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Old 4th January 2013, 01:47 AM   #11
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Quote:
Originally Posted by Mooly View Post
I know I keep banging on over this

Have you located the backup 5 volts supply (I know we're assuming it has one rather than non-volatile RAM) and done some checks ? Is the supply correct ? Is the supply maintained on power off ? Is the backup cap leaky and so pulling the supply down ? Remove the backup cap, discharge everything and try again without it fitted.

The uP is always always always the last suspect. I 've been here countless times and seen other technicians fall repeatedly into the same trap. 99.9% of the time its something simple. Is the keyscan OK to the uP ? No shorted tact switches or data lines being pulled down.
Sorry to show my lack of knowledge here, but I don't even know how to check the things you have suggested, although I am more than capable of giving it a go with a little TLC ;=}. I have a schematic from the service manual, if I shared that could you point out what to check and how? I have a V-O-M meter, but not a silly-scope. Anything is worth a try in my book. Thanks much!
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Old 4th January 2013, 07:34 AM   #12
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Its no problem

Here's the backup 5 volt supply. With the power TOTALLY OFF check what the voltage is on this cap and pin of the system control processor. It should be 5 volts.

Assuming it is, then what you then need to do is to discharge the cap with a resistor (anything from 100 ohm to 10K ohm).

You then have the option of trying it all again. If its still the same then repeat the discharge procedure and then totally remove the cap I ringed. Try it again and see if it will set up.
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Old 5th January 2013, 12:30 AM   #13
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Okay, I will try this in the morning. I don't have any resistors, but my neighbor might. I assume that I put the resistor across both leads from the cap? It seems to me that in a long ago and far away place I once learned that a cap could be drained by shorting it - is that not the case? Or (more likely) is it just a bad idea? What is proper procedure to use?

And, if the cap is drained and I still have no luck finding the correct frequency ranges, then I suppose I have gone as far as I can go - correct?
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Old 5th January 2013, 06:28 AM   #14
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Generally its not good practice to short caps, and particularly not large ones.

Backup caps are a bit different and have relatively high internal resistance and so you could just short it (but the mains MUST BE OFF).

If its still doesn't work or allow you to set it up after discharging the cap then REMOVE the cap completely and try again. If thats a no go then yes, you've gone as far as you can.
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Old 5th January 2013, 04:25 PM   #15
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Final results - found and drained the cap, no better outcome. Looks like it's headed for the scrap heap. Still, it was worth the effort. Luckily for me, I found another on Clist one town over for $50 just listed two days ago. This one cost $25 and was three years newer. Sigh ...

Post mortem: I learned a lot along the way, both about myself, and about the value of Internet 'friends' :=}. I am still 100% convinced that this could be salvaged, if only I knew how to program the Mp. The service manual was somewhat useful, but strangely silent on this aspect. Hope that my next experience has a better outcome, but I could not have had better help along the way. Many thanks for all assistance!
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Old 5th January 2013, 04:35 PM   #16
Mooly is offline Mooly  United Kingdom
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Thanks for the kind words... a pity it wasn't a better outcome.

I'd go along with your suspicions too, it doesn't sound like a genuine fault (as in a component fault).

The very final suggestion is to remove that cap and then put the whole thing on one side for a week or so and then power it up again (with the cap still out).

Better luck with the next one
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Old 13th February 2013, 05:13 PM   #17
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I stumbled on this thread (and forum) Googling specs for the RX-V480 because there's one for sale near me. There's probably nothing wrong with it; 76-90 is the FM broadcast range in Japan. That said, there may or may not be a setting to actually change it, so no big deal if you already tossed it. But if you haven't it might be worth playing around with or at least reselling.
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