Recently I enjoyed assembling the 50 watt power amplifier kit.? It was working perfectly until I got greedy for more power?
while adjusting gain with the R5 potentiometer.? ?I did not have an ammeter to measure current draw during adjustment
but instead stupidly thought I could watch output on my power meter and back off when it met the specified power on the?
power output chart.? Though I carefully and slowly turned the potentiometer there was a sudden failure as output power reached
about 30 watts on the meter.? I then noted an acrid smell and a small amount of brownish liquid coming from the edge of one of the 2 output IRF510 final MOSFET
transistors.? ?Stupid me.? But I learned something and hope others can learn from my mistake. Follow Hans instructions for adjustment.
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Now here is my question as I seek to remediate the situation and restore the amplifier.....
I have replaced both of the IRF510 output transistors with new ones from Digikey? Replacement went well, no solder bridges.? However on power up there amplifier function is not normal and I am wondering what other components would most likely have been damaged and need replacement?
Whereas before the accident keying the amp on or off was nearly instantaneous and generated about 20 watts even with the potentiometer fully counter clockwise, now THE RED TRANSMIT LIGHTS STAYS ILLUMINATED FOR ABOUT A FULL SECOND AFTER A KEY PRESS, and output power is only about 6 watts.
Another possible clue is that the 19 volt lap top charger I was using to charge it now shuts itself off quickly when I connect it to the amplifier. (I suspect the lap top charger power supply has some type of protection circuit in it as after I disconnect and reconnect it from wall outlet power it resumes its 19 volt output).
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Before I start removing and replacing other components such as Q4, Q5, Q6, or some of the switching diodes, etc. I would very much appreciate any guidance about how to best pin point the problem and proceed.? What other component(s) is/are most likely the remaining problem?? How best to proceed short of buying a new kit and starting over.? Thanks.
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