[R-390] PTO Problems

[Bob Camp]

Hi

If you throw it away you will have a major hit in your Karma account.  
The PTO is the crown jewel of the Collins design. Of course they also  
were the most replaced sub-assembly in the entire radio.

Back when I worked for Motorola, our engineering assemblers were ex- 
R390 people. They had not made R-390s for nearly 20 years at that  
time. The *one* thing they remembered vividly was the PTO assembly  
process. I think I listened to an hour of "information" when I  
happened to mention R-390's to one of them.  Never knew gray haired  
little old ladies knew all those four letter words ....

Bob


On Nov 3, 2007, at 8:31 AM, Jon Schlegel wrote:

> Craig,
>
> The desiccant.  So that's what all that stuff is.  There is no  
> evidence of any type of bag or container they use to contain that  
> stuff and only now have I put it all together as to what happened.
>
> Is there a specific procedure for setting the compensation stack if  
> it comes to that?  Also how easily should the shaft turn?  With the  
> Oldham coupler plate removed, the shaft is turnable with my fingers  
> but with difficulty.  This is the original reason I suspected a  
> problem in the PTO.  What about desiccant?  Should I insert a new  
> pack and if so, where?
>
> Jon
>
>
> At 04:55 AM 11/3/2007 -0700, you wrote:
>> Jon,
>>
>> I had the same issue with a PTO in a Motorola R-390A. After  
>> applying liberal
>> amounts of elbow grease, life was good. The desiccant was scattered
>> throughout the PTO, stuck to the shaft that moves the widget along  
>> the
>> corrector stack, ugly but fixable.
>>
>> First, I wouldn't do anything to move any of the plates of the  
>> corrector
>> stack! Clean the inside of the PTO as best as possible. Check the  
>> condition
>> of the little spring used to keep pressure between the widget and  
>> roller
>> which moves along the corrector stack. A little De-Oxit here didn't  
>> hurt my
>> PTO. A drop or two of synthetic 90 weight on the threads of the  
>> shaft didn't
>> seem to hurt either. Reassemble the beast and adjust the end-point  
>> per Y2K
>> manual. Keep your fingers crossed, the linear points are close and  
>> the
>> plates of the corrector stack are where they should be. If the  
>> plates need
>> adjustment, it will be a long night.
>>
>> Wd8kdg
>> Craig,
>>
>> -----Original Message-----
>> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net 
>> ]
>> On Behalf Of Jon Schlegel
>> Sent: Friday, November 02, 2007 10:17 PM
>> To: r-390 at mailman.qth.net
>> Subject: [R-390] PTO Problems
>>
>> Hi all,
>>
>> The PTO shaft seemed way too stiff so I opened it up and found this
>> amazing colony of crystalline entities growing all over inside.  It's
>> a real mess.  It looks like it had a LOT of moisture in it at one
>> time but the rest of the receiver doesn't really show signs of water
>> problems.  Nevertheless the PTO looks original to the receiver (both
>> Motorola).
>>
>> Should some kind of repair attempt be made or should go out with next
>> Thursday's trash?  I have an interesting photo but I suppose that
>> would be inappropriate for the list.
>>
>> Regards,
>> Jon
>>
>>
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