Vintage Synth Repair

>My Son tells me that his firm is instruction not use lead free solder on ANY
>military contracts. Enough said???
>

I expect this is to do with microelectronics rather than people's 
health. Lead solder has Uranium naturally present in tiny amounts. The 
ionising radiation from this can cause occasional errors in today's 
sub-micron digital chips. Lead free does not have this problem.