , it will quickly flash this colour and then fade to black ,to protect the CRT guns from buring out .

You can see this feature by using a games colour test pattern , It will display all colours at the same time like in a test pattern but not single colours for more than 1 second.

 

Also these chassis have a built in isolation transformer and auto sensing voltage select .

Basically you can power them straight from the mains , with or without a stepdown transformer , without having to adjust the chassis in any way , it's all automatic.

 

In summary , almost all 13 " to 21" chassis I come across are working to their maximum to display decent pictures , running way to hot causing all sort of heat related failures.

Keeping this in mind I worked backwards with this universal chassis , I designed it around a circuit that would drive a 38" Crt , what you will notice from this is that these chassis run very cool and very quite because they are only working at about half of the stress they were designed for .

 

Overall I am very happy with the results , hope you all are too :)

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Cheers Joey I was wondering what the plugs were for S,M,L. I think mines on the L and I remember having to wind the H-Size back a fair bit, should I just have swapped it over to M or L?

 

I do have to agree this chassis runs ultra quite.

Just one suggestion, a sheet with instructions on what the things do you have mentioned above would be great. I wouldnt have had a clue what the L,M,S was until I read this :)

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Cheers Joey I was wondering what the plugs were for S,M,L. I think mines on the L and I remember having to wind the H-Size back a fair bit, should I just have swapped it over to M or L?

 

I do have to agree this chassis runs ultra quite.

Just one suggestion, a sheet with instructions on what the things do you have mentioned above would be great. I wouldnt have had a clue what the L,M,S was until I read this :)

Great Idea Trav :)

 

You know sometimes us techie people expect everyone to just know everything :) so I am going to take that suggestion on board and make up an instruction sheet to include in all these chassis.

 

As for the H-Size Trav , I would wind the H-size back to about the middle and move the size pin to the spot that is as close as you need and then fine adjust with the h-size control .

This isnt really important though because as you can see there is a lot of range in the adjuster :)

 

TurboTom ,

 

There is a universal chassis for some 26" monitors , there is a lot more variants in these so I need exact specs match these up.

 

Yes it is :)

I should point out what Joe told me yesterday that these chassis can run on 240 volts so it removes the need for a stepdown transformer, pretty damn sweet.

It says on the sticker on the side 90-260 volts.

Part of my destructive nature here , I have tested these chassis from 60Volts to 310volts without any noticable difference in performance :)

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  • 1 month later...
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How big are these compared to the circuitry in a standard TV?

(I guess it varies a bit, but in general?)

 

ie, could you swap the TV PCBs for these to make a benchtop test monitor?

 

Yes you could although a Commodore 1084s is still the best test rig monitor :)

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  • 3 weeks later...
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Heres the new chassis Jomac have in now. I asked Joey about a uni chassis that had remote adjustments that would be ideal for cocktail machines(well any machine). Saves sticking you hand in back of the machine and risking getting fried...and here she is.

 

http://members.iinet.net.au/~golga/Unichassis.jpg

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I agree they are great... sure beats 20 year old chassis with crap controls...

 

I have just about finished two TV conversions... one for Elvis and one for myself... Mine will be my new test rig monitor complete with PSU and line V+ level indicators and adjusters.

Its fully documented and I will be posting the conversion on the arcade website soon...

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Do they run at 31kHz, or 15 only?

 

Cheers,

Chris

 

Joey has more than one model to choose from, the 15k unit is cheaper and the 31k is a different unit and cost a fraction more I think. He loaned me one for an experiment that failed but it was a very nice chassis :cool:

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  • 2 months later...
  • 3 months later...

Hey

Ordered my universal monitor chassis from Jomac on Friday and was here Monday, not bad considering it came from WA to TAS ( Wake up Aust Post):D .

So had to jump in and finish wiring the cabinet. Decided to stick with the harness that I had for the game which is the tehkan harness for the game Bombjack

First power on picture was distorted and inverted (like a negative) which proved to be the Sync from the PCB (weak solder joint)

then just adjusted the flyback for focus and picture brightness and I had "beautiful" scanlines :054:

 

The thing I have noticed is the discolouration/faded section which appeared on the right hand side and more near the bottom part it looks like when you have a speaker close by . ( my speaker is located above the monitor in the marquee). I am sure this is not a problem due to the chassis but some sort of interference but can't work out why?

 

Must say I am very happy with the Chassis and was suprised the old monitor I had kicking around ( yes it's probally been knocked around) worked , absolutely stoked but this interference thing on the colours gets me. Is it because of bad grounding?

(had some colour weirdness in the top half of the screen but put this down to pcb)

 

Well here's a pic ( thanks Prof for the Marquee)

 

Edit : forgot to add the picture on the screen sometimes hula hoops or shimmers then stays fine then wobbles like a big girl on the dance floor, sometimes it's stable then shakes like a rattlesnake???

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Hey DKong,

Does the discolouration make the blue look a bit purple? From here it looks like the screen needs a degauss with a degauss wand.

 

Sounds right the colours look really washed out on that part of the monitor..don't know what affected it..looking into it now. ( the weird thing was it started in the left hand (small) top corner then changed to the whole lower right hand side (big) section:unsure

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Yeah, when the screen is exposed to magnetic fields it does that, magnetising the screen. If your monitor has a degaussing coil, it may remove that when switched on from a cold start. If that doen't work, you can use a degaussing wand. You can use other methods instead of a degauss wand, but for the price of a degauss wand like this one on ebay I find it easier and cheap enough to buy. This will do the job for the home user. I have one of these and it works fine. I bought mine from a different seller overseas, cost me about $20 all up inc postage. Don't try to outbid anyone, there are plenty of these cheap ones available if you search.
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