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 Post subject: Question about SX-96 Audio Amp Section
PostPosted: Sep Tue 28, 2021 7:13 pm 
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Joined: Sep Thu 20, 2012 3:42 pm
Posts: 486
Location: Salem, OR
I recently acquired a pretty nice Halli SX-96 that works quite well. While inspecting the condition of this rig, I noticed that the audio amp tube, 6SC7, has been replaced with a 6SL7. I see where the tubes are very similar, but not exactly the same. It is difficult to tell if this was a factory change or an aftermarket modification, as the soldering job looks factory original for the most part.

My question is: Is the 6SL7 a later change to the SX-96, and if not can anyone comment on why someone would change this tube from the 6SC7 to the 6SL7?

Tnx,
Marc-k7wxk


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 Post subject: Re: Question about SX-96 Audio Amp Section
PostPosted: Sep Tue 28, 2021 8:03 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 8003
Marc,

Someone probably had one on hand and didn't have the original tube so they changed them out. Performance wise, it shouldn't make any difference but it would have required rewiring.

I doubt if it was a Hallicrafters running production change or otherwise the SX-100 would have used a 6SL7 tube. It is possible there was an odd shortage and Hallicrafters briefly used but I think it is far more likely it was done by the owner.

If you decide to leave it, mark the chassis to indicate the tube change since the pinout is different from the original.

Rodger WQ9E


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 Post subject: Re: Question about SX-96 Audio Amp Section
PostPosted: Sep Tue 28, 2021 8:08 pm 
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Joined: Sep Thu 20, 2012 3:42 pm
Posts: 486
Location: Salem, OR
Rodger,
My thoughts exactly, but wanted a second opinion. Both twin triodes, but one has only one cathode I believe. I am considering re-wiring back to original. Shouldn't require too much work. Then again, it works fine as is. Maybe just mark and enjoy.

Cheers,
Marc


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 Post subject: Re: Question about SX-96 Audio Amp Section
PostPosted: Sep Tue 28, 2021 9:34 pm 
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Joined: Jun Sat 15, 2019 7:43 pm
Posts: 1469
Both tubes are about the same performance wise but the 6SL7 is less microphonic.

DM


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 Post subject: Re: Question about SX-96 Audio Amp Section
PostPosted: Sep Wed 29, 2021 2:21 am 
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Joined: Sep Thu 20, 2012 3:42 pm
Posts: 486
Location: Salem, OR
Perhaps a good enough reason to leave as is.

Marc


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