[R-390] R390-A questions
n4buq at knology.net
n4buq at knology.net
Thu Jul 27 16:28:58 EDT 2006
If you are lucky enough to get the "driven" gear back onto the wide gear in
the same tooth as it was when the radio was last aligned, then you should
be okay; if not, you will probably have to do an alignment (or keep trying
to get the original teeth meshed).
If things have slipped enough, you may have to do a mechanical alignment as
well to ensure the cams are where they are supposed to be in relationship
with each other. It depends on which gear slipped as to whether this might
be necessary.
I'm not trying to scare you, but want you to know what all might have to be
done to get the radio back to operating as it should. You can do all of
this, but you might have to ask some more questions and feel free to do so.
Barry - N4BUQ
On Thu, 27 Jul 2006 15:43:58 EDT, Flowertime01 at wmconnect.com wrote :
> Bob,
>
> The problem you describe here reads like a RF band switch alignment
problem.
>
> You also describe a split gear slip problem. I though Barry did a nice
job
> responding to that problem for you.
>
> The spring in the split gears need not be maxed out to get the job done.
A
> wimpy spring or a missing spring in a split gear is not a show stopper.
Get
> enough tension on the springs by rotating one of the gears against the
springs in
> the gears to get some tension on the springs. then go a bit more or less
until
> the teeth on both gears line up. Then you need to slide the gear on or
off
> the shaft until the split gear runs against the wide gear and both sides
of the
> split gear stay engaged in wide gear and the tension remains on the split
> gears from the split gear springs.
>
> The idea of the split gears is to remove some of the gear lash when you
> change directions when tuning up and down in frequency. Too much tension
and the
> whole gear train give you R390 wrist. Too little tension and the springs
start
> to fall out.
>
> The minimum tension is longer gear life and you can live with a little
lash
> in the gear train when tuning. Nothing sacred in the gear train set. Play
with
> the clamps, alignment and adjustments until you get a feel for working
with
> them and getting them to run in line and smooth. If you brake a clamp ask
here
> on the reflector for a part. someone will make you a reasonable offer to
cover
> postage and aggravation of getting it in the mail.
>
> -------
> But now the first two bands do not work correctly unless the megacycle
change
> knob is tuned lower than the click stop (or whatever you call it).
>
> -----
> This stop would be the detent.
>
> The Rf band switch changes from 999. to 1.000
> at 1.000 to 1.999
> at 2.000 to 3.999
> at 4.000 to 7.999
> at 8.000 to 15.999
> at 16.00 to 31.999
>
> We would call these the RF band octaves. There is one set of RF
transformers
> and a slug rack for each of these band octives in the Rf deck..
>
> You can set the Rf band switch with a meter as described in the manual. I
do
> not recommend this operation. As you tune up and down the band and change
> octaves the RF band switch changes. Some gears take care of this. You can
read
> about it in the manuals.
>
> Do you have a copy of the Y2K manual from the Net?
>
> The RF band switch changes as needed. It should seat the switch wafers in
> their centers when the detent on the MC knob hits the center seat. You
can adjust
> the detent spring in or out for more or less tension. Again less tension
is
> good. But enough so the MC knob set still when the KC knob is spun.
>
> If you have to go past the MC change point and then back up to get the RF
> band switch to set up and enable an octave for you, the switch is out of
> alignment.
>
> The RF band switch alignment is independent of the cam alignment, Zero
adjust
> and KC band over run alignments. You can do the RF band switch alignment
and
> then do the other alignments without going back to the RF band switch.
>
> A real little bit. Just enough to be a pain.
>
> The best way to set the RF band switch is to pull the RF deck and adjust
the
> band switch shaft by eye ball. Worry not about pulling the RF deck. Read
the
> manual a bit. Find a long #1 Philips screw driver to reach the green
screws
> behind the RF deck. Find a couple 2x4 blocks to rest the frame on. These
leave
> the front panel hanging in free air. Thus you can drop the front panel on
to the
> bench and pull the RF deck.
>
> Some Fellows like to stand the stand the receiver on the RF deck end and
> remove the front panel. It then swings like a door at the bottom of the
receiver.
> You can get at the Dial lock, Oldham coupler spring on the KC shaft, BFO
pitch
> and bandwidth switch shafts.
>
>
> The RF band switch is a 6 position 6 section switch. Some of the switch
> sections carry B+. Not all sections line up real good. Look at the
schematic and
> find the switch sections that have B+ on them. You want this switch wafer
to
> align the best.
>
> Do not try to change the wafer contacts or rotate the wafer sections.
>
> Remember, yesterday this receiver worked today it does not work.
Something
> simple fell apart and some simple action will put it back together. The
effort
> to get to that simple loose part has nothing to do with the total
problem. The
> effort to get the receiver back together after fixing the simple problem
has
> nothing to do with the problem. All that extra exercise is just a slow
screw
> job and real work takes real time.
>
> After years the switch sections do not all fully mesh and align real good
on
> each wafer and each contact. If you just do an alignment by meter without
> looking at the switch you can get a working receiver. But you risk having
a wafer
> section where the contacts just bearly make contact. Over time this just
> bearly there contact will burn. If you look at your receiver you may see
a contact
> that has been burnt from a prior alignment that was just barely making it.
>
> Its a judgment call for best looks. Tune the receiver up through the
bands
> and down through the bands. Look and see how all the wafer sections look
at each
> change point. Loosen the clamp on the band switch and adjust it a little.
Run
> up and down the bands until the switch looks to get the best alignment
you
> can get. You want the Rf band switch to fully make at each change point
tuning
> both up the band and down the band.
>
> -----
> The feel of the knob is definitely not right especially when I go from 1
to
> 2 megacycles, there are two distinct clicks.
>
> ---
> Bob, you are right on here. One click is the RF band switch moving. The
other
> is the detent hitting center. They should both occur at the same location
of
> the MC knob. OK like closer than your receiver does so the RF band
switches
> clean without cranking the knob both directions.
>
>
> ----------------
> A few of the other bands also sometimes need to be fooled with
> (megacycle change knob rocked back and forth etc.) to come in right. It
> seems to me that the space where the springs are in between the two gears
> comes too close together at a certain point and this is when the spring
> falls out. Does this indicate worn parts? Also is this a major
undertaking
> like it seems it would be?
>
> -----
> Bob, Getting a split gear "loaded" so its springs do not fall out is
> separate from your RF band switch problem. Do fix the split gear loading
problem
> first.
>
> -------------
> Is it normal to have rezero the dial between bands with a newly aligned
> radio?
> ----
> I think Barry explained this one for you. But every band has its own
crystal
> in a conversion stage. Unless two crystals happen to have the same error
then
> you have to zero adjust for every KC band. Part of normal operation.
>
> ----------------
> And also is it normal to hear sideband artifacts
> on strong locals as far away as 10 khz on either side of the station with
a
> 400' antenna no matter which selectivity position is used or was this
thing
> knocked back out of alignment? Thanks,
>
> Bob
> Millbury, Ma
>
> -------------------
> Bob,
>
> One hears many thing with an R390 not heard with other receivers. Some of
it
> can be alignment. Some can be mechanical filter ring. 400 foot antenna is
a
> lot of signal grabber and some broadcast band filtering may be in order
for you
> or out right attention.
>
> You may want to go to a balanced feed antenna input so you can get the
> antenna balance and first stage of the RF transformers to tune and thus
filter some
> of the strong near frequency signals for you.
>
> Good Luck with this.
> If you have any questions to my cryptic response here, please send some
more
> mail back on the R390 reflector and I will do some more details.
>
> Roger AI4NI
>
>
>
>
> >
> >
> >
>
>
>
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