[R-390] R390A RF deck advice

Fri Jan 9 14:43:27 EST 2015

Roger,

The percentage out-of-tolerance was given as one point to consider as to whether to change the resistor(s).  Since there is considerable difference between 30% and 44%, I just wanted that clarified.  Again, I said that I might be being too picky...

As for whether carbon-comps get better with age, I don't know.  So many electronic devices get worse with age but perhaps carbon-comps don't?  Again, I don't know.

If noise is the primary consideration, then aren't other resistors a better choice than carbon-comps?

Regards,
Barry - N4BUQ

----- Original Message -----
> From: "Roger Ruszkowski" <flowertime01 at wmconnect.com>
> To: r-390 at mailman.qth.net
> Sent: Friday, January 9, 2015 11:57:19 AM
> Subject: Re: [R-390] R390A RF deck advice
> 
> 
> Barry,
>  
> What ever, 44.44% its enough to consider changing.
>  
> The 27 ohm resistors are inline parasitic suppressors.
>  
> After 50 plus years I would think they were getting well aged and quieting
> down.
> Why would you want to install new fresh noisy resistors now? You have just
> gotten these
> well seasoned.
>  
> Their exact value is not the function of the resistors.
> First we need to understand the function of the resistor in the circuit.
> Then we need to understand how it was suppose to provide the features we
> expected to get from the resistor.
> Then we need to look at the whole lot of modern resistors and decide which
> type provide the best performance
> features in the receivers circuit.
> 
> Do the carbon comp resistor get noisier over time and thus we should change
> them all every 20 years or so?
> Or do we think they quiet down over time and should be left alone even as the
> low current DC resistance value
> drifts up or down?
> 
> Are very old new stock resistors less noisy than when new?
> 
> Roger AI4NI
>  
>  
> -----Original Message-----
> From: Barry <n4buq at knology.net>
> To: Roger Ruszkowski <flowertime01 at wmconnect.com>
> Cc: r-390 <r-390 at mailman.qth.net>
> Sent: Fri, Jan 9, 2015 5:07 am
> Subject: Re: [R-390] R390A RF deck advice
> 
> 
> It might be picky of me, but, I think that's about a 44% error, correct?
> 
> Barry - N4BUQ
> 
> Sent from my iPad
> 
> > On Jan 8, 2015, at 10:49 PM, Roger Ruszkowski <flowertime01 at wmconnect.com>
> wrote:
> > 
> > 
> > 27 / 39 is about a 30 % error.
> > Consider your skill level and all that could go wrong. You may just want to
> leave it alone.
> > 
> > 
> > Roger AI4NI
> > 
> > 
> > -----Original Message-----
> > From: ngietz <ngietz at mymts.net>
> > To: r-390 <r-390 at mailman.qth.net>
> > Sent: Thu, Jan 8, 2015 2:50 pm
> > Subject: [R-390] R390A RF deck advice
> > 
> > 
> > Hi all, first I want to thank everyone who responded with advice about
> replacing
> > C227
> > (I think it was) in a general overhaul of this 1963 Teledyne RF deck.
> > Now, I have several more questions:
> > 1)How critical are the values of the 27 ohm resistors on some of the grids?
> > A
> 
> > couple
> > are up to 36 or 39 ohms.  What effect if any would that kind of difference
> have
> > on
> > receiver operation or gain?
> > 2)Some time ago I ordered some replacement slugs for the tuning coils and
> > they
> 
> > came
> > with brass slot head screws rather than the Bristol spline screws I was
> > expecting.  The
> > slugs are still coded with the red and white dots.  Is there a chance I got
> > incorrect slugs
> > or are the brass screw slugs just a late manufacturing change?
> > 3) Does anyone disconnect the heater line on HR202?  Seems to me the
> > crystals
> > and
> > associated components would last longer without all that heat.  That corner
> > of
> 
> > the
> > deck has the worst cluster of out-of-spec resistors etc., and I suspect the
> heat
> > did it.
> > I’d guess there might be a slight effect on stability, but I’m not using it
> for
> > RTTY.
> > Thanks for all your wisdom!
> > Nelson Gietz
> > ______________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:R-390 at mailman.qth.net
> > 
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > 
> > 
> > ______________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:R-390 at mailman.qth.net
> > 
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> 
>  
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html