[AMRadio] 51J3 or 75A3?


W5OMR/Geoff w5omr at satx.rr.com
Mon Mar 6 00:17:29 EST 2006


Barrie Smith wrote:

> I hate the thought of doing any modifications to any of my SX-73's, 
> but if I was to make one, it would be to change from single to 
> push-pull output 6V6's.
>
> That's plural, more than one SX-73?



yessir


> Well, I feel fortunate having one!


I got my first one, an R-274D/FRR, from John/W5MEU(sk - R.I.P.) back in 
1985.  Somehow, back in my 'Johnny Novice' days (triubute the 'Tron for 
that phrase) I managed to dump around 5 or 600w of RF directly into the 
front-end of that thing, and burned the coil front-end up.  Went back to 
John and he sold me (gave... think it was like $2.oo) a roll of 24ga 
wire.  I re-wrapped the inductor, did some 'under-the-magnifying-glass' 
soldering and that part of the reciever is still working.

Yeah, I've got three of 'em.  They've all three been modified, to some 
extent.  The one with no holes drilled in it only had a relay added (by 
John), to remove the B+ from the front-end tubes when activated.  That 
was the first one I got.  It's hum problem has been fixed, with a 
replacement electrolytic, but it now needs probably new tubes and some 
alignment/sensitivity adjustments made..  .

The other two are R-274's. (no letter designator) and while one doesn't 
need a lot of work done to it, it, too, needs alignment, and the springs 
replaced for the main-tuning dial.  I have no idea what someone was 
thinking, but there are two BNC connectors that were attached to the 
front of this reciever, and a standby switch that is in parallel with 
the Send/Recieve switch.  There's an aduio line coming out of it, as 
well, for line-level output for an amplifier.  I've not tried that, but 
am told that it sounds good coming out of the rreciever like that.

The R-274 that I'm using, has had the most extensive horrifications done 
to it, in that a previous owner replaced the RF Gain pot/AC Switch with 
a regular pot (no switch) and mounted an ugly, non-plastic protected 
toggle switch that is mounted in a rather hap-hazardly cut hole in the 
side of the chassis.  There's another hole drilled in it, in the front 
cover that I can't figure out what it does, other than change the output 
impedance (I think).  It works fine in one position, and that's the one 
I leave it in.  The only problem with it, is that the bottom cover needs 
to be removed, and some alcohol-dipped cotton swabs need to be used to 
remove the carbon traces and other reside from the turret connections.  
I need to do this, pretty soon.

heh - believe it or not, I got the last '73 in an even trade for the 
HQ-170A.

> The '73 is a better receiver than most folks realize, in my opinion.  
> I've never really attempted to measure audio quality, but it seems to 
> sound "good enough" for communication purposes, and the sometimes use 
> as a SWL receiver.


built like a battle ship, the components inside are well protected from 
one stage to the next.


> Still think that any of the Hallicrafters receivers with PP output 
> sound better than any of the other rigs I've owned, at least into a 
> good speaker.


No doubt.  I think p-p 6V6's would make that reciever 'sing'.  Heck, at 
16kc wide sensitivity it does a pretty good job, as it is.

--
73 = Best Regards,
-Geoff/W5OMR





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