Galaxy DX2517 Troubleshooting Help

[brandon7861]

Hey, wait a minute... 8.53v-(.65 x 3) = about 6.6v. I think you have D71 in backwards if you are getting 6.6v at the ???anode??? with the transistor removed.

Might explain the symptoms too, because now that I think of it this way, it is acting like the base of Q33 is floating.

 

[Junkyarddog76]

Hey, wait a minute... 8.53v-(.65 x 3) = about 6.6v. I think you have D71 in backwards if you are gettting 6.6v at the anode with no transistor in place.

I just realized that when previously repairing a trace in this area I attached the positive lead of d71 to the collector instead of the base of q33 this whole time! So do you think that may be the problem and I should fix that before reversing d71?

 

[brandon7861]

Be absolutely sure of the pinout. I am not familiar enough with that board to know where the diode is physically placed so I am a little mystified how it could get in the wrong place ~ unless it was one of those things where they ran the diode across the foil side directly to the leg, IDK.

Yes, make sure the anode (non-banded side) of D71 goes to the base of Q33.

 

[Junkyarddog76]

I'm going to reroute the anode of d71 to the base next and get back with you. The reason that happened in the first place is because the trace lifted and I had to add a little jumper lead to repair it. But when I did I must have soldered it to the wrong leg of the transistor on the board. The traces are so narrow and close together on this compared to the am radios I'm used to working on. And the traces seem to be super sensitive to lifting off the board and getting messed up even when I'm aware of this issue and am sure to be careful when soldering and using flux to ensure I'm not overheating the board or applying too much pressure or anything. I am sure of the pinout now after triple checking. I pulled up the schematic symbol from a datasheet and looked at the schematic on cb tricks to figure out that the center leg is the collector and not base. I think the problem was that I had previously repaired the trace and accidentally soldered it to the wrong leg. You telling me that d71 anode connects to the base, not the collector is what made the light bulb go off in my head. I think I need to remove the d71 anode end from the center collector leg and move it over to the right-hand base leg. This whole time the anode of D71 was attached to the collector of Q33 instead of the base..

 

[Junkyarddog76]

The traces are correct, D71 is in the correct direction based off of the symbol on the board and looking at another radio. I also removed the 3 series 4148 diodes I previously added for D71 and replaced them with a factory 2 diode assembly from another galaxy. It is still intermittent keying, one minute it will key up normal the next minute it might not switch to tx at all or will switch but the light wont switch completely to red or flicker. When it does switch, The D71 cathode is 8.62v in rx and 7.42v in tx. The anode is 9.09v in rx and 8.79v in tx.
Q33 Emitter RX- 9.6v TX-9.6v
Q33 Collector RX-0.4v TX-9.49v
Q33 Base RX-9.06v TX-8.79v
IC7 Pins 5 RX-4.98v TX-2.48v
6 RX-3.664v TX-3.634v
7 RX-8.64v TX-2.822v
8 RX-9.27v TX-9.19v
During the time I measured these voltages, it would switch to tx but the light would go from solid green to green with the red light partially on in the middle or would quickly flicker from solid green to solid red. and now right before hitting send on this message the light will switch from solid green to solid red. It's random and intermittent.

 

[brandon7861]

Those numbers look fine. Which of those measurements differ when it acts up?

This sure sounds like a bad connection somewhere, maybe the PTT button itself. I would jam a fingernail clipper handle in the mic jack and see if switching it into tx that way behaves the same.

edit' you could try switching it into TX using a 1k resistor across the op amp. Pin 4 to pin 5. Does it still misbehave switching it at the op amp?

 

[Junkyarddog76]

Those numbers look fine. Which of those measurements differ when it acts up?

This sure sounds like a bad connection somewhere, maybe the PTT button itself. I would jam a fingernail clipper handle in the mic jack and see if switching it into tx that way behaves the same.

edit' you could try switching it into TX using a 1k resistor across the op amp. Pin 4 to pin 5. Does it still misbehave switching it at the op amp?

Well I just found out the owner of the radio wants to get his radio back to take to a shop since he doesn’t want to use his backup radio anymore. It looks like unfortunately I won’t be able to see this one through to find the problem. This website is awesome and I appreciate the time and help from you and anyone else who had input to try to help me. I still got some experience and practice troubleshooting and getting familiar with this board. I’m sure I will be back in the near future hoping to learn some more. You da man and have a good night!!