Resque a Galaxy Saturn ept360011b

[bfrqrv]

well, this can be a start of a too big adventure but lets try. I have a Galaxy Saturn for decades now and after a few years I fired it up again just to see some problems from the very start I started the TX. The first days I only did some RX listening.
I am almost sure it was good when I putt in away a few years agf course its an old transceiver and everything can go wrong inside.

To be honest I am not the biggest electronic expert but I did some things through the years and have some experience. So everything involved I did hear about and I can do solder actions. I have all the diagrams and component names of the board.

The symptom is weird.

- Lost power on FM/AM but its very different per band. The A band does 2 watt, B,C,D,E does zero watt and the F band does 6 watt
- No modulation on AM/FM/SSB! So I cant test SS wattage, only the roger beep does swing out some power but nothing through the mic. I tested 2 mics that I know are good.

I know this sounds as if where do we start but I did try to make a start.

- TR 45 had 3 black legs so I de-soldered that one and did a measure. It is a 2sc2538 and it was still good. I replaced it with a 2sc1973 and the issue is still there of course.

I de-soldered the 2 finals and they are both good when I measure them. I didn't tested the 2166 yet.

Is there anyone that can try to shine some light on this? Do I have 2 separated issues or is there a possibility that the audio and power loss are the same component(s)

I know there are some measure point like tp 7,8,9 if I am correct, but I have no experience with those measure tecnics so when I have to do this through those points I need some help in what to use and how to use.

Any option is good, I need to find a new entree to start this adventure

 

[999]

The Galaxy Plus is almost the same radio as the saturn and the schematic should steer you in the right direction.

Galaxy DX Radios "Galaxy Plus"

ALIGNMENT PROCEDURES PLL Alignment Receiver Alignment Transmitter Alignment Alignment Locations SEMICONDUCTOR INFORMATION Active Device Function Location Layout (Main Board) Semiconductor Datasheets DIAGRAMS Schematic Diagram Picture Tour Of...

www.worldwidedx.com

 

[bfrqrv]

Thanks for your response and link to the data! I do have some schematics but the thing is that I find it very difficult to determine where to start when you look at my specific symptoms and measurements. What do you think where to start in this case?

 

[bfrqrv]

I did a measurement of pin3 of the microphone plug today and I am not sure if this is correct. I read between pin 3 and the chassis ground and the voltage is starting with 10 volt and dropping to around 3. Is it correct that the chassis ground is not connected to the DC ground? When I measure between the DC ground and pin3 I have 14 volt. Does this all sounds normal?

 

[Cable Guy]

Often chassis ground and dc or board ground are different. Measure ground from a tuning can, as it's connected to "board ground" and the chassis usually has isolation via ceramic capacitors. Most have a can that is bonded to a crystal with a wire, that's where I clip my lead grounds for all measurements needing a ground potential reference.

 

[Cable Guy]

Also, I'd look at the mode switch and circuit concerning your issues.

 

[bfrqrv]

Also, I'd look at the mode switch and circuit concerning your issues.

What do you think is it safe for testing purposes only to make a bridge between DC ground and chassis ground? Just to see if the microphone plug has good ground.

 

[Cable Guy]

Well, I wouldn't. Im recalling a mod, shorting all the caps from board gnd to chassis gnd in an attempt to make the Rx less noisy iirc but I tried it once with bad outcome. I'm not sure as to why you are probing the mic and wanting to short grounds? What are you looking for? To make sure the mic has its ground? Someone more experienced should chime in on shorting, I would not. Check resistance, using dmm, between mic gnd pin to the tuning can. If reading less than an ohm, assume the ground is present.

 

[bfrqrv]

Yes correct I don't want to make it worse, but in those complicated cases some tests can make a direction to search again. Because it was all good when I stopped a few years ago and now it starts with 2 serious symptoms, I think both issues have the same root cause. I just tested the PA and there is also no microphone sound there. When I press the key I hear the click and the echo switch makes the speaker siss but no voice sound.

The power is strange too. I did a more precise test and its:

A band 2 watt
B band 1 watt
C band 0.5 watt
D band 0.5 watt
E band 1 watt
F band 8 watt

Trying to find what circuit can cause both symptoms or maybe we are in bad luck and there are 2 issues at once

 

[nomadradio]

What do you think is it safe for testing purposes only to make a bridge between DC ground and chassis ground?

Best easy way to make a DC-voltage measurement in this kind of radio is to clip the meter's ground lead to the negative side of the large filter capacitor in the power supply.

We got in the habit of soldering a short bare wire to the ground foil alongside the large filter cap near the audio chip on the solder side of the pc board. The end of the wire gets bent around the tip of needle-nose pliers into a circle. This is where the ground clip for a 'scope probe gets connected, or a DC meter.

Connecting the DC-circuit ground to the chassis ground can create quirky feedback issues.

73

 

[bfrqrv]

Ok clear thx. I must say again that theoretically I am not capable enough to do those repairs but in all those decades I did have my eureka moments and I hope we can have one of those again. The bad thing is that I have to approach this one through the symptoms side. Also where I leave is nothing or nobody anymore that can dive in this professional, so we will see how far we come.

So resume what do we have.

- no mic audio on both FM and SSB
- no mic audio on PA
- Still that weird difference of (too low) power between the 6 bands. Today it looks like we have 8 watt on A and 8 watt on F and I am sure that was different yesterday, I wrote those numbers down in my earlier message

It looks like a disc type cap shorting or a transistor.
When you guys hear this what is the most logical circuit to suspect first?

Is it useful to do alignments when these symptoms came suddenly? I guess we are dealing with failed components so an alignment will not give us further information.

I think my only hope is that someone had similar symptoms and did the repair adventure.

 

[nomadradio]

I lost track. Does this mean you DO have mike audio on AM transmit? Only mentioned SSB, FM and PA.

73

 

[bfrqrv]

I lost track. Does this mean you DO have mike audio on AM transmit? Only mentioned SSB, FM and PA.

73

Sorry, no the mic audio is gone on every mode also AM

 

[nomadradio]

If you had an oscilloscope, this would be a matter of following the mike audio from the mike socket, through the mike gain control, into the echo board and then back out, and on to the mike amp circuit on the main circuit board. Somewhere in that sequence the audio will disappear.

If you have some header pins with 1/10-inch spacing, you can pull the two 3-pin plugs from the echo board, where one of them feeds mike audio in, and the other one feeds out. On each 3-pin socket, the pin closest to the other 3-pin socket is the keying line, coming from pin 3 on the mike socket. It just passes through the board. The outer pin on each socket is the audio, in on one, out on the other. Center pin is ground.

Turn the 3-pin sockets around to match keying pin to keying pin and audio pin to audio pin and plug each into one end of the three header pins.

This will bypass the echo board, and restore the mike audio if this is what's blocking the tracks.

Next in line on the hit parade is TR32. If it's present, unsolder the center pin so it won't touch the copper foil at the rim of its hole. If this brings back mike audio, you have a runaway limiter circuit, and the fault lies upstream from TR32.

There are other faults that can cause this. Kinda like "my car won't start". More than one failure can bring about that one symptom.

Ahh, you did try the mike on another radio, right? Would help to be sure it's functioning.

73

 

[brandon7861]

A typical DMM will have an AC response to at least 1kHz, so you should be able to hum a low note into the mic and search for the audio signal with that.

I have seen the 4558 audio chip go bad in one galaxy radio, two surround sound systems, and a powered subwoofer. They don't tolerate much abuse. See if you have anything coming out of pin 1 (audio output) while humming into the mic.

The other side of the 4558 works if the RB works, but the audio side of it could still be blown.

Edit: you can also use your PC soundcard line-in to probe for audio