Re: {Collins} R388 PTO

What is the purpose of the deep freeze treatment?


R-390A project

On 1/10/2012 7:18 PM, Steve Darveniza wrote:
Hi Buck, it is best to remove the pto and overhaul it on the bench if you can.
A screw driver will do a lot of damage to the locking collar on the band spread inductor shaft.
You need to make a special two pronged tool to lock/unlock the collar.
idealy it is best to open the can ,clean out the old hard grease and replace with fresh.There are some others who know of the best grease.
Do not touch the linearity " spine" until you have set the bandspread as accurately as you can.
They will go to within 30 hertz quite nicely.
When you done this you will see most of the non linear problems have evaporated.
The closer the bandspread the more linear right across the whole range.

If the PTO has not been used for a number of years  it is best to leave the PTO running for 2 to 3 weeks prior to any alignment.

Once you have aligned , wipe the O ring with rubber grease and use a hair dryer to heat and dry out the can and the pto itself.
Whilst still hot ,screw the can on and place straight into the deep freezer.
Leave in there for a few hours and all is done.

For fun ,you can do a linearity plot on graph paper at every 25 KHZ prior to and then after wards.
Hope this helps
73 from Steve VK4VN

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