# The ATP4 heater voltage

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Forum » Valves / tubes - Semiconductors » VALVES/TUBES / SEMICONDUCTORS in RADIOMUSEUM » The ATP4 heater voltage

Jacob Roschy
Moderator
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03.Aug.11 16:55

Count of Thanks: 3

There is contradictory information circulating about the heater voltage of the ATP4 of either 2.0 or 2.6 V. It seems not to be clear which of this information is correct.

2.0 V speaks for the filament glow color, which corresponds to the normal 2V - battery tubes, but at 2.6 V, the filament glows even unusually bright.

Also for 2.0 V calls the fact that this tube was very likely derived from the QP230, which has also the heater figures 2.0 V / 0.3 A, and the fact that most of the other tubes in this English army battery tube series, eg. the ARP12, are also rated at 2.0 V, but no other tubes with 2.6 V can be found.

Both in the heater voltage specifications of 2.0 V as well as 2.6 V a heater current of 0.3 A is given.

Since this is physically impossible, a series of experiments with 10 tubes ATP4 was performed with voltage measurements at a given heater current of 300 mA as well current measurements as at a given heater voltage of 2.6 V.

 Tube # Vf_ V If_ mA __ Vf_ V If_ mA 1 2,04 300 2,6 374 2 2,05 300 2,6 358 3 2,01 300 2,6 347 4 2,06 300 2,6 358 5 1,98 300 2,6 366 6 2,05 300 2,6 357 7 2,05 300 2,6 360 8 2,07 300 2,6 358 9 2,02 300 2,6 361 10 2,05 300 2,6 357

It was found that at 300 mA heater current the filament voltage is always close to 2 V, and at a heater voltage of 2.6 V, the heater current is always in the vicinity of 360 mA.

This clearly suggests that 2.0 V / 0.3 A must be the proper heater figures !

A statement in the "Codex" does not automatically mean that it must be wrong, and an indication in a "Specification MOS/CV1366 / Issue 6, dated 09/02/1946 by Ministry of Supply (SRDE)" does not automatically mean as being correct.

The specification of the heating voltage of 2.6 V could have been occurred by a poorly written handwritten note, where a number 0 was read as 6. A deliberately specified overheating is not entirely ruled out, but is not related to the heater current 0.3 A.

Emilio Ciardiello
Editor
I  Articles: 530
Schem.: 165
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03.Aug.11 20:41

Count of Thanks: 5

Dear Jacob,

probably the contradiction in the filament voltage arises from the reading of the CV spec sheet as a normal data sheet of a tube. But we must think of this sheet as the document for the acceptance, or even the reject, of any production lot by Military.

In the introduction we find generic data on the tube, kind of cathode, sometimes materials used for electrodes, base and pinout and operating voltages and currents. The second section is dedicated to the acceptance tests and to test procedures. Now we read 2.6 volts and 300 milliamps as ratings of the tube. This means that the tube was designed for operation centered around these values.

Then we jump to the acceptance tests, page 2 of the sheet, an here we find that filament current, plate current and other tests must be in agreement with the specified values or ranges when the filament voltage is set at 2.0 volts. No wonder that emission and other critical parameters were measured at the lowest espected heater voltage. Unfortunately the CV spec is at the moment the only source of information for this tube and we should believe it accurate, since was used through the years for all the tubes bought all over the Commonwealth.

Regards, Emilio

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Emilio Ciardiello
Editor
I  Articles: 530
Schem.: 165
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04.Aug.11 07:56

Count of Thanks: 3

AVO Valve Data Manual gives a setting of 2.0 volts for the filament supply selectors for the V248A.

A data sheet for the Mazda V248A is available in the site of National Valve Museum. Probably it was complementary to the CV spec sheet. Even this document gives 2.0 volts as filament supply voltage: here the 0 appears to be overwritten on a previous character, not clear but maybe a ‘6’.

According to the same data sheet, the tube was designed for WS-18, a battery operated transceiver. Few info found on this set. Maybe it was powered by lead storage cells. In this case the nominal voltage can be assumed in 2.2 volts, while 2.0 and 2.6 volts are respectively the discharge and the full charge limits.

The above data could lead to the conclusion that the filament voltage can be anyway between 2 and 2.6 volts and the tube must be tested for proper operation at the minimum value of 2.0 volts. In this case 2.6 volts could be assumed as the absolute maximum voltage: this is in line with 16 volts as maximum specified for 12 volt tubes intended for car radio applications. It is only a guess, I know, but could explain the contradictions found on this tube and the current drain values measured by Jacob at 2.0 and at 2.6 volts.

Regards, Emilio

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Jan Terranea

NL  Articles: 62
Schem.: 71
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04.Aug.11 12:28

Count of Thanks: 2

The ATP4 is the also transmitting penthode in WS38 and  WS38AFV.

The WS38 has a heater-battery of nominal 3 volts, and the heater of this tube is fed via an 1,7 ohms resistor, giving a drop of about 0,5 volts.

I use this WS38 from time to time, and I have noticed that the set works okay with 2 nicad-cells in series, giving 2,2 volts working tension, resulting in about 1,8 volts at the valve.

The WS38 AFV uses the car-battery of nominal 12 volts for heating.

It has 2 ATP4 valves, ( one in the separate power-supply/LF-amplifier) that get their heaters fed in series via a 24 ohms resistor. This rsistor gives a drop of 8 volts at 0,3 Amp, leaving 4 volts for the 2 valves in series.

In my opinion 2 volts must be considered to be the normal heating-voltage.

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Jacob Roschy
Moderator
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05.Aug.11 16:17

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From the findings of the previous discussion, I conclude that the center design heater voltage of the ATP4 must be around 2.3 volts.

Therefore a new test series with 15 tubes ATP4 was conducted to see which average heater current appears at 2.3 volts, which happens to be 336 mA.

Those tubes that corresponded to this average value are drawing 307 mA at 2.0 V as well as 368 mA at 2.6 V.

Summary of the average heater current:

307 mA at 2.0 V

336 mA at 2.3 V (may be considered as center design values)

368 mA at 2.6 V.

January Terranea gave us valuable information about real applications of ATP4. With this information it was possible to trace back the voltages the ATP4 was heated with.

Hence, in another experiment, a ATP4 was heated via a resistor of 1.7 Ω at voltages of 2.6 to 3 V.

It was found out:

at 3.0 V: I-f = 348 mA, U-f = 2.41 V

at 2.8 V: I-f = 331 mA, U-f = 2.25 V, regarding internal resistance and partially discharge of a dry-cell battery,

at 2.6 V: I-f = 312 mA, U-f = 2.07 V, regarding progressed discharge.

Now two ATP4's in series connection was heated via a resistor of 24 Ω at voltages of 12 to 14 V.

It was found out:

at 12 V: I-f = 323 mA, U-f = 4.36 V for both tubes, makes 2.18 V per tube, corresponding to a car battery in discharge mode,

at 13 V: I-f = 346 mA, U-f = 4.80 V for both tubes, makes 2.4 V per tube,

at 14 V: I-f = 368 mA, U-f = 5.22 V for both tubes, makes 2,61 V per tube, corresponding to a car battery in charging mode via the generator.

It looks as the center design heater voltage of the ATP4is is about 2.3 to 2.4 volts. A 2.4 V rechargeable battery may be the ideal voltage supply.

Of course any experiments was made without plate and screen current, which also will have a considerable influence.

Best Regards, Jacob

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