[HN Gopher] All American Five radio receivers
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All American Five radio receivers
Author : ronsor
Score : 30 points
Date : 2022-12-21 21:10 UTC (1 hours ago)
(HTM) web link (en.wikipedia.org)
(TXT) w3m dump (en.wikipedia.org)
| gumboza wrote:
| Definitely read the potential hazards section. Dangerous as hell
| these things.
| floren wrote:
| Dangerous to poke around inside when plugged in, but quite safe
| unplugged (unlike say an old TV).
| pyinstallwoes wrote:
| Why is an old tv unsafe?
| greenbit wrote:
| The CRT acts like a capacitor, storing charge for quite
| considerable lengths of time. Consider that a B&W would
| typically run 10kV to 15kV, and color sets easily 25kV, and
| that should give you some idea of how much energy one of
| those things can hold. And with those kinds of voltages,
| you don't even need to make contact to find you've become a
| discharge path, that stuff will reach out and grab you
| across considerable air gaps.
| dylan604 wrote:
| oh, boy. the temptations of telling how to find out on your
| own are strong!
|
| the capacitors in CRTs could store a charge for a long
| time. i've seen people that assumed the caps were
| discharged find out the hard way when they shorted the
| leads with a tool. the noise alone is enough to make one
| need clean shorts. the only good thing is that they
| discharge quickly, but they give you "both barrels" worth
| to borrow a phrase.
| kenny11 wrote:
| The CRT retains a high voltage charge even when the TV is
| unplugged.
| 123pie123 wrote:
| DO NOT ASSUME a CRT MONITOR or 'old' TV IS SAFE to poke
| around when unplugged!!!!!!
|
| https://www.instructables.com/How-to-take-apart-TV/
| floren wrote:
| Read what I wrote again carefully, paying extra attention
| to the word "unlike"
| 123pie123 wrote:
| "but quite safe unplugged"
|
| a CRT monitor is typically (I would not gamble on it -
| again!) not safe when unplugged
| dekhn wrote:
| yes, you two are in agreement. it's the radio receiver
| that's safe when unplugged.
| II2II wrote:
| Unlike means not like, so they were effectively saying it
| was safe to go inside radios but it is not safe to go
| into old televisions.
| 123pie123 wrote:
| appologies - I just re-read the article (and the other
| comments). I see where you're coming from
|
| I just saw the words "unplugged" and remembered the word
| vacuum tube - then massive emotions from my past came
| rushing through
| dylan604 wrote:
| Slap a "No user serviceable parts inside" sticker on it, and
| you have an unbeatable liability shield! /s
| jhallenworld wrote:
| Yeah, they are dangerous, but their safety can be improved: add
| polarized cord (probably have to move the power switch to the
| hot side for this) and replace the chassis ground capacitor.
|
| Table top FM radios and TVs also tend to be hot chassis.. (that
| mains transformer is just too expensive). Even today you can
| find capacitor dropper powered devices which also are hot.
|
| AA5s are nice in that you can almost always get them to work
| for cheap. I mean if you have an older radio with a bad mains
| transformer, it's probably not worth fixing.
|
| I don't think low end hot chassis radios were popular in
| Europe, they all seem to have a transformer. Maybe 220V is just
| too dangerous... (but you can certainly have a primary to
| secondary fault in a transformer..)
| Aloha wrote:
| They're perfectly safe to work on, just measure voltage between
| chassis and earth and make sure there is zero volts of
| potential - or be fancy and use an isolation transformer.
| userbinator wrote:
| Many consumer appliances are also still unisolated inside, it
| saves cost and you are unlikely to be touching anything inside
| if you don't know what you're doing (hence the usual "do not
| open" warnings on them.)
| zhrvoj wrote:
| Yeah, do not attempt to use. High voltage inside. Better to buy
| any new low voltage piece of shit. Throw this all away. Be very
| afraid of this old stuff. Hmmm....your Tesla, runs on 3.7V
| LiIon...safe.
| II2II wrote:
| It is better to say that you should not go inside of an old
| television unless you know what you are doing, _and_ don 't
| assume that you know what you are doing unless you have
| guidance from someone who is experienced. Reading about or
| watching someone work inside of high voltage devices should
| not be considered sufficient since it is easy for either the
| author or reader to miss important details.
|
| It is also worth noting that electrical safety depends upon
| far more than voltage. We think of 3.7 V battery operated
| devices as safe because our bodies are not very good
| conductors (when dry) and some types of batteries have an
| internal resistance that will limit the current draw. If I
| recall correctly, the internal resistance of LiIon batteries
| is sufficiently low that they are dangerous if not handled
| correctly (e.g. if you short them).
| Aloha wrote:
| I'm listening to an AA5 right now, a rather rare Zenith FM only
| unit - an H722.
|
| https://www.radiomuseum.org/r/zenith_h722wh_722_ch_6h066_h_0...
|
| It's brown if anyone is curious.
|
| The old Zenith stuff of this era is nice, because they used
| almost exclusively disc caps, which means if it doesnt work, all
| it needs is the power caps (and one more in the tone section
| usually). What that translates to, is it usually works out of the
| box.
| buescher wrote:
| The hot chassis design is mind-blowingly dangerous by
| contemporary standards. These things weren't designed to modern
| creepage distances either. I would worry about creepage to
| controls on these things. THe article mentions screws potentially
| being hot as well as other shock hazards finger-accessible
| through vent hols so no joke be careful to unplug a radio before
| moving it or otherwise handling it in a way beyond turning it on
| and tuning it. All of these safety standards are written in
| blood.
|
| Even with the RC network referenced in the wikipedia article,
| you're looking at leakage to the chassis of 4.5 to 11.3 mA:
| https://incompliancemag.com/article/electric-shock-from-radi...
| allenrb wrote:
| As a kid, I acquired a few of these from my grandparents' farm.
| At some level it struck me as odd that they shared so many common
| features and details. It was many years before finally hearing
| about the "All American 5" and then everything made sense.
| userbinator wrote:
| https://www.youtube.com/user/glasslinger is a good YouTube
| channel that shows the servicing of these and other vintage
| radios.
| Aloha wrote:
| She is the absolute best! Though the stuff she works on is
| typically much older than an AA5, shango066 is also great
| (though, his politics are somewhere between wacky-wacky-wacky
| and crazy town express), JordanPier too.
|
| Glassslinger is probably the best bench tech I've ever seen,
| she has an encyclopedic knowledge of vintage electronics.
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