K4900 Version vs Yoke Clarification and Info

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I have a pile of K4900 chassis I am starting to test/work on and have been compiling the below info (Thanks Ken Layton and Modesitt and ecwestjr) from numerous posts.

Info:

3 versions:

"Latest" version had Vertical Dampening pot and a Vertical Position circuit board attached to the main board. (-040 confirmed below)

-040 , -055, -057

Yoke: 2021111258 or 2021111264

"Intermediate" version had a Vertical Dampening pot and NO vertical position circuit board.

-034 , -037

Yoke: 2021111258 or 2021111264

"Early" version did not have either a vertical dampening pot or a vertical position board. (Confirmed Below)

-023

Yoke: 2021111194 or 2021111201

"The early version is not compatible with either the Intermediate or latest versions due to the yoke being slightly different. If you use an early chassis on either one of the later ones, you'll get a foldover you can't adjust out as stated in the bulletin."

Service Bulletin:

"This bulletins applies to 4900 series monitors with serial numbers of 400001 and above. They can be identified by the following:

A) The model number on the monitor is printed in red.

B) The part number on the deflection yoke is either 2021111194 or 2021111201.

C) The flyback transformer stabilizing bracket is labeled 611X0005-008 (note: from my own experience this label always falls off so look all around inside the game cabinet and underneath the monitor main board for it).

D) There is an additional control, the VERTICAL DAMPING CONTROL immediately to the right of the vertical hold control.

NOTE: K4915 uses different Yoke than the above

Yokes with part numbers 2021111194 or 2021111201 are for use with early production run 4900 series and should not be used with this version chassis as insufficient vertical deflection, vertical foldover, or improper blanking will result."

https://forums.arcade-museum.com/showthread.php?t=38883

https://forums.arcade-museum.com/showthread.php?t=326143

https://forums.arcade-museum.com/showthread.php?t=142056
 
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If the chassis is a 3 pot chassis it will not work with the deflection yoke for a 4 pot or a 4 pot with the vertical position adjustment chassis.

Also the 4 pot and the 4 pot with the vertical position pot chassis will not work with the yoke for the 3 pot chassis.

There are no K4900 chassis that will work on both deflection yokes correctly.
 
So is it safe to say that:

-023 or 3 pot chassis ONLY work with Yoke: 2021111194 or 2021111201

Every other chassis version will use Yoke: 2021111258 or 2021111264

?

If the chassis is a 3 pot chassis it will not work with the deflection yoke for a 4 pot or a 4 pot with the vertical position adjustment chassis.

Also the 4 pot and the 4 pot with the vertical position pot chassis will not work with the yoke for the 3 pot chassis.

There are no K4900 chassis that will work on both deflection yokes correctly.
 
That is correct. However the only other K4900 that won't work with either one is the K4915. It uses a completely different deflection yoke.
 
technically, it will work...i.e. you can plug any 4900 chassis into any 4900 yoke (except the med res 4915) and get a picture, you will just have distortion that can't be adjusted out. so if you were just testing a bunch of chassis or something to see if they come on, that would work. you just wouldnt want to put a mismatched yoke/chassis into a cabinet because it would look bad.
 
Yeah I mean they would all work - but I thought I was able to adjust a nice picture for both yokes using -034. But if you guys are saying no go I must just have thought that. I didnt spend enough time with the adjustments to get either dialed in perfectly.

Thanks guys
 
The distortion 87 t-66 is talking about is a form of vertical fold over.

At a certain point when adjusting the vertical height it will jump to the fold over. You can get a good picture. However you won't fill the screen vertically.

Hope that makes sense.
 
Yes that does clear it up for me I am sure thats what I experienced and just didnt fill the screen vertically when testing. Thanks

The distortion 87 t-66 is talking about is a form of vertical fold over.

At a certain point when adjusting the vertical height it will jump to the fold over. You can get a good picture. However you won't fill the screen vertically.

Hope that makes sense.
 
Guys, not sure if this applies but I came across something yesterday that I found interesting.

Was working on a Tapper with what looked to be a factory installed and already capped k4900. The pic was adjusted to about 50% of the tube to get rid of a vertical fold over at the top. Not knowing the age of the caps I decided to re cap it. Fold over was still there... Ugh... "Probably wrong yoke for the chassis" went through my head. Then I remembered that C311 is different on some chassis. The one that I pulled off the board was 4.7 @160, the one I installed was also 4.7 @160 but then remembered that the alternate cap was 10 @160.

Installed the 10 @160 and the fold went BYE BYE!!!!!!

Maybe thats the fix on these chassis that wont work with "X" yoke??

Check this manual out.

http://www.vernimark.com/arcade/archive/monitor/mon_rc__wg-19k-4901-06-51-56.pdf

In the parts list it shows C311 at 10 @160 but on the schematic C311 is 4.7 @160.

LOL!
 
no idea, the monitor is 1300+ miles away from me now so theres no way to know. It didnt have the dampener pot though.
 
about to do a tube swap on 4903 and figured I would provide this info. despite disagreement on usefulness of ohming out yokes, I am starting to track TV model, yokes etc, chassis, etc when working on monitors doing swaps. Looks like the more info tracked (exact monitor ver # and maybe even yoke #) maybe the better.

I have a 4903 (-55 under pcb) with dampening pot and vert position board, yoke = 2021111258
19VMKP22 19" CR-23 1 Video 2 6.3 116V No 4903 horz 2.6ohms vert =40.3ohms

another chassis I am working on
sticker says 4951 with -40 under pcb and 2021111264
19VLTP22 19" CR-23 1 Video 2 6.3 132V No K4900 horz 2.7 vert 38.1

Note:Vert Ohms on junknet = 34.6 but is missing context of chassis and yoke model

interesting that sticker on frame lists this tube in addition to the two above
19VMCP22 19" CR-23 1 Video 1 6.3 100V No 4903
 
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Tried unsuccessfully to pair a -024 Neck board with -037 Main board. Fixed the original cracked -017 neck board and chassis worked fine. I know there are differences in traces and cap placements but don't know details of why they are incompatible. Unless I screwed something up. https://youtu.be/wWVPv2IzJn8?t=214

anyway, figured I would document a few of the 4900's I have out of cabinets and this thread seemed most logical spot to document. Nothing I have found changes the chassis to yoke listed by Op but I have found some other interesting variances including the neck board incompatibility.

Joust 19K4903 (disclousure...may not be original chassis but one of tube serial#s and frame serial # match, has joust burn and a williams serial# on tube)
**edit**based on new info regarding c365 value .33uf, this is a 4901 chassis or a 4903 that they modified by changing c365. since it is pre -40 main pcb chassis, it has the horz centering jumper intact. **edit 1-15-19. based on screen burn at the top of tube I now believe this was in a moon patrol originally and that makes sense due to 4903 on frame.
chassis/frame serial no = 480598
tube wg serial = 480598
Main PCB -037 Neck PCB -017
Yoke 2021111264,
Vertical Damp Pot but No Vert Pos Board
Adjustment sticker 69x1178-100 (note: what is strange here is I have another sticker, that I will post next, that says 4903 chassis don't have Horizontal raster shift but this 4903 does and I have a 4903 that doesn't.
 

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Next one is a K4901 out of Track and Field Serial# on Frame matches serial # on tube but no guarantee on any of these that a chassis hasn't been swapped. This one I believe is original as neck board ground line was intact.
**edit**based on new info regarding c365 value .33uf, this is a 4901 chassis.
Yoke = 258
Neck = -024
Main = -040
Has Vertical position board
Sticker = 69x1252-100 (says 4903 doesn't have horz raster shift)
Serial = 632532

>>added pic of bottom of pcb. Mods are likely to support the vertical position board.
 

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Now this one I have no confidence that pairings are original and haven't validated the chassis works yet. Will circle back on that. The key thing here is the neck board is -017 and main board is -040. edit>>just fired it up on on T&F tube/yoke above (this tube has g1 short and other gun issues) and it works fine.

Game = No idea but has taito burn with big Game Over in middle and mcmlxxxiii so guessing Elevator Action

Frame says K4903
Yoke = 264
Sticker = 69x1178-100
Neck = -017
Main = -040
Vert Damp is there but no Vert Adj board. **edit note: this contradicts 1st post that says all -040 main boards have vertical pos board (aka p344)
Horz centering jumper is cut. c365 is 154 (.15uf) << looks like this is a 4903
>>added pic of the bottom of chassis. Not difference to 4901 with same -40 pcb

Edit>Adding my moonpatrol (not pictured and not original monitor not sure how I came about it)
Game= Legend of Kage (Taito)
Model= K4903
Serial#= 831360 both tube and frame
Neck= -024
Main= -055
Yoke= ..258
C365= 154 (.15uf)
Horizontal shift jumper doesn't exist
 

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Ok I haven't thought all the way through this post but having just worked on 4 4900 chassis, figured I would attempt to document some of the info for at least my reference back.

This manual helped out quite a bit. Applies to all serial #s 576001 and above
https://www.arcade-museum.com/manuals-monitors/WG K4900_Manual_B.pdf

So we have multiple revs of main pcb, covered by op and its yoke compatibility, but I haven't found anything on chassis version and game compatibility so thought this may be useful.

I haven't found a manual that details the difference from neckboard version -017 to -024. If someone has a manual with -024 neck board, please post it.

Pretty much you can tell a 4901,4902, 4903, 4914 from each other by looking at the value of c365. Very little, if any, other differences.

Not sure about the k4904 but assume the frame is different in addition to other changes.

Frame/Type ?? = Standard ,Other, Medium Res
type|horz model|vert model| c365 value|known game or vendor?

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Another interesting thing I found is the value of pot vr352 must not be that important. I checked at least 2 -040 chassis and vr352 was a 10k pot. Also, had a 3k pot at vr351 on one of them. Note the k4915 manual does state vr352 should be 10k so they may have just updated that on all later revision boards.

Not in the habit of pulling pots to check this so YMMV.

https://forums.arcade-museum.com/showpost.php?p=963749&postcount=6

According to post above and all manuals except 4915.

Main board
VR201 2k - Blk Level
VR301 5K - Vert Hold
VR302 5k - Vert Damping Later Boards
VR303 500 - Vert Size
VR351 2k - Horz Hold
VR352 2k or 10K - Horz Position/Shift
 
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Links to the original referenced service bulletin regarding yoke compatibility seem to be broke. However, it is an interesting read on why the yoke was changed and vertical dampening pot added to chassis serial #> 400001

https://www.arcade-museum.com/manua...onitor_(WG_Revision_K4900)_(72-00023-001).pdf

this one also has a bit of interesting info regarding vertical damping pot. Looks like an adjustment made for Williams games , maybe?
https://www.arcade-museum.com/manuals-monitors/69x1251.pdf

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