[R-390] Help with R-392

[Bruce Ussery]

Drew,
Good reminder about the crystal oven. I'll disconnect it soon to save those
watts. I'm sure I'll never be bothered by calibrator crystal drift. As for
the audio output power hog, at least the designers addressed that issue
later with the solid state module shown in the manual. I wonder it these
ever show up in later radios or as spares? Mine is rarely on more than 2 or
3 hours at a time, so heat isn't much of an issue. I have left it on
overnight before and the case does get a bit toasty...

Bruce
WA4ZLK

----- Original Message ----- 
From: "Drew Papanek" <drewmaster813@hotmail.com>
To: <r-390@mailman.qth.net>
Sent: Friday, January 23, 2004 4:34 PM
Subject: Re: [R-390] Help with R-392


> On Ronnie Davis powering his R-392, Bruce Ussery wrote:
>
> >For what it's worth, 3 amps sounds like about the right current draw.
Both
> >of mine draw about 2.6 amps; one fluctuates between 2.6 and 3 as the
> >calibrator crystal oven cycles (I assume).
>
> Reduction of internal temperature is of benefit to extend the components'
> lifetime.  If 3 amps continuous there is nearly 90 watts in the (sealed)
> box.
>
> It sounds like the calibrator crystal oven draws about 400 mA.
Additionally,
> the audio output tube heater adds about 15 watts of heat with its 625 mA
> heater current drain.
>
> Elimination of these loads would reduce total receiver consumption to 2
amps
> (easier on the power supply) and eliminate 15 to 28 watts of internal
heat.
>
> With the 6.3v calibrator crystal oven disconnected, my R-390A has no
problem
> with calibrator frequency stability.
> That may also apply to the R-392. The constant (high) temperature provided
> by the oven is of use when operating the radio in Antarctica-hardly the
type
> of service most of our radios see.
>
> The filament heat of the audio outputube can be eliminated by a solid
state
> repacement (blasphemy). Rovero's R-392 website shows a couple of different
> schemes.
>
> For the modification-averse, output tube could be removed and audio taken
> from one of the grids (the one driven by the cathode of the phase
splitter)
> to be fed to an external audio amp/speaker.
>
> Simplest heat reduction would be to slide the radio out of the case a bit.
>
> >And I gave up on AC power supplies after trying three. They all radiated
RF
> >noise, mostly below 8 Mhz, so I got a couple of big gel cells at a
hamfest
> >and a "wheelchair battery charger" through the internet.
>
> Most abundant are switch mode power supplies.  They are noted for
> compactness, high efficiency, light weight, low cost and high levels of RF
> noise.  What one needs is a linear power supply.  The attributes are the
> opposite of those listed above for SMPS's.  A simple unregulated
> transformer-rectifier-filter type supply might suffice if it has huge
filter
> caps for low enough ripple.
>
> Drew
>
> "Vicariously repairing and modifying R-390x via advice to others"
>
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