HD-1410 Keyer

[Michael Waldrop]

Hello all,

     This weekend I attended the Mena, Arkansas hamfest. While there I picked up 2 excellent, but dusty, HD-1410 keyers. The gentleman that sold them to me, at a great price I might add, said one worked fine with sidetone and the other worked "without" sidetone. Since I had one that was not working properly I figured I could swap a few chips and get both working.

     Brought them both home and did a quick check by powering them both up. Well, he was "sorta" right. Actually both had sidetone but only one worked properly. I put the working one aside and concentrated on the bad one. 

     The bad one had continuous sidetone and what appeared was a shorted output keying, at least that's what the initial indicators were. Blown keying transistor(s)? Possibly but lets look further. Pulling the speed knob out caused the keyer's sidetone to stop. Now that odd.

     Anyway, following the manual was part of the solution. The rest was looking "very closely" at the components. As it turned out, C6 and C7 were installed backwards which caused voltage polarity to be reversed that presented a constant keyed output and steady sidetone. Pulling and replacing them with new caps fixed the problem. In addition, I had to replaced U3 as well.

     So, when you can't seem to find the problem and voltage checks do not always measure up properly, look for those "backward" installed component. You just might be pleasantly surprised to find an electrolytic capacitor installed backwards that may just be the fix to your problem. All too often I've run across this in troubleshooting Heathkit equipment. If you run across this, I highly recommend replacing the component with a new one. You might get lucky by reversing the component in the circuit and it works but more often than not, its much wiser to replace the component.

73's,

Mike
W5RKL


 		
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