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Service mode in Car radios???

I can't find it now, must have been in an earlier vehicle, but I recall some statement to the effect that you could change channel spacing only once :-(

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
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Reply to
Jim Thompson
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Hi,

Does y2005 model car radios have a service mode for some basic configuration?

I posted a question here some weeks ago about reconfiguring a car radio in a US made car (US FM band standard) to the European FM band (with narrower channel selection).

I have dismantled the radio and checked which components were in the tuner. It is a Philips TEA6848H, (data here:

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This circuit is capable of tuning both US and European FM bands and I'm just curious if car radios nowadays have some kind of 'service-mode' which enable simple programming of parameters like regional radio standards and channel spacing etc..

If any of you have heard of something like that, I would appreciate information on how to invoke service mode and which parameters are programmable. The radio in question came in a new Dodge truck. The radio model label plate and tuner images can be founde here:

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Thanks for *any' information which might be helpful in having this box correctly tune the narrow European FM channels.

regards

Geir

Reply to
Geir Holmavatn

Hi,

Probably not a 'service mode' but it could well have a sequence of keys or combination of buttons that need to be pressed together to change the FM mode - this of course depends on whether the radio has a way to store this setting in some non-volatile memory. Does it loose all FM presets after the radio is disconnected from the battery for some time?. If it keeps all settings then it has some form of EEPROM which also has the capability to contain other settings. If it looses all memory when power is removed then any configuration may be hard wired, if the firmware in the microcontroller is capable of changing the FM mode then it may be determined by certain pins on the microcontroller being grounded or pulled to VCC. Sony radios often use this principle, even sometimes using an un-used ADC input on the microcontroller and a couple of resistors that have different values depending on the model or country that for which it is used - very strange things happen when those resistors change value!

You could try and find a schematic - post your links to the internals on sci.electronics.repair - in case anyone recognises or has a circuit diagram.

The real cunning hack would be to use a pic micro or similar to modify the I2C commands sent to the Philips PLL ic so it only receives commands to tune the wanted channel steps - completely not worth the effort of course for a car radio!

Philip

Reply to
Electric dabbler

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