[Biggles]

The burnt out 24-12V dropper is a familiar story. We used to look after NB3 mobiles fitted to a haulage company and we had a lot of trouble with linear droppers failing. Same story, after hours, the drivers would tap into the handy 12V from the dropper and plug in everything from the TV to a travel kettle. In the end I think we went over to using switch mode droppers made by Alfatronix and these would current limit when overloaded. The Motorola T310 mobiles used to develop an interesting fault. The volume pot was mounted so that it allowed slight movement when in use. This led to the earth end of the pot's wire breaking so the radio was at maximum volume all the time. Even when the driver wasn't on a call, the NB3 system cell hand over/acquisition tones used to sound with an earsplitting bloop. You could diagnose the fault from about half a mile away. The fist mics used to go faulty with no mod. Easy, the driver had dropped the mic onto the hard floor and the little gain adjust cermet pot inside had cracked. The standard Motorola fist mic was the best design I have ever seen, and could take some abuse after the pot was linked out. I remember having to install a radio in a massive mobile crane. Nowhere to mount the aerial to prevent fouling except the mudguard. Great. Then after I started drilling realised the steel was about half an inch thick. A Panorama M8A base was juuusst long enough.
Alan.