Galaxy Saturn (original) frequencies are out of wack....

[Lkaskel]

Hi Men,
Sorry to have post about multiple radios going at the same time!! I had to order parts for the 2547 and started a new radio while waiting for those parts. I am also unsure how all of the recent radios are all Galaxy's?

I have this older Saturn with the EPT360010A board in it. It is the 5 band model. On CBTricks it is the Saturn SSB Radio. The radio frequencies are way off. Band A starts at 25.610 (ch 1) and band E starts at 26.510 (ch 1). The user said that it was working fine and then one day....not so much. He used it mainly on band C which is 11 meters. I did re-flow a number of solder joints but that had no effect. The radio does transmit and receive on the frequency that is displayed on its counter. I did check the 10.240 crystal and it is on frequency. I could do a complete re-cap but I did not want to start with that.

Any thoughts?

Thanks as always!!!

 

[nomadradio]

Sounds way too much like IC6 and IC7. They are type 4008 4-bit full adders. They take the binary number coming out of the channel selector, and add another binary number that's set by diodes that are fed voltage from the band selector.

More than once we have seen the adder chips croak when an attempt was made to add another band, or to add a +10 kHz switch to a radio that lacked it.

And sometimes they just go bad.

The generic "4008" number will typically be "folded" into the full part number. Many brands have made/sold this one. RCA called it the CD4008. Motorola called theirs the MC14008. Other brands used their own prefix letters.

I do recommend installing a 16-pin socket any time a chip like this is removed from a circuit board. That way, another chip failure won't require a soldering iron to fix. And won't cause heat stress to the foil traces. Too many heat cycles cause the copper foil to "lift" and separate from the board's laminate. You don't want to have to heat this foil pads more than once to remove the old one, and once more to install the socket.

The only other common fault I can think of would be a bad connector to either the channel selector, or more likely the band switch.

Odds are that flexing these while watching the counter would immediately reveal if this is what's going on. It's probably not that simple.

73

 

[Handy Andy]

The radio does transmit and receive on the frequency that is displayed on its counter. I did check the 10.240 crystal and it is on frequency. I could do a complete re-cap but I did not want to start with that.

+1 with Nomad on this...

So the IF displayed is what the PLL is mixing with...

Now from that are two signals - one the PLL the other the X2 - which is 14MHz...

AND
(Emphasis needed)

Several other events...​

It is my hope that your COARSE clarifier side is lost voltage and pulls down the D37 VARACTOR voltage and kills the X2 to WAY BELOW OR WAY ABOVE...

Locate your COARSE clarifier, see if it's all one voltage or if it's even variable - there is a divider network that keeps the voltage slide range tight enough to allow LINEAR slide - if it's all scrunched up, look for voltage, test the output of the COARSE and See if R149 or R150 have failed open - it's possible - holding that Coarse tuning line too high or too low and your' mixing frequency is putting you in the basement.

 

[Lkaskel]

+1 with Nomad on this...

So the IF displayed is what the PLL is mixing with...

Now from that are two signals - one the PLL the other the X2 - which is 14MHz...

AND
(Emphasis needed)
View attachment 38488
Several other events...​

It is my hope that your COARSE clarifier side is lost voltage and pulls down the D37 VARACTOR voltage and kills the X2 to WAY BELOW OR WAY ABOVE...

Locate your COARSE clarifier, see if it's all one voltage or if it's even variable - there is a divider network that keeps the voltage slide range tight enough to allow LINEAR slide - if it's all scrunched up, look for voltage, test the output of the COARSE and See if R149 or R150 have failed open - it's possible - holding that Coarse tuning line too high or too low and your' mixing frequency is putting you in the basement.

Andy,
I checked R149 and R150 and both are ok. I also checked R148 and C122. C112 was way out of spec and I replaced it but it did not make any difference. The course (and fine) control both do change the frequency. The voltage on pin 50 (center of course control is 1.8vdc center position. It goes to .2 volts in one direction and 5.4 volts in the other. One interesting thing is that R276 and D115 are missing.



I am unsure if this was done by the owner or someone else or possibly they were not installed in this revision. Any thoughts? I am working through your troubleshooting before I look into Nomad's suggestions.

Thanks as always!!!

 

[Handy Andy]

This clarifier mod simply slides more - like 5kC up and down so you can tweak the nickels and dimes...

IF X2 and associated are working, the ADDER problem is a line that's "on" as one of the larger divisor pins.

Sine the 145106 has no "ROM" to stop it from bad programming - just use your band switch and note the high divisor pins - one would stay on all the time - forcing a divide by count to force channels lower - like the 10kC switch.

So since they did do something with the Coarse and Fine, there may be other mods you have yet to discover.

You have the main Xtal 10.240 ok - check the X2 and the 10;695 SSB one - make sure the AN612 is getting the correct frequency. Because of the 10.690 is not affected by the Coarse and Fine - it mixes with the output of the 10.240 and the 14MHz X2.

 

[NZ8N]

1 - When you turn the Coarse Clarifier from one end to the other, does the frequency counter track the difference?
2 - Have you checked the voltage at R148, C112 and L25 (same trace) to see if it is the same as Test Point 50 ??
3 - Does it have a Fine Clarifier or just the Coarse one?
4 - Have you tried putting the Clarifier at 12 O'Clock (Center Slot) and readjusted
L19 for AM
L20 for USB and
L21 for LSB ??

If it still will not go back on frequency, maybe the 14.460 MHz crystal is bad.

 

[Lkaskel]

Hi men, it's been a few days since I've had some time at the bench. Tonight I worked on the Saturn and was about to troubleshoot with some of the suggestions above. When I turned on the radio it was still at 26 MHz. I did check the clarifier again and it was working normally. At one point while looking at some solder joints I realized that the radio was at 28 MHz (band e). What in the heck was going on? What have I done to get that result? It is supposed to be on 28 MHz. While troubleshooting it now I had turned the power off and when I turned it back on it went back to 26 MHz. Good grief!! After some further troubleshooting I found that if I cycled the power quickly the radio would come back to 27 MHz. If I turn the radio of for even 1 second or 2 it goes back to 26 MHz. I have not yet re-capped this radio so all of the caps are original. I am trying to understand what component would be affected by a quick (blink of an eye) power cycle. I am considering the caps. Any other thoughts about this?

Thanks as always!!!!

 

[Handy Andy]

It may just be those caps - the older ones take more current off the line to "load up" to hold a charge.

When they get old and take too long to recoup their charge - you get these symptoms.

May not hurt to go after the switch contacts too - the front panel rotary is prone to the "oxides of March" with March being both marching onward in time referring to age and as the month of when the big melt occurs, during solstice transistion from winter to summer (in the Northern Hemisphere) and when the corrosion occurs quickly - due to moisture in the air and as condensate.

 

[Lkaskel]

Ok, so I am back to the Saturn (5 band). I have recapped everything except the echo board and I still have the same issue. When I turn it on it comes up (on band C 11 meters) on 26.280 (ch 40). If I fast cycle the power switch it comes up on 27.405 (ch 40). Logic says that it sounds like a cap issue but....

One other thing. I did find this modification on the bottom of the circuit board.



It does look like a factory update as it is done well but maybe not. Has anyone seen this update on another Galaxy Saturn or like radio?

Any thoughts on this would be wonderful as always!!! I am at a loss and need to get this off the bench.....

Thanks men!!!

 

[Handy Andy]

Is that by IC1 - the Quad op-amp in the center of the board?

...then that may be the 820 ohm and 103 Disc, that's an AGC "upgrade" (S/RF meter FM "tap")

You PLL issue may be more of the ADDERs those 4008 series chips...they can jump and "latch" up

You may need to see how the PLL "locks" onto the pins set by those Adders - it will be one pin at a time though...

This damage may have been from a static poke into the radio thru the channel knob.

Got a Truth Table?
PDF attached for that 145106...

About those two parts...
IT seems to be in the mess around L3 and IC1's D7 (AGC).

Had to borrow a page from an 88 to help sort this out - your part numbers will vary, but schematically - the one on the right in the above panel - should show C219 and R270 - goes between D7 and L3...on your radio...

That other part - is the Diode...

​

 

[nomadradio]

IC6 and/or IC7. We replace them only in pairs.

Another long-standing policy here: Any part with more than 5 pins gets a socket installed, then the part goes into the socket. Serves to protect the circuit-board foils from the heat stress of removing the next part to go bad in that spot. Murphy's Law says that a soldered-in chip will develop a fault of some sort later. A part that can be changed by simply unplugging it will never go bad.

73

 

[nomadradio]

One more detail that comes to mind has to do with troubleshooting this problem. The exact error might be important. If the radio is always the exact, same number of channels away from where it should be, that's one kind of error. A radio that is exactly 4 or 8 or 16 or 32 channels away from where it should be points to a problem between IC6/7 and the PLL chip.

And if the difference between the frequency you get and the frequency you should get is different as you change channels, that points even more strongly at IC6 and IC7.

73

 

[Lkaskel]

CD4008

Hi Nomad, its been a while since Iv'e been at the bench as my job has had me on the road for weeks. I did start looking at this radio again and I am in agreement that the two 4008 chips should be replaced (and add the sockets). I went online to find an appropriate replacement and I'm not sure I found the right replacement. Could you possibly recommend a part number that you are confident in?

Thanks!

 

[nomadradio]

Now here's a quandary for you. That number was listed in catalogs we saw for years. Digi-Key, Jameco, BG Micro and others right along with the rest of the "CD4000" series chips. Not so much any more. Digi-Key lists links to an outfit called Rochester Electronics. They're a high-dollar source used when your million-dollar assembly line shuts down because of an obsolete chip. A price of four bucks, or 17 per chip won't raise an eyebrow for an industrial buyer.

https://www.digikey.com/products/en?keywords=cd4008

Kinda discouraging, especially when I remember back to the thing being priced under a buck.

Decades ago.

NTE scraped the numbers off them and stamped "NTE4008" on the chip, and on the expensive printed heat-seal baggie. Ebay search for that version turns them up from four to seven bucks each.

Ebay search for 'CD4008' turned up multiple hits, including Toshiba's version the "TC4008".

But that's the world of obsolete chips. Constantly changing.

73

 

[Mk121]

Buy them direct from nte for a little over 2 bucks a pop.