Re: {Collins} 75S-1 Temperature Question - Thanks

----- Original Message ----- From: "Bill Turini" <ka4gav@xxxxxxxxxxxxx>
To: "Collins Mailing List" <collins@xxxxxxxxxxxxx>
Sent: Monday, November 04, 2013 7:38 AM
Subject: Re: {Collins} 75S-1 Temperature Question - Thanks

Thanks to all who replied. At least there doesn't appear to be anything out of the ordinary with the tubes.

I plan on installing a reduced voltage line in the shack to run my Collins equipment - a Winter project. The current line voltage is 122.5v.

For those who recommended putting the radio back as delivered, ALL of the tube sockets have bases for the IERC shields, and the connections to the sockets look original, or so much so that you can't tell the difference, and they have red markings! But I have removed the shield from the audio out put tube and will check the temperature once it's warmed up to see if there is a marked difference.

I work from home and my office is a bit on the cool side in Winter, so I try to keep a tube radio running to take the chill off. The KWM2-A does the job a bit better than anything else, but now that I have the 32S-1, it and the 75S-1 will take it's place while the KWM2-A is on the bench for alignment and repair.


AFAIK, the IERC shields will fit any standard tube sockets made for shields. Perhaps genuine IERC sockets have some difference. I have IERC shields in several pieces of equipment here, all fitted on standard sockets. I have seen an article describing temperature measurements using various shields but no longer remember where I found it. The short answer is that IERC shields _did_ lower the envelope temperature somewhat over bare tubes while standard shields raised it. FWIW, even the octal based tubes commonly used for audio, such as the 6V6GT run very hot compared to other types. Keep in mind that they have fairly powerful filaments and are _power_ tubes running Class-A with pretty much constant high plate dissipation.

Richard Knoppow
Los Angeles

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