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Help with Heathkit DX-40 PTT

T

T23

Active Member
Apr 17, 2010
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I recently purchased a heathkit dx-40 that works great. But some mods have been done. It transmits fine. Its supposecto have a ptt mod done, it has a four pin mic lug. Pin 1 is the audio and pin 4 is one of the two grounds from what I have found out. When I put it on "phone" and it is just keyed all the time, even though I dont have anything pluged into the mic lug. Shouldent it not transmit in the "phone" position till the relay has been tripped? It has an internal relay for keying thats part of the mod.

Any ideas? Maby I am missing something....

T23
 

The DX-40 has a function switch that normally would sit on "standby", I believe, and the operator would turn it to "phone" in order to transmit. For PTT, I'd guess the switch would have to be set to "phone" and the switched conductor would have the PTT switch in series, normally open.

Shouldn't be terribly involved in troubleshooting - IF you have the schematics and manual.
 
Well thats where I have the switch. In the phone position. But it just keys the rig as it would normally without ptt? Also someone has added a switch to cut on and off the plate voltage to the final, have no idea what that would be for. I have tried probing the lug pins for the mic connecter, wont key...
 
Do you have a key plugged in? If so pull it out and check again. I modded my DX-60 for PTT after the function blew up in a spectacular flash of light, smoke, and molten metal. I added a separate box with a CW/PTT function switch that controlled a relay.
 
The mic lug in the front is where the ptt wires are connected. I even saw "ptt" scribbled next to it on the inside when I had it open a few months ago. Or do you mean that the key would break the ground connection on the key jack?
 
There is no key in the cw jack. What I was reffering to was when the key is not pluged in. The middle tab at the jack is grounded when it is pluged in it lifts this tab so it can be keyed.


T23
 
I figured it out! I was right. Al I needed to do is have a plug in the cw key jack to open the ciruit. After that I probed the ptt pins again and got it to key and the relay to ker-chunk.

T23
 
i figured it had to do with the key jack but just not sure if it needed a key plugged in or not to work PTT. My suggestion was going to be to plug one if it it didn't have one or unplug it if it did have one plugged in. I couldn't remember which way it was supposed to be. I blame it on the night shifts. Oh well I worked my last one last night until January 8 so my mind should be a bit sharper now..............................after I get some sleep. :laugh: Been 28 hours and counting since I got up. :blink:
 

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