And very old CRT TVs that had no external connections except the antenna. The RF socket was partly isolated with 330 or 470pF capacitors. You could still receive an unpleasant shock if you touch it while touching a grounded object.
Do you always compare yourself to the worst? I've tangled with Phil before, usually without resorting to gutter language. At least he knows electronics. The other one is an egotistic idiot.
English is not my first language but I can be as crude as anyone else when dealing with someone who constantly spews out gratuitous obscenities. I just usually choose not to.
You're "can dig up an opamp" and know someone who has a breadboard? And you keep arguing over some elementary principle with someone who designs and works with opamps almost everyday.
So do the breadboarding already and be sure to post the result.
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** Some portable, SS colour TVs were "live chassis".I used to own a GE brand 12 inch made in Thailand that was isolated by a balun at the antenna socket. The rest of the chassis was "hot". It had full VHF and UHF plus IR remote control and was badged "class II"
The horizontal sweep circuit doubled as a SMPS.
.... Phil
I swear my brain is going. It took a while to rethink it but you are right about the OP AMPs. Not sure exactly what I was thinking there. But I got it , Since there is no current through the resistor it has no effect, whether the other end of it is ground or not. I will admit when I am wrong. I never happened across that situation before but that is no excuse. With that out of the way, unless you want ot pick on me a bit (you are entitiled) moving right along :
antenna. The RF socket was partly isolated with 330 or 470pF capacitors. You could still receive an unpleasant shock if you touch it while touching a grounded object. "
there were limits on the current, legal limits. Shops were expected to chec k it on all units leaving. In fact even not fixed, if there was a ground fa ult or anything that made the set unsafe to plug in I disconnected the AC cord internally. This type of fault was pretty rare.
Normally you could feel the line leakage when it is operating normally, but it wasn't strong. It felt alot stronger if you are barefoot in the baseme nt. A polarized cord did not help if it had dull wave rectification.
They went to great lengths to get video and audio inputs on direct line set s. They either used transformers or optocouplers for isolation. I don't see how that could be a very good way to do it, but they did it. the opto can; t be very linear and there is no practical way to use negative feedback. Bu t it worked.
As a kid I ran across a line operated record player. It had a satellite spe aker that slid into one side of the cabinet but could be removed for better stereo separation. Obviously it was isolated by the output transformer, an d thus had no direct feedback from the secondary. The whole thing was isola ted, even the turntable chassis which was metal, but the cartridge itself w as pretty shielded. The knobs were plastic of course. In fact with the dire ct line TVs I remember having to check the knobs, and one line of Magnavox IIRC (yeah right) supplied replacement VHF tuning knobs because they had le akage. This was REQUIRED, like the whole line leakage test was supposed to include even all the screw heads in the back, but if they were in plastic n obody got that presnickety about it.
Strange some of the things they did. All they needed was a power transforme r (the SMPs wasn't in use in consumer goods yet) that out out a little over an amp, but apparently it was too expensive.
Plenty of table radios, clock radios and what not were built that way. Some times I wonder how they got it past the UL, because a simple crack in the c abinet could turn dangerous real easy.
And when they did that then it required a startup circuit. And the yoke was then a critical safety component. (their wording for it here) But is was somewhat safer.
First of all after further thought I figured out that you were right about the OP AMP. Not sure what I was thinking. No current in those resistors so no effect, grounded or not.
Anyway :
a fairly good resource. So is "Transformerless Power Supply"
But those do not truly isolate, right? There is a limit on line leakage, not sure anymore what it is, but such supplies I imagine, if exposed, would be limited to supplying that amount of current or less which is not much.
No ?
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** Not even a tiny bit, they are all 100% LETHAL !!!!Any such circuit must be fully enclosed along with whatever it powers. No deliberate or accidental handling of the DC output allowed.
** Generally, the max earth leakage is under 1mA for earthed equipment and half that for class 2 stuff.Sony manuals often show a leakage test diagram with a 1.5kohm resistor bridged by a 0.15uF cap connected from the class 2 item's metal chassis to safety ground. An AC voltmeter reads the leakage across the RC combination and it must be under 0.75Vrms.
.... Phil
s
dramatic nonsense. Perfectly safe when not connected to the outside world a nd widely used in mains LED lamps.
There are also nonisolated CR PSUs that are safe to connect to the outide w orld, and that one can touch without problem. They're not afaik legal in th e UK, but they do the job safely. They use strings of Cs and Rs in both L&N lines to achieve well north of 1kV rating, and i_out is low enough to be n o shock risk to anyone, even if many of the parts shorted out. I'm sure I h ave one somewhere.
NT
Most full size TVs were live chassis for many years too
NT
eck it on all units leaving. In fact even not fixed, if there was a ground fault or anything that made the set unsafe to plug in I disconnected the A C cord internally. This type of fault was pretty rare.
ut it wasn't strong. It felt alot stronger if you are barefoot in the base ment. A polarized cord did not help if it had dull wave rectification.
ets. They either used transformers or optocouplers for isolation. I don't s ee how that could be a very good way to do it, but they did it. the opto ca n;t be very linear and there is no practical way to use negative feedback. But it worked.
peaker that slid into one side of the cabinet but could be removed for bett er stereo separation. Obviously it was isolated by the output transformer, and thus had no direct feedback from the secondary. The whole thing was iso lated, even the turntable chassis which was metal, but the cartridge itself was pretty shielded. The knobs were plastic of course. In fact with the di rect line TVs I remember having to check the knobs, and one line of Magnavo x IIRC (yeah right) supplied replacement VHF tuning knobs because they had leakage. This was REQUIRED, like the whole line leakage test was supposed t o include even all the screw heads in the back, but if they were in plastic nobody got that presnickety about it.
mer (the SMPs wasn't in use in consumer goods yet) that out out a little ov er an amp, but apparently it was too expensive.
metimes I wonder how they got it past the UL, because a simple crack in the cabinet could turn dangerous real easy.
plenty were dangerous without any cracks. Knob grub screw comes loose & kno b comes off? Zap. Kitchen steam bridges the small gap between grub screw & finger? Zap. Bracelet falls onto exposed spindle behind knob? Zap. You get the drift.
NT
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** Not where I live ( Australia) - hot chassis sets were a tiny minority of B&W sets and not manufactured here.... Phil
See... here is where it is. You just cannot grasp the fact that you do not say stupid shit like this and properly call yourself an adult.
YOU DIG, YOU ABSOLUTELY RETARDED STUPID FUCK!!!?
With the stupid, childish horseshit that comes out of you, somebody
*should* be taking yours off.I would prefer that they use a rack to stretch you out a bit first.
Apology accepted. There's no need to take it further.
Complaint sent to: snipped-for-privacy@aioe.org
Laugh sent in your face knowing their response. Grow the f*ck up, and stop backing up other putzes who haven't.
And if you can't get that one, pal... Fuck off and die.
There was also the All American Five radio.
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** How about a live chassis *guitar amp* ??The chassis connects to active or neutral, depending on how the AC plug is fitted. Or if it is poor fit, either way will do.
Players rely on C3 (0.05uF) never failing.
Made back in the late 60s and still changing hands at certain dealers and on-line.
.... Phil
ISTR a couple of band members getting nailed on a stage during a rain shower back in the '60s.
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** Little bit different.In the USA in the 1960s and even 70s, it was common practice for appliances including guitar amps to have only two pin plugs. 3 pin domestic outlets a nd plug strips were scarce - so amp makers allowed the chassis of audio ite ms to simply "float" at whatever voltage.
On stage, there are AC power extension leads and multi output strips all ov er the place - so it behove users to make sure none of them got wet. A part icularly nasty combination was if the PA system had a safety ground so all the mics were earthed BUT guitar amps were left floating.
These days and for a long time, nearly everything is safety grounded with 3 pin plugs. 60s and 70s guitar amps are routinely modified with new 3 wire leads and plugs PLUS if they happen to have a "polarity" switch the interna l film cap is removed.
.... Phil
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