Yamaha RX-V480 Tuner / FM Bands Wacky

[ANOLDSALT]

I have the subject receiver. It's 2nd hand to me and only cost me $25. I bought it for its' height - it is 5" tall and fits the available cabinet space for it just right. I like it very much, and wish to save it from the scrap heap. Recently, the tuner has started behaving weirdly. It only displays a frequency range from 76.0 to 90.0 for FM. I feel this might be some kind of a regional configuration issue? There is nothing in the Owner's Manual about how to set this, and a note to the Yamaha tech support team yielded nothing helpful. Oddly, there is a strong signal at 89.7 from a local station that the tuner is not pulling in, but then that is true of any signals at all. Everything else on the receiver works fine. Whenever I play a CD, it does a good job without any issues.

Has anyone ever encountered something similar, and if so, have any advice? Many thanks for all responses ...

[Mooly]

Problems like this can be down to numerous causes but if you suspect a software/configuration issue then check if the unit uses a backup battery or "super cap" to retain uprocessor settings. These can give weird faults when faulty. If it has one then it can be worth removing it and seeing if the fault clears although it won't remember any configuration settings etc.

A word of caution... altering software settings is done at your own risk and you have to be sure you know how to reconfigure any settings that might be lost.

[ANOLDSALT]

Originally Posted by Mooly

Problems like this can be down to numerous causes but if you suspect a software/configuration issue then check if the unit uses a backup battery or "super cap" to retain uprocessor settings. These can give weird faults when faulty. If it has one then it can be worth removing it and seeing if the fault clears although it won't remember any configuration settings etc.

A word of caution... altering software settings is done at your own risk and you have to be sure you know how to reconfigure any settings that might be lost.

Thank you for your recommendation. I was thinking along similar lines, as I found in the Owners Manual that if the unit was unplugged for one week or longer, the station presets would be lost. This made me think the config could be 'reset' as it were, by draining the cap that was backing up the settings. So ... I unplugged the unit yesterday. I will try it again after the New Year. Wish me luck!

[Mooly]

In rare cases (and again you need to be aware of the implications) you can place a piece of tinfoil over the uP and "press" it hard onto the pins to fully discharge everything.

You MUST be sure there are no higher voltages around that could cause damage though.

This is something that has got me out of trouble many times as a repair tech. In rare cases even leaving something unplugged for a week doesn't reset things.

Of course we are assuming this is the problem... it may not be

[MLStrand56]

Try to get the Yamaha Service Manual for your Receiver. Yamaha Receivers have for many years, had a built in trouble shooting problem. I found this out recently when I was given a RX-V540 Receiver. The Service Manual will tell you how to enter the troubleshooting program.

MLStrand56

[ANOLDSALT]

Originally Posted by MLStrand56

Try to get the Yamaha Service Manual for your Receiver. Yamaha Receivers have for many years, had a built in trouble shooting problem. I found this out recently when I was given a RX-V540 Receiver. The Service Manual will tell you how to enter the troubleshooting program.

MLStrand56

Could not find the exact manual, but found one for an RX-V440. Thinking it may be close in some respects, and out of curiosity, I dl'ed it. It was interesting to find a section on how to read the MP settings. Even more interesting to learn that there are tuner settings for the bands based on regions, which confirmed my intuition. What was missing was any detail on how to configure the MP. I think there must be some kind of bench diagnostic tool to do this. I also think that unless leaving it unplugged for an extended period does the trick, I am going to be out of luck. All advice is still welcome, and at least I am getting closer to a final determination. Much thanks all around!

[ANOLDSALT]

Today I plugged the unit in after a week off. Regrettably, it had no affect on the settings of the tuner. I tried resetting it to default factory settings per the instructions I just received from Yamaha tech support, with similar lack of results.

So ... I removed the top and peeked inside. The unit was amazingly clean, practically spotless with almost no dust at all. All the fuses were fine, no signs of anything, anywhere having smoked. I found what COULD have been the Mp and used the foil tip from Mooly. Again, no dice.

I am going back to Yamaha and ask them to contact the factory for me on how the settings were originally applied, as I am convinced it has to be some sort of regional configuration. Likely as not, it is done by some form of combining buttons that are pressed, and then reading the LCD panel, in a similar vein to the reset procedure.

[Mooly]

It was worth trying...

I see you tried the foil. Its worth physically looking for a backup cap to be sure and discharging it. They often look like this,
backup capacitor - Bing Images

As you say, it may well be a software setting that is corrupted.

[ANOLDSALT]

After I posted this today, I found a service manual online. It had information on what the default settings are supposed to be, and how to reset them, which I did. My unit is not lining up with what they should be according to the manual. I guess it is toast - disappointing! For the life of me, I don't know how this occurred, and why it cannot be resolved. As I thought about it, I seriously doubt that Yamaha is going to tell a user how to muck around with a unit beyond what they have provided me already. So, I either find another, or else I use this one for it's remaining capabilities. Thank you for your suggestions, I truly appreciate them.

[Mooly]

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.