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Sanwa 29e31s-b No Picture-total black

Posted: January 7th, 2020, 11:56 am
by Pa0l0ne
Hi all, I have received a naomi cab with this CRT but unfortunately the monitor is out of work with total no picture.
When i power on the cab i hear the classic snooze sound from the crt that let me to think the sanwa tube is not totally dead (?) but i receive no picture and the tube itself remain total black (no gray or something else that put me in direction of thinking that is correctly powered).
Initially i hear and see spike (!) from the cup on the tube regularly on all powercycle, but after discharging the flyback and clean the tube and the cup itself I DON'T have this issue anymore. Naturally the naomi1 vga output is good (tested on vga lcd monitor).
MY skills on crt are very poor, but not totally bad on low voltage circuits and pcb... So i need an help that put me in the right direction to go on on this case.
I have a fresh new compatible flyback too (bsc24-0107), JUST in case it's needed to SUCCESFULLY complete the job.

Experts... Please... Can you give me an Hope? 😁

P. S. I see some light on tube filament(s) in a black room condition (maybe the neck of the tube is not totally depowered (?)

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 7th, 2020, 12:18 pm
by nem
That means you have neck glow. What happens when you turn the voltage pot on the flyback? Does the screen get gray? Do you see raster lines?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 7th, 2020, 12:24 pm
by Pa0l0ne
No visibile change when i rotate the pots on flyback, no gray and no raster lines. This why in my poor skills state i suspect a clue on the flyback. Isn't it?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 8th, 2020, 8:04 am
by Pa0l0ne
A little update: yesterday when i take a look at chassis pcb i notice cold joints on rgb connector where the wires goes to the neck pcb. I have flux resoldered them and now when i try to power on the monitor i see a very fast light only on the exact momenti of the power on cycle, and a little bit white center point light when i power off it.
MAYBE the chassis doesn't open the screen but is still able to power it (?), but still no raster lines.. 🤔

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 8th, 2020, 8:56 pm
by Pa0l0ne
Image

Image

R456 value with my tester, wht do you think?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 9th, 2020, 9:22 am
by grantspain
its probably ok, only a super high quality meter would read that resistor correctly

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 9th, 2020, 2:47 pm
by Pa0l0ne
Ok, i don't have any other skill to go on, maybe i have to trash it :cry: but first i can try to swap the compatibile flyback JUST to see if i have any difference on the tube (raster lines that now i don't see).
Is there any troubleshooting on tube test, just to be sure if i don't have filaments problem or any related tube problem?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 9th, 2020, 2:59 pm
by nem
Please don't trash it. I will buy it from you if you can't fix it. I'll pay postage plus something for the board.

It could be the flyback, however it could also be something else. These are not easy chassis to diagnose faults on.

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 9th, 2020, 9:22 pm
by Pa0l0ne
I want to repair it with all my soul... Cause i don't want to replace it with 28" scart tv..... So i will try the flyback swap and take a look on whats will going on... 😁

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 9:14 am
by Pa0l0ne

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 9:40 am
by grantspain
new flyback?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 9:44 am
by Pa0l0ne
Yes, new flyback give a new life at my monitor!

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 10:18 am
by grantspain
where did you buy the flyback ?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 10:58 am
by Pa0l0ne
Tecknoservice on Ebay. They are located in Spain and offer a very great service at very great price. Really satisfied!

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 12:53 pm
by grantspain
expensive but he seems to have the remade these flybacks at the correct spec- unlike the hrdiemen version

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 1:12 pm
by zak
Are these the same flybacks used on a MS2931/MS2933?

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 1:18 pm
by Pa0l0ne
grantspain wrote:
January 13th, 2020, 12:53 pm
expensive but he seems to have the remade these flybacks at the correct spec- unlike the hrdiemen version
Yes, i confirm they have the perfectly remade units that not require any wiring adaptation or resistor mod.
The only recommended mod is a different bridge on one of the gnd (?) pad unlike this the chassis may remain in a protection state.
In my point of view is not expensive for a just like an original unit. I think it is professional rejuvenated and i'm very happy to see the monitor bring a new life again.

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 1:22 pm
by Pa0l0ne
zak wrote:
January 13th, 2020, 1:12 pm
Are these the same flybacks used on a MS2931/MS2933?
Sorry, i don't know but i think the nanao chassis had other flyback specs. Maybe the experts tell you more.

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 1:43 pm
by grantspain
zak wrote:
January 13th, 2020, 1:12 pm
Are these the same flybacks used on a MS2931/MS2933?
no but the same seller does stock them

Re: Sanwa 29e31s-b No Picture-total black

Posted: January 13th, 2020, 2:01 pm
by zak
grantspain wrote:
January 13th, 2020, 1:43 pm
zak wrote:
January 13th, 2020, 1:12 pm
Are these the same flybacks used on a MS2931/MS2933?
no but the same seller does stock them
Excellent! Thanks Grant.