Dead Galaxy DX2517

[liquidh8]

ROBB, yes. I was seeing 13+ vdc in, and 2.5 out. But last night is started sorta working.

Here is a recap. weirdest thing too.
It was a tech special. It would power up and work in PA mode, but I got no receive, no TX, no lights nothing in any other mode. I changed the Regulators, RX/TX transistors in the front, checked the finals and driver. The power supply is good. And even after all that, I wasn’t getting the 8vdc out of the regulator, ever after putting in new, and known good parts.

Fast forward to last night. While talked to a friend on the air, I plug it in, turn it on, still nothing in SSB/CW/AM. I turn the mode swith to PA, get lights, turn it back to AM, and I get the freq display, channel display, and I am receiving! So, I turn it to side band, I can kinda hear myself while transmitting in another radio right next to it, but the volume is all the way up and I have to have my ear right next to the speaker. Tried an external speaker and it is the same, low receive audio only in SSB. The S-meter really moves though.

So, I put a mic on it, go to transmit in SSB, I get a dead key, 10w+. USB and LSB. AM it seems to have worked.

To sum it up.
• To get the radio to power on, I have to turn on the power switch, switch to PA, THEN to another mode.
• Receives fine on AM
• Hardly any receive audio on SSB
• Dead key on SSB
I didn’t look any further last night.

This thing has a ghost, lol.

 

[AudioShockwav]

I think that feature is there for commercial use - think warehouse with a PA system that also uses cb.

As most base radios are a mobile radio stuffed in a large cabinet with a power supply, large meters and a headphone jack they simply added the feature that was already there.
Here is a great example:
This happens to be a Ranger base radio, but it is a great example.

If you look closely at the picture, you can see the intact mobile chassis mounted inside the base station enclosure, look for the hole the antenna connector, the hole for the socket that the power cord plugs into, the cutouts for the external speaker/pa jacks. There are also cutouts for a mic socket on both the left and right side of the radio. The power supply is mounted to the right side of the chassis that runs the radio.
The Brass inserts that the mounting screws for a mobile bracket are even there.
99% of the base stations that are sold are a mobile radio or mobile radio board installed into a base cabinet.
Another example is the Yaesu FT-857 and the FT 897. Both of these radios are the same inside, they use the same board, PA sections etc it is just that the 897 is in a bigger chassis and has more heatsink.
Very few base radios are built from the ground up.

73
Jeff

 

[Robb]

Sounds like you might have a bad wire connection or a cold solder joint if it is intermittantly working. Or even possibly a bad mode switch.

 

[liquidh8]

I had thought about the mode switch. Weird. Turn it on, no lights, sound. Rotate the mode switch to PA, PA works and I get lights, then turn it to AM, it works, ssb, the lights are on but rx and tx are messed up. I may poke around it a bit more this evening.

I was using the freeze spray, heat gun, wet finger, etc looking for solder joints. I didn't turn anything up.

 

[ExitThirteen]

I second the bad mode switch. I had one come across my bench with similar symptoms, and that's what it ended up being... I cleaned/replaced the mode switch and everything pretty much fired back up.

If you're getting 10W+ deadkey in SSB TX, that usually means that either the pass regulator transistor (2SB754) has gone fault, or the AN612 balanced modulator IC has gone fault.

What I'd do, is take and de-solder the mode switch, and drop the switch in a small cup of alcohol, completely submerge the switch. Let it sit a couple hours, then let it air dry, click it a few times, and re-install. That fixes the problems 99% of the time. I do that all the time with mode switches and it works great. Do this before you go probing around the pass regulator and the modulator IC.


~Cheers~

 

[liquidh8]

I thirded the mode switch, lol. Took it of the chassis, took it apart. (these are modular, two little rotary switches riveted together) Took it apart, cleaned it all up, same symptoms. The, it went back to what is was doing before. No 8 vdc feeding anything.

the ps is working, i am getting the 13.8-14.1 volts, the led is lit in PA, but half as bright. I have already changed the regulators, twice. One with new ones, and again with working ones pulled strait from another radio.

It appears something is keeping the 8 v regulator circuit from doing its job, ughh.

 

[ExitThirteen]

Is your 2517 the bipolar transistor version, or the mosfet version? Let me know and I'll look up the schematics and see if I can pinpoint something.


~Cheers~

 

[ExitThirteen]

Check Q30 and Q33, make sure those haven't gone fault, they should be 2SA1282. If one of those have gone short, it can potentially cause low voltage after them in the circuit.

When you checked for +8V, did you measure it right at Q37? You should get +13.8V on pin 1, and +8V at pin 3. Lift pin 3 of the voltage regulator off the board, and check for +8V without the pin connected to anything, and let us know how you get on.


~Cheers~

 

[liquidh8]

Ok, I did replace Q30 and Q33, snagged them from a parts HML33. But for hahas, I can sway them out again.

Also, I was checking for 8vdc right at Q37, but again am getting 2.5 vdc or so. I am getting 13.8 right at it also. But I can remember the pins, lol. I will go home tonight and give it a whirl.

I guess if I get 8vdc on pin 3 with the leg lifted, I have a shorted part after that. I know the regulator was good, I swapped it twice with a new one and a good used.

I'll keep the thread posted.

 

[liquidh8]

Ok. Came home, turned it on still nothing. I do the wet finder test again, and while the radio is in PA mode, I run my wet finger right by the regulator Q37, where d71 or d72 is, towards the back, the rx/tx LED comes to life, and I can switch the modes. So I am back to where I was a few posts ago.

I have to lift the 8vdc leg of Q37, and turn on the radio and see if it puts out 8vdc right away. As it sits now, it only goes to 2.5vdc, till I run my wet finder over that spot.

Oh, and I pulled a wire off the mode switch and now have no channel LEDS or mode LEDs, ughh.

 

[liquidh8]

Well, after fixing the mode switch wires, I changed d72, A MA27W-A diode. I used 2 1n4148's in series just to try. I also changed Q35, a 2sc945 just because. Plugged it in and voila, powered up. After a minute I saw some smoke. Quick shut her down. R213 is all black now. A 47 ohm resistor. So, I get my trust fluke, check the 7.5 volt zener on the diode setting, seems to test good. Hold the probe to the legs and power it back up. Well, getting 13+ volts on either side of the zener. Going to have to change it also it appears, and a new r213.

Also, when I had it powered on, ssb was still messed on on the rx. I have my washington right near it, and was talking. The s-meter was moving, but the audio is not there.

I have a few problems to chase down it appears.

 

[ExitThirteen]

I'm almost half tempted to have you send it to me so I can have a look... Very interesting problem this is. If you're getting +8V with the pin lifted off the board, but only 2.5V with it soldered back down, there's obviously something nearby that's loading down the regulator, I'm almost wondering if it took some static/electrical damage, or if some massive signal got shoved down it, and took out some components.


Looks like the zener diode has gone fault, along with R213. I have an extra MA27W-A diode if you need it. What is the number on the regulator at Q37? is it 2SA1869? Or is it a 2SC4369?


~Cheers~

 

[liquidh8]

Yeah man, pretty odd.

Since I subbed something in place of D72, MA27W-A diode, it starts up and I get my 8 volts on the regulator all the time now.

Something took out a few components in the regulator circuit. I still have to order a 7.5v zener and i will need that MA27W-A diode. I don't think RF parts has that one, i have to look today.

As far as Q37, I'll have to look when I get home. I put the upgraded part in there originally, then ended up using the stock green one, a 2sa473 i think it was. I may has a 2sa1012 to put in there when this is all figured out.

Also, you know of a source for the MA27T-A diode? Rf parts has the MA27W-A, and the zener diode I need. Gonna make an order here soon.

 

[liquidh8]

Ordered a bunch of spare parts from consolidated. All except for those MA27T diodes

 

[Robb]

I'll agree with Exit about some kind of static electricity may have zapped it - as to the cause of this radio's failure. With multiple part failure, that is a strong clue. Usually a part or two in one circuit is enough for a radio to go belly-up without the influence of static. Perhaps a nearby lightning strike was the cause?

Hope that isn't so; as I've read that this kind/source of damage will have you chasing your tail trying to make the whole thing right. Lightning damage on the West Coast is very rare; but not unheard of. Had a local friend's Icom 756 Pro take an indirect strike (1/8 mile away) when TXing and took out a bunch of the PA board.

If so; guessing that all diodes and transistors will be suspect.