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Digi Easy no ptt problem

codecxbox

Active Member
Jul 28, 2021
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Hi guys! the 2510 ssb is working great, was overgained..thks..
Now got this problem..no PTT from a Easy Digi board..serial usb cable is fine, sends 5 volts to the board everyday..but the PTT is not working..I see 2.3k ohms between PTT and PTT ground when I press Test PTT..the mic TX pin shows 6 volts as well..I was expecting 0 resistance..any help?
 

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Sure makes it sounds like a bad optoisolator. If you can measure DC voltage across pins 1 and 2 of the 4N25 optoisolator, you should have around 2 Volts DC when keyed, zero when receiving.

If you do, the isolator is probably bad. And if you don't, the problem is upstream from it.

73
 
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Sure makes it sounds like a bad optoisolator. If you can measure DC voltage across pins 1 and 2 of the 4N25 optoisolator, you should have around 2 Volts DC when keyed, zero when receiving.

If you do, the isolator is probably bad. And if you don't, the problem is upstream from it.

73
shows 1.1 volts keyed and 0.25 unkeyed..mic plug is not plugged..
can a transistor be driven with the DTR output (5v)?
 
I'd patch it to the amplifier's relay jack and then short across pins 4 and 5 with a screwdriver tip. If the amplifier still won't key, you have a problem with the hookup.

The voltage seen across pins 4 and 5 should be 12 Volts or more on receive. How this voltage changes when you key it would be enlightening.

Maybe.

73
 
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PTT through mic plug goes to a TRC-449..on receive, theres 11 volts between pin 4 and 5 from the opto..when I key, voltage drops to 7.5..but I would expect 0 volts, since the opto is supposed to short the TX mic pin to the mic ground..I can short 4 and 5 with a wire and get PTT, no problem..its something about the opto thats not providing complete passthrough to the mic ground?
 
I'd patch it to the amplifier's relay jack and then short across pins 4 and 5 with a screwdriver tip. If the amplifier still won't key, you have a problem with the hookup.

The voltage seen across pins 4 and 5 should be 12 Volts or more on receive. How this voltage changes when you key it would be enlightening.

Maybe.

73
Its seems the opto cant drive the TRC relay..
I rigged the Easy Digi to a HTX-10 and it PTTs just fine..but I cant use this HTX because the receive audio goes to the mic switch to common ground and the Digi does not provide this kind of loop..I will try with a HR-2600, as it doesnt pass audio through the mic..
However, the problem remains about PTTing the TRC relay..I have found the attached circuit..but will the DTS voltage provide enough current to light up the transistor base?
 

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Do you happen to have a spare generic NPN transistor on hand, like a 2N2222, TIP31, 2N3904, 2N4401 or the like?

The idea would be to connect the optoisolator "PTT" side to both the center pin of the amplifier's socket and to the collector of your added transistor. The "PTT Ground" is unhooked from the shield side of the amplifier cable, and now goes to the base of your new transistor. The emitter of the new transistor now goes to the shield of the amplifier cable.

If the opto's max output current is less than what it takes to key that relay, this 'buffer' transistor should take up the slack.

73
 
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Yay! I managed to TX digital with the 2510!
I had to use a 3.9k ohm resistor between the mic TX pin and the Easy Digi, cuz without it the Digi would not release PTT..I tried your suggestion with the NPN to the Radio Shack but it didnt work..Im guessing that the base needs ground, but where to get it?
 

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