No. They are made from different materials suitable for the specific purpose. You will understand and accept one day.
Somebody should go to his stock, grab a number of different PCC88 and check for filament voltages using a ccs supply.
Ok, maybe they are made of different materials, I never really studied it, but from a practical point of view and use, there is no big difference. Each tube should be provided with what the datasheet says, and that is enough. As far as I can see, the only real challenge as far as heating tubes are concerned are DHT/DHP. But that is off topic now.
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Any sources of that claim ?
Do you have any source for this ?
In fact some tubes like ECC8x all draws 300mA @6.3V and was used inside series strings TV sets.
I used PCC88 many times as direct replacement of 6922/ECC88/E88CC without any problems in terms of THD, gain, etc..... compared between them
Walter
Walter
P-tubes were designed to be powered by the mains voltage, which varies widly.
I got some E/PCC88s, some look like NOS, others clearly used, measured them in a simple common cathode circuit. Heater powered by 6.3V.
--------------Va1--Vk1---G1---Va2---Vk2---G2
19- ECC88---70.5--2.06--27.3---71.6--2.03--26.5
20- ECC88---76.1--2.00--28.55---71.7--2.04--26.6
21- ECC88---66.6--2.09--27.7---65.5--2.09--25.45
22- PCC88---69.7--2.03--30.4---69.6--2.02--31.05
23- PCC88---78.1--1.95--32.0---71.0--2.02--31.15
24- PCC88---71.3--2.03--29.8---69.2--2.03--31.4
25- PCC88---70.8--2.02--30.25---71.8--2.00--30.05
PS Bloody formatting!
I got some E/PCC88s, some look like NOS, others clearly used, measured them in a simple common cathode circuit. Heater powered by 6.3V.
--------------Va1--Vk1---G1---Va2---Vk2---G2
19- ECC88---70.5--2.06--27.3---71.6--2.03--26.5
20- ECC88---76.1--2.00--28.55---71.7--2.04--26.6
21- ECC88---66.6--2.09--27.7---65.5--2.09--25.45
22- PCC88---69.7--2.03--30.4---69.6--2.02--31.05
23- PCC88---78.1--1.95--32.0---71.0--2.02--31.15
24- PCC88---71.3--2.03--29.8---69.2--2.03--31.4
25- PCC88---70.8--2.02--30.25---71.8--2.00--30.05
PS Bloody formatting!
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Now the big question is : all had the same filament voltage ?
Please add Vb and/or Ra, Gx must be gain.
Please add Vb and/or Ra, Gx must be gain.
Added. I virtually forgot the most important thing 🙂
Vk (cathode) is basically the bias voltage. Vb is zero. Gx is stage gain, yes. Schematic used:
I have now added 3 options for both anode and cathode resistors via a switch. Unfortunately I measured the *CC88 before I added that.
Vb would be the supply voltage in my post.
100 kohms is a high plate resistor for 88 type.
Vk indicates that the current is unduly low.
100 kohms is a high plate resistor for 88 type.
Vk indicates that the current is unduly low.
Yup. At some point I will repeat my measurement. Now I have the following options:
Switch position (cathode and anode switches)
-----Up--Down--Middle
R5: 33.58K, 49.6K, 99.33K
R5’: 33.59K, 49.55K, 99.27K
R3: 104.47, 352.4, 978
R3’: 104.98, 352.3, 979
R6 Switch:
Up: 10K
Down: 1.3K
Switch position (cathode and anode switches)
-----Up--Down--Middle
R5: 33.58K, 49.6K, 99.33K
R5’: 33.59K, 49.55K, 99.27K
R3: 104.47, 352.4, 978
R3’: 104.98, 352.3, 979
R6 Switch:
Up: 10K
Down: 1.3K
Strangely enough we had this very debate on the Bigbottle Phonostage Builders thread. It seems that only Phillips give a voltage of 7.6 in their spec sheets, everyone else gives 7.0v. I realise they need 300ma, so the voltage given in the various spec sheets is obviously dependent on resistance across the heater. Which begs the question, do Phillips tubes have a higher resistance than other manufacturers?
Your experiments certainly confirm that the Phillips spec sheets are spot on for Phillips tubes.
The reason I'm interested in this is the Bigbottle preamp, which I built a few years back, and which I'm currently using, was originally designed for 7.6v, due to this info being on the Phillips data sheet. It was then modified (with a lower voltage zener) to 7v, the assumption being that the Phillips either ran at a higher voltage, or there was a mistake in the Phillips data sheet, and the normal ECC88 heater voltage is 7v.
I'm now wondering whether to change it to 7.6v.
Make it 300 mA. Stop thinking in filament voltage with P tubes.
ECC88 filament voltage is 6.3V not 7V.
So E: 6.3V @ xmA, P: 300 mA @ xV. Simple. No assumptions. Just correct usage as per datasheet/common knowledge. Certainly with meanwhile rare western made quality tubes instead of todays knockoffs.
ECC88 filament voltage is 6.3V not 7V.
So E: 6.3V @ xmA, P: 300 mA @ xV. Simple. No assumptions. Just correct usage as per datasheet/common knowledge. Certainly with meanwhile rare western made quality tubes instead of todays knockoffs.
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I'm actually talking about PCC88. That was a typo.
And to get 300ma with a set resistance you have to have the correct voltage.
And there are conflicting data sheets, Phillips say 7.6v, everyone else 7v.
Which was the whole point of the post.
Having a click look over the Philips datasheets. The heater of PCC88 is 300mA,7.6v, and for ECC88 is 6.3v,365mA; almost the same wattage (~2.3W), presumably because the cathode is of a similar size and needs to run at a similar temperature. The triode curves in the two datasheets look the same, and looking at your test results it is the curve at 6.3v 263mA (1.65W) that best matches the datasheet curves. At 8.2v 300mA your burning 2.46watts, so perhaps it is just a strong testing tube. If you were to run the heater on even less power you should reach an upper knee in the curves as the cathode can't provide the current. I would be inclined to run your particular tube at 7.6v or what ever matches the required wattage.
Regarding old TV series circuits which I am not familiar with, wouldn't they just be connected straight to the voltage transformer secondary, or did they use a constant current transformer ?
Regarding old TV series circuits which I am not familiar with, wouldn't they just be connected straight to the voltage transformer secondary, or did they use a constant current transformer ?
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