Plectron conversation piece

[medic8ted]

I've recently acquired a Plectron and we have not used low band for many years. I want to make a conversation piece from this and put a switch on it to set off the alert tone and replace the lights on the front with led's. I can't find a wiring diagram anywhere online and I'd rather not just start shorting out wires to see what trips it for fear of frying this piece of history for good. Any help would be appreciated. Its a 33.82MHz unit, Sentry I think. Model is 500 something I believe. Thanks.