GALAXY DX48T Big Rig Series

[EmptyPockets1013]

I brought a Galaxy DX48T off of flea bay for a decent price a few months back, I just finally got around to checking in out. So I setup it up on my bench with an O scope and my R&S CMU200 communication tester, the radio is super dirty. The wave form is nasty looking, box car. The spectrum analyzer shows two and three harmonics. But the main issue is it the amp section continuously goes into oscillation when you unkey. The ALC limiter is still intact, and I have tried adjusting L40,L42,L43,and L44 to tune out the harmonics, to see if the would help. No luck with helping the oscillation problem and I only got a little tuned out. I only got into working on radios a year ago and only work on mine so I’m still learning. Any help would be greatly appreciated. 73’s

 

[Shadetree Mechanic]

Sounds like something might have happened to the output tuning components.

 

[EmptyPockets1013]

I guess I need to pull the capacitors on the input/output transformer and check the values on them.

 

[hotrod]

dis you check to see if the amc has been didabled also? did ya try the vr for modulation ..this is often maxed out even if limiters are all in tact..what about swing mod??

 

[EmptyPockets1013]

I haven’t checked the amc circuit, I’m not sure how to tell just by looking at it. I will have to look at the schematic, the modulation VR does do a little bit. That isn’t maxed though. The VR’s in the radio very scratchy when I adjust them so will probably have to replace them. As far as I can tell no goofy mods or hack mods have been done.

 

[Shadetree Mechanic]

Maybe check the bias on the amp and radio finals. Maybe someone cranked the bias, trying to get more power?

 

[Handy Andy]

Or it just needs to be turned down

The wave form is nasty looking, box car. The spectrum analyzer shows two and three harmonics. But the main issue is it the amp section continuously goes into oscillation when you unkey.

The Bias as suggested by @Shadetree Mechanic - being turned down is another wise choice...

Maybe someone cranked the bias, trying to get more power?

Either way, you now have an experiment of a Galaxy DX 44 with a turbo - not unlike taking a regular engine and putting a turbo on it.

It can be done - just use restraint.