Sorry for the stupid question 😀
Do 300b tube have a guide pin or some sort of correct way of inserting them into the socket?
Do 300b tube have a guide pin or some sort of correct way of inserting them into the socket?
As stated there are two fat pins and two skinny pins. The sockets should have two pairs of different sized holes.
That said, I know that it IS possible with todays tubes and sockets of less than stellar quality control to fit a "budget" 300B into the socket wrong.
That said, I know that it IS possible with todays tubes and sockets of less than stellar quality control to fit a "budget" 300B into the socket wrong.
Some have guide pins, but many do not, worse when present they are not necessarily in the right place. I would avoid using vintage sockets with 300B unless you are sure the pin is not going to cause an issue.
JJ300B have guide pins, but I am not sure whether or not they are in the same location as a reference WE300B - I no longer have any WE to compare..
JJ300B have guide pins, but I am not sure whether or not they are in the same location as a reference WE300B - I no longer have any WE to compare..
I read that the difference between a 300A and 300B was the position of the locating pin when the sockets were all still twist lock types similar to 845s.
You are correct. The difference between the two types is that the pin is offset 45 degrees.
My JJ 300Bs have a black dot where the guide pin is supposed to be. It could be that later production has a real pin there (mine are around 15y old).
I remember the Chinese versions from the late 90s all had guide pins so they could be used in the (Chinese) twist lock sockets.
I don't think I ever saw such a socket in an amp though, only on the shelf in the shop.
I remember the Chinese versions from the late 90s all had guide pins so they could be used in the (Chinese) twist lock sockets.
I don't think I ever saw such a socket in an amp though, only on the shelf in the shop.
According to the WE 300B datasheet from 1950, the guide pin is in line with pins 1 & 3 and located at pin 3, 47 degrees offset. I also just checked my WE300B pair and the pin location is correct.
Regards, KM
Regards, KM
I built a DIY amplifier that used a 5Z3 - a 4 pin rectifier. During the initial build I used some cheap knockoff of the classic Johnson Ceramic socket.
I found that it was possible to insert the tube incorrectly, the tolerances of the small pin holes were loose enough that the big pins could slide in.
I ended up replacing the socket with an octal one and using the 5U4.
I found that it was possible to insert the tube incorrectly, the tolerances of the small pin holes were loose enough that the big pins could slide in.
I ended up replacing the socket with an octal one and using the 5U4.
Ha! I should have waited for your answers!
I did in fact insert 3 out of 4 Electro Harmonic wrongly (into a Chinese amp). Now 3 out of 4 test bad in my tube tester. When I plugged them back in, this time correctly, the channel with 2/2 testing bad plays low, the channel with 1 out of 2 testing bad, plays at higher volume.
I guess I'm in the market for some cheap 300b replacement then :/
I did in fact insert 3 out of 4 Electro Harmonic wrongly (into a Chinese amp). Now 3 out of 4 test bad in my tube tester. When I plugged them back in, this time correctly, the channel with 2/2 testing bad plays low, the channel with 1 out of 2 testing bad, plays at higher volume.
I guess I'm in the market for some cheap 300b replacement then :/
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