The uP is usually the last suspect unless you have very good reason to think otherwise but persistent latchups can and do occur.
One Sony VCR remote locked up in such a way that even taking batteries out for several days wouldn't get them to work correctly (neither would foil on these either) but putting the PCB on a really hot radiator or in a low oven would reset them after a an hour or so. My theory was retained charge internally and the heat caused enough leakage to dissipate it. It wasn't a one of either, I came across several of that type and all behaved the same.
One Sony VCR remote locked up in such a way that even taking batteries out for several days wouldn't get them to work correctly (neither would foil on these either) but putting the PCB on a really hot radiator or in a low oven would reset them after a an hour or so. My theory was retained charge internally and the heat caused enough leakage to dissipate it. It wasn't a one of either, I came across several of that type and all behaved the same.
I wanted to add my recent findings to this post. I’ve been having a similar problem - a85 won’t turn on. To be more specific, it actually won’t stay on. Posting the pose button causes the amp to start it’s person sequence but almost immediately shut down again.
i’d all but given up on it because the amp is all SMD so I thought I’d never fix it but reading this I thought there might be hope and was inspired to try again.
long story short, having taken the front panel off and pushing to follow the items described here I stumbled across a fix for my problem and wanted to share. I noticed the power button was slightly more flexible than I expected and behaved like a joystick. Pushing it to the side activates the switch but I was amazed to find caused the amp to power up fully and stay on.
I.e. if I push the power button, the amp won’t go/stay on. If I fired it to the side, it works.
i couldn’t get this approach to work with the front panel on. The button is too tight to the panel. Instead, I’ve removed tube button and simply poke the blunt end of a biro through the panel where the power on button was and this has fixed the issue.
presumably, replacing the surface mount switch would resolve the problem, but I’m happy with my biro.
i’d all but given up on it because the amp is all SMD so I thought I’d never fix it but reading this I thought there might be hope and was inspired to try again.
long story short, having taken the front panel off and pushing to follow the items described here I stumbled across a fix for my problem and wanted to share. I noticed the power button was slightly more flexible than I expected and behaved like a joystick. Pushing it to the side activates the switch but I was amazed to find caused the amp to power up fully and stay on.
I.e. if I push the power button, the amp won’t go/stay on. If I fired it to the side, it works.
i couldn’t get this approach to work with the front panel on. The button is too tight to the panel. Instead, I’ve removed tube button and simply poke the blunt end of a biro through the panel where the power on button was and this has fixed the issue.
presumably, replacing the surface mount switch would resolve the problem, but I’m happy with my biro.
things like that are not always obvious.
Most IR receivers are active low and my guess is that if the signal is stuck low, the processor will sit in a loop waiting for it to go high again as it's trying to receive the data. Hence the dead system.
Hi Tom,
I have an Arcam A85 and have some very similar problems that appear to be related to the microcontroller.
Pressing the power button caused the relay to momentarily engage, so clearly something was causing it switch back off.
I have followed the steps you took as best I could and then it started working all of a sudden without any explanation.
So I unplugged it and moved it to the lounge to connect it to a source and it didn't power on again, clearly unplugging it must have changed the state of the microcontroller.
Did you get to the bottom of what caused your amp to not power on occasion?