[R-390] Re: R-390/URR

[Bob Young]

I looked at it today and the PTO is turning fine and there is no play there, 
the problem is in the big front clutch gear (counter drive gear?) right 
behind the front panel. There is a little space between the clutch and the 
mating surface which is not in my other one. This allows the PTO to turn 
(had it opposite, sorry)  but the whole rest of the mechanism doesn't turn, 
you can feel it in the kilocycle knob, there is a little play in it which is 
why I called it backlash. I have loosened the clamp and moved the large gear 
to see if the gears were worn but this had no effect. I would say there is 
about 1Kc of play there in which the PTO turns but the readout doesn't, I 
judges this by the BFO. The PTO turns freely and there is no play there at 
all. The Oldham Coupler was fine.
I founbd out something else today, there is no spring on the PTO oldham 
coupler on my other one, does anyone know of a source for these?
Also I will measure those voltages on E210 today as I plan to do a rough 
line up of this one today,

Bob
KB1OKL

From: Tim Shoppa <shoppa_r390a at trailing-edge.com>
To: youngbob53 at msn.com, rbethman at comcast.net
Cc: r-390 at mailman.qth.net
Subject: Re: [R-390] R-390/URR
Sent: Sunday, October 28, 2007 2:35 PM
Bob Young wrote:
> >>> I'm working away on 2 390's also, got one running pretty well so >>> 
>far, it really just needed a good electrical alignment, I need a >>> couple 
>of crystals for it. I haven't checked the cams yet though. >>> The bands 
>are uneven. I changed the PTO in the other one, I'm >>> getting severe 
>backlash, not sure why yet, I think the oldham >>> coupler is hooked up ok 
>although it didn't have backlash until I >>> decided that the oldham 
>coupler two sides needed to be closer >>> together after I put it in.
> >>>
> >>> I'll check mine tomorrow for those readings and see what I get on 
>E210.

The most incredibly severe backlash I had on my 390A was when I
realigned the Oldham coupler and neglected to tighten all the set
screws sufficiently. It worked fine for a while. Then,
a few weeks later, all of a sudden the geartrain
would move but the PTO wouldn't, producing some severely disconcerting
results! I did not see the cause until I hooked a frequency counter
up and found that no matter how much I turned the front knob, sometimes
the PTO didn't budge :-).

So frequency counters are, in the case of doofus like me, capable
of detecting the set screw that I forgot to tighten. Never saw that
on the capability list of a frequency counter, huh? :-) (Others
would argue that the frequency counter was detecting a doofus!)

I'm willing to bet your backlash is because you didn't tighten all
the set screws back up after tinkering with the coupler.

Tim.