Resque a Galaxy Saturn ept360011b

[loosecannon]

bfrqrv,

I know it seems like if you give very good details that an experienced tech should be able to start you down the right path, but unfortunately there can be many causes for the same issues and you really need to understand the theory behind how all the circuits work in order to interpret the data you gather while you are troubleshooting.

also please understand that many of us have been down this road on an internet forum many times and have spent lots of time typing up long answers and suggestions/lessons, only to have the thread go nowhere once the OP realizes that they are just out of their depth. some come in and say thanks anyway, but most just disappear leaving a thread with no solution.

in your particular situation my advice is to find a voltage chart for all the ICs and transistors in that radio, and start going through each one, looking for voltages that don't seem to line up with what should be there.

if you find a section of the radio with a transistor that doesn't have the right voltages on it then we have a place to start helping.

also, know that electrolytic capacitors in particular have a life span and can eventually start to act like resistors when they get old and dry out.

many times, simply replacing all the electrolytics and aligning the radio can solve the problem. maybe not the best troubleshooting method but it has worked many times.

quite a few of us will not even take an old radio in for repair unless the customer agrees to have the radio re-capped.
shipping back and forth is expensive!
LC

 

[RollingStone]

Hi
I think you guys are over thinking this....
I replace the electrolytic caps in these epto3600 xx x boards and it usually fixes everything after they sit for too long, electrolytic caps have a shelf life of about twenty years. you can buy a modern cap kit from https://klondikemikescapkits.com.
use my custom made de-solder location map to simplify the task.

 

[bfrqrv]

Very very good info guys! I am one Big step further! I will explain.
Fist I want to say too loosecannon, you are totally right. And it's very difficult to determine what person is on the other side of the chat.
I can only say I do this hobby for about 50 years now and have some experience. But with only experience we can't come far, so I agree we need some real technical data to repair this one. I am not that strong in reading charts and schematics, but I can fight me through it and every info you guys give me here is for me a way to get data and learn.

Oke what did I find today. I de-soldered VR11 and it was in the Mega-Ohm, so I replaced it. And yes EUREKA moment was there and I needed that one, you guys know the feeling. The AM/FM power is back around 15 watt on all bands!

Still no mic audio, so I guess we did have 2 issue at once!

I did the TX alignment and that was how I discovered there was no MA in step 1 between the test pins. After replacing VR11 I manged to do step 2.

Step 3 and further I can't do without the proper tools.

I think we have won today because now we can only focus on the mic audio. I think that Rollinstone has a point with replacing all the caps or go the Nomadradio way I am not sure what the most logical step is here. (yes I tired a second mic)

I must learn first what caps are involved in the mic audio circuit so I can start with those?

I did saw a thread here about no transmitted audio but I think that's different because what I can see and hear is that I also don't have PA mic audio. But in that thread is much information about the audio circuit and parts.

What can help me is a list of the most common and logical parts in this mic circuit that can be broken like the dry caps, transistors, Diodes and IC's.

 

[RollingStone]

EPTO3600 XX X E-CAP LIST

 

[RollingStone]

Most of the caps on right side of radio when looking into case are audio circuit. I can give you a map if needed.

 

[bfrqrv]

Ah this is so wonderful thx. What do you mean with a map? Like a diagram? Yes when its not too much trouble because my solder level is 5.5 I can use all the help.

 

[RollingStone]

AUDIO CIRCUIT IN YELLOW BOX but it is always best to change all the E-Caps and re-align radio.

 

[nomadradio]

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

There ya go! They used to sell an audio amp in a box with a speaker and a probe on its input and call it a "signal tracer".

Good idea!

73

 

[Dr. Frankenstein]

The last time there was a radio with the "No Audio Problem" ...... it ended up being the Mic Gain potentiometer on the front of the radio after the guy chased his tail for days blaming everything else.

Just saying ...........

 

[bfrqrv]

New findings in the category EUREKA! The no mic audio was indeed the Mic Gain potentiometer. I did test that guy earlier quick and dirty, but when I de-soldered it, it was clearly faulty (Mega-ohms) thx Dr.Frankenstein for drawing me back to the basics.

Ok so we have power and mic audio! The Galaxy is alive again.

I have a question about the TX alignment. In step 2 I have to adjust VR10 to 50MA and then VR20 to 100MA. The 2 potentiometers are very unstable when I adjust them. I mean there is no nice linear movement, but I do get them on 50-100
When I check them back after 15 minutes again the MA is different, by example the test between pin 8&9 has then changed to 170MA.

Does this sound as the VR10 and VR 20 potentiometers are gone bad also? Is it common that those potentiometers gone bad also after so many years, or are there other components involved.

 

[nomadradio]

The bias diode on each final bears checking, just to make sure it shows the usual 6/10 of a Volt or so.

The bias trimpots get really squirelly on old RCI radios like that one. We adopted the habit of just replacing them. You can try a drop of control cleaner. What happened to us too often was that the trimpot would get noisy and erratic again a day later after cleaning. Seems like there is a wear-and-tear issue with these, not just old age. If that trimpot goes open, you can fry the final that it controls. A new trimpot is indeed cheap insurance.

73

 

[bfrqrv]

oke today I changed VR10 and VR20 and the MA measurement is much more stable. I do see change between cold and 15 inute safter and I see direct change in holding the key. Like it starts on 95MA and goes linear to say 110 MA.

I now have 12 Watt AM/FM and 15-21 Watt SSB it depends on what band. I can't adjust l42 because that can is full of wax and can be adjusted. I don't know if thats normal or did someone did this earlier?

So it seems I cant adjust much more to get the power even on all bands and I am not sure if I can be satisfied like this. What do you guys think? I think this board specs is 10 watt AM/FM and 21 Watt SSB is that correct? When that's a positive I think we leave it alone and be happy. I guess there are some disc capacitors also that are not having the right value, but that will be trial and error and de-solder them all?

 

[nomadradio]

Disc capacitors are not a common fault. They tend to be reliable. Nothing is fail proof, of course. Bad disc caps happen, but not frequently.

L42 should not have wax in it. Desoldering this coil from the circuit board will expose the opposite end of the tuning slug. Good chance you can back it out through the bottom and then (carefully) scrape the wax from the top end of the coil form. The peak on that coil tends to be somewhat sharp, so unless it's set perfectly, this could affect power. But removing it, using the 'bottom end' trick and putting it back will be the only way to find out.

Then again, the power you're seeing is 80 or 90 percent of what you could hope to obtain by tweaking the alignment. Doesn't sound worth the effort involved to get an increase that small.

My advice would be that it's not broke, and use it as it is.

73

 

[brandon7861]

I don't know if it is a frowned upon procedure, but I like to set my hot air station to 130°C and heat the can just long enough to soften the wax (but not make it liquid). Using a steel street sweeper bristle (found on any clean looking street after a block of walking), the majority of the wax is dug out from the top (edit: windshield wiper support strips are about the same shape and strength). Then I give it one more quick shot of hot air (again, not to melt, just soften) and back the slug out pushing the wax out with it. I then let the temp stabilize before continuing.

 

[bfrqrv]

Thx I repaired the Galaxy and in the mean time learned a lot extra. I noticed that decades ago when I did this with much less knowledge the puzzles are now coming together.

Another question just raised I hope I can explain it in reasonable English. I learned about PEP power and I do have a PEP watt meter. What I noticed is that when I talk on PEP monitor there is a better higher wattage then on AVG, I guess thats good and what PEP means. The thing is that I was thinking I could PEP more then 20 Watts when I switch to the PEP monitor on the Watt meter but it doesn't.

The only explanation I have is that a perfect whistle in the microphone is also the PEP power. So the PEP power will not be more then the perfect whistle is that correct?

Maybe I am totally wrong here and seeing things not clearly let me know.