[R-390] R-390 gear train

[Bob Camp]

Hi

You have pretty much all you need to do the gear trains. The video's 
are vital to the process (seeing it is a *lot* better than reading it). 
A second radio to look at as you put things back together is a very 
nice supplement to the pictures in the manuals. There are also some 
great pictures on the web that can be helpfull. The main thing that I 
find troublesome is getting the crystal deck timed right relative to 
the rf deck. It's well documented but I usually have to do it more than 
once to get it right.

About the only other thing you might want to pick up is one of Fair 
Radio's $35 rf decks. They are a good source of most of the things you 
will need to fix up an RF deck. The deck you get should have a full set 
of working rf coils and gears on it so it makes a pretty good spare 
part kit. Tearing one down to bits and pieces is a great way to get a 
feel for what is involved in the gear train rebuild without risking a 
good deck from a working radio. I have bought two or three of them over 
the years and been happy with all of them.

The main advantage of doing a gear train rebuild is that you get the 
grit out of the gears. Depending on how your radios spent their life 
this may be more or less of an issue on your radios.You can spray all 
kinds of junk on an assembled gear and still not blow the crud out of 
them. The grit makes the anti backlash gears hang up a little. This 
adds a bit of slop and friction to the tuning process.

The gear train process is more or less a day to tear it down, two or 
three days to clean everything and maybe two days to put it back 
together. Depending on how much double checking you do it might take 
you another day or two. As far as I can see there is almost nothing you 
can break in the process. Sometimes the clamps that hold things to the 
shafts crack but a spare rf deck has *lots* of them. The only way to 
fail is to simply give up on putting it back together. Even if things 
get a bit overwhelming a week time out can do wonders ....

	Enjoy!

		Bob Camp
		KB8TQ

On Jun 25, 2004, at 11:51 PM, Lee Bahr wrote:

> I got the above tapes from HiRes a couple of days ago and have been 
> viewing
> them.  (I'm about halfway through).  I'm glad I got them.  So far I've
> learned a lot from them and feel more comfortable dismantling my radios
> after viewing the tapes.  (At least I know what will not get me into
> trouble).  I was very fearful of the gear train timing.  I know this 
> wont be
> a problem if I leave that in place and I can still remove the RF deck
> without disturbing the timing.  All I have to do is note the dial 
> frequency
> and keep the PTO at the same place.  (Tape suggests 7.000+ which is 
> 8.000
> Mhz.  Tape says even if I move the PTO I can still easily get 
> everything
> synced again).
>
> I have not viewed the SP-600-JX tapes as yet.  I just started the 
> R-390A
> ADDENDUM tapes.  From my technical expertise and with the tapes, I 
> think I
> can get through this with my 3 receivers.  I think I have enough test
> equipment to do most things.  Not all, but most.  I don't think the 
> tapes
> will make me an expert on these radios but they sure educated me to the
> point I think I can logically work on them without screwing things up 
> and
> efficiently work on them.  All in all I am very happy with the tapes.  
> Would
> I like some things described better?  Sure.  Some of the verbiage 
> could have
> been clearer and some of the steps were vague.  You need some 
> expertise to
> understand some of the vague verbiage. (For example:  you are told to 
> use
> grease at some points.  I would have liked to have been given a brand 
> and
> part number.  You see a hand with a wand in the radio and you don't 
> see the
> meter scale being looked at while adjusting a slug).  This is OK for a 
> tech
> type person, but your grandmother is not going to be able to follow the
> process. These tapes are not totally doing A,B, C thru X, Y, and Z 
> without
> knowing the concept behind the process.  You need to know what you are
> doing.  Tuning this radio is not like building a Heathkit. All in all, 
> I am
> very happy I purchased the videos.  I know enough about restoring old 
> radios
> to have these tapes be a big help to me in restoring my 3 R-390As.  
> Just
> don't expect them to make a tech out of a person who has never worked 
> on a
> radio up until now.  I guess that was not their purpose anyway.
>
> Lee, w0vt
>
>
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