Modifying "old" 4600 chassis to support horiz. centering

DarrenF

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Modifying "old" 4600 chassis to support horiz. centering

So, I found Ken's details about the variations of the interface cards online: http://www.ionpool.net/arcade/tech/19K4600_pinout.txt

This explains that the P317 (which I have) includes the "highly desirable" horiz centering pot. However, I was a little disappointed when I discovered that my pot didn't effect the image at all.

It turns out that the P317, while presumably "compatible" with every version of 4600 main PCB, isn't "supported" by every 4600 main board--including mine. I dug up every 4600 schematic I could find (which turned out to be only 4 different versions). Two of them show "older" interface cards (P313, in the K4616A/4666A schems, and P305 in the K4606 schems), and two others show the P317 (4625/4626/4675 and 4625A/4626A/4675A).

On the "newer" main boards (which aren't identified differently, that I can tell), pins 1 & 2 of P202 are connected to each end of R635; of the "older" main board (including mine) those two pins are only connected up into an unpopulated area of the PCB. Also different: R635's value changed from 12K to 6.8K, and an add'l 6.8K resistor (R652) is added between R635 and P607.

So, I decided to modify my main board to support the P317 adjustment pot. I jumpered from P201 pin 1 to P502 pin 7; and from P201 pin 2 to the opposite side of R635. I swapped in a 6.8K 1/2W for R635. Finally I replaced jumper J19 with another 6.8K 1/2W resistor.

Works like a charm. Can now adjust horizontal position. Thought I'd share in case anyone else with an "old" 4600 main board ever had a P317 interface board in it and couldn't figure out why the adjustment didn't do anything (I know, slim chance...)
 
Pictures please!

Remember, the P317 and P318 have the horizontal centering pot. Also, these two boards use a standup black level pot instead of the usual lay flat pot like all previous video interface cards did.
 
Pictures please!

Remember, the P317 and P318 have the horizontal centering pot. Also, these two boards use a standup black level pot instead of the usual lay flat pot like all previous video interface cards did.

Yes, I only have a P317 interface card, but the same would of course apply to a P318. The point is that the "old" main boards don't connect pins 1&2 of the interface card to anything--and hence those won't do any horiz centering even if a P317 (or P318) is installed (unless appropriately modified).

Yes, my P317 has a stand-up black level pot, and a stand up horiz centering pot right beside it, both easily adjustable when installed.

I don't have any "before" pics, but I can surely take some after shots...
 
After shots would probably be ok. Did your main board also have the horiz and vert centering jumper wires/posts?

Yes my main board does have the jumper wires and posts, but they do NOT appear to have been factory original. There are jumper wires on the solder side, and resistors and diodes added in a very non-factory way on the component side (soldered to a jumper, no silkscreen label, using through holes for other unpopulated components, etc.). I'll point them out in the pics too. (Note that the jumper mods were added before I got the monitor--I only modified to support the horiz centering pot).

Now I gotta figure out this photobucket thing, since I can only attach pics up to 640x240 to the forum...
 
That's exactly how the Wells factory does things. This is undocumented.....or at least undocumented for public release.
 
Very interesting... We were just trying to help a local fella figure out why he couldn't get his K4600 to adjust far enough one direction. But his original interface board has no "P" number designation and no Horizontal Position pot. When trying an interface board with the pot it still wouldn't adjust....now we may know why, betting his chassis isn't wired for it like you described.

I don't think I have ever seen a P317 with the Horiz Centering pot and Black Level pot on the same side.
Makes me wonder how many versions of the "P317" there are.
I even have what appears to be an older one with locations for Horizontal Position components, but they were never installed.
 

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I had not seen those early P317 boards before. I had only seen the P317 that had both standup pots on the parts side of the board. The horizontal centering section on the video interface board only consists of two parts: VR102 (a 10k pot) and C204 (a 680pf ceramic disc capacitor).

I now have documentation and photos (front and rear) of these video interface boards:

P297
P298
P302
P305
P306
P307
P307 converted to P302
P308 parts layout & schematic only
P317 parts layout & schematic only

A thread has been started by me detailing the above boards.
 
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That's exactly how the Wells factory does things. This is undocumented.....or at least undocumented for public release.

Oh, well if that's how WG did/does things, then perhaps my H and V raster position jumpers are factory mods. They are pointed out in passing in my photos, but not really fully documented. I can take a couple more pics to detail the source of the jumper wires, and other details of the mods. I didn't dig into them as they were already done, and they seemed to work fine.
 
Very interesting... We were just trying to help a local fella figure out why he couldn't get his K4600 to adjust far enough one direction. But his original interface board has no "P" number designation and no Horizontal Position pot. When trying an interface board with the pot it still wouldn't adjust....now we may know why, betting his chassis isn't wired for it like you described.

I don't think I have ever seen a P317 with the Horiz Centering pot and Black Level pot on the same side.
Makes me wonder how many versions of the "P317" there are.
I even have what appears to be an older one with locations for Horizontal Position components, but they were never installed.

I'd bet if you look at your friend's main board, you'd find that pins 1 & 2 of the P317 board don't connect to R635 as they do on later main boards.

Your P317 boards have "85X0149" on them (bottom). Mine has "85X0150" (top).
 
Remember, the 4600 is really a converted Wells-Gardner home television set.

Never knew that. I guess that explains the large unpopulated areas of the main board, and why the power error amp board also has the word "audio" in its name on the schematics...

Say, in your original message on RGVAC (http://www.ionpool.net/arcade/tech/19K4600_pinout.txt) you mentioned "Note: schematics for the above boards are in W-G service manual #69X0942-100 (dated 9-80)." I cannot find the 69X0942-100 manual online. Can you point me to it (or send via PM/email)?
 
I think I have an original 69X0942-100 in my collection. I know I do NOT have it scanned and I don't think anyone else has scanned a copy of it.

EDIT:

When I get a chance I will scan it.
 
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It turns out that the P317, while presumably "compatible" with every version of 4600 main PCB, isn't "supported" by every 4600 main board--including mine. I dug up every 4600 schematic I could find (which turned out to be only 4 different versions). Two of them show "older" interface cards (P313, in the K4616A/4666A schems, and P305 in the K4606 schems), and two others show the P317 (4625/4626/4675 and 4625A/4626A/4675A).

Well, I guess this wasn't exactly news... it looks like Jed Margolin wrote about it back in 1982: http://www.jmargolin.com/vmail/Stat82.txt
_________________________________________________________________
To: Lynn Nyberg
From: Jed Margolin
Re: Composite Negative Sync for Wells-Gardner 19K4603 and 19K4633 color
monitors.

The Wells-Gardner 19K4603 and 19K4633 color monitors will accept only positive
sync. Testing games like DIG DUG with composite negative sync will require
either MTO'ing new monitors or replacing the interface boards in the
4603/4633's with P317's (the one in the 4625). The horizontal centering
control on the new board will not function with the older chasis, but that is
the only difference.
The P317 interface board costs $34.70; all inquiries
should be directed to Brenda Thompson.
 
This Piher brand pot from Mouser Electronics should work for the horizontal centering pot:

# 531-PT15B-10K (just 50 cents each)
 
All of the various "Pxxx" video interface boards are now detailed here:

http://www.arcade-museum.com/manuals/manuals_monitors.php

Just scroll down to the Wells-Gardner section.

There should also be the two horizontal and vertical raster postion jumpers on the main board. If these are NOT present on your particular 4600 main board, then it is an early production run.
 

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Say, in your original message on RGVAC (http://www.ionpool.net/arcade/tech/19K4600_pinout.txt) you mentioned "Note: schematics for the above boards are in W-G service manual #69X0942-100 (dated 9-80)." I cannot find the 69X0942-100 manual online. Can you point me to it (or send via PM/email)?

I have now scanned & cleaned up manual # 69X0942-100 and it is posted here:

http://www.arcade-museum.com/manuals-monitors/Wells Gardner 19K4601 service manual.pdf

It covers models 19K4601, 4602, 4603, 4604, and 4653.
 
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