Have a general here the tx/rx light is yellow will key up and transmit fine but will not switch back to rx Changed the 2 transistors up by the mic jack for switching already and a couple diodes in that area as well an idea where else to look at??
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General lee half in half out
- Thread starter Harley3315
- Start date
Sure sounds like D77.
Unsolder one end of D77 and see if the light goes back to green, and receive function comes back.
This diode can't be replaced with the generic 1N4148 diode. It has to have more than the 0.6-Volt forward voltage drop of a generic silicon diode. We use three of the 1N4148 soldered in series to replace D77 when the mike socket comes loose, spins around and shorts D77 to ground. Insulating sleeve over this contraption protects it from a repeat performance.
And if you still have this problem with one end of D77 unhooked, I'll be puzzled.
73
Unsolder one end of D77 and see if the light goes back to green, and receive function comes back.
This diode can't be replaced with the generic 1N4148 diode. It has to have more than the 0.6-Volt forward voltage drop of a generic silicon diode. We use three of the 1N4148 soldered in series to replace D77 when the mike socket comes loose, spins around and shorts D77 to ground. Insulating sleeve over this contraption protects it from a repeat performance.
And if you still have this problem with one end of D77 unhooked, I'll be puzzled.
73
Mic socket is on the front on this newer General Lee bubba and I replace d77 already with one out a Galaxy black diode with yellow stripe right?
I know it may be teaching you to suck eggs but have you tried it with the mike disconnected in case it's a problem with the mike?
Have you remove the microphone plug from the faceplate and checked the pcb it's soldered to? I've seen them short out from a cracked disc capacitor to the metal front plate, shorted wire etc.
Seeing this is a General Lee my guess would you have a bad solder joint somewhere in the section with wax in it.
When D77 or any of the RX TX switches go bad, best to replace all of them with known good - from good sources.
Been seeing several Galaxy radios with Nomads reference to the Diodes not having the proper voltage drop to make the logic switching the transistors play in - work correctly - the replacement of the transistors also ensures that the original one's whether leaky or bad - were also replaced to increase the reliability.
Been seeing several Galaxy radios with Nomads reference to the Diodes not having the proper voltage drop to make the logic switching the transistors play in - work correctly - the replacement of the transistors also ensures that the original one's whether leaky or bad - were also replaced to increase the reliability.
Ok, that simply means that D77 is not the culprit to hold RX on while in TX.
Re-install the D77 - and hope like h*ll the thing is not blown shorted or the Diode it was, is no longer a "Diode".
So, we go further - the RX side uses two transistors to "flip flop" the switch, so it can "turn on" the RX side.
The Diode it uses - is a Zener that is triggered by the rise in the voltage from the "power good" side of the 4558 chip. It's this trigger that turns on Q37 an NPN (945) to toggle Q36 a PNP (934) to on.
If one of these RX transistors is shot - like blown shorted, it can't revert the toggle to OFF state so it stays on and so you see yellow - the two will have to be removed and tested independently out of circuit to verify.
So go back to the post of the Voltage chart, watch the voltages see if they match what it should do Yellow means RX and TX are holding up - but you say it TX's fine - but RX is nothing.
To me this needs to have the voltages checked then get back with us to help you decipher the results.
Here's more on the 4558 chip
This could also be something as simple as a shorted power leads trace due to a solder blob or bad solder jumper, not cleaned up well.
Re-install the D77 - and hope like h*ll the thing is not blown shorted or the Diode it was, is no longer a "Diode".
So, we go further - the RX side uses two transistors to "flip flop" the switch, so it can "turn on" the RX side.
The Diode it uses - is a Zener that is triggered by the rise in the voltage from the "power good" side of the 4558 chip. It's this trigger that turns on Q37 an NPN (945) to toggle Q36 a PNP (934) to on.
If one of these RX transistors is shot - like blown shorted, it can't revert the toggle to OFF state so it stays on and so you see yellow - the two will have to be removed and tested independently out of circuit to verify.
So go back to the post of the Voltage chart, watch the voltages see if they match what it should do Yellow means RX and TX are holding up - but you say it TX's fine - but RX is nothing.
To me this needs to have the voltages checked then get back with us to help you decipher the results.
Here's more on the 4558 chip
Pretty sure 36 and 38 are those 1280's? sound right like they used on the old galaxy radios for switching
The question I have is, how old are those parts?
IF they are newer than the board - we may have a bigger problem.
You've got a voltage chart - check them using that chart.
IF they are newer than the board - we may have a bigger problem.
You've got a voltage chart - check them using that chart.