[R-390] help needed on RF deck mechanical alignment

[Grayson Evans]

Thanks Bill, 
After digging around in the manual, I came across this “ohm meter” method that you mentioned.  Once I figured out what the proceedure was trying to tell me, I was able to get the bandswitch aligned, I think correctly.   
Also turns out I had the Geneva thing gear in the wrong position, spent awhile fiddling with that thing.
THanks!

On Mar 15, 2015, at 6:09 PM, Bill Abate <wabate at verizon.net> wrote:

> Grayson,
> 
> I had the same problem.  This worked for me.
> 
> I set the cams where they belonged at 7 +000 but then found out the bandswitch was not synchronized.  I found the section on synchronizing the 6 position RF bandswitch that showed you get a 56K resistance between two points (page 110 of TM 11-5820-358-35) when at 7 +000 setting.  So I loosened the gear on the band switch shaft and rotated the switch shaft until I got the 56K reading and then an infinite reading when switched to 8 MHZ.  You must satisfy both requirements. When that got satisfied I reassembled the rig but I still could not get the radio to align.  Turns out there is more than one shaft position that satisfies the test.  After studying the schematic it turns out the easiest way to synchronize the band switch is to look at the rear wafer and verify B+ to the 17 MHz oscillator when in the 00 to 07 positions.
> 
> GK,
> 
> Bill, K3PGB
> 
> Grayson Evans wrote:
>> Finally rebuilt the RF deck on my early Collins 390A, but having some head scratching trying to get everything back aligned.
>> I used the nice pictorials by Scott Seickel that shows closeups of how to put it back together.
>> (by the way, there is an error in the reassembly steps)
>> Unfortunately, his closeup photo of where the bandswitch should be does not look like my bandswitch.  I assume this is because I have an older version than he did.  My contacts are in a different location and the wipers are different.
>> I have tried to use where I think the switch should be but very hard to see where the wipers are on the other switch sections.   I can’t find anything that says how the contacts are numbered so I could use the schematic to try to set. Any help on setting this thing would be appreciated.
>> Grayson
>> TA2ZGE - Ankara, Turkey
>> KJ7UM
>> Follow the Hollow-State Design Blog
>> hollowstatedesign.tumblr.com
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Grayson
TA2ZGE - Ankara, Turkey
KJ7UM
Follow the Hollow-State Design Blog
hollowstatedesign.tumblr.com