cantankerous depth sounder connection

[stevepick]

Re routing the connection from my (fairly old) navman depth sounder transponder to instrument, I had to cut the phono jack connector. Having resoldered a new phono jack( the original was a molded on connector- I thought a new one would preserve the co-ax type ground screen better) on the wire the unit did not read depth when connected. Eventually removing the new jack and "fiddling" a connection by hand got an intermittent correct reading for a few seconds. Any ideas why this connection is so flukey? Is there a "special" impedance phono jack that should be used? Or is it just my bad soldering?( no obvious shorts/opens when tested) I note the transponder impedance is a around 600 ohms which is nothing like the usual load driven by phono connectors?

 

[captainslarty]

Hi Stephen,
sounds like a faulty soldering job, or more likely, the end of the coax you used is broken inside a few inches back.. chop another foot off the coax and try it again, that kind of shortening wont make any difference.. no problems with phono plugs and 600 ohms is a common audio impedence..

Joe

 

[stevepick]

Thanks Joe,
Hadn't considered the possibility of the coax being broken . Will cut back and try again with soldering iron .

Steve

 

[captainslarty]

Best of luck Stephen, it is quite common where the original plug was due to the bend where it fits the instrument..

Hope you get sorted !.
Joe

 

[leadersail]

If you found the soldering tricky and heated several times you may have melted the inner plastic isolating sheaf causing the inner core wire to touch the braided outer .