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QMX+ - Should there be resistance between T501 primary and secondary windings?

 

Greetings all,

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I am currently assembling a Rev 3 QMX+ and have a question regarding T501. When it comes to continuity between an A point and a B point, my DMM (a Fluke 12) does not beep, though it does display '2.006' on the screen. If I switch the meter to measure impedance, measuring from any A point to ground or a B point results in the meter showing a resistance of 9.77k ohms. Is this to be expected? Note: when I was separating out the winding leads when winding T501, there was NO short-circuiting between the primary and the secondary.

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I appreciate the help!

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Charles Johnson

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PS While I don't think that it would make any difference, for the record, L502 has already been installed, but the BS170s have not (I'm going to socket them, which means that it's easier (at least for me) to install T501 first).
 

Hello Charles.
Upon rereading the instructions, there is no mention of testing between A and B. I believe the continuity tests should be run separately (from A to A and from A to ground then from B to ground). Do not mix A and B.
--
Marc-Andre Gendron
VE2QVL
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Hans changed the wording in the QMX+ manual. For the QMX, the manual says "there should be NO connection between A and B." whereas the QMX+ manual says "Check that there is NO DC continuity from the points marked A, and ground".

Charles - I would suggest ignoring any impedance reading and measure at DC...

72 de Russ, va3rr
 

On Wed, May 28, 2025 at 12:55 PM, Charles Johnson wrote:
When it comes to continuity between an A point and a B point, my DMM (a Fluke 12) does not beep, though it does display '2.006' on the screen. If I switch the meter to measure impedance, measuring from any A point to ground or a B point results in the meter showing a resistance of 9.77k ohms.
I just re-measured this on my fully assembled QMX+, which happens to be open and easy to measure.
In resistance mode, my digital multimeter measures about 9.8Kohms between A and B after a few seconds of settling time.? So you are probably OK.
Stan

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