System Red Amplifier probs
(2017-04-18, 02:06)BobW Wrote: I think you've definitely pinned it down to the AMP. Something appears to be dragging the +5 down. Trick is finding what, and there really isn't too much that can do it. There's like 8 chips and the micro. I think if the micro was doing it, it wouldn't recover. So, i'd power it from something that could deliver some current, but not enough to burn traces. Maybe 4 AA batteries through a diode -1n4001 or something - to drop the 6 volts to 5.3 and a 10 ohm resistor to keep the current down to less than a 1/2 amp if hard short. Your USB supplies - charger or PC - are going in to hard limit, and not putting much current out if they see a short. 

So, something dragging the +5 down, if you can let it draw some current, will make heat, and be easy to find. Be careful when using your finger to find it so as not to burn the chip logo into the blister. With the powering arrangement I described, it might become self evident via it getting hot enough to smoke. If so, make sure you don't let it be hot long enough to burn the board. The amp normally draws nearly nothing, so it working properly, it should run fine powering it through the arrangement below. If something drags the 5 volt line down, that thing should get hot, but 1/2 amp shouldn't be enough to damage traces. You could also probe around with a meter to the different parts on the board that get +5 and find the minimum point referenced to the - power input. Do not just connect it to a high current power source - nicad or power supply - without the resistor, as you will smoke a trace if the short is hard enough on the board. 

                                                               Diode    10ohm
                                                       + ------|>|----/\/\/\/------- + to amplifier
   (Battery or other 5-6 volt source) - ----------------------------- -

You probably have it, but schematic on page 11
thanks for that. I'll need to take a trip to the local electronics shop to pick up the resistor/diode as don't have spares so will try this on the weekend. I have an IR thermometer that can do continuous readings so might try that instead of my finger to check it out.

I've reseated the atmega chip and since doing that it appears to have stopped reconnecting over and over again. While initially looking good I'm not confident that's it so for now I'll monitoring and will try your suggestion this weekend.

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Messages In This Thread
System Red Amplifier probs - by ShimmerNZ - 2017-04-17, 06:53
RE: System Red Amplifier probs - by BobW - 2017-04-18, 02:06
RE: System Red Amplifier probs - by ShimmerNZ - 2017-04-18, 10:16
RE: System Red Amplifier probs - by BobW - 2017-04-19, 01:26
RE: System Red Amplifier probs - by ShimmerNZ - 2017-04-23, 06:58
RE: System Red Amplifier probs - by BobW - 2017-04-26, 03:11
RE: System Red Amplifier probs - by Dale.Reid - 2017-04-24, 01:32
RE: System Red Amplifier probs - by ShimmerNZ - 2017-06-04, 03:56
RE: System Red Amplifier probs - by ShimmerNZ - 2017-06-20, 08:56

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