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JLHD 750Watts - high rail voltage
JLHD 750Watts - high rail voltage
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Old 2nd October 2015, 07:11 AM   #1
nonprof is offline nonprof
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Default JLHD 750Watts - high rail voltage

Hello!

I want to restore this amp after a couple of years stuck. But I think my limitation had reached on this amp, the rail voltages is too high, it produces high AC voltage up to 110V. Putting back the rectifier diode the DC voltage reached up to 120VDC and this diode gets too hot...

I measured the PS switching freq around 49Khz. I have a perfect gate square wave into IRF3205s mosfets.

Please help...

Last edited by nonprof; 2nd October 2015 at 07:23 AM.
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Old 2nd October 2015, 09:35 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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If too high I expect the regulation has failed. The PSU will be either pulse width modulation or frequency regulated. In the latter, the frequency rises and the transformer gets less efficient so the voltage produced gets less.
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Old 2nd October 2015, 09:53 AM   #3
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Quote:
Originally Posted by JonSnell Electronic View Post
If too high I expect the regulation has failed. The PSU will be either pulse width modulation or frequency regulated. In the latter, the frequency rises and the transformer gets less efficient so the voltage produced gets less.
So do you mean I should get higher frequency to make the voltage lower? This amp is PWM or a frequency modulated? I've seen the McIntosh amp, it is PWM regulation.

I have schematic of this amp, could somebody tell me which part of the circuit detects the output voltage? or any sensor?

Last edited by nonprof; 2nd October 2015 at 10:00 AM.
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Old 2nd October 2015, 10:05 AM   #4
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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A schematic would help. I will be able to help further if you can post a copy or link.
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Old 2nd October 2015, 05:21 PM   #5
Perry Babin is offline Perry Babin  United States
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Post a photo of the drive/control section of the amp for that power supply.
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Old 22nd October 2015, 02:27 AM   #6
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thanks...but another problem exist, I will fix this first
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