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Can excessive swing cause a key up "snap" noise?

secret squirrel

Lustrous Potentate
Oct 5, 2008
657
1,451
153
Washington, PA
I have a Texas Ranger 696 FD1, same board as Galaxy 959. I had the Top Gun Modulator installed years ago. It was installed by Bob F. The radio does not have a reduced DK, Bob originally set it to 0.5 watt DK when he installed it, but the SWR would not calibrate so I had him reset the DK comparable to a regular peak and tune. The RF meter needle bounces like a bobble head. Its always sounded good to any report so I just left it that way. I have been spending more time setting up a radio bench and I noticed that when I key the radio you hear a "snap" in the external speaker. I had been wondering if its the microphone switch on the 636L that I use on the radio. I played with the mic gain and no change. Its the only radio I have that does it. Then I tried another mic and "snap" If it went "ping" I would probably think its cool. Anyway back to the question could this be because of the Top Gun modulator.
 

This is a trough question.

The Top gun modulator - if you hear a "snap" - it may not be from the modulator - it may be from the Audio chip "mute" is not quick enough.

How do you determine that?

Well, the Top Gun Modulator - it needs clean power - so if he simply "overlayed" the part on top of the parts that are original and interfaced with...I can only imagine the TGM unit may be asking for more power than the line it's powered by - is not sufficient - meaning the power feed can't be thru a resistor - it can delay the action - either or, the delay in the mute line on the Audio Chip or the quickness of the TGM showing instability during power up - there's your quandary,

So, the TGM usually gets hooked up to the 12V Battery in feed. - and there is a separate switch to turn it on or off - to bypass - but if the installer put the TGM in the 8 volt line - this may be that problem - low-voltage - nothing big, but if he's set up the TGM to switch on in TX mode, versus all the time on and you need to switch it off (Bypass) - there is a delay in the power up - causing the "crunch" or snap.

IF the unit is on all the time, it needs 12 Volts constant to work. IF it's set up for 8 volts, may or may not work "operate" quickly enough - causing you to hear the noise.

Else, if the radio is old, there may be a cap in the Mute line that is taking it's time to discharge, that may be C180 or C181...if both caps are installed - remove the larger value of the two - leave the other in place.

upload_2020-7-25_23-41-56.png

In the above graphic, the Yellow arrows show two caps, C180 is the Oblong One - which is Tantalum - if that has gone bad, that can delay the switchover, hence the snap - see if removing that cap quiets that noise...If it gets worse, then change the cap to a simpler 2.2uF to help with the noise spike of the switching..

You cannot remove all the capacitance for it's part of the Feed for the NFB Equalizer - but Tantalums as they age show their age quicker than typical Electrolytic. So if you feel there is a quality issue, just replace C180 with a Fresh Tantalum of 2.2uF 16~35V rated - you should be ok.

The "bobble" of the RF meter may indicate this condition - you may have had it for a long time (low-frequency "swoosh") - check the soldering around that area of C180 and C181 - make sure it's clean - reheating won't hurt to reflow solder in that area.
 
Thank you gentleman, for your answers much appreciated. The radio is at least 13 years old. It was a factory refurb from Ranger. Sold to me by Sparky. I am pleased with it. If I let it warm up before a lot of SSB talking the clarifyer seems not to wander like I hear some complain the Galaxy radios do. Its had sat in storage in a dry, but not climate friendly garage/workshop area for a while. 'Going through bad divorce. I had sent it to DTB to unlock the clarifyer after I got it. It was not packed correctly for shipping back to me, got knocked around, and would not TX/RX, power on only. Bob repaired the damage from shipping. Bob showed me the damage. A chip that resembled a laptop SDRAM chip was knocked out of socket. Bob later put in the Top Gun Modulator, it is on all the time. Bob has been the only person in the radio ever since.
 
Wow, knowing it suffered some bouncing - that kinda changes the playing field.

IT's not as simple as a "change this" due to that...

On top of...

You have a radio that has capacitors known to execute their pop-up timers as they get past ten years...

If the bouncing of the shipping issue didn't cause any severe dents in the case or bent now-lobbing knobs that don't rotate evenly - if you have that straightened out. Then most likely due to the nature of the beast - and if talkback doesn't have a blown cap or cracked trace - it is in level of PRIORITY - it is the "first jack" the audio gets sent to. And the one that uses the internal contact switch to reroute from it, when it's empty, to the internal speaker

Because if you use the EXT Speaker Trace routing, note that the wiring from it to INTERNAL speaker uses a Cap C245 (103) 0.01uF DISC) - when you use EXTERNAL speaker jack, you use the jacks own return and ground not the "DISC cap" that acts like a ripple, ground loop - filter for it's NEGATIVE lead that goes to the INTERNAL speaker. So if there is a cracked trace in and by those jacks - that can explain this far easier than a Tantalum going south - which too - is still possible DUE TO AGE.
upload_2020-7-26_18-9-50.png

It is my fear there may be some issues around Case and Foil Board grounds causing
this snap...​

As you can see, C246 is really C245 and that the Speaker returns are different.

Changes the ballgame.
 
994FE934-C40A-4D11-8D8A-98F6B3840B92.jpeg

The Apache 3800 Transport Case.

That, or the slightly smaller 2800 case at Harbor Freight. Cheap compared to Pelikan.

No more shipping damage.

I’ve been buying 2-3 at a time. And I sure ain’t rich. While everything else isn’t inexpensive, losing a radio to avoidable damage is more than I can afford.

One-time insurance payment.

And if you sell it or make it a gift, the case sure makes a great impression.

(When Handy Andy says, “Wow”, the hands on the clock stop).

“Boy, you in a whole heap o’trouble, now”.


.
 

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