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Old 18th January 2012, 02:09 PM   #781
BMW850 is offline BMW850  Netherlands
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Default FAKE CMJE 15030

I've done a HFE measurement of the FAKE CMJE 15030 ...(99)
And a measurement of the original MJE 15030 ...(52)

A picture says more than thousand words.
Can someone tell me what can cause this difference to the amplifier?

Regards,
Rudy
Attached Images
File Type: jpg Fake CMJ 15030.jpg (307.2 KB, 231 views)
File Type: jpg MJE 15030.jpg (307.8 KB, 199 views)
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Old 18th January 2012, 02:26 PM   #782
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The cmje has higher hfe because it has smaller die inside which would not be able to sustain SOA figures if used as drivers. The mje figures correspond well with those of datasheets. What position are those cmje in??
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Old 18th January 2012, 03:26 PM   #783
BMW850 is offline BMW850  Netherlands
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The CMJ 15030 put on the place of the small heatsinks.
The CMJ 15030 that I solder out today, I measure HFE 122

Regards,
Rudy
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Old 18th January 2012, 04:33 PM   #784
BMW850 is offline BMW850  Netherlands
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Have now tested, and now I measure 1 millivolt from emitter resistor.
The 100R resistor I measure 4,27 volts.
And the 60 Watt light bulb tester glows only when I switch on the power supply, after 3 seconds glows the lamp no more.

Regards,
Rudy
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Last edited by BMW850; 18th January 2012 at 04:48 PM. Reason: Typo
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Old 18th January 2012, 04:36 PM   #785
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Sorry BMW850 im not familiar with this amps layout but if youre using them as vas transistors they should work without problems, theres much less current flowing there although to say what the effects might be would be pure speculation as we dont know exactly what the fakers put into that piece of plastic.
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Old 18th January 2012, 04:49 PM   #786
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Rudy, this looks good.

So you have a quiescent current of about 42mA.
The bulb tester will only light in the first second(s): during the time of the inrush-current and the time it takes to charge the big reservoir caps.

The bulb-tester will not light, when a very small load of only 42mA is drawn.

Find out the next steps: how to correctly adjust the quiescent current.

Best regards - Rudi
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Old 18th January 2012, 05:02 PM   #787
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I cannot Change the bulb to a higher wattage because I don’t have higher one, and now I can power up directly from the mains I suppose?
And measure the same things again and put the amplifier on about 1 hour and feel if something get warm.
If not, then I put in de fuse and measure again and trim the bias to 1 millivolt.

After that, I short the input signal hot to signal ground.
Measure the output offset at the speaker terminals.
Measure the output noise at the speaker terminals.
Power off. Let the amp cool a bit.

Regards,
Rudy
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Old 18th January 2012, 05:10 PM   #788
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Rudy,

what did Carlos tell you about the adjustment of this AMP?
Is the quiescent current of 42mA (voltage drop of 4.2V over 100 Ohm resistor) the value that Carlos recommends?

Rudi
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Old 18th January 2012, 05:12 PM   #789
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Rudy, have a look a Post #681 or search this thread for "ADJUST".

Rudi
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Old 18th January 2012, 05:16 PM   #790
BMW850 is offline BMW850  Netherlands
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Quote:
better to use the resistor and to measure the voltage drop over it, into it's terminals, measuring DC voltage..... then, let's say your amplifier is fine..you gonna measure from 4.7 to 8.0 Dc volts.
I measure 1 millivolt over the emitter resistor.
I measuring 4.7 volts over 100R resistor, that is good.

Regards,
Rudy
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Last edited by BMW850; 18th January 2012 at 05:17 PM. Reason: Typo
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