Adding 'Timer Record' to a JE480

[stevecole]

I purchased a second-hand JE480 recently, as a backup for my overworked JE780. I was aware of the differences between the two at the time, but I now realise that the lack of 'Timer Record' is a nuisance. Does anybody know if there is a simple way to retro-fit this feature onto the 480? I could live with a discreet switch on the back of the unit to activate this if it were possible.

[stevecole]

To update this post, I now know how the Timer/Off/Play function is implemented in my JE640. The switch determines the voltage present at PIN 136 of IC1 the Master Control device (M30805SGP), derived from a 10K + 10K potential divider across the 3.3v supply. With the switch at 'Off', the divider puts 1.6v into IC1. At 'Play', the bottom leg of the divider is shorted to ground, so IC1 gets 0v. And for 'Rec', the bottom leg is disconnected, so IC1 gets 3.3v via 10k. The big question now is whether the JE480 uses the same 'Master Control' IC as the JE640/440, because if it does, then adding Timer Record will be easy, just 2 resistors and a switch. Anyone know?

[sfbp]

Dunno, those are of the same generation exactly, but the service manuals aren't on the site. You can probably find one by paying for it.

Stephen

sent you a PM

[stevecole]

By way of an update - basically if you are considering doing this, forget it! I added the 10k pull-up resistor to the circuit (marked on the PCB as R92), which I'd hoped would permanantly send the machine into Timer Record mode, but unfortunately nothing happened. I can only conclude that machines made without this or other options run different software to those with them 'built-in' from new. Any un-expected inputs, such as my +3.3v applied to pin 92, are ignored! Oh, well, never mind!