[R-390] R390-A questions

[Flowertime01 at wmconnect.com]

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




> 
>   
>