Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old June 3rd 19, 06:12 AM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On Sun, 02 Jun 2019 12:29:53 -0700, Jeff Liebermann
wrote:

On Sun, 02 Jun 2019 12:56:58 -0400, Pat
wrote:

On Sun, 2 Jun 2019 15:57:22 -0000 (UTC), Cursitor Doom
wrote:
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.


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.


Ah yes, but you can get far more efficient Sovtek 5Y3GT tubes
(thermionic valves):
https://shop.ehx.com/item/5y3gt/tubes-vacuum-sovtek/
which features a filament that draws only 2mA +/- 0.2mA 5V or 10
milliwatts.

I like the description on the data sheet:
https://shop.ehx.com/catalog/addimages/5y3gt-sovtek.pdf
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.


What about cold cathode tubes?

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Old June 3rd 19, 08:30 AM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On Sun, 2 Jun 2019 15:57:22 -0000 (UTC), Cursitor Doom
wrote:


Gentlemen,

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.



I melted solder on top of 5Y3GT


Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place



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Old June 3rd 19, 09:26 AM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

Sjouke Burry wrote:

On 02.06.19 17:57, Cursitor Doom wrote:

Gentlemen,

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.




Draw a lot of current and you get a lot of heat.

Dont want the heat?
lower the current, or use bigger components and cooling.


Just a little nit-pick he

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.


--
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(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
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Old June 3rd 19, 10:07 AM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On 2019-06-02 21:29, Jeff Liebermann wrote:
On Sun, 02 Jun 2019 12:56:58 -0400, Pat
wrote:

Ah yes, but you can get far more efficient Sovtek 5Y3GT tubes
(thermionic valves):
https://shop.ehx.com/item/5y3gt/tubes-vacuum-sovtek/
which features a filament that draws only 2mA +/- 0.2mA 5V or 10
milliwatts.

I like the description on the data sheet:
https://shop.ehx.com/catalog/addimages/5y3gt-sovtek.pdf
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.


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...

Arie

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Old June 4th 19, 06:50 PM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On Sunday, June 2, 2019 at 11:57:25 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

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.




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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 series
with a non-linear resistance and a source of potential which is connected by 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 also 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 made for
the first calculation should be readjusted when the results are known, in order 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 rectifiers
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 account the
maximum permissible ratings for peak current, average current, and peak inverse
voltage. The design of the following filter will influence these last two factors particularly;
the type of filter, either choke or condenser input, will be determined partly
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 Class 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 rectifiers 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 operating 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 rectifiers 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. output voltage when a condenser input filter may be used;
(3) self protection against accidental over-load due to the fairly high internal
impedance of the rectifier. Use can only be made of this last point when the
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 complication 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 rectification is required. With low impedance rectifiers as used in a.c.jd.c. receivers (e.g. 2SZ6-GT) it is desirable to limit the peak current by some series resistance. When two units are connected in parallel it is also desirable 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.
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Old June 4th 19, 10:15 PM posted to sci.electronics.repair
Al Al is offline
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Default Another old-timer tube/valve question

On Tue, 04 Jun 2019 10:50:27 -0700, three_jeeps wrote:

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...)


Clear as mud!
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Old June 4th 19, 10:26 PM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On Tuesday, 4 June 2019 22:15:20 UTC+1, Al wrote:
On Tue, 04 Jun 2019 10:50:27 -0700, three_jeeps wrote:

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...)


Clear as mud!


which bit/concept is not clear?


NT
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Old June 5th 19, 12:47 AM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On 04.06.19 19:50, three_jeeps wrote:
On Sunday, June 2, 2019 at 11:57:25 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

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.




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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.


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...)

Cut
Googled...downloaded..... checking. (Thanks)

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Old June 29th 19, 10:08 PM posted to sci.electronics.repair
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Default Another old-timer tube/valve question

On Sunday, June 2, 2019 at 7:54:17 PM UTC-4, Cursitor Doom wrote:
On Sun, 02 Jun 2019 23:40:29 +0200, Sjouke Burry wrote:

Draw a lot of current and you get a lot of heat.

Dont want the heat?
lower the current, or use bigger components and cooling.


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.


Though, how would you say captain obvious in dutch maybe? Kapitein duidelijke?


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