8908 power tubes

[Colas LeGrippa]

Hi everybody !

I have purchased a Traynor amplifier with 8908 power tubes in it. They look like 6BQ5 / EL84 but I can't find specs on the net. The pinout is the same: tha amp was working when I bought it.
Anybody has an idea of the specs ? Power, voltage and so on. The preamp tubes were 5814A (12au7) instead of 12ax7 and it seems to me that the last overhaul has been performed by a tech who used what he had on hand...

Thanks

Colas

[DummyLoad]

6kg6/el509 will replace with a sockets swap. 8908 available on ebay as well...  both 6kg6 and 8908 are 40W plate diss.

8908 tube   6KG6/EL509 tube
Pin 1=G1           Pin 1=G1 (also--Pin 8=G1)
Pin 2=G3           Pin 2=G3 (also--Pin 7=G3)
Pin 3=G2           Pin 3=G2; (also--Pin 6=G2)
Pin 4=cathode    Pin 9=cathode
Pin 5=G1           Pin 8=G1 (also--Pin 1=G1)
Pin 6=G3           Pin 7=G3 (also--Pin 2=G3)
Pin 7=heater      Pin 4=heater
Pin 8=heater      Pin 5=heater
3/8" Plate Cap   1/4" Plate Cap

--pete

[Colas LeGrippa]

I don't understand why the 8908 work then if the pinout you gave me is correct because the amplifier I have is wired for two el84 The heaters of the el84 are pins 4 and 5 . 

[DummyLoad]

I don't understand why the 8908 work then if the pinout you gave me is correct because the amplifier I have is wired for two el84 The heaters of the el84 are pins 4 and 5 . 

8908 are NOVAR socket with a plate cap - not NOVAL socket. perhaps the amp has been rewired for 6KG6 already? 6GK6 has same filament pins as EL84. are you SURE those are NOVAL (EL84/12AX7 type) sockets and not NOVAR? is there a plate cap? if not, maybe it was rewired for 6GM5? 6GM5 datasheet attached.

MAGNOVAL/NOVAR socket.
https://tubedepot.com/products/9-pin-novar-magnoval-socket?gclid=CjwKCAiAn5rUBRA3EiwAUCWb21ERabtLbNIga6rNWGnFxrUFyFZSYdqzQPwtFjF4MUEHLG80VKtc-hoCEUMQAvD_BwE


NOVAL socket.
https://tubedepot.com/products/vintage-9-pin-noval-socket?gclid=CjwKCAiAn5rUBRA3EiwAUCWb23P9cX0L1DdU3Pb5Fv7iHvrqLDc7dv9wVPzAp0KhyjZLo99xKnXGzBoC6w4QAvD_BwE


--pete

[Colas LeGrippa]

uffffff, I am lost. Are you trying to tell me that a 8908 won't fit in an el84 socket ? Ok I will try to fit in a 12 ax7 just to see. What is the idea of replacing a 6BQ5 by a 8908 ?

[sluckey]

Post a pic of those 8908 tubes.

[kagliostro]

Ciao Colas

I've find a link were a guy say he subbet the 8908 with 6LW6

https://groups.google.com/forum/#!topic/rec.radio.amateur.homebrew/XTS1TndfVfA

http://tdsl.duncanamps.com/show.php?des=6LW6

----

this is from e-bay (a bit expensive  ) and didn't seem to have a noval or magnoval socket

https://www.ebay.com/itm/8908-TUBES-HY-GAIN-AMATEUR-RADIO-LINEAR-HI-POWER-TUBE-RARE-SET-/263146554910



Are you sure about the number ? Is 8908 designation correct ?

Franco

[sluckey]

I think Colas is mistaken about the identification of his tubes. He says they look like EL84/6BQ5s and have the same pin-out.   

[kagliostro]

I've a tube in my mind that remember an el84 but is a bit larger (and may be have a socket similar to the el84)

but I'm not able to remember the designation label, I only remember that this tube is still manufactured (newly remanufactured, may be by HH)

Franco

[sluckey]

7189 is a more powerful EL84 and it can be wired the same. It can also be wired a bit differently so you must check the actual wiring before just swapping one for the other.

6973 (I used in my Supro) looks like an EL84 but has a completely different pin-out.

But no way does an 8908 even begin to resemble an EL84. That's why I want Colas to post a pic of the tube he says is an 8908. Maybe we can figure out what he really has.

[Colas LeGrippa]

I will post a pic when back to my shop later today. But definitely the picture of the 8908's  taken by Kagliostro doesn't represent the 8908 I have. Mines are identical to EL84's and the pinout is the same: the socket wiring hasn't been modded and the amp is working.


Colas

[kagliostro]

Waiting for pictures


Franco

[Colas LeGrippa]

here are the 8908 pics:

[VMS]

What are the markings above the 8908?


Looks little like a 6p14p tube

[DummyLoad]

8908 is the date code or lot number. they are russian EL84 equivalent.

cyrillic alphabet translation to latin alphabet - 6P14P  is what is marked above the date code.

--pete

EDIT: attached bi-lengual datasheet.

[kagliostro]

 

Ah, OK, that is a Russian 6П14П (6P14P), a very good substitution for EL84

I can't see well the label on the tube, is 6П14П followed by other caracters ?

Use this to interpret the added characters if present

E (russian E) - long life (5000h and more)
D (russian Д) - ultra long life (10000h and more)
V (russian B) - vibration proof, high reliability
I (russian И) - for impuls mode (high emission of catode)
K (russian K) - vibration proof
R (russian P) - vibration and radiation (nuclear reliability) proof

so 'EV' (rus EB) is 'long life' + 'vibration proof, high reliability' etc

also stamps:
ОТК - standard quality
ВП - military
ОС - ultra stable parameters

Franco

[Colas LeGrippa]

Exactly, that's what it is, with russian caracters stamped above. It's the first time I see these tubes. It seems they are hard to find. The amplifier sounds VERY good. In fact it is the best sounding Traynor amp I have ever owned .


Thanks guys !!!


Colas

[kagliostro]

I forgot

here the correspondence between our characters and russian characters

http://tdsl.duncanamps.com/cyrillic.php




Franco