I understand what shielding is for (in most electronics) but on tubes, does this serve the same purpose?? Shielding against RFI, and other interference?? Also is shielding (metal covers) on some tubes used as a heat sink?? I have a radio that looks like it's missing a shield and it gets VERY hot (output tube). It's a 6F6G on a Philco 37-84.

Joe Ferris

6F6 is an audio power output tube. It will get hot in normal operation and usually wouldn't be shielded. Shields are usually used to prevent stray pick-up or RFI in RF, IF, and audio pre-amp stages. The shield is not a heatsink. In fact it probably makes tubes run a little hotter as they don't radiate the heat quite as well. A shielded tube usually has some kind of clip at the socket so that the shield can be grounded to the chassis.

Rich
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:I understand what shielding is for (in most electronics) but on tubes, does this serve the same purpose?? Shielding against RFI, and other interference?? Also is shielding (metal covers) on some tubes used as a heat sink?? I have a radio that looks like it's missing a shield and it gets VERY hot (output tube). It's a 6F6G on a Philco 37-84.
:
:Joe Ferris

Rich,
Thanks for the input. The tube socket DOES have some fingers which is why I thought it was missing a shield but as long as it's not for heat sinking, I'm ok. Radio works GREAT after recapping and fine tuning. Was more of a curiosity question.
Joe

:6F6 is an audio power output tube. It will get hot in normal operation and usually wouldn't be shielded. Shields are usually used to prevent stray pick-up or RFI in RF, IF, and audio pre-amp stages. The shield is not a heatsink. In fact it probably makes tubes run a little hotter as they don't radiate the heat quite as well. A shielded tube usually has some kind of clip at the socket so that the shield can be grounded to the chassis.
:
:Rich
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Hi Joe
Would your radio be a Canadian made Rogers or some variant? I have seen some of them use a spray shield tube in the output stage and that would explain the fingers.
Greg

:Rich,
:Thanks for the input. The tube socket DOES have some fingers which is why I thought it was missing a shield but as long as it's not for heat sinking, I'm ok. Radio works GREAT after recapping and fine tuning. Was more of a curiosity question.
:Joe
:
::6F6 is an audio power output tube. It will get hot in normal operation and usually wouldn't be shielded. Shields are usually used to prevent stray pick-up or RFI in RF, IF, and audio pre-amp stages. The shield is not a heatsink. In fact it probably makes tubes run a little hotter as they don't radiate the heat quite as well. A shielded tube usually has some kind of clip at the socket so that the shield can be grounded to the chassis.
::
::Rich
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:

Greg, It's Philco 37-84. I saw one pic recently online of the back of this unit and it had a tube shield on the output. I wasn't sure WHY there was a shield on the output which is what sparked my concern about the temperature of the tube when operating. It does play very well and of course, can't find the original shield anywhere. Haven't seen a close-up pic of the dial online but mine is missing the dial needle and can't seem to find this anywhere either. Also, when re-capping the unit, noticed that the volume control in the unit does not match the print for the unit. Hard to find this part also. Sorry, I'm a Virgo and seek perfection. Put this unit aside for now and on to the next victim on my shelf.
Joe
:Hi Joe
: Would your radio be a Canadian made Rogers or some variant? I have seen some of them use a spray shield tube in the output stage and that would explain the fingers.
:Greg
:
:
::Rich,
::Thanks for the input. The tube socket DOES have some fingers which is why I thought it was missing a shield but as long as it's not for heat sinking, I'm ok. Radio works GREAT after recapping and fine tuning. Was more of a curiosity question.
::Joe
::
:::6F6 is an audio power output tube. It will get hot in normal operation and usually wouldn't be shielded. Shields are usually used to prevent stray pick-up or RFI in RF, IF, and audio pre-amp stages. The shield is not a heatsink. In fact it probably makes tubes run a little hotter as they don't radiate the heat quite as well. A shielded tube usually has some kind of clip at the socket so that the shield can be grounded to the chassis.
:::
:::Rich
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