Galaxy 2100 frequency counter problem

[Gman]

My prized Galaxy 2100 frequency counter went out. Radio works fine though. I replaced all electrolytics, even scraped out the dried up glue. The rest of the radio also had all the electrolytics replaced. Freq counter board # EPT210010A. Radio stamped Taiwan. On the counter board, 3.2768mhz xtal and 10.6975 mhz xtal oscillating. 8 volt regulator good. Tuning the coil next to the 10.6975 xtal displays (on the freq counter) either 10.695, 21.390, or 32.085. Where do I go from here? Per the schematic, looks like there is 1 wire on the counter that takes input from the main board. Anyone know what that signal is?
Thank you.

 

[Gman]

Found some things on Secret CB #26 Im going thru now too.

 

[nomadradio]

That counter can be a hair-puller when it breaks. It takes the 8 Volt regulator output and passes it through a 3-Volt zener diode to supply the 5-Volt chips. We got in the habit of taking a 3-terminal TO-220 7805T regulator and placing it face down with the input and output pins in the holes where the zener had gone. Needed a wire on the center leg for its ground connection. Never did have one of them break down, but that zener could cause headaches. Probing the 5-Volt side of the zener with a 'scope will reveal if you have noise spikes riding on the 5-Volt DC supply. That can cause quirky issues. I was immensely relieved when RCI stopped making that counter module in 1995 and went to the surface-mount counter module. Couldn't be serviced if it broke, but it was a lot more reliable.

Checking the 5-Volt supply may help to explain the gremlins.

73

 

[Gman]

Thank you sir. Im on it.

 

[Gman]

OK I replaced the zener with a 7805 regulator. Nothing changed. Now Im really stuck. But I did see a company with replacement boards. Will check that out asap.

 

[brandon7861]

Tuning the coil next to the 10.6975 xtal displays (on the freq counter) either 10.695, 21.390, or 32.085. Where do I go from here? Per the schematic, looks like there is 1 wire on the counter that takes input from the main board. Anyone know what that signal is?

If it is outputting the mixer input (and its harmonics when the coil is adjusted), pretty safe bet it's not mixing (pin 4 signal missing or low). Seems like you were already suspecting that asking where that wire goes.

That wire supplies the VCO signal which comes from (galaxy plus schematic) L22. The PLL loop mixer takes 14.01MHz at pin 2 and mixes the VCO signal (16.xxx MHz) from pin 5 and outputs the downmix at 2.xxx MHz on pin 6 for the PLL. The VCO signal also goes to pin 7, which the mixer IC buffers and outputs on pin 9. This copy of the VCO signal is cleaned up with L22 and sent to the counter.

Is there any chance that L22 (which does nothing else but serves the counter) got screwdrivered to the point the counter is not seeing enough VCO signal? Peak L22 and see if the counter comes back to life.

 

[nomadradio]

Hmm. Displaying 10.695 does make it sound as if the PLL's 16 MHz output isn't getting into the counter module. Not since about 1973 have I tried to troubleshoot a counter problem without a 'scope. And that counter used vacuum tubes.

Did get it working, though.

I did have a schemo for that counter, but it's not in the archive here at home. I'll see what I can turn up at work. Haven't tried to fix one of those modules in quite a while.

73

 

[brandon7861]

Top one was found online, the middle one came from CBTricks DX88HL section



This last one here is from secret cb