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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 23rd Jun 2022, 9:07 pm   #1
DMcMahon
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Default What is the device below the co-ax aerial type socket

Detailed in my TK 8 R2R Thread post 2.

https://www.vintage-radio.net/forum/...d.php?t=192169

David
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Old 23rd Jun 2022, 9:13 pm   #2
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Default Re: What is the device below the co-ax aerial type socket

Looks like a slide switch without the "lever".

Perhaps factory set?

Cheers

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Old 23rd Jun 2022, 10:13 pm   #3
Dave Moll
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Default Re: What is the device below the co-ax aerial type socket

Or is it simply a label? Is the cover openable?
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Old 23rd Jun 2022, 10:17 pm   #4
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Default Re: What is the device below the co-ax aerial type socket

Do you mean the white bit ? it does not appear to be a label and it feels solid/not removable ?

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Old 23rd Jun 2022, 10:19 pm   #5
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Default Re: What is the device below the co-ax aerial type socket

The back sure looks like a slide switch.

Have you tried to slide it using a sharp tool?

like a small jewellers screwdriver or a skewer?

Cheers

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Old 23rd Jun 2022, 10:25 pm   #6
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Default Re: What is the device below the co-ax aerial type socket

Is the "antenna " socket another input?. It could be a switch thats broken and the switch could change the input from microphone to line ?. Maybe ?.

Joe
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Old 23rd Jun 2022, 10:44 pm   #7
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Default Re: What is the device below the co-ax aerial type socket

No idea at this stage Joe, unless I have missed it I cannot see the switch on the schematics I have looked at. Not mentioned in the User or Service manuals either.

Because the rectangular cut-out in the amplifier cover is roughly cut it looks like the socket + switch have been added post original build of the recorder.

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Old 23rd Jun 2022, 10:45 pm   #8
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Default Re: What is the device below the co-ax aerial type socket

Quote:
Originally Posted by Cobaltblue View Post
The back sure looks like a slide switch.

Have you tried to slide it using a sharp tool?

like a small jewellers screwdriver or a skewer?

Cheers

Mike T
Not yet but I will.

David
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Old 24th Jun 2022, 6:48 am   #9
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Default Re: What is the device below the co-ax aerial type socket

Looks like an input select SW or tape out? Maybe it's one of those SW's that needs a screwdriver blade to shift the SW like on a PC ATX PSU that selects 110/230v? That or a broken SW and someones shoved some card over the damage?
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Old 24th Jun 2022, 11:30 am   #10
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Default Re: What is the device below the co-ax aerial type socket

Found that by poking firmly the white plastic piece with a small screwdriver blade could get it to move left and right and it felt like it was actuating the switch.

Could not see or get to all the switch contacts as partially covered by large pre-set (R42 EM81 Magic Eye sensitivity adjustment). Tried to remove R42 by unsoldering but not keen to come off terminal strip, so had to remove the Paxolin board that socket & switch are fitted to.

By measurement the white piece when moved does change the 2 way/2 pole slide switch setting to the other set of contacts. The socket connections go to one side of the switch and two 2 core screened cables go to the common contacts of the switch and the other side of the switch. So looks like the switch is switching 2 signal lines either to the socket or back into the amplifier circuitry. The outer connection of the socket is not grounded.

Trying to remove the pre-set had to lift one end of C23 (0.25uF) which measured bad, so will renew, there is another Wima capacitor hiding under C23 so will replace that before replacing C23.

Trying to trace where the two 2 core screened cables go to but it is very difficult.

David
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Old 24th Jun 2022, 6:49 pm   #11
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Default Re: What is the device below the co-ax aerial type socket

Partially have traced where the two 2 core screened cables connect to.

The cable (black outer insulation) to the slide switch common terminals ends up disappearing down a hole in the top metal plate to which the heads and other bits fit onto.

It is impossible (without doing a biggish strip down) to see the wires that go from and to the Play/Record head, but pretty sure the cable must connect into the Play/Record head wiring.

The cable (grey outer insulation) that connects to one switched side of the slide switch ends up at a switch wafer at the main Selector switch, not yet worked out which wafer # (there are 4) and which wafer contacts.

David
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