[R-390] six position rf bandswitch

[Roy Morgan]

At 01:30 AM 12/2/2005, Norman J McSweyn wrote
>... The six position rf banswitch won't align properly(they all do work, 
>however!). I have had the deck out three times and it's still not right. 
>When tuning, sometimes you have to go below (electrical) the band and come 
>back up.

Norman,

Make sure the wafer is not worn at the point that the switch shaft goes 
through it.  This can cause enough play to create the trouble you describe 
above. The moving wafer positions correctly when moving clockwise but not 
when moving counter clockwise (or vice versa).

I have a Crystal Oscillator module with a shim jammed in the hole where the 
shaft passes through the wafer. NOT a good solution.  Some kind of surgery 
on the wafer may be in order, such as epoxy-ing a section of metal or 
phenolic onto the wafer to re-create the correct face for the shaft to bear 
against. (Saran Wrap will keep the epoxy from sticking to the shaft and 
causing other troubles.)

 From the "GOOD ole Days":
The RAL and RAK and the RBA -B, and -C radios have ceramic band switches. 
The rotors have a central metal bushing staked to the ceramic rotor and 
having a square hole for the shaft.  The R-390 folks could not afford this 
kind of build quality.

The manual is pretty vague, such as: "center the contacts on the switch".
>Not very helpful.

That means "center the moving contact within the fixed switch contact and 
tighten the gear clamp for best alignment throughout the range of the switch."

I was a kid when they were writing those manuals.

Roy



- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --