[R-390] Fwd: need help with intermittent gear aka Geneva gear

[Roger Ruszkowski]

Phil,

 
Pull the RF deck one more time and do not put it back in until you get it aligned.
 
Stage one of two.
You want to see the intermittent gear move the band switch as the Mega Hertz shaft is rotated.
Going up the range you need a shift from .5 to 1, 1 to 2, 3 to 4, 7 to 8, 15 to 16.
Five shifts for six octaves. 
Going down the range you need a shift from 16 to 15, 8 to 7 , 4 to 3, 2 to 1, 1 to .5
 
This will be right or wrong. 
 
Start in the mid range to avoid the bottom end stop on .5
As you change the Mega Hertz shaft and move the dial counter between 7 and 8 you need the band switch
to shift positions.
You need a nice clean start, shift and rest of the switch as the shaft goes from detent stop to detent stop.
 
The R390A TM and the Y2K manual show the same gear train drawing and part numbers.
 
Looking in from the bottom of the RF gear train right behind the dial counter is a short shaft.
>From front to back is a small gear a big gear (66) a clamp (71) and small gear (79).
 
If the switch is not moving at the right time and centered in motion between the Mega Hertz detent stops.
If the motion is not quite centered going both up and down at all the switch points, turn the Mega Hertz shaft
 until the intermittent gear completes its motion. Then loosen the clamp (71) on the small gear. Dial the Mega Hertz shaft
over to where it needs to be in a detent stop and tighten the clamp.
 
You may need several shots at this to get the operation smooth and well centered at all five of the switch
 points going both up and down the range of the gear train.
 
This adjustment is just to get the  intermittent gear switching at the correct points.
 
Stage two of two.
Adjusting the band switch position.
The band switch has 8 wafers with 6 positions each this is 48 contacts that must make well.
 
There is a spot between the band switch gear and the band switch shaft where all is well.
This is an eye ball value. Do it by sight and not with a meter like it says in the TM.
Each wafer and contact will be a bit different and not exactly center.
 
Run the gear train from end to end both up and down. Watch the switch settings as the  intermittent Geneva gear 
settles after a shift. You may need to loosen the switch shaft gear clamp and nudge the shaft a bit one way or another to better
ensure each switch wafer contact makes at all the points. You will eye ball 48 contacts coming and going and then try for a best fit where 
every thing works when needed. 
 
Once you get the Geneva gear moving at the right octave change points and the band switch shaft timed for good switch contacts on
each wafer point your good on this part of the alignment.
 
Phil, Just because I think this reads well does not mean that it does.
If you have questions please put up another post.
 
Roger AI4NI



I just can't seem to get this one right....I've got all the rest of
the gear train set up and aligned but I can't seem to get the
intermittent gear on the bandswitch to work correctly and the
drawing in the manual is not much help.  I know that some of
the teeth on the little gear between the intermittent gear and
the bandswitch gear are longer than others and I suspect that
these are not in sync with whatever on the intermittent gear.
I have been told that these longer teeth are supposed to run
up/down with the bandswitch in the 7 mc position but I've
tried this in conjunction with what I think is the correct setup
for the intermittent gear according to the manual drawing.

I've been working with this so much that I can go from complete
rf deck on the bench down to the intermittent gear and back 
fully reassembled in less that 15 minutes which shows
that I've had a lot of practice :-)

Can anyone offer any help or instructions on how to get these
gears positioned so they work correctly?

thanks, Phil   W5BVB