Vintage Synth Repair

Hi!

It's well known that Roland custom made chips for Juno 106 (VCA/VCF 
80017 and dual oscillator MC5543) fail frequently. My Juno has only 
two of six 80017 original and one MC5543 has gone either. I've been 
wondering what is the cause of such common failure.

Some lots are know to be bad. In this case there are nothing to do 
but change the damaged IC but... would it be an excessive heating 
damaging good ones??? I noticed that these ICs, specially 80017A 
works so hot, even for 80's industry standards. Considering one can 
get high temperatures frequently at stage would it be the cause of 
ICs going dead?

If heating is the problem I believe there is space into the cabinet 
to mount three small fans, one over each set of oscillator/VCA/VCF. 
Would it save my Juno voices?

Regards and Happy 2001!
Arnaldo.