What would be the best way to get 6.3 volts - Page 1
Forum section: electronics / beginners

author: Rick699
author_rank: Newbie
timestamp: June 10, 2013, 05:20:19 pm
content: So to go a little more about it, What would be the best way to get 6.3 volt @ 160 Amps , Continuously in a 12volt mobile applicationThis is for a large transmission tube.The voltage must stay within 5% of 6.3volts dcI was thinking about building a large voltage regulating circuit, But is this the best way?Is there any ideas out there?

author: KJDS
author_rank: Super Contributor
timestamp: June 10, 2013, 05:52:27 pm
content: If you've just got one tube then you'll need a switch mode, if you've a pair of tubes can you run them in series?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: June 10, 2013, 05:59:58 pm
content: Hi,This is serious amount of heater (filament power)!! Never mind the heater, where are you going to get the plate (anode) supply from ?Jay_Diddy_B

author: Rick699
author_rank: Newbie
timestamp: June 10, 2013, 06:21:14 pm
content: Have the anode figured out, I have special transformers made to run 15volt ac pri , "powered by alternators" that steps up the voltage well into the kv range

author: Rick699
author_rank: Newbie
timestamp: June 10, 2013, 06:27:12 pm
content: Quote from: KJDS on June 10, 2013, 05:52:27 pmYep just have one tube, Switch mode power supply that will run on 12volt dc or are you talking about running a invertorthat will run a 110ac switch mode power supply?

author: IanB
author_rank: Super Contributor
timestamp: June 10, 2013, 06:56:54 pm
content: Quote from: Rick699 on June 10, 2013, 05:20:19 pmIs there really such a tube design?The operating filament resistance would be 6.3/160 = 0.04 ohms, which means the cold resistance would be somewhat less, maybe 0.004 ohms? That filament is going to look somewhat like a short circuit, and the wire thickness to convey 160 amps without significant voltage losses is going to be enormous. It is not typical to power 1000 W loads from a 6.3 V supply because of the design challenges involved.

author: KJDS
author_rank: Super Contributor
timestamp: June 10, 2013, 07:01:53 pm
content: I've jsut checked the datasheet for a 3cx1500a and that only want's 10.5A at 5V and is good for 1500W of RF. You'll need a very big alternator to power whatever behemoth you're working on.

author: c4757p
author_rank: Super Contributor
timestamp: June 10, 2013, 07:10:05 pm
content: What kind of tube takes 160A at 6.3V?? Most of the big transmitting tubes tend to take 5V at a few tens of amps, and I've yet to see ashort circuitwelderfilament that gulps 160A!

author: Fraser
author_rank: Super Contributor
timestamp: June 10, 2013, 07:11:07 pm
content: http://www.g8wrb.org/data/Eimac/4CX10000J.pdfhttp://www.g8wrb.org/data/Eimac/4CX15000J.pdfThese were in Racal transmitters and they were 3 phase 240V ac.

author: c4757p
author_rank: Super Contributor
timestamp: June 10, 2013, 07:14:47 pm
content: Quote from: Aurora on June 10, 2013, 07:11:07 pmAny tube people know why they couldn't just do 3.2A at 240V or something?

author: Rick699
author_rank: Newbie
timestamp: June 10, 2013, 07:26:13 pm
content: Yes this is a very large tube "3cx15000a7" The anode will be powered by 4 Leece Neville alternators @ 270amps eachI can add another alternator to get the 6.3 volts but I don't like how the voltage can change per the rpms.Looking out of the box to find some thing different. Maybe better!

author: G7PSK
author_rank: Super Contributor
timestamp: June 10, 2013, 09:17:18 pm
content: A good alternator with an AVR board should stay pretty steady on the voltage over a fairly wide rpm range especially if the prime mover is fitted with an electronic governor,A diesel gen set will inherently be more stable on the rpm any way, otherwise generate at a high voltage and use a motor generator set as they used in the old days, whatever you use it is not going to be that portable it will have to be truck mounted.Out of interest how thick are the filaments in this tube, I have some tungsten rods for tig welding and the 3.2 mm ones will run at about 90 amps go much above 120 amps and they melt.

author: Fraser
author_rank: Super Contributor
timestamp: June 10, 2013, 10:06:38 pm
content: Its not a singe filament per se, it is many in parallel. See the attached picture. Its the white 'drum' on the right of the picture. The grid assembly (middle of picture) fits over the filament drum as this is a directly heated cathode valve. The filament supply stud on the bottom of a 4cx10000 is the diameter of your thumb!Lovely tubes. I sold an old one for US$75 a few weeks ago. The buyer is going to use it in a transmitter so it will 'live' againI have a nice shiny one on a teak plinth as a memento of working on Racal TA1812 10kW transmitters in the good old days. You touch the HT on one of these, you dieAn interesting page on such tubes here:http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm

author: c4757p
author_rank: Super Contributor
timestamp: June 10, 2013, 10:09:25 pm
content: Those look more like some bizarre variation on car parts than electronics. They are beautiful, though. I doubt I'll ever get over the attraction of being able to see the working parts in a tube - that is cool.

author: Fraser
author_rank: Super Contributor
timestamp: June 10, 2013, 10:19:43 pm
content: I love electronics and fine engineering. Thermionic tubes satisfy both of those

author: rsjsouza
author_rank: Super Contributor
timestamp: June 11, 2013, 08:08:27 pm
content: I did not look into all the details, but I wonder if you could potentially get a 12V power supply (or even the alternator) and associate several of thesemodulesin series/parallel to get the 6.3V...I only consider this alternative as I am very crusty in switching PS designs (it's been almost 20 years) - obviously things progressed and a beast likethisis possible, but not sure how easy it is to modify it to achieve the specs you need... Maybe it gives you some ideas...

author: Rick699
author_rank: Newbie
timestamp: June 13, 2013, 05:55:05 pm
content: Quote from: rsjsouza on June 11, 2013, 08:08:27 pmThanks rsjsouza I am looking in to the modules right now , think that's the way I want to go !

author: vk6zgo
author_rank: Super Contributor
timestamp: June 14, 2013, 01:57:23 am
content: As there is no practical use for such an installation, it looks suspiciously as if the OP is involved in the seriously stupid activity of CB keydown competitions,where they make ridiculous mobile power amps & (somehow) measure either the power output or signal strength at a remote point.If the former,have you seen how big a test load is for the power levels they claim?(I've read reports of 50 KW outputs etc----"They're dreaming!")If the latter,someone with a better antenna would beat a nominally higher power amplifier any old time,but CBers love to kid themselves!

author: codeboy2k
author_rank: Super Contributor
timestamp: June 14, 2013, 03:31:24 am
content: Good Lord! I didn't know this existed ... check out the pic of the alternators...

author: G7PSK
author_rank: Super Contributor
timestamp: June 14, 2013, 07:42:13 am
content: Quote from: codeboy2k on June 14, 2013, 03:31:24 amThat's just plain daft, those belts will shred very fast, it would be far better to use one large alternator directly driven from the flywheel with a fenner-flex coupling.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 14, 2013, 08:02:59 am
content: Or a real Diesel driven Standby power alternator.They could mount it on a big rigid tray truck,but I guess that wouldn't leave much space for the HT & filament transformers,the blower motor & ducting,& the amplifier itself!The giveaway with these things is when they start rabbiting on about "Leece Neville alternators".They all congregate on a car park somewhere in the USA & take turns in "keying down" the heaps of crap on 27MHz (& umpteen harmonics).The power levels they claim seem very unrealistic to anyone with experience of real high power transmitters.

author: amyk
author_rank: Super Contributor
timestamp: June 14, 2013, 11:01:32 am
content: People will always find ways to say "I'm better than you"...

author: codeboy2k
author_rank: Super Contributor
timestamp: June 14, 2013, 09:22:39 pm
content: Quote from: vk6zgo on June 14, 2013, 08:02:59 amThey must have some rules , perhaps everything must fit on a standard class recreational vehicle, be 12V powered, etc. etc... because I started googling around and watching youtube videos yesterday, these guys beef up their suburbans, add 6,8,10 alternators or more (!) and build massive out-riggers to hold arrays of antennas, all on their vehicle.clearly the best way is to haul a diesel generator, power converters and a transmitter on a flat bed

author: vk6zgo
author_rank: Super Contributor
timestamp: June 15, 2013, 01:30:34 am
content: The thing is,it's illegal!Not just some newbie getting a slap over the wrist for running a few mW too much on a homemadegadget ,but full-on "Bubba's new roommate" illegal!

author: peter.mitchell
author_rank: Super Contributor
timestamp: June 16, 2013, 02:39:23 pm
content: holy crap, even the harmonics would be stupidly powerful at those ratings.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 17, 2013, 02:28:43 am
content: I'm still quite dubious about their measurement methods,so the 20 & 50 kW claims are probably horse faeces,but even 5kW with poorly designed amplifiers could cause serious interference on harmonically related bands.