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Old 26th September 2005, 09:32 PM   #1
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Question Perplexed by 5AR4 Tube Socket? Picture Included

Guys, can you help me out? I unearthed a terribly dusty, but nice Pilot EL84 Push Pull Integrated Amplifier. It's missing the rectifier tube and as you can see in the picture, the socket is clearly marked GZ34/5AR4.

I have a 5AR4 tube but it does not fit in the tube socket. The key is too large in the center of the tube to fit. Did they make different socket bases for this tube, or am I completely missing something here?


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Old 26th September 2005, 09:38 PM   #2
Yvesm is offline Yvesm  France
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Remove the base of the old broken tube wich is still in the socket !
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Old 26th September 2005, 10:08 PM   #3
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Default 5AR4

That is not the base of an old tube, that is an octal plug. However the result is the same, just pull it out and then you can plug the 5AR4 in the socket.
By the way looking at the condition of the amp, I would bring the voltage up with a variac and check B+ voltage as you bring the variac up very slowly.
No variac, then wire a lamp in series with the line cord to the amp and start with a 15 w bulb and work up to a 100w and see if everything is ok before you hook the amp directly to ac while monitoring B+ voltage.
Hope this helps
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Old 26th September 2005, 10:41 PM   #4
SY is offline SY  United States
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It is possible that someone soldered in some silicon diodes, then stuck the plug on there to prevent a tube from being inserted. Take a look underneath before plugging in a new GZ34.
“Instead of Rational Law, objective truths perceptible to any who will undergo the necessary intellectual discipline, Knowledge will degenerate into a riot of subjective visions. . ." - Auden
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Old 26th September 2005, 11:04 PM   #5
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Damn, you guys are good!!! Many thanks for the excellent posts.

SY, you are a very smart guy. I had popped the bottom cover and did not even notice the tiny diodes soldered across the rectifier socket.

Okay, time to dig out the variac and hope this girl does not like to smoke!
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