Noise power supply switching Crown I-Tech T6000. |
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mj15015
New Member Joined: 16 July 2017 Location: Argentina Status: Offline Points: 5 |
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Posted: 16 July 2017 at 3:35pm |
Hi everyone, Greetings from Argentina, I am an audio technician today I am repairing the power supply of the crown t6000 I arrived with a burned mosfet mmbf170 I replaced it and I kept walking but my doubt is because it makes noise the source? Is by the type of modulation of face (Phase Shift Modulation)? I have already controlled the whole diagram, capacitors ok, voltages +20 and -20 ok + 15v and -15 ok ref. 5v ok +180 Y-180 ok, SG3525 seems to be working well in the video the oscilloscope is showing pin 11 of the SG3525, someone who works and repairs any of these models I4000, I6000, I8000 can answer my question. I leave a link to the video where you can hear the noise; It looks like a spark jump but none of that is happening ... Edited by mj15015 - 17 July 2017 at 2:58am |
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U.Viktor
Young Croc Joined: 04 May 2010 Status: Offline Points: 716 |
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Without seeing the main power circuit it is impossible to say the exact topology and modulation scheme used in that power supply.
The MOSFET failed looks seriously undersized in that position, it is just a half-Amper FET , I would put at least 2-3A type there. If you see these gate driver FETS making not only the gate clocking signal but also the full power for the isolated gate drivers across the gate transformer. Driving 3 or more of the power devices I guess @50KHz or more would needs larger FET for safe operation. Otherwise the whole floating gate driver section looks utterly over-complicated, so many CMOS gates just for local UVLO when simple and more reliable integrated solutions exists since ages? Weird.. The SG3525 drives pair of gates and flip-flops looks "poor man's phase shift modulator" anyways :-) Edited by U.Viktor - 17 July 2017 at 5:37pm |
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mj15015
New Member Joined: 16 July 2017 Location: Argentina Status: Offline Points: 5 |
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I really do not understand how Works phase modulation with cmos 74hc74......
Edited by mj15015 - 15 September 2017 at 9:12pm |
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mj15015
New Member Joined: 16 July 2017 Location: Argentina Status: Offline Points: 5 |
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mj15015
New Member Joined: 16 July 2017 Location: Argentina Status: Offline Points: 5 |
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RobinMatrix
Young Croc Joined: 23 August 2013 Location: Kidderminster Status: Offline Points: 567 |
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Jeezus ... I never bothered to look at this PSU before, but 24 power devices in the PSU? That's a lot of work to save paying for a decent sized IGBT!
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Matrix Pro Audio ::http://matrixproaudio.com/"
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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I always thought this generation of crowns was just the designer going a little bezerk. Since production is outsourced to China, I guess the number of parts are less of an issue...so why not fill your boots!
A couple of years ago a spilled pint on the amp rack wrote-off an entire stack of XTi's. The high-density boards went off like a box of fireworks and there wasn't alot left. |
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Kevin
North Staffordshire |
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nopamp
New Member Joined: 07 December 2017 Location: Portugal Status: Offline Points: 2 |
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Hello, have you already discovered what is the problem?
I have one unit with same problem that I will investigate this weekend in case I get time. Sincerely, Joel |
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nopamp
New Member Joined: 07 December 2017 Location: Portugal Status: Offline Points: 2 |
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I think I discovered it :)
Turned it on and no longuer makes that "transformer like" noise. |
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patryk1305
Registered User Joined: 13 December 2012 Location: United Kingdom Status: Offline Points: 488 |
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Then share your findings in case others have similar issues
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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Details please or it didn't happen |
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Kevin
North Staffordshire |
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geovanebr
New Member Joined: 24 April 2019 Status: Offline Points: 1 |
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Hello Everyone, could someone send me the schematics for it-6000, please? |
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