An archived post indicates that the center pin on the 12v DC input for the MCL 2 Expander is NEGATIVE. Can anyone else confirm this with absolute certainty?
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DC Polarity - MCL 2 Expander
7 replies
Login to view image I can confirm that my MCL2AV also has the center pin negative (even though the service manual diagram for that shows the opposite). If you wan't to be sure and have acces to a multimeter you should make a continuity test between the center pin and a ground point like the shield screw terminalLocation: Denmark
Thank you, Madskp for confirming the center pin has negative polarity. I located the original 12-volt power supply that was used with this system for the last 25+ years. A multimeter reading does indeed show negative polarity (the DC output voltage on the old unit is now indicating 19-volts, hence the need for the new 12v DC power supply).
In this instance I definitely needed a new power supply (see photo of the scorch mark on the MCL Expander board). This area was extremely hot when the old power supply was connected. I'm still trying to work through a problem of no LED lights and sound on the MCL boxes that are now attached a "certified-working" used MCL Expander box that just arrived from the UK (using the correct DC polarity from a new power adapter that was installed this morning).
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