[ARC5] Hallicrafters S-38 is dangerous

[Richard Knoppow]

    Well, the feedback network around the IF (gimmick condensers) did 
make it regenerative. It was both the BFO and also probably somewhat 
sharper than in AM. I wonder if anyone has ever actually measured this, 
I've never seen anything about it.  There was also a gain change made by 
switching in a resistor to ground from the AVC bus. I've been saying it 
lowered the gain but I am not sure it did not raise the gain, probably 
to get the IF to oscillate.
On 11/16/2015 7:21 PM, Fuqua, Bill L wrote:
>    Every household had at east one AC/DC radio and sometimes a AC/DC TV although in the 506 and early 60s most TV's had transformers but later went to
> voltage doublers wit solid state rectifiers.
>    Saying that. Imagine how a S-38 would have performed if:
> 1. Used replaced V5, with a 12SA7 and made it a BFO and PRODUCT detector!!!
> 2. You had put some adjustable feedback in the IF to make a sort of Q-multiplier for CW.
>   Now that would have been cool.
> I don't see why product detectors did not catch on earlier.
>   
>     73
> Bill wa4lav
>
>   ________________________________________
> From: ARC5 [arc5-bounces at mailman.qth.net] on behalf of Richard Knoppow [1oldlens1 at ix.netcom.com]
> Sent: Monday, November 16, 2015 6:17 PM
> To: arc5 at mailman.qth.net
> Subject: Re: [ARC5] Hallicrafters S-38 is dangerous
>
>       Badly designed only if a great many other AC/DC sets are also.  The
> S-38 and later receivers are made with the chassis insulated from the
> metal cabinet. Unless the insulation is gone due to age nothing on the
> outside of the receiver is connected to either side of the line.  There
> were certainly other AC/DC devices, such as cheap code practice
> oscillators, where the chassis _was_ connected to one side of the line
> was was hot with regard to a house ground such as a steam radiator if
> the plug was in the wrong way. Since neither plugs or sockets were
> polarized it was a matter of a 50/50 chance of getting bitten. Most home
> radios and phonographs with AC/DC supplies were in wooden cases which
> provided the insulation. However, the shafts of pots and tuning
> capacitors could be at chassis potential. If someone pulled an insulated
> knob off they could be in trouble.  Hallicrafters used Bakelite rods for
> the tuning controls and plastic knobs. I don't remember if the volume
> control or bandswitch was hot. Given its simple circuit the performance
> is quite good.  A great many five tube wonder radios were on the market,
> mostly bc band only but some with one or more short wave bands.  The
> AC/DC supplies were mostly to cut costs but there were parts of the U.S.
> with DC current until fairly recently and many ships had only DC current.
>       The main danger from these sets are to the service people who work
> with the chassis out of the cabinet. An isolation transformer will
> prevent getting directly across the line but many are foolish and  work
> without them.
>
>
>
> On 11/16/2015 2:33 PM, J Mcvey via ARC5 wrote:
>> That radio is a badly designed AC/DC set with several ways to give you the "shock of your life".
>> Check out info on how to modify it for safety. I've done a few of these for people and I was amazed that this designed was allowed to be sold back in the day!As they age, the danger increases too.
>> Just another type of  Hallicrafters design debacle. No wonder they are not around anymore.
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> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL