[R-390] R390/URR Gear train
jgedde at optonline.net
jgedde at optonline.net
Mon Jun 10 10:16:46 EDT 2019
Good call Alan. It was the 390 pF cap in the second RF can. Hit the can down one of the screw holes with freeze spray and the radio went nuts! It’s replaced and the radio is quiet now. She’s “Cracklin’ Rosie” no more.
John
From: Alan Victor <amvictor at ncsu.edu>
Sent: Monday, June 10, 2019 11:02 AM
To: jgedde at optonline.net
Subject: Re: [R-390] R390/URR Gear train
John,
Silver mica "disease"... metal migration may not require any applied voltage to occur and its affect is the noise bursts you describe. A possibility?
Alan
On Mon, Jun 10, 2019 at 4:11 AM <jgedde at optonline.net <mailto:jgedde at optonline.net> > wrote:
Thanks Don. I am an engineer/engineering manager/project engineer by day. I design ultra-high reliability, radiation hardened, motion controllers and motor drivers for space use. My company's main product line is motors, gearboxes and actuators for space applications. For example, the Mars Curiosity rover and the upcoming Mars 2020 rover - we designed and built those actuators. Being exposed to that sort of thing, I work with very, very smart people who are the top experts in their fields. People from JPL, NASA, Northrop Grumman, Lockheed, BAE, etc. Needless to say, I pick up a thing or two about mechanical engineering...
Right now, my controller designs are in orbit around the earth deploying mechanisms and controlling the movement of solar arrays. It's very rewarding to see a launch go well and having something one conceived come to life and operate.
Getting back to R390 talk... I too suspect something with one of the transformers, but as you point out, testing by substitution is a good way to test. Alas, I don't have substitutes, so I have to debug the problem using other methods. I suspect a problem with the first can as I can see junk on the grid of the first IF tube. My mental block is reasoning out why. The grid is biased by the AGC line and the problem still occurs with the radio in MGC with the AGC line pulled to ground. That point makes me wonder... My crackle sounds very much like what you hear when lightning is around. But, there's no voltage on the first can when in MGC mode. So, what could be breaking down? Or, is anything breaking down? I find myself wanting an old school signal tracer...
The radio has only two issues left to resolve before tackling cosmetic restoration. The crackling and the PTO endpoint adjustment. It's come a long way since I got it. Back then it had a bum power supply/regulator, dead bands, poor sensitivity, a wacky carrier meter (tracked down to loose resistance wire coils in the carrier meter adjust pot which were moving around during adjustment), an inoperative calibrator, RF geartrain issues, etc. etc.
John
-----Original Message-----
From: Don Heywood <wc4g at knology.net <mailto:wc4g at knology.net> >
Sent: Sunday, June 9, 2019 10:35 PM
To: jgedde at optonline.net <mailto:jgedde at optonline.net> ; 'Francesco Ledda' <frledda at att.net <mailto:frledda at att.net> >
Subject: Re: [R-390] R390/URR Gear train
I am really impressed with the way you lubricated that RF deck, you sure know your lubricants. Maybe I can help with the crackle on the 1-2 mc band.
Inside those RF transformers are mica caps across the coils, I have found thru substitution of these RF transformers a few instances where these mica caps are breaking down. It has gotten to the point that they are failing, especially the ones with B+ on one side. To bad you don't have a second source of these RF transformers, I have a couple of junker RF decks which come in handy for substituting these transformers to find the offender and replace its caps. A cap checker may be of some help, but you need a higher voltage to make these caps fail.
Regards,
Don WC4G
-----Original Message-----
From: jgedde at optonline.net <mailto:jgedde at optonline.net>
Sent: Sunday, June 09, 2019 8:14 PM
To: 'Francesco Ledda'
Cc: 'Don Heywood' ; r-390 at mailman.qth.net <mailto:r-390 at mailman.qth.net>
Subject: RE: [R-390] R390/URR Gear train
Thanks! One thing I forgot to write...
It's all back together and guess what... It STILL crackles on 0 MHz. It's hard to pin down because it comes and goes. I get into it with the test equipment and it always stops whilst I'm trying to debug. Whatever it is, it's early in the RF deck chain. But I can now have the rf deck in and out in 30 minutes or less now that I've done it a few times - if I need to get it out again.
-----Original Message-----
From: Francesco Ledda <frledda at att.net <mailto:frledda at att.net> >
Sent: Sunday, June 9, 2019 8:08 PM
To: jgedde at optonline.net <mailto:jgedde at optonline.net>
Cc: Don Heywood <wc4g at knology.net <mailto:wc4g at knology.net> >; r-390 at mailman.qth.net <mailto:r-390 at mailman.qth.net>
Subject: Re: [R-390] R390/URR Gear train
Very nice job!
Sent from my iPad
> On Jun 9, 2019, at 18:41, <jgedde at optonline.net <mailto:jgedde at optonline.net> >
> <jgedde at optonline.net <mailto:jgedde at optonline.net> >
> wrote:
>
> Thanks Don!
>
> Oh yes, I am indeed familiar! Too much so. When I set the MC gear I
> ran it fully counterclockwise and installed the deck with the MC band
> set slightly below zero, but not as far as where it stopped. So, when
> it's been installed I hit the 10-turn stop before I hit the end of
> travel for the deck itself.
>
> That RF deck geartrain is definitely not for the faint of heart. I
> took the deck off to fix a crackle I get on the 0 MHz band. Thinking
> it was the switch, I went in there with intent to clean the switch up.
> Being able to see the gears up close, I decided all that gunk HAD to
> go and that started the ordeal. All pieces apart and cleaned in an
> ultrasonic cleaner with Purple Power/water and the gunk all came off
> although it took several runs to get it all off. Changed out the
> water/purple power three times because it got so dirty I couldn't see
> the parts anymore! The KC dial has a nice feel now. Before it was
> very loose and sloppy feeling and bound up every now and then. Now it
> has a slightly snug (damped feeling), slop free feel, yet turns easily
> enough that I can spin the dial with one finger.
>
> Interestingly, whatever it the crap was, mineral spirits didn't touch
> it (no I didn’t put MS in the ultrasonic cleaner 😊 ).
>
> The gears are now lubed with Mobil Vacuoline machine tool way and gear
> oil from my home machine shop which is basically a detergent free
> medium weight oil with a tackifier additive so it stays put. It's
> made to be such that it stays where you put it, but doesn't make a
> mess, doesn't attract dirt more than any oil, doesn't have an
> offensive odor, and works with a very thin film. The gears, shafts,
> bushings, etc. are well lubricated but you're hard-pressed to look at them and tell there's oil on
> them. Just the way I think it ought to be. The tackifier additive Mobil
> puts in there makes the oil kind of like you see in those auto parts
> store demos with the crank and gears where it makes the oil stick to the gears.
> (but for goodness sakes, don't put that Lucas snake oil, junk in your
> car's engine oil!!! I have a some tribology background and climbing
> oil is NOT what you want to happen inside your engine. But I
> digress...)
>
> While I was in there, I cleaned the Veeder-Root in the ultrasonic
> cleaner with a well diluted mix of water and purple power, then
> repainted the shield/fingers over the numbers with thinned satin black acrylic enamel.
> Looks like new!
>
> A pic of the RF geartrain back together is attached.
>
> John
>
> -----Original Message-----
> From: Don Heywood <wc4g at knology.net <mailto:wc4g at knology.net> >
> Sent: Sunday, June 9, 2019 6:18 PM
> To: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Subject: Re: [R-390] R390/URR Gear train
>
> Congratulations John, that RF deck is no easy task. There is one thing
> I have discovered you may be interested in, I will try to explain:
>
> When you turn the MC knob down to zero you will notice that it goes
> just a little farther 'below zero'. This is where the ten turn stop
> should be set.
> Any further rotation should be stopped by the ten turn stop on the MC
> shaft.
> If this is not properly set the force will be applied to the Geneva
> Mechanism, no Buenos... By now you should be familiar with what I am
> saying.
>
> Good Luck and I was glad to help. 73 Don, WC4G
>
>
> -----Original Message-----
> From: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Sent: Sunday, June 09, 2019 5:35 PM
> To: 'Don Heywood'
> Subject: RE: [R-390] R390/URR Gear train
>
> It's all back together and everything is preloaded properly. The KC
> dial takes a slight bit more effort to turn, but there's no slop
> whatsoever (it feels like my R390A). The gunk is all cleaned off the
> gears, the rf deck has been reinstalled and the radio aligned. It
> didn't really need that much adjustment which means to me I put the
> geartrain back together correctly.
> What an ordeal though. I won't do that again any time soon...
>
> John
>
> -----Original Message-----
> From: Don Heywood <wc4g at knology.net <mailto:wc4g at knology.net> >
> Sent: Saturday, June 8, 2019 5:28 PM
> To: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Subject: Re: [R-390] R390/URR Gear train
>
> OK, John, I turned one of my receivers up on end and can see that
> those gears with the four holes will mesh with the small gear on the
> PTO shaft when you reinstall the RF deck and mate it with the KC knob
> mechanism. I took a picture and attached it.
>
> -----Original Message-----
> From: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Sent: Saturday, June 08, 2019 4:12 PM
> To: 'Don Heywood'
> Subject: RE: [R-390] R390/URR Gear train
>
> Hiya Don,
>
> I get the preload thing there are about a half dozen other ones I
> already did in putting it back together. This one is different as it
> doesn't seem to be able to lock itself. What I mean is this... All
> of the other split gears get preloaded then the preloaded gear engages
> itself in another gear - a single one so as to be able to spring open
> within the gear profile of the regular gear and eliminate backlash...
> The key thing with this is that the split gear spreads between teeth on a single gear. Easy.
>
> Now, the one I'm asking about preloads but engages in to*two* separate
> gears. One preload gear for each of the two normal gears. In other
> words,
> the preloaded gear engages to another split gear except that gear
> doesn't have springs nor is the split laying on top of each other.
> There's a spacer between the two gears. It's very strange. If you
> look at the bottom of my picture you'll see a steel gear with four big holes in it.
> Directly behind that gear is another just like it. There's a spacer
> between them. One of those two gears is connected to the shaft and
> the other can freely rotate on the shaft. Above that gear to the left
> is the split gear. It's much bigger than all of the other split gears
> and is made of brass. It has no holes in it apart from where the
> springs are located. See it? That gear can be preloaded but each of
> the sprung pair engages to a separate gear and the preload just
> unwinds! That's what's throwing me.
>
> John
>
> -----Original Message-----
> From: Don Heywood <wc4g at knology.net <mailto:wc4g at knology.net> >
> Sent: Saturday, June 8, 2019 2:59 PM
> To: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Subject: Re: [R-390] R390/URR Gear train
>
> John, I know the section of Pearls I referred you to is for the "A"
> model but the preload information still applies, in fact a lot of the
> pearls also affect the older model we work on. There has been a
> section added just for this older radio the R-390/URR!
> I can't see any number 79 in your picture, but if the gears have a set
> of springs between them then they need to be preloaded.
> This preloading procedure takes practice, slide one gear carefully to
> disengage from the gear it meshes with leaving its mate engaged, then
> using your thumb and forefinger slide the gears to overlap a tooth or
> two and while holding this relationship slide the first gear back onto
> the mating gear. If the springs come loose reinsert them with fine
> needle nose pliers of forceps.
>
> I am only trying to help. I had to learn all this the hard way.
>
> Don
>
>
> -----Original Message-----
> From: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Sent: Saturday, June 08, 2019 2:30 PM
> To: 'Don Heywood'
> Subject: RE: [R-390] R390/URR Gear train
>
> Hi Don and thanks,
>
> You pointed me to the R390A pearls and I'm working on a R390. The
> R390A from what I can see, doesn't even have the gear I'm talking
> about. There are a bunch of preloaded gears, but it's the one in
> particular I'm referring to. It doesn't seem to have any way of
> holding preload. Is it some kind of sprung thingamabob to prevent
> excess force on some part of the mechanism? I understand the purpose
> of the split gears to eliminate backlash, but this gear has nothing to
> lock to since the gears it meshes with are both freely rotatable.
> It's hard to explain. In my photo, the two spaced gears on the part
> marked 79 can both rotate independently. It wasn't preloaded to start with either yet everything seemed to work...
>
> John
>
> -----Original Message-----
> From: Don Heywood <wc4g at knology.net <mailto:wc4g at knology.net> >
> Sent: Saturday, June 8, 2019 2:07 PM
> To: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Subject: Re: [R-390] R390/URR Gear train
>
> Hi John, please go to: <http://www.r-390a.net/Pearls/> and look under
> the RF deck mechanical section and then do a work search (cont. f) for
> "preload"
> and see all the data. This preloading is to keep tension on the teeth
> to preclude any backlash when tuning back and forth, hence - no slop -
> have fun , 73, Don WC4G
>
> -----Original Message-----
> From: jgedde at optonline.net <mailto:jgedde at optonline.net>
> Sent: Saturday, June 08, 2019 1:39 PM
> To: r-390 at mailman.qth.net <mailto:r-390 at mailman.qth.net>
> Subject: [R-390] R390/URR Gear train
>
> I took apart my geartrain for cleaning this morning on the 390. No
> end to solidified lubricant. Now I'm putting it back together. I
> noticed before I took it apart that the big brass split gear (part 73) wasn't preloaded.
> Nowhere in the manual does it say how this should be done or what it's
> supposed to preload. What is this for? It meshes with another gear
> assembly (79) that has two gears separated by a spacer.
>
>
>
> I've attached a photo of what I'm asking about.
>
>
>
> John
>
>
>
>
>
>
>
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> <clean gears.jpg>
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