You just have to fault find based on the situation as it stands now. If it is in protect mode (so I'm assuming all outwardly OK but speaker relay not connecting) then you have to begin with things like looking for DC offset and so on.
I've got it working. The broken front board is a later revision than the other. There was a dead cap I missed right at the top. It's an anomaly because it was a 100uf 16v and all the other electrolytics are 22uf 50v. Even in the service manual it should be a 22uf 50v although if the board is a later revision then it might be legit.
Its never the big chip
Having replaced two of the main micros on this particular model (and micro's on many other products) I would have to disagree.. - it does happen, but of course one should always check the vitals, supply, clock , enable and reset first.
There is also a bulletin about the processor on this model, the original 4bit variant was superceded by an 8 bit, but both were still available for service (that might have changed today though lol) - the bulletin was dated 2007
There is no compatibility between the two variant processors.
4 bit variant - 4822 209 15719
8 bit variant - 90M-HU100750R
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I've got it working. The broken front board is a later revision than the other. There was a dead cap I missed right at the top. It's an anomaly because it was a 100uf 16v and all the other electrolytics are 22uf 50v. Even in the service manual it should be a 22uf 50v although if the board is a later revision then it might be legit.
Well done that's great news.
Having replaced two of the main micros on this particular model (and micro's on many other products) I would have to disagree.. - it does happen, but of course one should always check the vitals, supply, clock , enable and reset first.
If it is a part that has a proven track record of failure then that is fair enough It becomes a stock fault related to that model.
My own experience working in a large service dept as both bench tech and also supervisor and so overseeing the work of others was that in the majority of cases the uP was usually the last thing to suspect... or I suppose more correctly was the easiest to suspect but was rarely the cause of the fault.
That doesn't mean they never fail but it was pretty rare for it to be so.
or I suppose more correctly was the easiest to suspect but was rarely the cause of the fault.
It's becoming more common for customers to say "my mate think it's the power supply that's gone ...." or "it's just a capacitor"
Where's it gone then ?
Just tell me the symptoms and let me get on with it