What are the typical average/maximum operating temperatures of a full wave rectifying tube/valve? Is it normal for them to become too hot to touch after only a minute or two? I'm talking specifically about the 5Y3GT in this context.
-- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Vacuum Tubes (Valves) work by heating the cathode to "boil off" electrons. The 5Y3 has a 5v filament that draws 2 Amps. So that's 10 watts even without any current flowing in the plate circuit. So, yes, I would expect it to get hot quickly.
Thanks, guys. They'd juxtaposed it with a VR150 which quickly reached a similar temperature due to its proximity. I just thought that was a rotten layout, but clearly it's not a concern in that case.
-- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Voltage drop times current, filament (cathode) to plate, plus voltage times current across filament. Never measured temperature, but energy has to go somewhere. Gets hot, radiates.
That is not even counting on power flowing in the tube as you mentioned.
With out looking it up, I would expect the tube to drop around 20 or more volts. So at 100 ma and 20 volts, that is another 2 watts to add to the 10 watts of just the filament.
Even some of the smaller glas tubes can get hot enough you can not pull them out after short time unless you have asbestos fingers.
Ah yes, but you can get far more efficient Sovtek 5Y3GT tubes (thermionic valves): which features a filament that draws only 2mA +/- 0.2mA 5V or 10 milliwatts.
I like the description on the data sheet: MINIATURE DOUBLE ANODE KENOTRON IN GLASS DESIGN WITH OXIDE-COATED INDIRECTLY HEATED CATHODE INTENDED FOR RECTIFICATION OF COMMERCIAL-FREQUENCY ALTERNATING CURRENT. That explains why one gets frequent commercials on TV sets that use Sovtek 5Y3GT kenotrons.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Er, yes. That wasn't quite what I meant, but never mind. My fault for not being clear enough having re-read it.
--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
Thank you, Captain Obvious. I can't see what was so misleading about the wording in my original question that's causing some folks to misinterpret it. Anyway, the first two respondents told me all I wanted to know so many thanks to them and their excellent comprehension skills.
--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
You will get exactly the same quantity of heat (energy) if you use bigger components and cooling - but you will get it at a lower temperature.
This leads to the curious situation that if you need to dissipate a lot of energy, it should be possible to do it in a smaller space by using valves rather than by using transistors which have to run at lower temperatures.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Fortunately the datasheet really specifies 2A not 2mA. I was already imagining a fake tube with 2x 1N4007 inside, and a 2mA LED to 'light up' the cathode...
It looke like someone just screwed up on the ad and not the data sheet. The 2 amps and not milliamps is more like it. Maybe a translator form Russian to English missed typed the information.
From the Radiotron Designers Handbook, RCA, 1952: pages 1164-1168 (I could not paste in a number of curves, one of which is Direct Voltage at input of filter versus DC Load in mA.) (This book is in my library but also in .pdf's around the web...)
Equivalent circuit of high vacuum rectifier:
The high vacuum rectifier can be considered as being an ideal switch in ser ies with a non-linear resistance and a source of potential which is connected b y the switch to the load when the polarity is that required by the load (Ref. 7). As the switching gives rise to pulsating currents (and voltages) it is necessary to assume a linear resistance which is equivalent to the non-linear effective resistance of the rectifier during this pulsating or conduction period. The conduction period (1)), and therefore a lso the magnitude of the current pulse, will depend on the loading and the type of filter connected to the rectified supply. Certain approximations which must be mad e for the first calculation should be readjusted when the results are known, in o rder that a second and more accurate calculation can be made. Mercury vapor rectifiers In the case of mercury vapor rectifiers the voltage drop in the valve is a constant value of the order of 10 to 15 volts over a wide range of currents. These r ectifiers are generally used with choke input filters to provide good regulation for class B amplifiers. The direct voltage output of such a system is equal to 0.9 times the r.m.s. value of the input voltage minus the valve voltage drop. g. Output voltage = (0.9 Erma - 15) volts. (ii) Rectifier valves and types of service Rectifier valves may be subdivided into the following groups :(
1) High vacuum (a) High impedance (e.g. 5Y3-GT) (b) Medium impedance (e.g. 6X4, 5R4-GY) (c) Low impedance (e.g. 5V4-G, 35Z5-GT) (2) Mercury vapor-(e.g. 82, 83). The choice of a rectifier valve for a particular service must take into acc ount the maximum permissible ratings for peak current, average current, and peak inv erse voltage. The design of the following filter will influence these last two f actors particularly; the type of filter, either choke or condenser input, will be determined par tly by the demands of power supply regulation. In supplies feeding Class A output stages the choice will probably be a condenser input filter, but where Clas s ABsub1 and ABsub2 output stages are to be supplied, the regulation of the power supply becomes a significant feature and choke input filters with low impedance r ectifiers must be used.
The following examples represent typical practice. c. radio receivers with Class A power stage :High vacuum full wave (e.g. 6X4, SY3-GT, SU4-G). A.C. radio receivers with Class ABsub1 power stage :-
116S With self bias-high vacuum full wave (e.g. SY3-GT, SU4-G, SR4-GY, SV4-G) With fixed bias-low impedance high vacuum full wave (e.g. SV4-G). A.C./D.C. radio receivers:- Indirectly-heated low impedance high vacuum half-wave types with heaters op erating at 0.3 A or O.IS A (e.g. 2SZ6-GT or 3SZS-GT).
In England, heaters operating at 100 rnA are widely used. Battery operated radio receivers with non-synchronous vibrators:Indirectly- heated low or medium impedance high vacuum full-wave types (e.g. 6X4).
Amplifiers :- As for radio receivers except that mercury vapour types may also be used. In general for radio receiver and small amplifier design high vacuum rectif iers are to be preferred to mercury vapour types because of- (1) long and trouble-free service; (2) the lower transformer voltage which can be used for the same d.c. outpu t voltage when a condenser input filter may be used; (3) self protection against accidental over-load due to the fairly high int ernal impedance of the rectifier. Use can only be made of this last point when th e supply is for use with a Class A output stage, when good regulation is not a major consideration and a high impedance rectifier may be used.
With directly-heated rectifiers it is generally found preferable to connect the positive supply lead to one side of the filament rather than to add the further comp lication of a centre-tap on the filament circuit. Parallel operation of similar types of vacuum rectifiers is possible but it is preferable to connect together the two sections of a single full wave rectifier and to use a second similar valve as the other half-rectifier if full-wave rectif ication is required. With low impedance rectifiers as used in a.c.jd.c. rec eivers (e.g. 2SZ6-GT) it is desirable to limit the peak current by some ser ies resistance. When two units are connected in parallel it is also desirab le to obtain equal sharing, and in such cases a resistance of SO or 100 ohms should be connected in series with each plate, then the two units are connected in parallel.
Mercury vapour rectifiers may only be connected in parallel if a resistance sufficient to give a voltage drop of about 2S volts is connected in series with each plate, in order to secure equal sharing of the load current.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.