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29E31S Chassis - Pincushion issue

mathewbeall

mathewbeall

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This is slowly becoming the bane of my garage... :)

I got a second 29E31S chassis and got it all hooked to my tube out of my WMMT2 cabinet - picture comes up, but severe pincushion. I adjust the POT and the front falls off it - no problem, I have another chassis - I replace the VR pot (200ohm)... i fire it up - and still nothing, adjusting the POT doesn't do anything....

Is there anything else to check/adjust?

Matt
 
Downloaded the manual from ArcadeOtaku. Tested everything from the circuit block diagram that leads up to the horizontal coil. That includes testing transistors out of circuit and swapping them out from another chassis just to be 100% certain, swapping ICs, testing diodes and resistors and recapping all the electrolytic caps. I even changed the high voltage polypropylene caps.

And the result? Absolutely no change at all.

That just leaves one thing, the flyback. There's a HR Diemen flyback that will fit this chassis with some small mods. I will order one and try it out. The mod includes swapping in a different resistors and adding two jumpers. Full details here:

http://www.neo-arcadia.com/forum/viewtopic.php?t=46038
 
I have a working flyback on another board that I can swap out - I will do that in a week or so and report back.

Thanks!

Matt
 
nem said:
Downloaded the manual from ArcadeOtaku. Tested everything from the circuit block diagram that leads up to the horizontal coil. That includes testing transistors out of circuit and swapping them out from another chassis just to be 100% certain, swapping ICs, testing diodes and resistors and recapping all the electrolytic caps. I even changed the high voltage polypropylene caps.

And the result? Absolutely no change at all.

That just leaves one thing, the flyback. There's a HR Diemen flyback that will fit this chassis with some small mods. I will order one and try it out. The mod includes swapping in a different resistors and adding two jumpers. Full details here:

http://www.neo-arcadia.com/forum/viewtopic.php?t=46038
Click to expand...
I don't even have one of these chassis (yet?) but thanks to going to all that effort and posting back findings here
 
@nem :I have one of these with the exact same issue(s) hourglass deforming screen and size issue which i can't adjust.
The HR 46274 should work with those mods, but these chassis are ~50 bucks and a THT is the same + shipping.
I'll keep it as a spare for now, but am curious to see if this fixes your problem :)
 
@Asure - do you have a source for these chassis’s at $50? I haven’t been able to find very many - and not that cheap.
 
They're super cheap in Europe. Probably the most common chassis in upright Naomis. I've seen them even given away, because they're not compatible with other yokes and the original Shanghai Novel monitors have a habit of the electron guns dying.
 
@nem - I have some searches on eBay - but if you see some around - can you send them over to me? I have two tubes that aren’t bad that I need working chassis’s for :)
 
Alright, I had some extra time today, so I thought I might as well give this a shot.

So here's the problem monitor shortly after turning it on:

29e31s_flyback_swap_1.jpg

When this pic was taken both horizontal and vertical size were at their lowest setting on the remote. If you give it an hour both the top and bottom will stretch horizontally way past the edges of the screen leaving only the center narrow. Like I said, I swapped absolutely everything on this chassis and nothing made a difference. There's just the flyback left to swap.

Time to break out the desoldering gun. 10 minutes later the flyback was out. Out with the old, in with the new:

29e31s_flyback_swap_2.jpg

Original flyback left, HR Diemen 46274 on the right.

The new flyback comes with instructions to jump some pads:

29e31s_flyback_swap_3.jpg

So I did just that:

29e31s_flyback_swap_4.jpg

Notice the missing resistor R447 at the bottom right. The original 33kohm resistor was supposed to be replaced by a 68k one according the instructions in the Neo-Arcadia thread, however, the pics in that thread show that the image is pinched in on the left hand side. Grantspain recommended a 47k or 56k resistor in this thread on Arcade-Otaku. Resistors are cheap, so I bought all three.

Soldered the leads to the neckboard:

29e31s_flyback_swap_5.jpg

Thicker lead goes under the cap of the neck connector, thinner lead next to the connector.

I first soldered in the smallest resistor, 47k. Connected the chassis to the tube and flipped the switch. Thankfully no smoke and no bang. Turned up the voltage on the flyback to get a bright image. Geometry looks great. Image is a small square in the middle of the screen, which is what it's supposed to be because I still have the horizontal and vertical size pots at their minimum setting. Adjusted those to get a full size image. Unfortunately, there's an issue. Both the top and bottom of the screen have a shimmering effect. 47k is no go.

Took out the chassis and swapped in the 56k resistor. Turned it on and image is now visibly larger. Turned down the horizontal and vertical size pots. No shimmering anymore! I played around with the focus pot on the flyback, however, I couldn't get it pin sharp. It looks OK, but visibly soft.

Anyway, it's good enough for now. I'll mess with the yoke rings and try to get it looking better at a later time.
 
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Thanks for the update - I will get one of those and get my chassis back up and working.

Matt
 
I would probably hold off buying a HR46274. Less than 10 hours of use and the screen has gone out. Turning the monitor back on, the picture looks fine for around three minutes and then starts pulsing and soon goes out.

I ordered a few of them, so I will try with another one. This time with a 68k resistor.
 
nem said:
I would probably hold off buying a HR46274. Less than 10 hours of use and the screen has gone out. Turning the monitor back on, the picture looks fine for around three minutes and then starts pulsing and soon goes out.

I ordered a few of them, so I will try with another one. This time with a 68k resistor.
Click to expand...
I would like to know if the 2nd flyback died or if something else caused it to die. I just ordered one those flybacks to fix a 29e31s as a temporary replacement for one of my blast monitors
 
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The chassis was fine apart from the flyback. Fingers crossed the 46274 I installed was just a dud. I'll let you know at the end of the week.
 
Well, the other monitor has now been running for 16 hours, so I don't know, maybe the flyback before was indeed somehow faulty. I'll report back if this monitor stops working at some point. The picture is a lot sharper than what was on the other monitor too (which could point to some internal fault in the flyback).

Also, the 56k ohm resistor is perfect. The 68k makes the picture too big.
 
Thanks - I will look for another update in a while and then go ahead and get those ordered.
 
awesome, I did my order a week ago for the flyback hopefully it wont take too long to the get to the states
 
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