Galaxy 2100 - EPT360011Z VCO

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486dx4
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Galaxy 2100 - EPT360011Z VCO

Post by 486dx4 » 27 Mar 2018, 01:45

I have been playing with a Galaxy 2100 radio with the EPT360011Z board. I am trying to get it back on frequency because it is currently way way off where it should be. Right now it is putting out an extremely low signal around 22 Mhz. For some reason you can tune L17 to get the radio to go into transmit. The signal is not very stable either. The band switch does not seem to make much of a difference in the frequency. I have tried looking into the VCO section around TR25 and TR26. I have read about testing the VCO by breaking the PLL loop and injecting 3V DC into TP2/R109 allow for testing to see if the VCO section is bad somewhere. Supposedly the VCO section is supposed to be running around 16 Mhz but with my testing I get only in the high 13's to 14 Mhz by tuning L!7 and testing with a cope and frequency counter at TP3/R74 I actually checked all of the components that are part of TR25 and TR26 including the varactor diodes (even replaced them) and transistors TR25 and TR26 - all checked out fine. All components seemed to check out fine yet the VCO will not run at 16 Mhz which supposedly all Galaxy radios run at - not sure if this is true or not.

Is there anywhere some kind of block diagram that is specific to this Galaxy 2100 model? I am using the info on cb tricks.com where they have a schematic for the Excalibur SSB base radio. The part numbers do mostly line up fine with the EPT3600 11Z board that I have in this 2100 but of course there are some differences. I have a block diagram for an EPT360014B board but that is different as well in some areas versus the EPT360011Z board. The 14B board has an IC10 where the 11Z board has transistors that do the same function as that IC. I am not sure which transistor does what for

I'm not quite sure where to go next to look for potential faults. I think its something with the VCO but after checking components out I am not so sure.

By the way the radio as found had a mod which looked like something that would have extended the radio further into the 10 meter ham band as per some mod info I found that described the changes. I put the radio back to its original state before the mod and this did not seem to make any difference.

If anyone has any tips or knows of a place to go for better documentation on the Galaxy 2100 that would be great - thanks

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Re: Galaxy 2100 - EPT360011Z VCO

Post by sonoma » 27 Mar 2018, 04:26

go over to cbtricks and into the secret cb section and look in the by radio option and it will bring up a lot of info on this radio. several pages in fact.

http://www.cbtricks.com/pub/secret_cb/index.htm

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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 27 Mar 2018, 08:11

The fact that someone has had it working on 10m previously for me rings alarm bells . Your PLL obviously isn't locked . As you say the radio should be up in the 16/17Mhz VCO range . Later models used an IC for that stage . Have any tracks been cut ? Has the LO crystal been changed ? How's the 10.240 crystal . Is there power to the channel selector ? Is the PLL good ? That's where I'd be starting . After that it's a case of getting in there with the scope to try and pin point the fault .
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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 27 Mar 2018, 14:53

Just for my own curiosity . Does the front of your radio have both crystals fitted , like this ?
P1010204.jpg
Sammy
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Re: Galaxy 2100 - EPT360011Z VCO

Post by 14CS06 » 27 Mar 2018, 15:36

Hello

At first it would test the Galaxy in all its functions (in TX and RX) by unplugging the frequency
Because if the post is normal HS that the frequency meter is wrong values
When the Galaxy is ok reconnect the frequency

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Re: Galaxy 2100 - EPT360011Z VCO

Post by 486dx4 » 05 Apr 2018, 03:44

Sorry for the delay in my response - The picture shown with the two sets of coil cans is the board I have. On the schematic I have they are labeled as A, B , and C and the diodes and fixed coils around them are not greatly detailed (no values, part numbers, etc.) Yes, the later Galaxy boards had an IC10 that took the place of this. Since last writing I have done the following

- Checked all components around TR25. TR26, and TR29 with either an LCR meter, DMM, or transistor tester as needed. Nothing appears to have failed. Replaced varicaps d30 (two of them on the board to extend range I guess) with SVC251's. No differences noted.

- On a guess since no components tested bad replaced L17 from a junk SS3900 with the same board - this brought up the VCO frequency into the 16 MHz range no problem whn I broke the VCO loop and tested the VCO by tuning L17 which I could not do before. Not sure why that coil failed. The existing coil can on the board was labeled 12000 while the replacement from the ss3900 board was 12017 (which matches part numbers on other radios with that board) so something was different perhaps.

- the 10.240 MHz oscillator seems to be working fine and is making it to pin 3 of the MC145106 PLL chip

- Some of the wires from the clarifier were moved to the trace side of the board and not the correct number locations on the component side of the board. Also some components were moved and added by R191/192. I'm not sure what was going on there. I copied the parts layout on the SS3900 board I had to make things as they were before as best as possible.

After all of this what seems to be happening is that somehow the downmix oscillator or loop oscillator section is not working right. I'm new to how all of the parts of the PLL setup works but from what I understand the downmix oscullator with TR29 is supposed to present a low enough frequency signal to the MC145106 chip (IC5) pin 2 so it can process it - like less that 3 MHz. The problem is that the PLL is seeing signals maybe in the 17 Mhz range which means nothing will work. And on the scope I have the signal to Pin 2 there seems to be much distortion in the signal as well. I can tune L17 and sometimes get the radio to transmit but the frequency is not stable and is nowhere near where it should be. And it seems to be mode dependent from what I found since what I described just now happens on AM. When I go to SSB and transmit the radio does appear to be very close to where it should be - like on channel 1 in the US CB band its transmitting on say 26.971 with a stable signal and I can receive on another radio tuned to that frequency no problem - audio is good, etc.. And putting a scope on Pin 2 of the IC5 PLL chip the frequency is under the 3 Mhz limit. I'd say for this the PLL is locking in this case

On the downmix oscillator section I checked the crystals by the two sets of coil cans (L21,L20,L19 and A,B,C). X2 which is the crystal in front of L19-L21 has a 15.360 MHz crystal and A,B,C has a 14.010 Mhz crystal in front - sometimes called X3 from what I have been able to find out. I am guessing these coils are controlled by the Hi Lo switch on the radio. I would think that with the Hi setting the 15.360 crystal is in use and on low the 14.010. On SSB modes this seems to be the case - one crystal is operational where the other is not. but on AM if you go into the Hi mode you check the crystal oscillation with a scope and you get a frequency of like 11.1 MHz on X3 and around say 10.1 MHz on X2 - like both crystals are on when I think it should be one or the other. On Lo mode the 14.010 X3 crystal seems to be the only one operating I would guess that something is keeping the two crystals operating in the AM mode. I'd love to find a schematic that show how the Hi Lo and mode switch makes these X2 and X3 work. Also if there was something to show the board connects of the front panel controls to the board that would be great as well. The schematic I have does help but there is no hi Lo switch in the schematic I have. I have found on this board under a topic "Superstar 3600 xtal x2 Help" a schematic that shows the A, B, C coils with the L19, 20, and 21 coils but if the whole schematic was around somewhere that might be a big help. And also a board layout detailing the parts for the A, B, C coils would be nice as well... who knows....

Sorry for the long winded reply but I did not want to leave anything out. Thanks to all of you for the replies - everything helps and if I can't get this working I did learn much about how the VCO/PLL works in these radios.....

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Re: Galaxy 2100 - EPT360011Z VCO

Post by 14CS06 » 05 Apr 2018, 09:52

Hello

Is it okay for you :?:

Image

Image

Image

Image

Image

Image

Image

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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 06 Apr 2018, 07:46

486dx4 wrote:
05 Apr 2018, 03:44
I did learn much about how the VCO/PLL works in these radios.....
That's how I figured it out too 😀 I'm overseas right now and can't reply fully at the moment. I couldn't find a correct diagram with the hi/low switch either. Actually I replaced my hi/lo switch with a 3 pole 6 way band switch. You need to power one crystal section and ground the other. Plus you need to feed the capacitance to the VCO. I'll get back to you next week.
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Re: Galaxy 2100 - EPT360011Z VCO

Post by 486dx4 » 07 Apr 2018, 02:18

Thanks for the diagrams and pictures.... All of it helps at this point. The thing is I do not understand why in modes like AM you put a scope to both crystals on the downmix oscillator sections and you get a signal from both. And this only appears to happen when the switch is on high from what I can tell. Its all kind of confusing as to what may be causing this. But this fact that with high or low only one downmix section is operational (15.360 or 14.010 MHz - never both)is a good thing to know. I'll look at those schematics and see how much further I can get.

Thanks again everyone.....

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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 07 Apr 2018, 10:49

The mode switch shouldn't affect which crystal is in use. That's done by the HI/LOW switch only. If I were you I'd concentrate getting the radio working with one crystal only first. I think I made a drawing of the switch wires. I'll have a look for it and scan it if I can when I get back to the UK next week.
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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 07 Apr 2018, 13:25

I found a small diagram that I made when I was working on mine.
rps20180407_134953.jpg
It might not make much sense to you. Things to note. There are only 2 wires that control the bands. When nothing is connected then you're just using the straight output from the channel selector which gives you bands A or D. Each of the other 2 wires will give you either B and E , or C and F.

8V is supplied continuously to each crystal stage. The hi/low switch connects or removes the 0V line to the affected oscillator section. Bands A,B and C get 0V connected to the VCO control section , and bands D,E and F get +.8V

As I said before. If I were you I'd concentrate on either band A or D. They don't use the diode matrix. Once you've got one band working on all modes then take it from there.

Sammy
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Re: Galaxy 2100 - EPT360011Z VCO

Post by 14CS06 » 07 Apr 2018, 14:47

Hello

I found that :arrow:

Image

Image

Who is the draftsman :?:

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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 07 Apr 2018, 15:28

Hi Claude !

That diagram of mine isn't for the 11Z. It's the wiring for converting the 3900 (EPT360013/14) with 3 way band switch , to a 6 way. The 11Z is more complicated due to the twin crystal stage.

The first diagram might be right , but the colours differ , depending on the radio.

Sammy
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Re: Galaxy 2100 - EPT360011Z VCO

Post by 486dx4 » 17 May 2018, 22:37

Thanks for all of the diagrams - they are very helpful and they did give clues as to what or what may not be connected right. It has been a while and since the last post what I noticed after checking components was that L22 (fixed inductor) looked like it took a dead short For some reason it had no inductance but there was continuity. I replaced the inductor and the VCO seemed to start working as it should after aligning the PLL section. Since that L22 was no longer blocking ac signals that could explain along with that L17 coil why the VCO was not able to operate properly. As was mentioned you switch HI one loop oscillator is activated (L19-L21) and when you go LOW the other one is (the "A" B" and "C" coils). It is just two wires from the front panel that are doing this switching. That inductor being faulty never switched one oscillator off when the other one was on.

I then went on to looking at the receiver which needed alignment. The alignment made the receiver better but it was still kind of deaf except for very strong signals Found the FL2 (10.7 Mhz ceramic filter) filter was broken on the output lead so I replaced that and the receive came back to life.

Then to the transmit side. Someone removed TR32 which looks like the its part of the AMC circuit (limiter). Put that transistor back. Also the driver transistor TR44 had an NTE equivalent device installed which seemed to be ok but I was not able to set the bias correctly which may be due to it being a sightly different spec transistor. I put a 2SC2166 in its place and the bias was able to be set. After aligning the transmit (bias, power level, ALC level on the scope, etc) transmit seems to be ok.

So not it looks like the radio is working at this point. I just wanted to write back about the results since many write about a problem and if they manage to solve it you never hear from them again. Yes, some don't write back because they did not get to figure out the issue Thanks everyone for the diagrams of the wire hookups and schematics. All of it was a big help

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Re: Galaxy 2100 - EPT360011Z VCO

Post by cb4ever104 » 18 May 2018, 19:56

Good news !! And thanks for posting back. My old 87 11Z SS3900 is one of my favourite radios. Real solid radio.

Sammy
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