[HN Gopher] All American Five radio receivers ___________________________________________________________________ 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. ___________________________________________________________________ (page generated 2022-12-21 23:00 UTC)