I would like to know the reason that I sometimes see that all un-used pins (terminals?)on a tube socket under the chassis are grounded. I have a EICO AF Sig Gen 377 that had been re-worked by someone and all the pins not used were grounded. I have not been able to get a copy of the construction manual so I don't know if that is the way EICO planned it. I do know that if the metal tubes are used the #1 pin should be ground. The reason for that grounding is to keep the metal at ground potential so that it does not act as an element in the tube (I had originally supposed that there was a glass tube inside and clad in metal, not true, the tube is the can with a glass base sealing the bottom). I basically rebuilt this unit and did not ground any terminals unless the schematic called for it. Also,I broke two pins un-soldering, the prior assembler hat attached all leads with 18o degree wraps around the pins and it was tough getting them off. I only repace one that had broken off at a point where it would still lock in place, the other I'm debatining whether to replace it from another socket or not. All comments and idea gladly accepted. PL

Grounding unused pins will keep noise and capacity to signal pins at a minimum. A floating pin will have some capacity to surrounding wires and pins.

This is most important at very high frequencies. Even if grounding unused pins isn't called out it's usually a good idea.

Norm

: I would like to know the reason that I sometimes see that all un-used pins (terminals?)on a tube socket under the chassis are grounded. I have a EICO AF Sig Gen 377 that had been re-worked by someone and all the pins not used were grounded. I have not been able to get a copy of the construction manual so I don't know if that is the way EICO planned it. I do know that if the metal tubes are used the #1 pin should be ground. The reason for that grounding is to keep the metal at ground potential so that it does not act as an element in the tube (I had originally supposed that there was a glass tube inside and clad in metal, not true, the tube is the can with a glass base sealing the bottom). I basically rebuilt this unit and did not ground any terminals unless the schematic called for it. Also,I broke two pins un-soldering, the prior assembler hat attached all leads with 18o degree wraps around the pins and it was tough getting them off. I only repace one that had broken off at a point where it would still lock in place, the other I'm debatining whether to replace it from another socket or not. All comments and idea gladly accepted. PL

This idea is especially useful for "early-stage" preamp and sensitive low-current stages of the circuit.
One caveat, I must mention is that from the older "G" versions to the "GT" versions of the tubes, some pins are not grounded the same way, and you must check the tube manual to see the real deal, to not do so would be almost certain to create a short or some severe problem.

:Grounding unused pins will keep noise and capacity to signal pins at a minimum. A floating pin will have some capacity to surrounding wires and pins.
:
:This is most important at very high frequencies. Even if grounding unused pins isn't called out it's usually a good idea.
:
:Norm
:
:: I would like to know the reason that I sometimes see that all un-used pins (terminals?)on a tube socket under the chassis are grounded. I have a EICO AF Sig Gen 377 that had been re-worked by someone and all the pins not used were grounded. I have not been able to get a copy of the construction manual so I don't know if that is the way EICO planned it. I do know that if the metal tubes are used the #1 pin should be ground. The reason for that grounding is to keep the metal at ground potential so that it does not act as an element in the tube (I had originally supposed that there was a glass tube inside and clad in metal, not true, the tube is the can with a glass base sealing the bottom). I basically rebuilt this unit and did not ground any terminals unless the schematic called for it. Also,I broke two pins un-soldering, the prior assembler hat attached all leads with 18o degree wraps around the pins and it was tough getting them off. I only repace one that had broken off at a point where it would still lock in place, the other I'm debatining whether to replace it from another socket or not. All comments and idea gladly accepted. PL

Thank you for the responses. I still have guestions as to how the pin(s) which are isolated from the chassis and the tube can add capacitance to the circuit. What I am trying to say is that basically they are small pieces of metal connected to nothing. I still have the unit on the work bench waiting for parts so I have some time to decide to ground every un-used pin or not. It seems to be unnecessary clutter and some sockets would look like crowns with all the ground wire circling them, not that appearance is paramount. PL

:This idea is especially useful for "early-stage" preamp and sensitive low-current stages of the circuit.
:One caveat, I must mention is that from the older "G" versions to the "GT" versions of the tubes, some pins are not grounded the same way, and you must check the tube manual to see the real deal, to not do so would be almost certain to create a short or some severe problem.
:
:
::Grounding unused pins will keep noise and capacity to signal pins at a minimum. A floating pin will have some capacity to surrounding wires and pins.
::
::This is most important at very high frequencies. Even if grounding unused pins isn't called out it's usually a good idea.
::
::Norm
::
::: I would like to know the reason that I sometimes see that all un-used pins (terminals?)on a tube socket under the chassis are grounded. I have a EICO AF Sig Gen 377 that had been re-worked by someone and all the pins not used were grounded. I have not been able to get a copy of the construction manual so I don't know if that is the way EICO planned it. I do know that if the metal tubes are used the #1 pin should be ground. The reason for that grounding is to keep the metal at ground potential so that it does not act as an element in the tube (I had originally supposed that there was a glass tube inside and clad in metal, not true, the tube is the can with a glass base sealing the bottom). I basically rebuilt this unit and did not ground any terminals unless the schematic called for it. Also,I broke two pins un-soldering, the prior assembler hat attached all leads with 18o degree wraps around the pins and it was tough getting them off. I only repace one that had broken off at a point where it would still lock in place, the other I'm debatining whether to replace it from another socket or not. All comments and idea gladly accepted. PL

If you are using metal tubes look at the pin out and ground the one that is connected to the tube's outer casing. If you don't ground the tube shield it will either radiate RF, be suseptable to interference, or pick up hum. Esentially it adds to the stability of the radio. You should not have to worry about the other unused pins. If you are dealing with very high frequencies then the unused pins might pose a problem but not in your typical radio. Just a few cents from one with very little change.

MRO

I would think that in either case of grounded or ungrounded, a proper alignment would negate the effects of these very small capacitors. If large enough to become an appreciable part of circuit elements, the effects are greater, but we're not talking high VHF/UHF here. In those 2 cases, special socketing arrangements are of the utmost importance, and often the strays are designed into the hardware.

marv

: I would like to know the reason that I sometimes see that all un-used pins (terminals?)on a tube socket under the chassis are grounded. I have a EICO AF Sig Gen 377 that had been re-worked by someone and all the pins not used were grounded. I have not been able to get a copy of the construction manual so I don't know if that is the way EICO planned it. I do know that if the metal tubes are used the #1 pin should be ground. The reason for that grounding is to keep the metal at ground potential so that it does not act as an element in the tube (I had originally supposed that there was a glass tube inside and clad in metal, not true, the tube is the can with a glass base sealing the bottom). I basically rebuilt this unit and did not ground any terminals unless the schematic called for it. Also,I broke two pins un-soldering, the prior assembler hat attached all leads with 18o degree wraps around the pins and it was tough getting them off. I only repace one that had broken off at a point where it would still lock in place, the other I'm debatining whether to replace it from another socket or not. All comments and idea gladly accepted. PL