[R-390] R-390A RF Bandswitch Gear Alignment Question

[Flowertime01 at wmconnect.com]

Russ,

A couple things you need to know.
What you find is true.
I cannot seem to locate the non-mar clamp that is associated with the cam 
for 8 - 16 Mc. I'd appreciate help from anyone on the list. 

Two problems here. You start with Band switch Gear Alignment Question and 
then ask about cam alignment.

I take this as two separate maintenance actions.
First some words on the band switch.
Then some words on the cams
Then an alignment procedure.

The band switch adjustment is separate from the cam adjustments. You will 
do the band switch adjustment after the cam adjustments. Most time you can do 
the cam alignment and not need to do a band switch adjustment. The band 
switch moves on a change of the MHz from octave to octave and not related to 
cam position. You can move the cams a lot and not impact the band switch 
position. That is all an advanced (day three topic) lecture on the R390 gear 
train and its step wise function of the band switching scheme.

If you need to do a band switch adjustment, the proper method is to remove 
the RF deck and do that adjustment by eye ball of the switch. The band 
switch is six sections of wafer switch with six positions each. 6 x 6 is 36 
contacts and they make both going up and down. You want an adjustment point that 
provides the most metal to metal contact on each wafer at each of the six 
positions. By eye its about a 30 second adjustment and 6 minutes of shaft 
turning and eye balling to make sure you are very happy. You may do this once in 
the ownership of your receiver. Twice if a clamp slips. (You will know it 
that clamp slipped.) It takes longer to pull the deck than to do the 
inspection and adjustment.

There is no adjustment for the 8 - 16 (fifth octave) cam. Just like you 
find.

Cams counter, VFO alignment goes in the following order. After all this you 
would do a band switch alignment if necessary (some / all octaves do not 
work at all. Or some octaves only work when dialing up or only down or by 
rocking the knob around It just is not smooth and automatic and seam less as 
expected and should be.)

The help starts here.

1 Find the zero adjust knob and set it to its center. (This is a feel thing 
and couple marks on the KHz knob and front panel with a pencil may help.)

2. Dial up on 7+000 MHz.

3. Move the KHz knob any where you need to so the 8 - 16 MHz cam aligns 
with its mark. (This should be close. If not you have a major clamp and gear 
misalignment. If this is true please send more mail and say so. This can be 
fixed. It is not normal unless there has been a real clamp come loose and 
things are out of "sync" by a whole lot. It got this way on a loose clamp and so 
can be fixed by loosing a clamp. Just like a rubic cube it can be all 
backed out to the start position.)

4. This is now at the zero point.

5. Run the dial lock down on the KHz knob and lock the KHZ shaft. (OK so 
you may want to unlock the shaft so you can spin some other shafts around to 
get to the clamps with the spline wrench. If it looks like the clamps can be 
reached at this time things are close.) This is where you want to be in zero.

6. Open the dial cover bezel and reset the counter to 7 +000. and close.

7. Adjust any of the cams as needed to get to them aligned with their marks.

8. Be careful as the VFO may be far enough off to hit and end point.

9. Release the dial lock and run the KHz knob to the top end. Over run 
should be 27 to 33. A little more or less is not a worry. This is not an exact 
value.

10. Dial the KHz knob all the way to the bottom end. Feel that you do not 
hit the VFO end point but come to the end of the 10 turn stop on the KHz 
shaft. Under run should also be -30 again any value is OK. These are not exact 
but do tend to be equal on both ends.

11. If you receiver is not balanced with almost equal over run on each and 
you feel compelled to make it so, you start disassembling gears and slipping 
things over a tooth and see if you went the right way. Not some thing you 
likely need to do unless things really were taken apart in the past and not 
exactly reassembled. This is an advanced topic but can be cured if necessary.

12. Set the receiver to 7 000 or back to 7+000 and turn it to the Cal 
position. Loosen the VFO clamp and adjust the VFO to zero on the cal tone.

This completes the mechanical alignment of the cams, zero adjust, dial 
counter and VFO.

Now inspect the band switch operation by getting a Cal tone on each MHz and 
at least each 100KHz of one of the MHz. Ensure the band switch makes 
contact on each transition of the octaves (.5 -.999, 1-1.999, 2, 3.999, 4- 7.999, 
8-15.999, 16-31.999) As you go from 1, 2 on the MHz you expect the band to 
change smoothly. Each of the five transition points going both up and down. 
This is simply a mechanical inspection and listen to the cal tones. If this 
works the band switch is OK and needs no adjustment. If this does not work, 
understand the difference between a MHz or several not working and a band 
switch needing adjustment problem. 

Now having moved a cam clamp the dial counter and the VFO, a full 
electrical alignment is in order. But you should never again need to perform any 
mechanical adjustment of the gear train until dome thing breaks or comes loose.

Good luck with this mechanical problem and enjoy.

Roger Ruszkowski 33C4H 68-75
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