AGAIN: Sanwa 29E31S... No! its a B!!!

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davidcoolman
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AGAIN: Sanwa 29E31S... No! its a B!!!

Post by davidcoolman » November 23rd, 2018, 6:40 pm

Hi all,
Yeah we all know that Sanwa 29E31 chassis suck... but we are in 2018 and replacements are getting harder to find so why not fixing 'em?
I would appreciate your comments on this screen of mine that seem to have a Red gun that looks off.
It goes well father (on the right side) than the 2 others causing "leaky" redish coulour

If it was the coulour guns, i was told that the 3 would be off. before doing a shootgun capkit, i was interested in a more subtle way...
What woukd AO people do?

Thanks
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nem
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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by nem » November 23rd, 2018, 6:50 pm

You have red gain too high? There's a pot for it.

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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by Asure » November 23rd, 2018, 6:59 pm

I'd get out the tube rejuv and see what the guns read as. Not rejuv it, they die easily. Just read how much life is left in it.
Whilst in there sort out the focus as it's out of focus as far as i can see.
With the back of, the r/g/b cutoff on the neck board can be adjusted to see if i can get it better that what you see there. Should be able to turn down red on the neck.
If it won't work out, idd swap in a known good neck board to rule out the drive transistors on the neck, and if i didn't have a spare board neck board, i would have to swap out the red with green drive transistor to see if the green then overdrives/leaks/whatever.

Alternatively if the remote board has rgb adjustment, try that first, I don't have any 29e31 in my cabs and don't remember them having the pots on the remote or not. :)

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grantspain
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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by grantspain » November 23rd, 2018, 10:38 pm

red gain pot on neck is too high, i doubt its tube as sanwa tubes normally go weak on colours and i have never seen a gun go strong without it being short full on with flyback lines
do not try to over analyse faults, start with the most simple explanation as 90% of time it tends to be the problem

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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by davidcoolman » November 25th, 2018, 9:22 am

ITS WORKING ITS WORKIIIING :awe:
Dear Sir, thank you for your help. I can now enjoy my Naomi after 2 years :oops:

It wasn't actually the red gain that was too high but the "SUB CONT" was visually too much turned clockwise.
Puting it back to its original position solved the thing

For those interested it's the upper left one on the neckboard (VR903) that according to service manual:
SUBCONTRAST ADJUSTMENT Adjustment for the maximum CONTRAST
It's now time for the shootgun capkit.
Why is it recommended to change all the caps at once? It's easier to troubleshoot if you change them few by few... I mean It's not intended to go wrong but there's a bunch of repports of failure after capkiting

Maybe one more question. The image tends to vary in size with full bright withish images. I've been told that changing plastic caps of high voltage area removes this "pumping image" phenomenon.

Anyways Thanks againg for the insights :D
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grantspain
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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by grantspain » November 25th, 2018, 11:51 am

most monitor will behave like that with a bright white image or flash, some can handle it better than others
replacing the caps you mention would be wise but please be careful when doing so

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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by davidcoolman » November 25th, 2018, 7:33 pm

@grantspain thank you for the confirmation. can you please develop on what behind being careful?

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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by grantspain » November 25th, 2018, 9:02 pm

being careful means putting the correct value cap , correct polarity and good solder work

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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by Kevindg86 » December 7th, 2018, 5:01 am

I have one that is doing the white screen distortion that someone mentioned earlier, I recapped it and didn't fix it. Flyback looks rough and I cannot find a replacement. Anyone out there know of a suitable replacement?

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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by nem » December 11th, 2018, 2:31 pm

grantspain wrote:
November 23rd, 2018, 10:38 MP
i doubt its tube as sanwa tubes normally go weak on colours
I while back I picked up a faulty 29E31S. Repaired the chassis (bad caps) and tested it in a Naomi cab I have on the floor. Everything works, great. Today connected it back to its original tube thinking I'll just dial everything in. Turned it on, no green. Connector another chassis to the tube, no green again. Connected a CRT analyzer to it, green gun is dead :problem:

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nem
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Re: AGAIN: Sanwa 29E31S... No! its a B!!!

Post by nem » December 13th, 2018, 1:09 pm

Continuing from above, I pulled another monitor that had a Shanghai Novel tube from storage. It's a monitor I haven't seen before. It has a 15khz Sanwa chassis. Even though the yoke looked 100% same, it measured higher resistance on both horizontal and vertical deflection. Tube was exactly the same, just older. So swapped the yoke from the 29E31S, connected up the chassis and turned it on.

:problem:

This time there's no red! What the #&¤! is up with these monitors?

Connected the B+K CRT analyzer to it and sure enough red gun is showing 0. Started rejuvenating the red gun and by some miracle after 10 or so seconds the needle on the meter started moving. Meter read bad, but at least it was showing life. Rejuvenated it another time. Connected the chassis to it, and what do you know, red is vibrant even at regular gain level. Result.

Today's lesson, don't toss your tubes before giving them a whack with a rejuvenator. Thanks, B+K.

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