[R-390] Differences between the various URM-25 generators?

[Bob Young]

I just bought a URM-25F refurbished on epay am expecting it today or tomorrow,

bob Young
Millbury, Ma




----------------------------------------
> From: Flowertime01 at wmconnect.com
> Date: Tue, 28 Nov 2006 21:41:00 -0500
> Subject: Re: [R-390] Differences between the various URM-25 generators?
> To: r-390 at mailman.qth.net
> 
> Tom,
> 
> I hope you get a nice long response to your question with more knowledge than 
> I have.
> 
> There were A, B, C, D, E, F, and a G.
> There was also a civilian model.
> 
> There were many other flavors.
> 
> We should have a link to a schematic for each model on your R390 pages.
> Maybe they should be an add on to the Y2K CD.
> 
> The tube set did vary from model to model.
> The internal drum / tuning section / mechanical vary from model to model.
> 
> The later models are considered "better" than early models.
> 
> The best change is to solid state the rectifier tubes like we do with the 
> R390's.
> This of course changes the B+ and frequency. So you need to re calibrate.
> 
> This change does get a heat generator out of the case and lets the unit run 
> cooler.
> 
> The D model are considered Good.
> 
> No problem keeping any of them running. Check the tubes every 4000 hours and 
> calibrate whenever the signal gets so far off the dial number you cannot stand 
> it any more. replace the dial lights as needed. Watch for the blue gas glow 
> in the tubes. The tubes will still test good in a tube checker. But get them 
> out of the signal generator. New tubes will drift. Just leave the generator on 
> for several days to "cook the new off".
> 
> Microphonic and noisy tubes are my worst problems. You can hear the generator 
> noise in the receiver headphones when you bump the generator around on the 
> bench. This noise is not a problem. 
> 
> Roger AI4NI
> 
> 
> 
> 
> 
> 
> > 
> > 
> 
> 
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