E288C Valve

[Barry]

THanks Barry

2 and 7 are the same for the ecc88/ecc83 and 30/40 ma is a setting...excellent we are getting some where.

Is annode the same as filament ? I need the filament voltage.


Let you know how it works....


Regards D S D L

Neil, there seems to be some confusion here.

The E288CC and ECC88/ ECC83 are double triodes, that is two separate devices enclosed in a single glass envelope. Does your tester, test each triode separately? The pin connections for the first triode are:

anode, pin 1
grid, pin 2
cathode, pin 3,

and for the second triode:

anode, pin 6
grid, pin 7
cathode, pin 8.

The heaters are attached to pins 4 and 5. Heater voltage is 6.3V (that's what the 'E' means in the nomenclature) and the heater current will be 475mA (roughly 30 -60% more than for the ECC83 and ECC88).

No, the anode is not the same as the filament. I'm trying to find a simple to read guide on vacuum tube parameters, so that you can understand/interpret the data sheets that Mike has sent you. This is not really my field; I'm a 'sandman', to use the current colloquialism and I has been fourty years since I last built a valve amp. If all else fails you could try the 'World Design' forum; the people there seem to be more DIY with valve circuits and will be able to help you.

Regards

Barry

[Spectral Morn]

Yes you do the test twice...in the case of an ECC83 you test set to 2 and then do it again set to 7. This according to the book that comes with the tester. You just follow the guide...understanding is not required.

Thanks for your help. Its at times like this that my subjective expertise fails and I realize just how little I know about the technical side of things. In your day and I mean no insult based on age you guys learn't about the way things worked built your own kit etc....I never have. I never felt the need to do so...yes I do know some things about the way things work but at a fairly shallow level...oh to have more depth.

Maths, physics, Science and the like were not high on my interests at school I was more into Art, History, Geography , Wood work and Metal Work.....and writing...reading etc.


Regards D S D L

[Mike]

Is annode the same as filament ? I need the filament voltage.

Filament = Cathode

Plate = Anode

According to Wikipedia that is!... http://en.wikipedia.org/wiki/Triode

Although I've seen the heater referred to as 'filament' also, just to confuse matters!... the second data sheet quotes for Vf and If ('f' meaning filament perhaps?) which are clearly figures for the heater.

What options for 'filament' does your tester have Neil?

More about triodes... http://www.allaboutcircuits.com/vol_3/chpt_13/3.html

That bit would indicate to me that the cathode and filament are one and the same thing in a directly heated triode only. When talking about indirectly heated triodes I'm pretty sure that filament = heater.

Maybe...

[Mike]

What options for 'filament' does your tester have Neil?

Neil, after peering at the picture of your tester, I'd put money (not too much though ) on the 'filament' control being the heater voltage selector.

Probably...

[Spectral Morn]

Hi Mike

From the instruction book...

"Filament This switch selects the filament voltage applied to the tube under test from 1 to over 50 volts . The twelve position switch selects a range of voltage and the unique design of the filament transformer, the tube under test will load the transformer to obtain the correct voltage for testing." This is switch B on the tester.

Does that help ?



Regards D S D L

[Mike]

I've just downloaded the manual for your tester Neil. I'll take a look.

[Spectral Morn]

Hi Mike

I had just taken photos of the manual......great minds think alike...


Thanks Mike


Regards D S D L

[Mike]

Right, I've had a look and now I'm quite certain that the 'filament' control selects the heater voltage!

It gives an example for the 6JE6 which is also a 6.3V heater. Set the filament control to '6'.

[Spectral Morn]

And pin isolation to what Barry suggested 1 and 6 or something else ? In fact maybe if you tell me exactly what to set for all the parts please it will make it easier...



Thank you Mike

[Barry]

Hi Neil,

I think I‘m beginning to understand your confusion. Your ‘tube’ tester is an American make (if British, it would called a ‘valve’ tester). According to both American and British terminology the ‘filament’ is the same as the heater. There are differences in terminology as Mike has pointed out:

Plate (American) = Anode (British).

The use of the term ‘filament’ for cathode stems from the days of directly heated cathode valves where the cathode and heater were one and the same. Such valves are still used today in SET (single ended triode) power amplifiers. Examples are the 300B and the 2A3. SET aficionados claim that directly heated triodes are the most linear audio devices around; but this is deviating somewhat from your query.

The valves you have will almost certainly be indirectly heated devices, and so will have at least:

a heater = ‘filament’,

a cathode, a grid and

an anode = ‘plate’.

Your tester can test for ‘shorts’, ‘emission’ and ‘grid leakage’. To explain what these tests do, I’ll quote from F. Langford Smith ‘Radio Designer’s Handbook’, Iliffe 4th edition (1960):

p.91 ‘Shorts and continuity – It is important to ensure that the electrodes such as control and signal grids and suppressors, which do not normally dissipate any power, should not be subjected to any appreciable power dissipation during the shorts and continuity test, otherwise the valve may become damaged as the degassing treatment of these grids during manufacture is normally much lighter than that of electrodes which are required to dissipate power. In addition the cathode current drawn, should not be excessive. It is also important that shorts be checked between the various electrode pin connections and pins designated as no connection, also that the continuity of internal jumper connections between base pins can be checked.’

p.92 ‘It is also essential that in any shorts tester that the cathode-to-grid voltage and filament (heater)-to-grid voltage be kept to a value not exceeding approximately 100 volts.’

I don’t think you will run into any problems here with your tester. Basically if the valve fails the short test, the valve is damaged, either through physical damage to the electrodes, or the glass seals have leaked compromising the vacuum and the valve has become ‘soft’.

p.94 ‘Emission – The purpose of the emission test is to ensure that the cathode emission is adequate to provide the peak and average space currents for the application of the type by a margin which has been found to be satisfactory for good life and performance.’

‘Emission is normally tested by applying a suitable direct positive voltage to all grids connected together with the anode, and measuring the total cathode current.’

‘Because of the very high value of the emission current normally drawn from the cathode, the resulting excessive dissipation of the inner grids and the gas produced as a result of this dissipation and also as a result of ion bombardment of the cathode, the emission test is a damaging test and should be performed as seldom as possible and always very carefully.’

‘In order to avoid damage to the cathode by this test, the applied voltage must be sufficiently large to approach current saturation without drawing sufficient current to damage the valve due to excessive dissipation of the inner grids. At the same time the test must be of sufficient duration to enable the stability of the emission to be indicated without being so long as to give risk of poisoning[*] the emission. A safe value generally accepted for the duration of the emission tests is 3 seconds. During this period the emission should not fall below a value recommended by the valve manufacturer. In general, emission is a minimum reading.’

p.95 ‘Amplifier valves are normally tested for emission with an applied voltage of 30 volts.’
[*] ‘Valves having an oxide-coated cathode have a very high degree of emission as compared with other forms of emitters but require very great care during manufacture since they are readily poisoned by certain impurities which may be present in the cathode itself or which may be driven out in the form of gas from the glass enclosure or the other electrodes.’

Grid leakage

p.102 ‘Leakage current is measured with a voltage applied between the grid and each electrode in turn, with the other electrodes floating.’


To obtain all the information you need on the pin connections and value of the various valve parameters this web site is very useful:

http://tdsl.duncanamps.com/tubesearch.php ,

Just enter the name of the valve (ECC88, EF86 etc.) and the various data sheets are returned.

Finally the web site that Nick has suggested is a good one and explains how a valve works and what some of the valve parameters mean.

Apologies for the ‘information overload’.

Barry