[R-390] wow... the R-391A does exist - Video Update

Wed Apr 12 01:48:02 EDT 2006

Evening Barry...

Enclosed link shows one of the R391 positioning heads partially 
disassembled for clutch tightening from a civilian assembled FRR-33 WA2NPL 
and I cobbled together some years back...

http://mysite.verizon.net/vze4brdx/DSCF0033.JPG

Earlier than this pix, this particular head had been totally disassembled 
for cleaning and reassembled/installed in the r-391 shown below but during 
testing it became apparent that it was slipping... its supposed to slip in 
operation anyway but this one was slipping a bit too much and was removed 
for adjustment and photo op...

Anyway you can see the eight individual cam pawls and the pawl selecting 
mechanism, each corresponding/mechanically linked to one of the 8 numbers 
on the round black dial under that little window that once activated, hold 
the selected pawl in the desired position for a given frequency... so in 
operation, its a matter of synchronized positioning heads which are also 
synchronized to the drive shaft as well as each other, counting turns from 
a zero point to individual points corresponding to  the 8 individual 
stopping positions denoted in part by the rotary switch under the 8 
position dial under that little window and re-zeroing to allow only the 
selected pawls in both heads to then find their individual slots in their 
associated tuning shaft washers stalling the individual heads with their 
individual clutches howling, at that selected numbered point during the 
final pull in for the frequency desired... hope I said that right... anyway 
its multiplied by three in the FRR-33... two R-391 radios and a CU-286 
tuning unit... watching all three units spin up independently but yet land 
where they're supposed to is quite impressive...

This system is truly "THE" Harley Davidson of all the radios from that 
era... a radio man's radio and then some...

Pix of the rig that head was from...

http://mysite.verizon.net/vze4brdx/DSCF0034.JPG

Pix of our civilian FRR-33

http://mysite.verizon.net/vze4brdx/DSCF0035.JPG

http://mysite.verizon.net/vze4brdx/DSCF0036.JPG

Ott

At 11:05 PM 4/11/2006, you wrote:

>Bob wrote:
>
>>Can anyone explain how the R-391A auto-tuning is accomplished?
>
>Not completely, but I can give you an idea and where to go to get the 
>whole story.
>
>>Given the technology available at the time, I'm guessing it might counts 
>>pulses from a cam-actuated electromechanical contact, with one or more 
>>stepper relays as the memory element.
>
>Not exactly.  There are cams of sorts and relays, but no pulses in volved. 
>It is totally electromechanical and has no electrical/electronic 
>conneciton to the receiver, which is really a stock R-390/URR all 
>respects.  All the modules are the same.  The unique components consist of 
>two positioning heads -- one for the MC and one for the KC. They are 
>identical except that the MC unit has the detent spring on it.  There is a 
>motor, a sealed relay, a drive shaft geared to the motor with three worm 
>gears on it.  There is also a control head that contains a couple (or 
>three) rotary switch wafers and a one or two small relays (as I recall) 
>... and there's the channel switch.  The mainframe/chassis is the same as 
>a regular R-390/URR with a few exceptions -- the wiring harness behind the 
>front panel, the 28 vdc supply connection (though I think R-390's have 
>this too on the 4-pin power connector), and the front panel has three mods 
>-- hole and markings for the channel switch and a peephole for the channel 
>indicator which is a wheel/dial with 1 through 8 on it, mounted to the 
>front of the control head. (The third thing is that plastic card for 
>marking down which channel is what frequency.)  The three worm gears drive 
>the MC and KC positioners and the control head.  All the autotune 
>components are mounted on a cast frame that's behind the lower 1/3rd of 
>the front panel.
>
>The autotune doesn't even draw any power from the receiver -- an external 
>28 vdc supply (probably 7 amps or more) is needed.  The KC and MC 
>positioning heads are strictly mechanical, with a stack of spring-loaded 
>pawls with hook-shaped ends which catch into disk-cams and there's a 
>clutch affair. (Paul Anderson described some of this in an earlier 
>post.)  There are no electrical connections to these positioners.  Wiring 
>is involved in the motor, control head, sealed relay and the channel 
>switch.  To use the autotune, you first tighten the locking keys on both 
>the KC and MC knob (or else!) and then change channels.  As soon as the 
>channel switch is changed from the channel shown in the window, it 
>triggers the cycling.  When you loosen the locking keys and manually tune 
>the rig, you are changing the setting for the channel that is showing 
>through the little window.
>
>That's as far as I can go.
>
>>But I know the auto-tune transmitters use a phase comparator and 
>>closed-loop analog feedback, so an all-analog design using a multi-turn 
>>pot would be another possibility.  Either method could  explain why it 
>>seems to drive to a "home" position and then reverses direction.
>
>Has nothing to do with it.  That much I can tell you.  Beyond this, unless 
>Paul A. is up to it ;-), I suggest you check out the R-391 manual which is 
>on the Bama site.  It has an explanation of the internal workings of the 
>beast.  I found some of that hard to follow.  The explanation in the 
>R-105/R105A (ARR/15(a)) manual is somewhat clearer and the design is very 
>similar, though it is driving a much different rig -- and all R-105's are 
>autotuned. The manual for that radio is also on Bama.  The positioning 
>heads look almost identical inside.  They remind me of stuff you'd find in 
>an old mechanical adding machine or calculator -- either that or a 
>combination lock.  Keep in mind that old technology.  Remember the more 
>complicated mechanical calculators that would multiply and divide - -I 
>think they all had carriages, like typewriters that went back and 
>forth?  Remember doing division on them? It would take ten-15 seconds to 
>get the answer to 4 over 2.  Well maybe not that bad, but the consequences 
>of all the stacked parts 'n pawls on common shafts was similar when the 
>fine machine oil turned to glue or grit got into the works -- not only 
>wrong answers, but they wouldn't stop going katchokity-katchokity and the 
>carriage would keep slamming down one end.  All you could do was pull the 
>AC plug.  With the '391, when the same thing happens and the autotune 
>slams against the 10-turn stops, the same emergency action is called for 
>-- except you have to cut the DC.
>
>So, after all that, in brief, Bob, it's not even up to "analogue" -- it's 
>relay and mechanical "logic".   And, as was the case with those 
>electromechanical calculators, very often we'd reach for the keyboard and 
>go "uh-uh -- nah" and do some long division with paper and pencil.
>
>Barry
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