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

[Bill Abate]

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
> 
> 
> 
> 
> 
> 
> 
> 
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>