[R-390] R390A RF deck advice

[Roger Ruszkowski]

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
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