[R-390] RF deck removal

[Roger Ruszkowski]

Alan,

You asked -----------


Thanks Roger. On the adjustment, could you please claify, what am I adjusting? The Geneva gear rotation? I understand the goal, just not sure of what mechanical element must be adjusted to reach the best overall contact location for all bands. 
------------------------------------
 
Alan,

 
The shaft through the band  switch assembly has a clamp where the shaft and Geneva gear mate.
Setting that shaft in the gear is just like setting one of the cams to its alignment
mark in the mechanical alignment process.
 
Think of the Geneva gear as being the detent in a rotary switch.
In a switch you can not adjust angle between the switch detent and the wafer switch sections.
The switch stops were it stops and you hope the manufacture got the wafers to assemble in a way that
leaves the wafer switch wiper setting in the middle of the contact at each detent position of the switch assembly.
 
In the receiver the switch shaft is clamped into the Geneva gear.
The Geneva gear assembly acts as the detent stops.
If the clamp comes loose (they do) then you can spin the knobs all day long and the band switch does not change position.
You need to get the Geneva gear into a detent and set the shaft to the correct set of switch contacts and tighten the clamp
to get things back into working order.
 
OH IF WERE JUST SO SIMPLE.
 
The problem with the band switch is there is no exact alignment mark. 
The shaft rotates and the wafer wipers move to different contacts.
 
Where the shaft stop rotating with the Geneva gear is dependent on the mechanics of the gear assembly.
The stop point will be different for each Geneva gear shift point.
The number of degrees the shaft rotates for each detent shift may not be exactly the same.
And the stop point will be different as you tune up and tune down because of small differences or lash in the drive train. 
The corners of the gear works are OK but not necessarily exact to any wafer switch section.
 
You may have a wonderful set of wafers that line up real good, give you lots of over lap of the contact to wiper at every switch position
while tuning both up and down and wonder what this subject is all about.
 
In reality the angle between the contacts on the wafers is not exact.
Contacts will be skewed on a wafer due to the wires (do not try to rework these if you do not have to). 
Wafers will have a rotation skew of their own (do not work on this either).
 
SO
 
There are 8 wafers with 6 contact, thus 48 points that must be optimized both coming and going.
And just one small bolt in a clamp to control it all.
 
It really is an eye ball and judgment  call.
There is no measured maximum.
At a minimum some band will not work and you can start burning contact corners off with arcing B+.
 
With the gear lash, the switch may work going one way but not the other way.
So you work on it until you get it looking good.
Very small changes.
 
You find as you tighten the clamp the shaft and gear changes.
How much extra position change do you set in so that as you tighten the clamp you end up where you want to be.
It is a touchy feely adjustment thing.
 
I hope this helps you can see clearly through the mud to find a solid bottom.
If not please ask again and I will take another shot at this for you.
 
 
Roger 
 
-----Original Message-----
From: Alan Victor <amvictor at ncsu.edu>
To: Roger Ruszkowski <flowertime01 at wmconnect.com>
Sent: Sat, Oct 11, 2014 9:54 pm
Subject: Re: [R-390] RF deck removal


Thanks Roger. On the adjustment, could you please claify, what am I adjusting? The Geneva gear rotation? I understand the goal, just not sure of what mechanical element must be adjusted to reach the best overall contact location for all bands. 
 
Alan 

On Sat, Oct 11, 2014 at 11:25 AM, Roger Ruszkowski <flowertime01 at wmconnect.com> wrote:


Alan,

Looking ahead is the RF band switch.
About six wafers and six contacts on each wafer.

With the RF deck out, adjust the RF band switch by eye ball.

Tune both up and down the full range of megahertz.
As the Geneva gears rolls the switch one contact,
look at the wafer wiper relative to the wafer contact.

Look at all the points.
Now its a judgment call of the eyeball.
Set the switch for the best contact of all the wipers to all the contacts on all the wafer sections.

The adjustment will be a very very small amount to be optimum.

Your worse fear is that some where in the past the switch was not well adjusted
a some corner of a contact is burnt off giving you less metal than you would like.

You do not want to get into tinkering with wafers and contacts.
Just accept what you have and set it the best adjustment point you can.
It has been good enough for the last 60 years.
It is still good enough to work.
Your goal is not to make the situation worse buy leaving it in a less than best it can be state.

Roger Ruszkowski


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