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Tinman
Joined: 09 Mar 2006
Posts: 1326
Location: Carson City Nevada
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| Posted: Wed Jun 19, 2013 12:47 am Post subject: |
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I have not seen those fail, but that doesn't mean they won't.... someday.
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This space for rent.
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the big E
Joined: 20 Apr 2013
Posts: 1928
Location: speedwell Tn.
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| Posted: Wed Jun 19, 2013 12:49 am Post subject: |
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| Tinman wrote: | | I have not seen those fail, but that doesn't mean they won't.... someday. |
Well if they do it will be the perfect excuse to buy another projector from curt 
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crt king of black
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Thu Jun 20, 2013 3:50 pm Post subject: |
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Did further investigation, yesterday and today it seemed the squealing is connected to scan frequency / refresh rate. Without any source on RGB (15kHz/38Hz) it gave different sound than with video input (15kHz/50Hz), now I pulled out the power supply to took a closer inspection. While the PG/PG+ power supplies were made by Rubycon, this one is totally different (made by Iriichi), literally no Rubycon caps inside, instead Nichicons, I pulled out some of them, but no visual sign of leaking and they were measured good too. I found one cooked resistor instead, see attachment, I circled the resistor in question.
Where it belongs that is the coil that supplies the main horizontal deflection voltage, as you can see that is an RC network in parallel with the rectifier diode (not sure why), the resistor is marked to have special safety charachteristics, probably flame proof. The outer painting of the resistor is quite burnt, but it still holds its resistance precisely, however its solder joint was totally burned, the small ceramic capacitor (C58) measures also good, but have no clue how it behaves under high tension and in warm environment. Colud this be my problem? Any ideas from switching PS experts please?
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_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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SisterOfMercy
Joined: 31 Oct 2007
Posts: 155
Location: Zwart Nazareth, The Netherlands
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| Posted: Thu Jun 20, 2013 4:42 pm Post subject: |
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Do all resistors in the schematics look like that? Perhaps they mean it's a wirewound version.
A capacitor parallel to a diode is often done, to lessen the effects of EMI noise. An RC parallel is a snubber:
http://www.hagtech.com/pdf/snubber.pdf
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The kissing and the colour come crashing down
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the big E
Joined: 20 Apr 2013
Posts: 1928
Location: speedwell Tn.
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| Posted: Thu Jun 20, 2013 4:42 pm Post subject: |
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| gjaky wrote: | Did further investigation, yesterday and today it seemed the squealing is connected to scan frequency / refresh rate. Without any source on RGB (15kHz/38Hz) it gave different sound than with video input (15kHz/50Hz), now I pulled out the power supply to took a closer inspection. While the PG/PG+ power supplies were made by Rubycon, this one is totally different (made by Iriichi), literally no Rubycon caps inside, instead Nichicons, I pulled out some of them, but no visual sign of leaking and they were measured good too. I found one cooked resistor instead, see attachment, I circled the resistor in question.
Where it belongs that is the coil that supplies the main horizontal deflection voltage, as you can see that is an RC network in parallel with the rectifier diode (not sure why), the resistor is marked to have special safety charachteristics, probably flame proof. The outer painting of the resistor is quite burnt, but it still holds its resistance precisely, however its solder joint was totally burned, the small ceramic capacitor (C58) measures also good, but have no clue how it behaves under high tension and in warm environment. Colud this be my problem? Any ideas from switching PS experts please? |
If it has a loose soldier connection it more then likely is the culprit
You have two choices resoldier the connection and hope the resistior doesn't fail
Or you can replace the resistior with a new one and watch it to see how it proforms under stress over time
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crt king of black
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Mon Jun 24, 2013 6:40 am Post subject: |
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So I cleaned the oxidation off the legs of the resistor, cleaned the traces, and resoldered on friday. So far so good.
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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the big E
Joined: 20 Apr 2013
Posts: 1928
Location: speedwell Tn.
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| Posted: Tue Jun 25, 2013 4:30 am Post subject: |
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| gjaky wrote: | | So I cleaned the oxidation off the legs of the resistor, cleaned the traces, and resoldered on friday. So far so good. |
Is it still working without issue??
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crt king of black
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SisterOfMercy
Joined: 31 Oct 2007
Posts: 155
Location: Zwart Nazareth, The Netherlands
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| Posted: Sat Jun 29, 2013 10:53 pm Post subject: |
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| the big E wrote: | | Is it still working without issue?? |
No, it has spawned offspring!
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