[Boatanchors] National NC-183, questions

Carl km1h at jeremy.mv.com
Sun Jul 25 21:34:17 EDT 2010


A NOS 717A may help a little on 10 and 6M but it will mess up AGC action on 
other bands with big signals and result in overload.

If you carefully select front end tubes and do a alignment then 10M AM 
sensitivity will be under 1uv for 10dB SNR. Its a pretty hot radio as 
designed

Carl
KM1H




> Hi All,
>
> I have acquired an NC-183 (not "D" model), said radio to be the
> "Boatanchor" in my modest radio collection (I don't have room or funds
> for a really large collection).  This is one that I recapped and
> overhauled for someone a few years back (I did three around that time, a
> rack model, a "D" and this one), and it's in good working order.
>
> Here are a few questions about the rig and a possible mod (except for
> the overhaul, the set is basically unmodded).
>
> 1.  The owner of one of the "D" models I'd worked on had me substitute a
> 717A (electrically similar to a 6AK5)  sharp cutoff pentode for the
> first RF amplifier, a 6SG7 semi-remote cutoff pentode.  I believe the
> purpose was to give a lower noise figure in the front end at higher
> frequencies.  I DO remember there was some controversy, pro and con
> about this mod, but I tried to Google it and came up with nothing.
>
> IS it worth while doing, and what are the downsides?  (I have a possible
> source for the 717A).
>
> 2.  The two dials are a nice even amber color (not the white that I
> believe they left the factory with).  But like I said, it's even so I
> would suspect that the set didn't sit with a sun exposure on the dial.
> The amber looks nice, fits with the age and I have no problem with it,
> EXCEPT that a large area of the red print for the BCB band is faded
> almost to oblivion, mostly in the area of 600-1200KCs.   If you look
> close you can read it.    Oddly enough the black print is fine.  I'm not
> sure if this was due to someone trying to clean the dial, or faded due
> to light exposure.
>
> I'm considering removing the dial and by hand re-do the red printing
> with a fine red "Sharpie" marker.  It shouldn't be too difficult if I
> take my time.  Question is, has anyone tried it, and does a "Sharpie"
> write nicely on this plastic or acetate  type dial?
>
> Also, if I decide to go this route, how does the chassis  come out of
> the cabinet  to gain access to the dials.  The manual doesn't show it
> and it appears that the set was designed to work on by just removing the
> bottom cover plate.
>
> NOTE:  I submitted an application to join the National mail list a
> couple days ago, but am still waiting for moderator approval.
>
> -- 
> 73 de Phil,  KO6BB
> http://ko6bb1.multiply.com/ (My OTR Blog)
> http://www.qsl.net/ko6bb/   (Web Page)
>
> RADIOS:
> Yaesu FT-2000 Xceiver for "hamming" and LF Beacons.
> Zenith "American" Royal-7000 Transoceanic Portable.
> Zenith "Taiwan made" 7000-2 Transoceanic Portable.
> Radio Shack DX-380 digital portable.
> 6 Hz Audio filter, Tunable LF Pre-amp for NDBs.
>
> Merced, Central California, 37.3N 120.48W  CM97sh
>
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