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Old 10th November 2007, 11:19 PM   #1
fredos is offline fredos  Canada
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Default Need service manual or schematics of behringer PMH1000 mixer

I need service manual for a broken ( switching amplifier section and power supply...) PMH1000 powered mixer...Yeah I know it's only a Behringer, but I whant to fix it for a friend...First of all, booth power mosfet and drivers have blow in the power stage (dead short) and this may have blow PFC stage in the power supply. Only the section with TopSwitch work, no power output.

At least, if nobody have it, I will just do an un-powered mixer with it....

Thanks

fredos
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Old 11th November 2007, 06:41 AM   #2
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here
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Old 11th November 2007, 06:04 PM   #3
fredos is offline fredos  Canada
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Thanks a lot! I will fix it, just wish that the HCA4001 is not blow...It's look like a Zetex chip...


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Old 11th November 2007, 08:35 PM   #4
Eva is offline Eva  Spain
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Thank you very much oldmaelstrom2 for this nice pdf.

If they got the current limiting feature of the PFC to work properly, it should survive dead shorts on the outputs without problem.

SHAME on the way current limiting is implemented in the class D amplifiers, though.
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Old 13th November 2007, 12:15 AM   #5
fredos is offline fredos  Canada
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Repaired!

No Eva, I dont think they have done a great job on the protection schem...Power supply blow after dead short on amplifier mosfet...

So the HCA4001 seem to work well. The sound of this crap is like all berhinger crap...Bad! But power amp seem efficient, duty cycle is limited into the HCA4001, so no need to find a way to keep gate charged...Power supply provide +/- 56V, very well regulated..

Some ugly 60Hz noise inside transformer, specialy with 200 watts load and more, but still regulated. Began to drop over 460 watts until 0V with a PAR 64 1000 watts lamp. Did'nt try short, I dont whant to blow it again!

Thanks for serviec manual!

Fredos
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Old 13th November 2007, 12:19 AM   #6
fdeck is offline fdeck  United States
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Was I missing something? It did not look like there was any current limiting on the power amp circuit, only the current sense transformer in the power supply. Is this typical of Class-D?
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Old 13th November 2007, 12:31 AM   #7
Eva is offline Eva  Spain
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Congratulations

This noise in PFC inductors and transformers is quite usual and is a consequence of sub optimal PFC performance. If you look carefully at the AC current waveform, you will notice discontinuities near zero crossing...
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Old 13th November 2007, 12:39 PM   #8
fredos is offline fredos  Canada
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So I will have to increase PFC Choke (330uH)? I whant to fix this, I dont like it!

Fredos
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Old 14th November 2007, 02:56 AM   #9
Eva is offline Eva  Spain
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In my PFC designs I got smooth zero crossing by allowing up to 100% duty cycle and by optimizing frequency compensation of the average current control loop. A too *high* PFC inductor value can also produce this behaviour but only for heavy loads. In a finished product the noise is not that easy to fix.
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Old 14th November 2007, 04:20 PM   #10
fredos is offline fredos  Canada
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100% duty cycle did not imply short on HV bus under heavy load/low voltage condition????

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