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Problems with amplifier MX50 SE
Problems with amplifier MX50 SE
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Old 5th May 2013, 03:20 PM   #1
arielgam is offline arielgam
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Default Problems with amplifier MX50 SE

Hi
I bought two plates of this amplifier (ebay chine)
I've ridden and I've fed AC35+35 (DC50+50)
I have been burned when ignition resistance.
Turn repidamente.

I have not tried the other channel because I have fear of burning.

As I can find the problem.
Thank you.
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Old 5th May 2013, 07:19 PM   #2
djk is offline djk
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Post the schematic link, and identify the reference number of the burnt resistor please.
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Old 5th May 2013, 08:57 PM   #3
arielgam is offline arielgam
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burned resistance is 68 ohom

attachment scheme

Thanks
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Old 7th May 2013, 01:48 AM   #4
djk is offline djk
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There are more than one 68Ω resistors, which one (use the reference designator on the schematic please).
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Old 7th May 2013, 03:24 AM   #5
Ian Finch is offline Ian Finch  Australia
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The resistor is probably R25 (closest to R23 and the PNP driver). The OP may be having a similar problem with the schematic as anyone else trying to follow it. It is bogus - I'd say intentionally, to foil copyists, as it specifies darlington drivers but the fitted transistors are apparently the Chinese versions of 2SD669/2SB649. Further, the part numbers are not reproduced on the overlay. There likely will be more errors to ensure failures if building from scratch using that version of the schematic.
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Old 7th May 2013, 08:59 AM   #6
djk is offline djk
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Are those 669/649 full-pack? Or are they missing their insulators, I can't tell.

He has the C12 100F cap in backwards, the resistor is probably R29. Cap shorted, resistor burned.

http://www.ebay.com/itm/LJM-MX50-SE-...-/230909190448
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Old 7th May 2013, 09:31 AM   #7
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LJM MX50 SE 100W 100W Power Amp Kit Stero Amplifier Kit DIY | eBay
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Old 11th May 2013, 04:39 PM   #8
arielgam is offline arielgam
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Quote:
Originally Posted by djk View Post
Are those 669/649 full-pack? Or are they missing their insulators, I can't tell.

He has the C12 100F cap in backwards, the resistor is probably R29. Cap shorted, resistor burned.

LJM MX50 SE 100W 100W Power Amp Kit Stero Amplifier Kit DIY | eBay
You're right.
It was a mistake of mine.

I solder a capacitor backwards.

Thank you all.
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Old 20th May 2013, 05:56 AM   #9
augustoriodosul is offline augustoriodosul  Brazil
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Hi all,

I found it interesting parts welded far from the pcb, this should cause some loss in signal quality. I've assemble some of these MX50-SE but with SANKEN transistors - 2SA1186 Ft 60 MHZ and 2SC2837 Ft 70 MHz.The result is great mids and highs in a multi-amplified system. A simple amplifier, but it looks very good. Some pics in https://www.facebook.com/augustojose.hoffmann
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Old 20th May 2013, 02:56 PM   #10
arielgam is offline arielgam
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I've installed everything and have already exploited the two channels of amplification.
I've ridden with NE5532 preamp.
Have coupled the midpoints of the two transformers at the output of toroidal coils.
First you burn an amplifier and then the other amplifier.
Before turning to audio cocnector touch several times to prove that it worked, and then burned.
The preamp volume was the maximum.
The toroid is in AC-DC-35 +35 50 +50.
The smaller toroidal AC-12 +12

That problem could happen?
Problems before the amplifier output directly to the PC and sounded good. Warmed much heat sinks but not burned. (Only burn the filter upside down )
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