Path: ...!news.mixmin.net!weretis.net!feeder8.news.weretis.net!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: liz@poppyrecords.invalid.invalid (Liz Tuddenham) Newsgroups: sci.electronics.design Subject: Re: Circuit Symbol Date: Thu, 19 Dec 2024 09:56:33 +0000 Organization: Poppy Records Lines: 93 Message-ID: <1r4t4ei.1nxzftop16fu4N%liz@poppyrecords.invalid.invalid> References: <4v46mjpnmfi29eka4juuklv2fcd7nv6etd@4ax.com> <86q6mj59dfa4q39fsoj3a1kp75lu26415t@4ax.com> X-Trace: individual.net nooK8vlJxgAUZUqG1ZidgAxnk4V+ygm4rIFXuMEynubFDgEGSS X-Orig-Path: liz Cancel-Lock: sha1:RvgLEINNZl1mFQlMkaxYC2BgzA8= sha256:3BLZODogeHomTbVOzKFiKqiw8BOt4exQsYdPKeqKmNA= User-Agent: MacSOUP/2.4.6 Bytes: 4969 Cursitor Doom wrote: > On Wed, 18 Dec 2024 16:30:57 -0800, john larkin > wrote: > > >On Wed, 18 Dec 2024 23:55:14 +0000, Cursitor Doom > >wrote: > > > >>On Wed, 18 Dec 2024 11:25:27 -0800, john larkin > >>wrote: > >> > >>>On Wed, 18 Dec 2024 19:00:01 +0000, Cursitor Doom > >>>wrote: > >>> > >>>>On Wed, 18 Dec 2024 10:57:10 -0800, john larkin > >>>>wrote: > >>>> > >>>>>On Wed, 18 Dec 2024 18:38:55 +0000, Cursitor Doom > >>>>>wrote: > >>>>> > >>>>>>Gentlemen, > >>>>>> > >>>>>>A chum of mine who's into classic cars has asked me to take a look at > >>>>>>the radio out of his 1938 Bentley which has never worked in all the > >>>>>>years he's had it in his ownership. Obviously, given the year, this is > >>>>>>an all-valve job (if you're in the US, I'm referring to what YOU call > >>>>>>"tubes"). There isn't a single semiconductor in this thing cos they > >>>>>>weren't invented until much later. The valves require an anode > >>>>>>("plate" if you're in the US) voltage of 235V so there's a DC to DC > >>>>>>up-converter to generate that from the 12V battery. Rather interesting > >>>>>>approach they've used and one can see an embryonic SMPS in there! > >>>>>>Anyway, there's a schematic symbol I can't identify for sure. Could be > >>>>>>a fuse, could be a link or jumper, could be a current test point, I've > >>>>>>no idea. So can some kind, intelligent soul enlighten me? They're > >>>>>>labeled V1 through V8. Here's a pic: > >>>>>> > >>>>>>https://disk.yandex.com/i/mIv_txLia6Xx4Q > >>>>>> > >>>>>>TIA, > >>>>>>CD > >>>>> > >>>>>Probably the tube filaments. > >>>>> > >>>>>Incidentally, I have seen people selling solid-state plugin > >>>>>replacements for vibrators. > >>>> > >>>>Splendid suggestion, John. I must admit that never occurred to me. > >>>>I'm afraid this chap is a stickler for originality and wants > >>>>everything done with old parts. I did venture to suggest a modern, > >>>>monolithic converter but that was rebuffed most vociferously. Sigh... > >>> > >>>I'd stick a transistor radio behind the old knobs. > >>> > >>>It may have a dynamic speaker too, which could be hard to replace. > >>> > >>>Buy the vibrator replacement and rub some dirt on it, or stuff it into > >>>the ugly old can. > >> > >>That's what I'd do if it were my car. You can get AM radios on 1/2" > >>square boards; just add your own L and variable C and a TDA2611A for > >>the audio. All sorted out. I told him I'd do it that way for free, but > >>if he wants to do it the hard way I can only offer guidance and > >>whatever vintage spares I have. > > > >I recall that vibrators weren't reliable. Finding a replacement would > >be tricky. > > Simple enough to contrive a replacement using an old telephone > exchange relay if he'll accept that. It's miraculous they functioned > for as long as they did, given the hammering they took due to the way > they were wired. The early designs were a bit unreliable but it was often due to contact damage when the suppression capacitors failed. Later designs were much better engineered, with extremely ingenious mechanical arrangements to minimise contact bounce and ensure that everything worked correctly at the resonant frequency. The later ones were surprisingly quiet, both mechanically and electrically. They carefully arranged the centres of mass of the vibrating parts so that they didn't translate the vibations into unwanted modes. If the set was specifically designed to only work with a vibrator, the rectifier could be omitted and a second set of synchronously-vibrating contacts would do the rectification. That more than made up for any efficiency losses in the vibrator itself. -- ~ Liz Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk