I'm inspecting the pins on an actual 8BQ5 tube, the data sheet says that pins 1, 6 and 8 are not connected. Looking at pins 6 and 8 it obvious that those pins go nowhere within the tube, I can clip those terminals off my tube socket. However, that's not the case for pin 1, pin 1 is connected to one of a pair of similar uprights. The other upright in that pair (that looks like the one connected to pin 1) is connected to pin 2 the grid! What is going on here? Is pin 1 really perhaps an internal shieled of some kind? even though the data sheet says it is not connected? If it's a shield should I ground pin 1?
1) NC (or is it?)
2) Grid
3) Cathode
4,5) Filament
6) NC
7) Plate
8) NC
9) Screen
https://frank.pocnet.net/sheets/127/8/8BQ5.pdf
1) NC (or is it?)
2) Grid
3) Cathode
4,5) Filament
6) NC
7) Plate
8) NC
9) Screen
https://frank.pocnet.net/sheets/127/8/8BQ5.pdf
For EL84 / 6BQ5 / 6P14P pin 1 is not used in the circuit .
And in datasheets IC means internal connection not NC that there is nothing inside the tube .
And in datasheets IC means internal connection not NC that there is nothing inside the tube .
I don't know about the xBQ5, but in 6P15P pin 1 is internally connected to pin 6. I remember that the 6P15P can be used in circuits for 6P15P / EL84 / 6BQ5, if you pay attention to the wiring for pin 1 at the tube socket.
https://frank.pocnet.net/sheets/113/6/6P15P.pdf
Perhaps a similar thing is going on with your 8BQ5 ?
Regards, Claas
https://frank.pocnet.net/sheets/113/6/6P15P.pdf
Perhaps a similar thing is going on with your 8BQ5 ?
Regards, Claas
Thats not the case, pins 6 and 8 simply end just past the glass so 6 can't connect to anything. The data sheet says 1, 6 and 8 are "ic" internally connected? But in reality only pin 1 is actually connected to something, but who knows what that is! The mystery pin, best to leave it floating and don't use pin one on the socket as a terminal.
The 6bq5 and similar 7189 tubes have pins 1, 6, and 8, listed as internally connected, meaning there was no definition in the standard for the tube, and manufacturers could do what they wanted with those pins. 7189A has pine 1 connected to the grid, pin 6 to g2 (along with pin 9), and only pin 8 is left to the manufacturer for whatever purposes they wanted to use. Best choice is don’t use the unused pin as tie points For other parts of the circuit.
You maybe can see what pin 1 is connected to if you use your ohm meter or a continuity tester. You might find it connected internally to one of the other pins. Check first and see if it is connected to pin 2.
I’ve heard that early ones had pin one connected and at some point it was no longer used. So if your tubes are pre 1980 or so it might be connected.
Best not to connect those pins - there are variations by maker and date. And when testing them, ignore "shorts" on pins 1, 6, and 8 - which again will vary with maker and vintage.
ITT is my 8BQ5 stash maker. Both pins 1 and 2 are grid pins. One on each of the two grid support posts. Later today I will inspect all the 10BQ5 tubes I have, as well as the various brands of 6 bolter's I have. Good to know that mfg's did this if given an opening.
OK here's the deal with some other "BQ5" tubes...
10BQ5 "Japan"
All of my 10BQ5 tubes are "no name" tubes that simply have the word "Japan" printed onto them (I'm hoping these are sleepers that really sound good). Those tubes have pins 1, 6 and 8 ALL attached to something, but I cant discern to what exactly, unlike the 8BQ5 pins 8 and 6 dont just stop after the glass they penetrate the bottom mica, and pin1 does the same. Perhaps these are simply riveted to the mica and stop there (like 6P14P below) but its all hidden so I cant be sure if they connect or if they stop at the mica.
6BQ5 "GE"
All of my GE 6BQ5's use pin 1 as an additional grid just like the 8BQ5, but not connected to the other grid post, instead it is welded directly to the pin #2 pin right at the base. It wouldnt need an additional grid stopper, but the 8BQ5 since it connects pin #1 directly to the grid support and #2 to the other grid support, those may need a stopper on pin #1 as well. Not sure but I'll float pin #1 anyway and use #2 as the grid.
6BQ5 "RCA in 1970 style box"
These are constructed just like the GE tube above, pin #1 and #2 are welded right at the base. Pins 6 and 8 are chopped off right at the base.
8BQ5 "ITT" (usually this is a serviceman's brand I've found)
As mentioned pin #1 on these is definitely an additional "true" grid pin meaning it actually connects to the second grid upright (not just welded to pi #2). Pins #6 and 8 are safely just clipped off, they do not progress to the mica.
It would be interesting to see how my 6P14P tubes are wired...
Beautiful tubes these are. On 6P14P pins #1, 6 and 8 appear to just rivet to the bottom mica, that's very close to the plate for my taste, but probably lends better support. You can see the top of the rivet, unlike the 10BQ5 above which also pass into the mica but you cant see whats happening beyond that.
So there we have it. When wiring the sockets for "BQ5" tubes definitely it is probably best to literally clip off the socket pins for # 1, 6 and 8 before you even mount the sockets, that way nobody can use those as a tie points. Also clipping pin #1 for the tubes that use that as an additional grid wont be creating an "antenna" needlessly, especially in the case of 8BQ5 which is a "true" additional grid not just a doubling of pin #2.
I have no time to do continuity testing just visual. I have some Sylvania's and Tung Sol's and some European EL84's somewhere but not motivated to look for them at this time, I learned enough.
10BQ5 "Japan"
All of my 10BQ5 tubes are "no name" tubes that simply have the word "Japan" printed onto them (I'm hoping these are sleepers that really sound good). Those tubes have pins 1, 6 and 8 ALL attached to something, but I cant discern to what exactly, unlike the 8BQ5 pins 8 and 6 dont just stop after the glass they penetrate the bottom mica, and pin1 does the same. Perhaps these are simply riveted to the mica and stop there (like 6P14P below) but its all hidden so I cant be sure if they connect or if they stop at the mica.
6BQ5 "GE"
All of my GE 6BQ5's use pin 1 as an additional grid just like the 8BQ5, but not connected to the other grid post, instead it is welded directly to the pin #2 pin right at the base. It wouldnt need an additional grid stopper, but the 8BQ5 since it connects pin #1 directly to the grid support and #2 to the other grid support, those may need a stopper on pin #1 as well. Not sure but I'll float pin #1 anyway and use #2 as the grid.
6BQ5 "RCA in 1970 style box"
These are constructed just like the GE tube above, pin #1 and #2 are welded right at the base. Pins 6 and 8 are chopped off right at the base.
8BQ5 "ITT" (usually this is a serviceman's brand I've found)
As mentioned pin #1 on these is definitely an additional "true" grid pin meaning it actually connects to the second grid upright (not just welded to pi #2). Pins #6 and 8 are safely just clipped off, they do not progress to the mica.
It would be interesting to see how my 6P14P tubes are wired...
Beautiful tubes these are. On 6P14P pins #1, 6 and 8 appear to just rivet to the bottom mica, that's very close to the plate for my taste, but probably lends better support. You can see the top of the rivet, unlike the 10BQ5 above which also pass into the mica but you cant see whats happening beyond that.
So there we have it. When wiring the sockets for "BQ5" tubes definitely it is probably best to literally clip off the socket pins for # 1, 6 and 8 before you even mount the sockets, that way nobody can use those as a tie points. Also clipping pin #1 for the tubes that use that as an additional grid wont be creating an "antenna" needlessly, especially in the case of 8BQ5 which is a "true" additional grid not just a doubling of pin #2.
I have no time to do continuity testing just visual. I have some Sylvania's and Tung Sol's and some European EL84's somewhere but not motivated to look for them at this time, I learned enough.
Those internal connections can be easily checked with a multimeter , but anyway you should just follow the datasheet and let the socket pins 1 , 6 , 8 floating in the air how was allways done ...
I looked at pin 1 of a GE (General Electric) branded 6BQ5, and it appears to connect to the control grid (G1).
My GE ones simply welded pin 1 and 2 simply "doubling" pin 2, pin 1 didn't go all the way back to the remaining grid support post. But the 8BQ5 did have pin 1 as a true dedicated path back to the remaining grid post, not just a doubling of pin 2. In both cases #1 is a grid pin, yes, but how they do it is different.
In all of my - old - EL84's pin 1 is connected to the grid g1 with the same kind of wire that is used for it's connection to pin 2. So is it in my 7189's. Please do not connect pins called i.c. to anything!
Best regards!
Best regards!
Data sheets lie and this is one place I've found them to tell them.
Ge lists pin 1 as no connection, many tubes are built that way, but just my luck, I used the pin 1 for a tie point, and created a short when i put a GE 6bq5 in.
Data sheet says no connection.
The parts in my hand show that they (1+2) are connected.
Believe what you see in your hand, and know that data sheets are not always right.
Pin 1 is not a "free tie point" on the 6bq5 family.
Funny that it was GEs data sheet and a GE tube which was in reality, not wired according to the sheet.
Ge lists pin 1 as no connection, many tubes are built that way, but just my luck, I used the pin 1 for a tie point, and created a short when i put a GE 6bq5 in.
Data sheet says no connection.
The parts in my hand show that they (1+2) are connected.
Believe what you see in your hand, and know that data sheets are not always right.
Pin 1 is not a "free tie point" on the 6bq5 family.
Funny that it was GEs data sheet and a GE tube which was in reality, not wired according to the sheet.
This General Electric datasheet for the 6BQ5 - 8BQ5 says about pins 1, 6 and 8: "Internal Connection".
6BQ5 - 8BQ5 General Electric
So you have a different datasheet than this one?
6BQ5 - 8BQ5 General Electric
So you have a different datasheet than this one?
It appears to be a question of definition: Some manufacturers indeed say n.c. = i.c., some don't. Precautiously pins named either way must not be connected to anything.
Best regards!
Best regards!
I can't honestly say, which data sheet I looked at, but it showed no connection.
I figured it out...
Hopefully I can prevent someone else from creating a bunch of work for themselves by pointing out that you should verify what you read matches what's in front of your nose.
This specific mistake cost me a lot of time in finding and correcting my error...
I figured it out...
Hopefully I can prevent someone else from creating a bunch of work for themselves by pointing out that you should verify what you read matches what's in front of your nose.
This specific mistake cost me a lot of time in finding and correcting my error...