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Chip Amps Amplifiers based on integrated circuits

LM3886 Inverting/Non-inverting on one PCB build
LM3886 Inverting/Non-inverting on one PCB build
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Old 6th October 2019, 01:55 AM   #31
Dadbeh is online now Dadbeh  United States
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Originally Posted by tomchr View Post
No, but you might want to consider that I can't read your mind and sharpen up your communication accordingly. You don't say 40 V anywhere, only "40 V". There is a difference.

If the supply voltage droops from 40 V to 25 V, there's something wrong or you're using way too little supply capacitance. I'd use at least 2x4700 F plus the local decoupling on the amplifier board.

I see. these two filtering capacitors are 10000 micro farad nichicons, they are very very well used though. I got them used years ago and they have been continuously used for years. it is possible that they might have reduced capacity. i can check that using an ESR meter that I have. I will not continue with this project though.
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Old 6th October 2019, 02:05 AM   #32
tomchr is offline tomchr  Canada
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I suggest checking the capacitance of those before using them in another project. Load them with 1 kΩ (use a 5 W type). Turn the power on. You should see nearly 40 V. Turn the power off. It should take about 50 seconds for the caps to discharge to 0 V. If they discharge significantly faster than that, I'd toss them.

An even better test would be to measure the capacitance with a capacitance meter. Should be within 20% of 10000 F.

Best of luck.

Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD.
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Old 6th October 2019, 02:11 AM   #33
Dadbeh is online now Dadbeh  United States
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Will do. In my previous post i mentioned using an ESR meter to measure the capacitance, i meant this: LCR-T4 ESR Meter Transistor Tester Diode Triode Capacitance SCR Inductance M328 606098871258 | eBay

it has worked great so far and it is a great cheap capacitance meter. I will make a point to check the capacity of those caps. I also have another bipolar unregulated power supply specifically for LM3886 but it needs repair, that's why i used the old power supply from the LM3875. I already have new 50V and 63V caps for both of these power supplies and i will take care of that tonight. also the seller also refunded me for those boards. I should have stuck with the tried and true XY boards instead of taking a chance on this awful board.
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