Find Potentiometer Size and Resistance? Hitachi GMK-29FS2

[yagamikun]

So - in my ongoing struggle to get this Neo 29 cab to work, I need to replace the potentiometers on the remote board (the V-Hold specifically). Thing is, I can't find any information on a Hitachi GMK-29FS2 remote board anywhere online. There is no manual scan I've been able to find after an hour of tedious searching, and the candy cabs that use this monitor - those manuals do not have that type of detailed information. The pots themselves have nothing written or etched on them, only a part number: J502E.

I've emailed Peter at Arcade Parts and Repair and he needs that information to find the correct pot. I sent him some pictures, but it's guess work on his end as he is (and I'm finding most people) are not familiar with this sort of repair on this monitor.

Using my multimeter with one lead on ground: One side measures at 2.5 and the other can't hold a steady readout. When I test the two pins (no ground) it will stabilize at 1.5, but when I turn the knob to the other end the readout wavers between 4.x and 5.x.

Thoughts? Am I doing something wrong? Thanks for all the help, everyone. Sorry for so many posts about this damn cab, lol. Edit in these new forums won't let you update the thread title, or I'd use my original post from a couple weeks back and just update it.

 

[daskrabs]

You could try desoldering another functional pot on the remote board and measuring resistance when it's fully cranked. You prob won't find an OEM pot, but digikey would likely have something usable.

 

[MKL]

502 suggests 5k ohm which is the same value as on the Nanao MS8 chassis so it makes sense. Clearly not all the pots will have the same marking. I suggest to desolder it and measure the resistance across the external pins as that gives the overall value. Maybe the pot is good and just needs a good cleaning with a degreaser. Or is it visibly broken?

 

[yagamikun]

502 suggests 5k ohm which is the same value as on the Nanao MS8 chassis so it makes sense. Clearly not all the pots will have the same marking. I suggest to desolder it and measure the resistance across the external pins as that gives the overall value. Maybe the pot is good and just needs a good cleaning with a degreaser. Or is it visibly broken?

Thanks, MKL. The pot isn't visibly broken, but the remote board was snapped in half at some point, glued back together, and the contacts resoldered (badly). This was prior to my ownership. I'm hesitant to even move the board for fear of it snapping - let alone put it on my bench to try to desolder the points. I'm getting more confident in my soldering ability, though, so I'll try that. Not much to loose at this point. heh.

Unfortunately, in trying to fix this V-Hold issue the cab began playing blind (again), so I have a much larger problem to deal with now. I got the chassis back from PNL for repair for the same issue a week ago, and have been dealing with this v-hold issue since which led me down the path of finding the right pot. Now that it's playing blind again I can't even the pot/v-hold issue! haha, I can't catch a break with this thing. It had a new cap kit installed recently, so I'm not sure where the issue could possibly be. The light doesn't even fire in the neck board, but the flyback gets power. It's very weird.