Yamaha RX-V373 "internal error"

[AlOOZ]

Hello.
I had this "internal error" appear after ten years of faultless operation.
With help from the RX-V373 service manual, in the self-diagnosis area of the unit I found the error was "MODEL/DEST ERR", specifically the "DEST" setting was blank???
I've read that some Yamaha receivers can forget where and what they are, supposedly to do with an on-board battery failing.
Anyway, setting the "DEST" to my country code "A" made the unit work perfectly again!
Why it's only the "DEST" (destination) setting that is lost is a bit of a mystery.
Disconnecting the unit from the mains supply for a few minutes led to a return of the "MODEL/DEST ERR" message, so it could be a battery/memory problem. I've had similar problems with dead RTC batteries in computers.
Anyway, time will tell.
Anyone have any thoughts on this?

[wasedadoc]

I spent 5 minutes looking through the Service Manual but didn't find a battery.

[David_AVD]

The service manual (page 49) seems to suggest that info is stored in IC22 (EEPROM) on the digital board. Could be a flakey chip or corrosion around that area?

[AlOOZ]

Thank you.
I've done some reading. (Look out, danger ahead!).
Looks like I'm lucky that the model/destination options stored permanently at manufacture (in IC222 maybe?) are still intact and can still be written to IC221 (and saved as long as mains power [standby power] is maintained):
"This menu is used to write the model name and destination to the back-up IC (EEPROM: IC221 on DIGITAL P.C.B.).
My unit "forgets" where it is when mains power is disconnected, but remembers its model name ?? - not a standby-power problem at IC221 it seems.
Possibly a failing chip or corrosion/solder joint problem as you said. (8 pins on IC221).
I forgot to mention that this "internal error" happened after a 7-hour mains power failure, which led me to think an onboard battery might be involved.
(As you can see, I'm an electronics ignoramus!).

[David_AVD]

I don't see a backup battery or super cap. Maybe it's just as simple as U221 (the EEPROM) being old and flakey?

[wasedadoc]

I would expect more than the destination to be in that chip. Do other user settings such as tuner presets get forgotten too?

[AlOOZ]

Yes, other settings and functions are lost too when mains power is disconnected - tuner included. (The unit did produce sound but at very low volume and quality).
The error referred to the model and destination settings, the model number was correct but the destination was blank?
The unit was sold in many countries and with two model names, and all the country codes and both model numbers are still selectable in the unit, thankfully. So wherever that info is stored is still good.
I guess the country codes set the appropriate tuner ranges for the selected destination, among other things - different mains voltages even?
The service manual says that the unit will not function if the destination is not set in the back-up IC EEPROM: IC221, so that would be done before despatch from the factory I guess.
When the unit is powered on, I guess that the back-up IC221 provides the destination and model info which was set at the factory, and the unit "sets itself up" accordingly (??).
It's odd that it only loses the destination setting (and everything associated with it).
So far, with stand-by power maintained, the unit is "remembering" the destination setting. As said, the error occurred after a long mains power loss (7 hours).

[wasedadoc]

The list of options for each of the settings is not stored in the EEPROM but in the microprocessor's ROM or the flash memory.  The specific selections stored in the EEPROM are not read regularly but only when needed such as after a reconnection to the mains supply.  The microprocessor runs all the time that mains power is present, even when powered down in standby mode.  That you noticed the fault after the 7 hour power loss just means that the fault occurred some time - possibly a long time - before that.

Most likely there is something amiss with he EEPROM or the voltages and signals on it.  Page 64 of the Service Manual. You can check for the 3.3 Volts between its pins 8 (VCC) and 4 (GND) though I expect that will be OK as the microprocessor is on the same supply.  You really need a digital scope to check the MISO, MOSI and CLK signals as they are not repetitive.  There are no connectors or series resistors on those lines to the microprocessor so unless there is track damage or a solder joint that was initially poor but working and has now failed, then replacing the EEPROM may be the best option.

[AlOOZ]

Thanks very much for all the info and advice everyone.

The RX-V373 has been good for more than 10 years so can't complain really, and although it's far from high-end, the sound quality is very good, to me anyway (the ancient Marantz and Wharfedale speakers probably help).
It's still functions as well as ever and who knows, I might get a few more years out of it before something more serious fails. It lives in a tropical climate.

Thanks again.

[SpecialK]

Try searching Youtube for Yamaha repairs on the sme series of receivers for instance this repair of a RX-V673 which is a bigger brother in the same family and probably shares much of the same logic.

[AlOOZ]

Try searching Youtube for Yamaha repairs on the sme series of receivers for instance this repair of a RX-V673 which is a bigger brother in the same family and probably shares much of the same logic.

Thanks.
Yes, that was one of several vids and articles I looked at. The service manual explained how to get into self-diagnostic mode, which revealed the problem ("DEST ERR") and thankfully a fix.
The unit is working properly again so I'll let sleeping dogs lie for now. Not sure that's a wise attitude though.
I wondered about updating the firmware but can't find any updates. Not a surprise, given the age of the RX-V373.

[wasedadoc]

You probably tried it already but if not, doing the "Initializing the back-up IC" procedure on page 22 of the Service Manual won't do any harm.