Galaxy DX 2517, stange xmit sound...

[Hawkeye351]

Been listening to a local on his 2517 (practically new) lately. Noticed after about 45 minutes of normal talking, the xmit will have this low "belly growling" sound. It doesn't hurt his signal or modulation at all. Several people have informed him and he tried a different mic and changing the battery in the Golden Eagle D104 he usually runs on it.

It doesn't have that sound for the first 45 minutes or so of conversing, but then gradually comes in with his xmit. I've asked him if his wattage is changing any on his watt meter when he's told it's doing that noise and he says it doesn't drop or increase in wattage, it's steady. The longer he talks on it, the louder it gets, but never to the point it hurts his audio.

Sounds just like a low "stomach growling" noise after about 45 minutes or so of talking, then slowly gets louder. This is with or without an amp on.

Things he's tried:
New battery in D104,
Different mic,
New jumpers,
Amp out of line,
Adjusting mic gain,
Adjusting RF Power,
Different watt meter...

Any ideas guys?

 

[Brother DXer]

Is it doing this on AM, FM or Side Band? Or all modes?

 

[nomadradio]

If it's practically new, it has MOSFET transistors in the RF driver and final stages. I would suggest pulling out the "mirror" board and connecting a current meter to check the zero-signal "idle" current in all three MOSFETs. All too often we see a radio that this adjustment was set to increase the wattmeter reading. Tends to make those transistors run too hot.

A problem that develops like this usually turns out to be temperature related. And if the bias adjustment for any of the MOSFETs is turned too high, you can see issues that only happen when a transistor's temperature approaches the danger level.

I need to track down a YouTube vid that shows how to adjust the idle-current bias properly on those radios. Just not up to describing it in detail yet another time right now.

Always check the easiest thing first, and that's where I would look.

73

 

[Hawkeye351]

Not sure of whether it happens in SSB or FM modes, haven't got him to try the other modes yet, but I will tomorrow.

As far as idle current on the fets, I know how to check that, but not sure what the current should be set at. I always set the bias on fets for 3.80v on all fets, including the driver.

 

[nomadradio]

As far as idle current on the fets, I know how to check that,

At least 10 mA per transistor. The old standard of 60 mA from the old bipolar-transistor days is too high for some radios.

Good chance that your "3.80 Volt" setup will reveal idle current a lot higher than recommended. Setting idle current from gate-bias voltage is playing pin-the-tail-on-the-donkey.

73

 

[Hawkeye351]

Update:

Checking current draw on the finals showed close to 35ma per fet. Adjusted them all down to 10ma, but that caused the deadkey to start creeping up within 25 seconds of keying up, and continuing to climb. Set them back to 35ma and creeping output stopped and held a steady key with no climbing or dropping at all. Gate voltage ended up being 3.75v driver, 3.82v 1st final and 3.90v last final.

I also noticed the last final ferrel insulator that the screw slides in to to tighten the final down was cock-eyed and not seating properly. Removed the screw and fitted the ferril in snug then screwed it back down.

Sound was still there on xmit.

Prodded around the mic amp section with my nylon tool and found a couple cold solder joints that would cause terrible static in the output with mic gain off (front corner edge at mic circuit), even showed on the watt meter. Fixed those joints and solved that issue but still had that belly growling noise. Fiddled around with wire jacks plugged in to the board and found 2 in the mic circuit that wasn't fitting snug. Unplugged those, plugged them back in and the noise was gone.

Growling noise disappeared.

While I have it, I decided to check for other issues.

I noticed if I fiddled around with the wires going to the ext speaker jack in the rear of the radio the receive volume would drop out and come back. Removed all solder from the incoming wires on that board, applied fresh solder, seems to have fixed that issue.

Sprayed all bias VRs, carrier VRs, modulation and SSB VRs also with contact cleaner.

Seems to be steady with no sounds on xmit at all.

Long story short, although it's practically a brand new radio, it's eat up with bad solder joints and unsnug plugs on the board not fitting snug.

Keeping it overnight to keep an eye on things.

 

[Eldorado828]

Update:

Checking current draw on the finals showed close to 35ma per fet. Adjusted them all down to 10ma, but that caused the deadkey to start creeping up within 25 seconds of keying up, and continuing to climb. Set them back to 35ma and creeping output stopped and held a steady key with no climbing or dropping at all. Gate voltage ended up being 3.75v driver, 3.82v 1st final and 3.90v last final.

I also noticed the last final ferrel insulator that the screw slides in to to tighten the final down was cock-eyed and not seating properly. Removed the screw and fitted the ferril in snug then screwed it back down.

Sound was still there on xmit.

Prodded around the mic amp section with my nylon tool and found a couple cold solder joints that would cause terrible static in the output with mic gain off (front corner edge at mic circuit), even showed on the watt meter. Fixed those joints and solved that issue but still had that belly growling noise. Fiddled around with wire jacks plugged in to the board and found 2 in the mic circuit that wasn't fitting snug. Unplugged those, plugged them back in and the noise was gone.

Growling noise disappeared.

While I have it, I decided to check for other issues.

I noticed if I fiddled around with the wires going to the ext speaker jack in the rear of the radio the receive volume would drop out and come back. Removed all solder from the incoming wires on that board, applied fresh solder, seems to have fixed that issue.

Sprayed all bias VRs, carrier VRs, modulation and SSB VRs also with contact cleaner.

Seems to be steady with no sounds on xmit at all.

Long story short, although it's practically a brand new radio, it's eat up with bad solder joints and unsnug plugs on the board not fitting snug.

Keeping it overnight to keep an eye on things.

Those newer boards are covered in flux and adhesives, almost like they weren't properly cleaned after the flow process. Gunk like crazy in the plugs and probably the reason for the bad solder too.

 

[Hawkeye351]

Everything in this radio looks stock. I can only assume there was no "quality control" checks on some of these newer radios, just a rush job to get it off the production line and make that money.

Poor craftsmanship from the factory.

As I always say, "Old school is always better".

 

[nomadradio]

Poor craftsmanship from the factory.

Welcome to my world. Can't bring myself to criticize, though. Too much like biting the hand that feeds me.

73

 

[Hawkeye351]

Got the radio back to the owner, he is extremely pleased with the results. He's getting a bunch of compliments on the signal and modulation.

 

[nomadradio]

Rock on! Gotta love it when a plan comes together.

Congratulations for sticking with it.

73

 

[Hawkeye351]

I honestly owe a lot of what I know to you guys. The info you guys share is extremely helpful.

I'm an old school hack-a-day hack-a-way tech from years ago when I was young and dumb on this stuff.

If it could be clipped, snipped, yanked out, stressed out, I was one of those guys. But since I got back into it the past few years, I've learned to do it right and how to get the audio GAIN out of them without worrying about the meter readings. The VCO Buffers I never knew about til I got back into it and realized that is where all the audio GAIN and sensitivity comes from, along with the importance of the PLL oscillators / carrier oscillators.

I've learned a lot just by scouring this site for others issues and following along with what you guys recommend or inform others about.

You guys ROCK, for real.
Thank you guys, I give you guys all the credit.