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Old 17th July 2003, 09:40 PM   #1
dtm1962 is offline dtm1962  Canada
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Default Switch on Transients for GainClone

I have built a Gainclone using the LM3875 chips, using basically
Joe R. circuit (tubeless) using a 10K pot.

Has anyone experience Switch- On Transients to the point where
a 3 Amp FastBlow fuse (temporary as I will use 2A Slo-blos) will blow on Turn-on.

I seemed to have DC offset on turn on (as the woofers will move in/out on start up), but my steady state DC offset is 1.6mV
& 2.4 mV for each channel.

I am using a single 300W Plitron 20+20V dual secondaries for the
Xformer and a total of 8000 uF for PS Capacitance.

There is no cap/resistor across the Power Switch at this time.

Is there anything I could add to prevent transient thumps etc on Power Up.

Any help would be appreciated.

Thanks in advance
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Old 18th July 2003, 10:57 AM   #2
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that might be because on cap charges faster than another...leading to the offset and stuff...try no cap or a smaller cap...no cap for testing only~!
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Old 18th July 2003, 11:23 AM   #3
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Toroids have big inrush currents at turn on.
Put a 10 Ohm 7~10 watts resistor in series with one of the primary wires.
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Old 18th July 2003, 11:30 AM   #4
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Or you could use a NTC termistor...
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