I have not encountered this particular myth in almost 30 years, before which it was an almost everyday mention for me. So it really does take me back a bit.
Everyone knows what i currently do, but back in my teens i was very heavily into the radio decoding scene. As is the case now, i never do things by half and although i wrote my first ever decoding software on a ZX spectrum, i quickly migrated to the then emerging PC's and i supplied equipment on 386 16 MHz grey scale laptops to almost everyone, including Phillips themselves.
I therefore happen to know how and why this myth came about and once upon a time, in the very earliest days of coded radios, Phillips did use an antequated code storage technology (ER1400) for a radio that the user could optionally set their own 3 digit code in (22DC751/2) and as it was such an early storage device, it was really RAM based, and it could possibly be reset if you upset the devices input pins sufficiently or found a way to short the Ram to ground.
However at best, the process was tricky and putting the whole Radio in a freezer could theoretically reset the device if you were lucky, but it was infinately more likely to just ruin it completely. So no matter wha, simply do not try this, no matter what.
Land Rover have always used Clarion Radios, until the BMW days anyway.
The first examples, as used in classics (PRC XXXX) did not even use any form of electronic storage, but had a set of about 10 solderable jumpers spread around the PCB. Once upon a time, my party trick was to pull the lid off a clarion radio, look at the board and manually calculate the code for it in my head.
They then went through a series of diodes, that had some cut out to give a code, but eventually did the same as everyone else and used an 8 pin EEPROM. They did start off with the usual industry standards, but by the time the P38 was introduced, they were using their own variation called the S2430. This was actually a re named industry standard device, but had its pins rotated clockwise by 2. It is usually found underneath the Cassette mechanism.
The radio does keep a count of invalid attempts in this EEPROM and increases the delay between attempts accordingly, but as far as i know, there is no total lockout situation.
If you do not know your code, any of the Radio decoding services should now easily and cheaply be able to read it out from this Chip for you.
I hope this helps and thank you for taking me for a trip down memory lane.
