[ARC5] Hallicrafters S-38 is dangerous

[Howard Holden]

Can't speak for the S-38, but in the S-120 and WR-600 as you approached 
regeneration, the AM did indeed get sharper, and more amplified. At the 
crossover into oscillation, the CW was amplified and sharp, weakening and 
getting broader as the control was advanced full CW. Oh yes, the 
S-120/WR-600 was also an AC-DC set. And they were metal cabinets. Never gave 
it a thought in those days. But I lived through it!

Howie WB2AWQ

-----Original Message----- 
From: Richard Knoppow
Sent: Monday, November 16, 2015 9:02 PM
To: Fuqua, Bill L ; arc5 at mailman.qth.net
Subject: Re: [ARC5] Hallicrafters S-38 is dangerous

    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

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