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Old 7th Jan 2021, 6:45 pm   #88
Boulevardier
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Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,642
Default Re: Grundig TK20 and Truvox R82. Help Required Please.

Quote:
Originally Posted by DMcMahon View Post
With PB head wiring disconnected use a DVM (ideally with a low value resistor in series) to measure the resistance of the head. This could (but in my experience normally does not) partially magnetize the head (if head not open circuit) then possibly later requiring the head to be demagnetized later for best HF reproduction.

David
Actually David, he could just measure the resistance from EF86 pin 9 to chassis (without the extra hassle of disconnecting the head), since the only other paths to chassis should be the 2.2 M ohm grid leak resistor and the grid resistance of the EF86 itself - neither of which will affect the measured head resistance significantly (I'm assuming that it's the Mk 2 schematic we're working from). Doing it this way will also check that switch S1 is doing its job. The DC resistance of the head is specified as 1.1 kilohms.

Mike
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