[R-390] Mystery Component

[Barry]

Hi Jacques,

One end is connected to R560 and the other end is connected to Z503.  I'm not sure but I think it's R554 and was likely changed from 2.2k to 470 ohms.  Either that, or R554 was mislabeled from the beginning.  I do see where that resistor is still 2.2k for the R-390A/URR so not sure how it ended up being 470 ohms in these radios.

Thanks again,
Barry - N4BUQ


> Hi Barry,
> 
> Eeer... Is that "470 ohms" resistor connected at the same post than the 56K in
> the picture ??
> Where the other end of it is going ?
> And if your R560 measures 68K, change it !
> It will affect the Carrier Meter calibration and the AGC time constant in "slow"
> mode.
> 
> 73, Jacques, VE2JFE in Montreal
> 
> -----Message d'origine-----
> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la part de
> Barry Scott
> Envoyé : 13 octobre 2024 23:03
> À : Jacques Fortin <jacques.f at videotron.ca>
> Cc : R-390 Mailing List <r-390 at mailman.qth.net>
> Objet : Re: [R-390] Mystery Component
> 
> I'd originally started looking at R560.  It's about 68k in mine.  Not really
> sure how critical that is and I think at most it might have some effect on the
> AGC time constant.
> 
> I'm pretty sure now, though, that the "mystery" component is a 470 ohm resistor.
> Another list member sent a picture of a couple of his IF modules and one is
> clearly 470 ohms.  That last band is brown instead of orange.  Mine is checking
> a bit over 500 so probably good enough as-is.  Odd, though, that they used one
> of the "older" style resistors there.  That's what threw me off more than
> anything.
> 
> Thanks,
> Barry - N4BUQ
> 
> On Sun, Oct 13, 2024 at 8:41 PM Jacques Fortin <jacques.f at videotron.ca> wrote:
>>
>> Barry,
>> That "mystery" component is R553.
>> From your picture, a 1W, 47K ohms, 10% IRC brand resistor (maybe not the
>> original one, but who knows ??).
>> It connects the 180V supply to the screen grid of V509.
>> R560 (56K ohms) can be seen in the same picture.
>>
>> 73, Jacques, VE2JFE in Montreal
>>
>> -----Message d'origine-----
>> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De
>> la part de Barry Envoyé : 13 octobre 2024 18:15 À : R-390 Mailing List
>> <r-390 at mailman.qth.net> Objet : [R-390] Mystery Component
>>
>> Maybe not really a “mystery” but I can’t identify the dark brown cylinder with
>> one yellow and two brown(?) stripes in the AGC time-constant compartment in my
>> R-490/URR. A 410-ohm resistor?
>>
>> If those are actually violet stripes then I’m even more confused.  Anyone know?
>>
>>
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