[ARC5] ARC-2 Information
Scott Johnson
scottjohnson1 at cox.net
Sun Sep 6 22:11:55 EDT 2020
I inherited an Edu-kit from my uncle in the early seventies, when I was about 9 or 10, I thought it was cool, but I was frustrated, you had to dismantle one experiment to make another! Incredibly, it sold in the same basic form from at least the early fifties to the early eighties!
Scott V. Johnson W7SVJ
5111 E. Sharon Dr.
Scottsdale, AZ 85254-3636
H (602) 953-5779
C (480) 550-2358
scottjohnson1 at cox.net
scott.johnson at ieee.org
-----Original Message-----
From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf Of Hubert Miller
Sent: Sunday, September 6, 2020 7:06 PM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] ARC-2 Information
I don't think so. From the 1940s at least, there was a "ground" and a chassis, with some capacitor like 0.05 mFd connecting the two.
The Regressive Edu-Kit really surprised me. I have the manual and the kit, and I don't recall a word of warning that your headphone wire could with a flip of coin, be AC hot. When I first saw the Edu-Kit manual, I saw the 3 wire line cord and first thought it was wired for safety, but one wire was just a resistance.
BTW, around 1985 I wrote an electronics magazine and asked if they should still be running Edu-Kits' ads with the testimonials from 1947 customers. I also questioned the usefulness of the 1985 Edu-Kit suggestion that printed circuits were the up & coming thing.
The magazine editor wrote me back ( this was in the Paper Age ) that Edu-Kits always paid their bill.
I should have kept that letter with my Edu-Kit manual.
I should also have kept the letter from Tom Kneitel telling me I didn't know enough to criticize and that he owned a Trans-Am and a boat and so there you go.
-Hue Miller
>I can attest to that! Having worked for several years in a TV/radio
>service shop in the early 1970s, I can verify that AA5s of that era
>always had the chassis hardwired to one side of the AC line. The
>nominal filament voltages added up to 121V for a reason. Classic
>problem was replacement of a frayed cord or bad plug by the consumer,
>who had a
50-50 chance of tying the chassis to the hot side of the line. Murphy guaranteed that I would only see that 50%.
The Progressive/Regressive Edukits not only did the same thing, but with resistance wire to drop much of the line voltage to drive the filaments.
My next door neighbor replaced the cord with a regular piece of zip cord. The result was much unhappiness.
-- Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 9/6/2020 18:38, Scott Robinson wrote:
> Actually, quite a few AC-DC radios DID have their chassis wired to
> one side of the line Some mid-30s examples are a horror--easily
> touched live parts. Late _mid-fifties and on (Zenith, in particular),
> did a very good job isolating the chassis in their AM-FM table radios.
>
> Since most small TVs had metal cases, I bet they are isolated.
>
> Scott Robinson
>
> PS-I hate AC-DC radios.
>
> On 9/6/20 6:08 PM, Hubert Miller wrote:
>> Except: Scott, the machines with one side of the AC line connected
>> directly to chassis were bottom end, such as the buzzbox welders
>> advertised in magazines and kit radios for young people. (
>> "Regressive Edu-Kit" was one ) TVs and radios did not have the
>> chassis connected DIRECTLY to AC line.
>> ONE ham rig did, I think SBE-13. I have one somewhere. Had a safety
>> indicator lamp on front panel.
>> -Hue Miller
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