Hey Folks,
Craig and I found one analog board in our Color Classic lot that we think is modded for 640x480 but in a weird way.

Instead of modding the sense lines they removed Jumper 19 from the top of the board and added a bodge wire from one point on j19 to capacitor cp44 on a rev D analog board.

The board isn't working atm so we can't test that this mod is for 640x480 until we get the board going again but based on the bodge to the Horizontal Deflection Voltage it seems to make the most sense that this would be what its for.

Has anyone seen this mod done before? Thanks!

The YELLOW wire in your photo shows it is the standard 68.4V VGA Mod (not the 84V 13" Hi-Rez Mod), and that is also shown below...




I've never see anything like your BROWN wire though. Maybe @Kay K.M.Mods has seen it before?

Well I got the analog board working again. A color classic logic board works fine although a bit distorted with the voltage change. A 575 board on the other hand just gives the standard bus error when you try it on a unmodified analog board. So not sure what that brown bodge is meant to do but It doesn't seem to work for me.

There is no reason to boost the voltage to 68.4V like you have when using the stock motherboard. Yes, you can leave it that way by simple making screen adjustments via the analog twistable knobs on back but it's generating more heat for no gain whatsoever. The voltage boost is only needed when also modifying the sense lines to get higher resolutions. My 84V Mod Video explains the different voltages and compatibility benefits.

The LC575 board only works with the 68.4V or 84V mods which have the sense lines changed, but never with the stock Analog Board with no mods.

The stock CC motherboard will not work with the 68.4V mod that has the sense lines changed. So if you are able to get your stock motherboard to work in that 68.4 V modded analog board, it means the sense lines have not been changed. And it such a case, you basically don't have the VGA mod. You only have the voltage boosted 68.4V in such a case, and I don't know what that Brown wire is used for.

Watching my 84V Mod video makes everything I just said clearer.

So to clarify im aware the voltage change isn't needed for the color classic board. I was just testing the board as it was after recapping
it to see if i would get video. Given this weird unidentified brown bodge wire.

I tested first with a color classic board then again with a 575 board. I was curious if this brown wire was some alternative way to change the sense line but given the results id say it is not or it wasnt complete.

The fun of buying a random board off ebay never know whats been done to them.

Here is the horizontally flipped version of your BROWN WIRE photo...

[Image: 1767317175014.png]

And here is the component side (not flipped), perfectly matched to the above photo...

[Image: 1767317214203.png]

Here are the two photos overlaid atop each other with the brown wire photo partially transparent so we can see the connections...

[Image: 1767317269698.png]

Here is my red line drawn to better illustrate that jumper J19 is being tied to the GROUND side of the capacitor at left, which in turn leads to the middle of 3 pins of that transistor....

[Image: 1767317355902.png]

Here is a clearer view of the same...

[Image: 1767317387093.png]

And here is the final result, which is the mystery question I will leave you to resolve because I cannot answer the question you see me ask below...







I only have top-down photos and my CC is not handy. I cannot read the markings on that 3 pin transistor, and I am just ASSUMING it is a transistor. You will need to read the markings and get a data sheet for that 3 pin component.

If it is a transistor, maybe the previous owner determined it was dead and decided to permanently tie the Collector and Emitter of the transistor (assuming it is an NPN BJT transistor) together, assuming that it's OK if the transistor stays "permanently switched"?

Again, this is the mystery you will need to investigate.

And here is the final result, which is the mystery question I will leave you to resolve because I cannot answer the question you see me ask below... Click to expand...

LOL but that's the part I can't figure out! ;)

Oh btw J19 was cut in half on the top of the board so the brown wire only attaches at one half and isn't connected to the other half.

When we received this board it had this bodge on it along with the voltage change so you would think it would have something to do with the 640 resolution but apparently it doesn't at least it doesn't seem to from my limited testing. I'll probably just take it off now and finish the conversion for 640x480 by changing the sense lines. It's just so strange...what did the person who did this mod think they were going to accomplish? There was a reason for this -- flawed reason or not.

OK. J19 is cut in half, as you say. That only means the two pins on that part (transistor? something else? You'd need to read its P/N to find out) are NOT tied together. Fine and well. But it means this is true...



Ignore that little red wire connected to pin20 at right because that's a photo of my board with sense line mods. What you must look at in the above is the fact that PIN-1 at the upper right is being tied to the middle pin of that transistor (or whatever it is -- you've not checked its part no. yet) via the BROWN WIRE. But PIN-1 (upper right in the above) is not part of the sense lines, I don't think. What does it lead to?

In other words, is the BROWN wire really a SENSE LINE mod like you are guessing it is, or is the BROWN wire instead trying to fix something broken, which would result in Analog Board malfunction if the BROWN WIRE is blindly removed without knowing what it does?

My view of the component side is blocked by the metal shield so I cannot trace out PIN-1 to know what it is...