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Old 12th February 2011, 12:47 PM   #1
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Default NMOS200 247 PLS HELP

WHAT IS THE ADJUSTMENT OF V1 AND V2?
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Old 12th February 2011, 06:14 PM   #2
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finaly i got this,

Final Set up And Adjustment

No attempt should be made to set up or test a power amplifier module that is not correctly mounted
on a heatsink. Make sure the main power supply is fused and the work area is clear. First check all
your work and make sure the output devices are insulated from heatsink. The set up is done without
an input or a load connected to the power amplifier.

1. Check the power supply is operating correctly and verify the rail voltages. Switch the power
supply off and check with a multimeter that the rail capacitors have discharged.

2. Correctly connect the ground, positive and negative leads to the power amp module.

3. Remove the PCB fuses and replace with 100 ohm 5 watt resistors. Connect a multimeter
that is set to the 20 volt scale across the positive rail 100 ohm resistor.

4. Check that the power supply connections are correct one last time and switch on. If the
multimeter reading goes off-scale, turn off immediately and find the problem. Check also the
100 ohm 5 watt resistors; they may have gone open cct.

5. If everything seems ok adjust VR2 to set the output stage bias current, by measuring the
voltage across the positive rail resistor. Adjust for a reading of 3 volts per output FET pair. I.e.
For a 6 FET board set for a voltage of 9 volts. This equates to a bias current of 30mA per
FET pair or 90 mA total. For a 10 FET board set for a voltage of 15 volts.

6. If everything seems ok, check the output offset voltage and adjust VR1 to achieve an offset of
less than 10 mV.

7. All being well switch off, back off the bias control trimmer (VR2) and replace the 100 ohm
resistors with 10 ohm 1 watt resistors. Switch on again and re-adjust VR2 to get 0.3 volts per
per FET pair across the positive rail 10 ohm resistor.

8. Switch off, remove the resistors and put the fuses back in. Switch on, re-check the offset
voltage and adjust with VR1 if necessary.

The amp module is ready, connect the input and output and enjoy.
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Old 14th March 2011, 05:58 PM   #3
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do not try this amp useless .
the transistors get very hot so u need big heatsink.
preset adjustments are very difficult.
don't try,don't try,don't try.
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Old 14th March 2011, 06:05 PM   #4
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
Then you have built it incorrectly or your MOSFETs are fake - many here have built the NMOS200 design and had it work perfectly
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Old 14th March 2011, 06:51 PM   #5
norazmi is offline norazmi  Malaysia
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Join Date: Feb 2008
Absolutely right jaycee, i also have build this amp NMOS every version of it, and i dont have problem with thermal, doesn't have big issue with it, maybe your mosfet are fake or bias too high, always check bias voltage before put final output power transistor
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Old 15th March 2011, 01:04 AM   #6
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Join Date: Jun 2004
Location: HKSAR
Hi nazirdigi,

Do not irritate Quasi's fans, there are quite a large number of them. There is a saying "when you point your finger at others, there are 3 pointing at yourself".

Try to make sure what is wrong with your own work rather than saying someone else work is no good. Make good use of resources from this forum. Ask instead of accuse. I think many will be more than willing to help. But with this kind of attitude, you will go nowhere.

There are hundreds of way to blow a project but there are only a few ways to success. Check you own work over and over again before making comments like this. There may be a thousand success but you may not the the next one.

Sorry if you find this rude but just try to straighten out some attitudes.


BP
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Old 15th March 2011, 02:31 PM   #7
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Join Date: Oct 2009
Quote:
Originally Posted by norazmi View Post
Absolutely right jaycee, i also have build this amp NMOS every version of it, and i dont have problem with thermal, doesn't have big issue with it, maybe your mosfet are fake or bias too high, always check bias voltage before put final output power transistor
i remove the fuse and put 10ohm resistor in series and set the bias to 0.3v .but whithout no signal input mje 340,350 all getting very hot. my dc offset set 7mv.

after input signal and working condition output transistors getting very hot.
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Old 15th March 2011, 02:48 PM   #8
jaycee is offline jaycee  United Kingdom
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What size heatsink are you using? A Photo would probably answer this question best.
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Old 15th March 2011, 03:04 PM   #9
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Quote:
Originally Posted by jaycee View Post
What size heatsink are you using? A Photo would probably answer this question best.
one feet heatsink i used. this heatsink used in ground audio 2400(2400w). it is used 8 transistors 2sc 5200,2sa1943. i can post photos tommorrow.

what is the maximum voltage for nmos200 247?
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Old 15th March 2011, 03:16 PM   #10
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
http://sites.google.com/site/quasisd...ries/nmos200-1 is the new website. 50V rails max.
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