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Author Topic: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A  (Read 555 times)

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NightWolfx03

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I have a Sanwa 27Z21C-A74A monitor I am putting a new flyback on, as the old one got a crack in it and it was leaking high voltage. On power up it arcs out and blows the main chassis fuse.

The question is, I found a new flyback and obtained it from Russel Industries, and I want to install it, but I found some scorching under the old fly back. I don't want to have the new one fry, so I figured I would see if anyone has any pointers on things to check before I replace the flyback and power this chassis up again.

I have done board repairs before, but I have never had anyone experienced to work with and learn from  ??? , so I am just looking for advice and pointers. I would greatly appreciate any help or input  ;D .

I cannot LCD swap this machine as it uses light guns, being Time Crisis 3.

I apologize in advance if this is a bit spammy with the pictures.  :blah:

Pictures as follows.

Failure point of old flyback


Scorch Mark


Scorch Mark


Cleaned up PCB
« Last Edit: January 25, 2017, 02:09:21 pm by NightWolfx03 »
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ed12

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #1 on: January 25, 2017, 02:12:47 pm »
well u have got most of the carbon tracking out
 >black< but i can see a tiny bit between 2 pins..scrap it out on the top side
and then fill the gully u will make scraping with some ptv silicon
so it will not want to track again
give a shot of the bottom traces (foil side of the chassic) around the flyback
as i want to be sure it is >track free<

ed
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NightWolfx03

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #2 on: January 25, 2017, 02:47:02 pm »
Pre / Post Desoldering. I will clean it good with alcohol and/or acetone before putting the new one in. The traces seem fine, they were a slight PITA though because of those grommet things in the holes, carefully used a heat gun to to get the flyback to come free after the majority of the desoldering was done with wick.



« Last Edit: January 25, 2017, 02:48:55 pm by NightWolfx03 »
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ed12

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #3 on: January 25, 2017, 02:54:15 pm »
na that bottom looks clean
the crabon tracking was caused by the leak in the flyback to ground

ed
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NightWolfx03

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #4 on: January 25, 2017, 03:06:20 pm »
So after I clean up the rest of the carbon, is there anything else I should check or test, or should I be good to replace the fuse and try powering it up ?

Here's the cleaned up spot, I just used a file and scraped the last bits of metal and carbon off. Not the prettiest (I do better work with a razor / dremel and smaller areas), but I think it should do.



« Last Edit: January 25, 2017, 04:11:36 pm by NightWolfx03 »
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Nexus13

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #5 on: January 25, 2017, 06:55:08 pm »
Well done!  Looks very clean!

ed12

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #6 on: January 25, 2017, 08:07:29 pm »
na its clean
the scratching is where i was trying to say put the silicon
this will stop tracking of any kind

ed
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NightWolfx03

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #7 on: January 26, 2017, 03:55:14 pm »
Checked HOT and nothing looked shorted, added silicone, installed flyback, replaced fuse, and made connections. Will test tomorrow and see if it works or dies (I want to let the silicone cure).

Crossing my fingers. :notworthy:

Silicone


Soldering


Flyback


Caged In Flyback


NeckBoard Connections Done


Finished Chassis


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NightWolfx03

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #8 on: January 27, 2017, 12:39:24 pm »
Ok, installed chassis, crossed fingers and flipped the switch. No Bangs, No Sparks, neck glow, turned the screen up on the flyback and discovered I appear to have no vertical output. Now to see where I need to go from here, guessing the vertical IC might be damaged :hissy: from the flyback arcing to the heatsinking / chassis ?

Actually, I have another chassis with no vertical, maybe I can fix both at the same time   :dunno (the other is a Toshiba in a DDR cabinet)

Let me know what you think





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ed12

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #9 on: January 27, 2017, 02:45:26 pm »
nice work so far
ya with acring u can never tell where it will go or fry on the way
chk resistors for an open 1
around flyback

ed
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NightWolfx03

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #10 on: January 27, 2017, 03:02:01 pm »
I'll check it shortly, either today or next week when I am in, I think I did smell something like something was hot but not burning, will check resistors and see if I can probe the vertical IC as well.
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NightWolfx03

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #11 on: February 16, 2017, 02:50:14 pm »
Found 2 issues so far.

The Input pin is shorted to the output on the Verticle IC.

1 of 2 resistors that are connected to the Input Pin on the Verticle IC is showing high resistance.

Should I look for the same wattage resistor to replace and would this have damaged anything else or would this be a good point to replace those 2 parts and test it ?

Diodes near and around the IC appear to test out ok.









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lilshawn

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Re: Looking for Input / Advice on Sanwa repair in progress. 27Z21C-A74A
« Reply #12 on: February 16, 2017, 04:01:21 pm »
it's quite common if the vertical IC goes short, it takes out the power feed resistors.

check R302 as well.

might as well replace C314 and C305 they may have been overvolted in the short and weakened.

  
 

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