[R-390] Collins R 389 PTO

[2002tii]

Cecil wrote:

>Well I have to ask...what was the military standard operating 
>procedure to keep the operators from damaging the things....I can't 
>believe Collins would design a radio that would self destruct in the 
>hands of an operator?
>
>I realize I am showing my lack of knowledge of this particular radio 
>but that is less important than understanding how one was to operate 
>the thing as Collins designed and have it survive.

PTO failures are generally caused by a confluence of factors -- a 
sticky clutch, plus running the PTO to its end stop (generally with 
the motor, but it can happen by hand tuning, too).  Back in the day, 
the clutches were a lot closer to fresh than they are now, they got 
scheduled maintenance, and everything (switches, limit stops, etc.) 
was usually in adjustment.  Not so anymore, so there is less margin 
for error than there was back then.  Also, the materials in the coil 
form, the ferrite itself (internal stress cracks), etc. are much more 
fragile now than they were then.  So the next thing that goes wrong 
could actually be the second or third factor in the confluence, but 
you won't know it until too late.

Don't forget, Uncle Sam had a big pile of replacement PTOs and a 
never-ending supply of radiomen, so it didn't matter so much if one 
failed.  Now, it does.

If you rebuild everything, set all the clearances, stops, etc. 
perfectly, then perform full depot maintenance twice a year, you may 
get away with using the motor tuning.  In my book, prudence counsels 
using R-389s as manual-tuned radios in the 21st century -- after the 
clutches are carefully rebuilt and adjusted, and hopefully everything else.

Best regards,

Don