Comments on: Electronics Repair Questions/Answers and Testimonials- Part 74

By: ALABI

ALABI — Fri, 01 Mar 2019 12:41:15 +0000

Please sir, my strong decoder srt 4675 is not detecting signal. The signal level just remain at 37% not responding.pls what could be the problem?

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By: Jestine Yong

Jestine Yong — Fri, 25 Jan 2013 02:22:12 +0000

In reply to othman.

Hi Othman,

Ada power tak? Kamu dah check samada voltan kat output SMPS?

Jestine

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By: othman

othman — Thu, 24 Jan 2013 11:45:20 +0000

Saya menghadapi masaalah tv samsung plasma 42inc yang tidak mengeluarkan gambar dan suara.Mohon En jestine membantu saya

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By: admin

admin — Fri, 25 Mar 2011 14:54:59 +0000

Hi Daniel,

Congratulation!

Jestine

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By: Daniel F

Daniel F — Fri, 25 Mar 2011 02:54:34 +0000

Update: Regarding my post about the 17" Dell monitor above;

Hi Jestine,
For your information the AP1506 was acting unusual so I replaced it with the AP1506 from DIODES INC. and it has fixed the problem. 24 hours burn-in and it still okay so I guess the lesson here is sometimes you should go with your instinct.

Thanks again.
Daniel

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By: admin

admin — Thu, 24 Mar 2011 01:18:45 +0000

HI Emmanuel,

Did you check all the components in the power side? Have you replace the power IC and retest?

Jestine

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By: Emmanuel N

Emmanuel N — Wed, 23 Mar 2011 07:01:55 +0000

I have bought your books on repairs and they are wonderful. I am fixing a PS3 sony computer entertainment, on the power supply board I replaced to burn down electrolytic capacitor of value 420V, 130uF with 400V, 100uF. I was able to measure about 320V across the capacitor when plug to the power supply but am not getting and out to PS circuit control board. Please can you help me with out.

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By: admin

admin — Tue, 22 Mar 2011 01:19:18 +0000

HI Daniel,

Thanks for the photo. If all the corresponding components are tested ok then you need to direct replace and retest the set. The ic inside have lots of components and it could be the components inside the ic that cause the problem. As for the scope you need a similar working machine to compare the waveform. By just measuring the points in the circuit one would not know if the component is weak unless you really have experiences in troubleshooting this model many times.

Jestine

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By: Daniel F

Daniel F — Sun, 20 Mar 2011 11:29:45 +0000

Hi Jestine,

I've finally installed your rss feed into my mail client so I can read all your posts at a glance.
Thanks for introducing that feature.

Anyway, I have a query.
I am repairing a dell 17" lcd computer monitor which won't power on after a power cut, no leds light.
I'm certain the fault is a tiny electrolytic somewhere in the startup circuit. I've attached a photo for reference. The 1506IC I have circled is a Buck DC-DC Step Down converter;

http://pcserv.org.uk/images/dell17.jpg

http://www.diodes.com/datasheets/AP1506.pdf

I can sometimes trigger the monitor to start up (turn on) if I use my multimeter on DC to probe the pins of the 1506IC or surrounding area. The charge in the multimeter probes must be initiating the startup circuit which leads me to think this circuit has some weak electrolytic somewhere. When the monitor is off, there is 12v on the vcc pin of the 1506IC which is correct, but there is nothing on the output pin (normally 5v) or feedback pin (normally 1.2v). However when I trigger the monitor to come on, everything works fine.

With your advice I purchased the Blue ESR and RING tester. So I used the ESR tester but couldn't find any bad caps at all. I also checked every component possible around the primary/secondary circuits and found nothing wrong. I have access to a 100MHz scope so my question is; is it possible to trace weak / problematic components with a scope? Is is possible that they will show some reading as they try to start?

Thanks for your time Jestine, I very much appreciate you taking time to answer everyones questions.

Regards
Daniel

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By: admin

admin — Fri, 11 Mar 2011 18:15:51 +0000

HI Thomas,

The VDD should have about 20v (according to the ic spec) when you turn on the equipment. If you are getting only i.7 volt this mean either the ic itself have problem or the corresponding component is bad. Try get the part from the below link:

http://www.utsource.net/sg6840.html

Jestine

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