6J4P 6Ж4 Pentode tube Russian

[Ed_Chambley]

I had an amp dropped off, No schematic and it is a build from somewhere.  Anyway the russian tube is toast and I have read where the 6AC7 is a substitute, which I have a few.  Can anyone confirm if this is a direct substitute.  Are there any other substitutes that may glass.  Should I just get a Russian version?

[st]

No idea whether it's a direct substitute. I do know, however, that Russian NOS tubes are relatively cheap, easy to source (at least in europe) and often of superior build quality (old stock are often mil spec). So why not go with that?

[DummyLoad]

it's similar to 6AU6/EF94/6136/7543 any of those should work. i prefer the 6136 sylvania gold brand or GE7543.


--pete

[DummyLoad]

sorry ed, my mistake - that's the shuguang designation - 6J4P is the same electrically as the US 6AC7. 


--pete



 

[st]

Be carefully! There's a 6j4p (chinese? = 6ac7) and then there's a the russian 6zh4p. I believe you're looking for the latter.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.radiomuseum.org/tubes/tube_6j4p~2.html&ved=2ahUKEwiX0LKev8bhAhXFblAKHcedDZsQFjABegQIBRAC&usg=AOvVaw2Y-yOkS9BinKSMK_XGTxiU&cshid=1554932592779
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.radiomuseum.org/tubes/tube_6j4p.html&ved=2ahUKEwiX0LKev8bhAhXFblAKHcedDZsQFjACegQIBRAJ&usg=AOvVaw07O-c_Ow4GRf37FwRbsxg4&cshid=1554932592779

[PRR]

https://www.radiomuseum.org/tubes/tube_6j4p.html
https://www.radiomuseum.org/tubes/tube_6j4p~2.html
One is miniature, one is octal.

[DummyLoad]

he seeks the octal 6J4P shuguang / US 6AC7 RF pentode.

--pete

EDIT: Ed could have eliminated confusion by initially stating the part is an octal tube. hindsight...   

[Ed_Chambley]

he seeks the octal 6J4P shuguang / US 6AC7 RF pentode.

--pete

EDIT: Ed could have eliminated confusion by initially stating the part is an octal tube. hindsight...   

I forgot to mention, this is an octal tube.   
However I did ask if a 6AC7 was a direct replacement.  Never tried to get one seated in a 9 pin socket.

[Ed_Chambley]

Thanks, and I mean it.  I haven't drawn a schematic for this amp, but it sure sounds good.  I am not familiar with using a 6AC7 in an amplifier, radio yes.  Seems to accept line level well, but is certainly built to overdrive the KT88 in it.  It has a 6AC7 and sounds fine with a 6Sj7 to a 6SN7 using both triodes and a switch to change coupling caps to reduce bass.  That is it.


It looks like about half of stereo Hifi.  It is a simple point build.

[kagliostro]

https://tubes-store.com/product_info.php?products_id=873

They accept PayPal

Ciao

Franco

[Ed_Chambley]

Since the original post, I have found some HiFi guys using and preferring Sylvania Sylvania 6ac7,  keep wanting to type 6ca7, flip a couple letters and change the world.


Checking the amp closely, it needs a real chassis, so it is going to get one. I checked my radio tube stash, something I normally only do to fix a radio. 6ac7, guite a few boxes.


I have not had time to see what the tube really does in the circuit, but it did come with a real GEC KT88. Maybe I will get lucky and find a match. The 6ns7 is not bypassed, just 2 resistors. Very easy to overdrive at the input using any preamp.


Anyway, thought I might follow up and say the from brands of tubes of the 6ac7 I cannot hear a difference. Even RCA and I have special place in my heart for RCA Tubes. 


Also, may respond to a guitar volume knob better than anything I have played.