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karatzdi
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Last Activity: 06-11-2024, 10:02 PM
Joined: 12-29-2022
Location: Nicosia
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  • Denon AVR 1908, High pitch noise on Surround back Left channel after long overhaul

    Hello,

    I know some might say... just buy another one. Sell it as parts..!

    So had this AMP for quite some time. Recently I saw light smoke coming out of the AMP. Had my fire extinguisher close by. Just kidding. Turned immediately all devices off from mains.
    Let things cool a bit, and opened up the amp device. I clearly saw on the main board which hosts the 5X amp (5.1), 3 10 ohms 1W resistors had their leads looking black, while the rest of the remaining 2 x 10 ohms were brownish as being installed from factory.

    Spent some time downloading the Service...
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  • Hello,
    Am and old guy born in 1966 originating from Cyprus.
    Radio Amateur 5B4ZC, and electronics graduate from US of A during 1989.
    Worked as a Nakamichi technician in my early days in the local distributor here in Cyprus.
    I was mostly repairing / Servicing Denon and Nakamichi decks and amps, up until 1992
    I then joined various other IT companies like Data General and then IBM.

    I have a small bench with mostly all equipment required to fix amps and Decks and am now fixing them at home.
    Although I graduated with a degree in Electronics Engineering,...
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Thanks for input there R_J. The Resistance of the test leads is 0.2 to 0.21 ohms when shorted....
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Iotas, thank you very much for all efforts. It seems that this diagram is very close to what I have on the PCB am currently trying to fix. Actually ZD905 is located physically and connected to Ground (one leg), whilst the other is located to the last 2MΩ resistor. The locations are indeed different. But not the physical locations of the parts on the PCB.

    May be because you have schematics of a different revision from my board.
    So the Zener is 7.5v.. I got one for 10v on the PCB. Not SMD though...
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead




    Hello..Sorry I completely missed your questions here !.

    Ok the problem is that the TV has no power. Not even getting into the Standby mode when turned on from the power switch. It has no reaction from the Remote control, because the standby circuit is not working because the ZD905 got shorted out the 1ohms resistor got a bit hot and deformed / altered its value. I am not sure about the luck of IC901. There was a quote or reply to me that since ZD905 is now burned, IC901 is compromised. Therefore I did...
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    Last edited by karatzdi; 01-06-2023, 09:59 AM. Reason: Name wrong.. Iotas instead of RJ

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  • Re: Phillips 520FL3603D/F7 Power Supply Dead

    [ATTACH]284658[/ATTACH]

    [ATTACH]284659[/ATTACH]

    As promised I reversed engineer a bit the circuit around IC901 so as to eliminate the relation of ZD905 to the IC.

    The help of the users Iotas and RJ were great. Basically the circuit is the same with a few differences which I post in my own drawing. Look closely so you can see the differences noted with either a (?) or any other notes I left on the paper. Last 2 posts from Yokoono and nomoresonys stated that ZD is usually 15v and is there to...
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    Last edited by karatzdi; 01-05-2023, 10:53 AM. Reason: Attached another diagram

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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Your schematics resemble the de-ciphering I did on my Board.. Lets se if its exactly the same though. Thanks for posting...
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Correct RJ. However it seems that the 1Ω Resistor in place R929 is a bit deformed and it reads 2.1 Ohms. Brown black Gold Gold ! Surely that will need to be replaced and try a zener 7.5v from info that was given in this thread.

    Thanks much...
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Hello many thanks for help. Well the diode reads 0.0001v and beeps either ways I place the test leads around it. I.e reversing polarity on it.
    Ok 7.5v Zener diode I will check and place one...
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Good morning. Yeah, unfortunately no schematics. If anyone has one to download or purchase let me know. !

    But the Phillips manual I found has everything in schematics [B][U]except[/U][/B] the power supply. All other PCBs and Circuit diagrams more or less are in that manual. Bummer !Re: Phillips 520FL3603D/F7 Power Supply Dead



    Good morning. Yeah, unfortunately no schematics. If anyone has one to download or purchase let me know. !

    But the Phillips manual I found
    ...
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead



    Hi and many thanks for such quick replies.

    Ok.. The zener Diode is of smd type and its super miniature. I know its zener, cause its sitting in position referred to as ZD905 (ZD=Zener Diode).

    I took it to a friends microscope (cause I don't currently have one after your suggestion) and there are no tiny letters on it, except from two Grey stripes,

    The Diode either in reverse polarity or FWD biased polarity it reads short-circuit and DMM beeps while testing it in Diode mode....
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  • Re: Phillips 520FL3603D/F7 Power Supply Dead

    Hello newbie in this forum.

    I got a question if anyone knows ? What is the value of ZD905 which is used around the circuitry of IC 3BS03 ? Is it 9.1v or 6.2V. I found a zener at this location which is short circuited. DMM reads short circuit both ways.

    Also the 1Ω Resistor R929 is a bit dodgy... Its a bit deformed.

    Fuse F2 is short circuit i.e is not open therefore from your descriptions in this thread the chip does not seem to be the problem.

    Any help will be appreciated....
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