Ikegami TM20-20RH horizontal linearity

[jamon1567]

Hi all,

I wanted to post here in a last gasp effort to hopefully resolve an issue I've been having with an otherwise perfect monitor that I absolutely love and would like to get running flawlessly. Basically I'm having a horizontal linearity issue on my Ikegami TM20-20RH and can't find any adjustments for it, either in the menu, or on the deflection (or any of the video boards etc for that matter) board. If I'm looking at a crosshatch the squares are a bit wider on the right, and get skinnier as you get to the left hand side of the screen. You can see how when playing old sidescrollers, which is a lot of what I'd be using it for, it can be rather annoying now that I'm aware of the issue. I actually spoke to (savon)Pat about this, and even though he didn't know anything about Ikegami's, we figured a recap would fix the issue. I sent my board out to him, and surprisingly, everything on it was in perfect condition.

So here I am now, back to square one with a monitor that I love (and had been looking for for quite a while), but can't really get past the one imperfection. I saw one other post on here (subject: Ikegami TM2080 capkit) where someone had a similar issue, but it didn't look like anyone found a resolution, and the person that created the post hasn't answered the DM's I sent him. A member did suggest the below, but I wouldn't really know where to look, or necessarily feel comfortable screwing around with the transformer. If anyone has thoughts or suggestions, I would really appreciate it!


"If it is a horizontal linearity issue then I doubt you will find any adjustments for it, not unless it has an adjustable horizontal linearity coil which i doubt but then I suppose you never know until you look.

The culprit will be somewhere on the horizontal output circuit or even the flyback transformer itself but less likely. If you are lucky it might be an electrolytic or ceramic cap but blanket replacing the whole lot will be expensive and could end in disappointment. It could also be the horizontal linearity coil itself but good luck in finding a replacement if so."

[MKL]

It could be an S-correction (or S-shaping) capacitor gone out of specifications. It's a polypropylene capacitor, not electrolytic, in series with the horizontal deflection coil. S-Correction should be a symmetrical issue (picture compressed or expanded near the left and right sides) but it doesn't hurt to check anyway.

[jamon1567]

Thank you, Ill see what I can find.

[Sefirosu789]

You should only need to adjust the horizontal linearity coil inside the monitor (assuming caps aren't bad). You can probably use the service manual to locate it. Hopefully Ikegami is not like some of the JVC models where at the factory they would coat the coil in glue/epoxy so you can't adjust it.

[kel]

What does the horizontal linearity coil look like in that monitor? Just asking because in one of my Elecrton IIblue monitors instead of just a coil wrapped around a core it was a coil with magnets either side inside a plastic case and submerged with potting compound. In my case the potting compound had deteriorated to the point where the coil and magnets had become dislodged. Unfortunately finding a replacement was impossible but after removing the coil and magnets and all the remaining potting compound from the casing and then putting them back in with some new compound my linearity problems were gone. Whilst researching that particular linearity coil for a replacement I'm sure I remember reading a post somewhere that certain arcade monitor chassis use them also and suffered similar issues so it's a long shot but worth checking to eliminate the chances that your Ikegami might have a coil similar to that.

[jamon1567]

If I had to guess, and that's all this is because I'm no expert and can't find a service manual (only the operations manual), I believe the linearity coil is the piece in the middle of both pics of the deflection board I've posted below. It's the piece with 1565A stamped on top. Now that said, I can see no way to adjust it. It doesn't seem to move or have any way to tweak it. Any thoughts?

https://drive.google.com/file/d/1XrTIAt ... sp=sharing
https://drive.google.com/file/d/12vfbUH ... sp=sharing

[kel]

Maybe, wouldn't know for sure without being able to trace the circuit but I would expect the linearity coil to be much closer to any of the large polypropylene caps. What's the white block in the top right corner or the smaller black block just below the transformer?

None of them look exactly the same as the one that I had issues with though but then from here it looks like the two components that I pointed out above could have anything inside them including a coil and potting compound.

[jamon1567]

I can't tell what either of them are, but the white block does have a pot in it that can be turned with a screwdriver. I suppose I could try adjusting it, but I don't know what it is as the board isn't labeled and I don't have that service manual....

[jamon1567]

Here's a pic of the white piece for reference.

https://drive.google.com/file/d/15enoDj ... sp=sharing

[kel]

It is possible that it could be an adjustable linearity coil. It does seem to be in the right place if those four wires and connector at the top go to the deflection coils, also the three large diodes nearby could be the damper diodes, Tr405 the HOT and then the large polypropylene capacitors being the snubber and S-correction caps. I could be wrong though as there seems to be a similar layout near the bottom of the board too.

Other than tracing the circuit from the horizontal def coil to be sure, the only way to find out is to try adjusting it like you said. Don't forget to mark the original position first though just in case.

[jamon1567]

I'm gonna try to get to testing this in the next day or two so I'll let you know how it goes.

[jamon1567]

I had meant to get back sooner, but the power went out here for an entire weekend not long after my last post, then Thanksgiving etc, so I hadn't had time. I finally got around to testing and the pot on the white piece was indeed the culprit! I had a few other issues where I thought I blew the thing up (it must've reset at least some of the menu settings after I had it apart, so when I went to try to tweak things over RGB it was all messed up since it set that connection back to YPbPr), but I'm happy to say that she's up and running better than ever! And boy does she look nice....I have a D32 here as well, and while that thing is just amazing beyond words, I almost like playing better on the Ikegami! The curved screen and the shadow mask are just perfect for old school games. If anyone has the chance to pick one up, I couldn't recommend them more. They have a lot of nice features and just look damn cool. This one is 480i only, but if I ever have a chance (at a reasonable price) I would like to pick up one of their multiformat monitors as well.

Anyway, thanks again for the help! Now I just need to figure out how to get this probe to work, but that may be a separate post

[kel]

Glad to hear that it turned out to be the linearity coil in the end, let's hope that you get many more years to come out of the monitor.

I would love to get my hands on an Ikegami monitor one day. I was made an offer for one once but turned it down as I was picking up a monitor that was more important to me at the time and it seemed like too much hassle to get both. One of those moments where you look back and wish that you'd gone to the extra effort/expense in hindsight.

[kukrapok]

After reading this thread I realized I had never answered your pm and I deeply apologize, I always reply to everyone I don’t even remember reading your message lol I must have been drunk
I’m glad you were able to fix your linearity issue, i assume you found out how to use the probe in the meantime? I no longer own my 2080RP but iirc the calibration process was really easy. I do remember about that chroma error though, I think I went the alternative route (without chroma or something).

Never sell your Ikegami like I did... they basically provide you with the most authentic “retro” experience!

Ps: I messed around with the phase and h.center settings to improve the linearity on mine:

https://ibb.co/F8LJyG4

[jamon1567]

I'll have to try that on mine. I messed around with phase a bit and didn't notice it doing anything other than moving the picture left and right. Your crosshatch looks better than mine though....the pot that I messed with to get mine to where it was acceptable didn't so much move the linearity right to left like I thought it would (the vertical linearity operated in this manner) so much as it adjusted the size of the grid on both the inside and outside of the picture if that makes any sense. As it is, the very center of the screen seems a bit thinner than the outer edges. Although, rereading what you said again, perhaps I need to mess around with h.center. I did plan on going back though and really dialing everything in again, but the main issue with my linearity seems to have been, at least, mostly solved. Enough to where I wanna game on it now

As for the probe, no I can't get it to work. If you think you can help though, I'd LOVE to know what you did.