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Minor issue....I think?

144inBama

144inBama

Sr. Member
Apr 22, 2020
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OK, so I'm running the Galaxy 99v2 (35 PEP AM 40 PEP SSB) to drive a DonkeyStomper 1X4 (all 2879s) and it's fully biased, even the driver section. On SSB, upper & lower, with the mic gain and RF Power turned all the way down, I'm getting a .5 (1/2) watt PEP dead key. When I first key, it'll shoot up to maybe 5-7 watts then drop back down to the 1/2 watt, it doesn't do that on AM. Now normally this wouldn't bother me much BUT when running the amp, when I key it's giving me about a 400+ watt dead key for a second or so then back to the 100 watt dead key, yes a 100 watt dead key on SSB. I've replaced the same transistor twice in about 6 months (I did replace the other one in the bank so they'd be balanced) and sending it back to Chad this week for him to go through it again, as I have no blown 10 ohm but it's only doing 200 PEP (so I'm guessing it's another blown transistor). Now the questions....
Is it normal for a Galaxy to have a small carrier on SSB or for it to act this way in general?
If not, what needs to be done that I can do without scopes and the such?

I just purchased a 959B from CB Radios Pronto, tuned, aligned, and receive enhanced. I'm hoping this will fix the issue.
 

To keep this simple...

Locate the 959's VR6 - SSB Carrier BAL.

DX959_AdjPoint.GIF
​
That may just need a "tweak" to reduce the carrier "leakage" - it's what the adjustment is for - to "Center" the SSB IF on the Upper OR Lower sides of the Mixed carrier and Audio from the Balanced Modulator.

When you turn VR6 - you're changing the level of mixing - MORE IF Less Audio - Less IF MORE AUDIO sort of thing. This changes the amount (volume) of signal going to be filtered by the Crystal Filter before it heads off to the TX side.

To Fix this requires the Amp and the Radio into a Dummy load.

You set up the system to load up into the Dummy load and "listen" on the Monitor Radio or watching on the RF POWER meter you'll have to put in line with the Dummy Load to look at the Amps output so you can catch that moment it does this and reset VR6 to correctly offset both sides of the Carrier in USB and LSB modes.

VR 6 is not perfect, but this should help you see when this event happens - and if kept low enough - won't send a carrier out or at least one strong enough to trigger the AMP on.

Now the suggestion is only to see if a bigger problem exists - as in you can't tune it out by tweaking VR6.

So if mods have been done, you may need to rethink some choices and you may not like them - considering the several ways you've improved the system from a typical user which would not always see this problem.

You're Biasing and if installed, remote TX key up - setting Bias to make the SSB side work - at the same time using the remote TX key from the Handset - can cause this - it's not your fault, but it is a Galaxy's inherited trait of why they sound good, but perform so terribly...when it comes to audio.

upload_2021-7-13_8-3-15.png​


Now, if the carrier problem with 400+ watt carrier above can't be solved by tweaking VR 6, you may have a MOD-squeal just on the verge of forming from too much RF in you mike ringing back (like a feedback squeal) - that can be from ALC adjust onto a cap change - look up at the Graphic.

It's C149 - I've seen this so many times - people install a BIGGER value cap and don't have this problem - yours in unique in that the BIAS itself makes the system SENSITIVE to the SSB signal side of audio and so you have this condition...a small leak and WHAM - birdies and phantom keying...it's stray RF leakage.

Might want to lower C149 - if it's stock then you have even fewer choices - including backing off the Bias AT the amp (Amps own Bias) just enough to allow the Carrier "ring" to dissipate on it's own and not pass into the Amp to throw your carrier.
 
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I looked through the amp again (with better light) and found the 10 ohm on the driver lightly scorched, pulled the transistor and yup, blown. That pretty much tells me, I believe, with 99.99982% certainty that the radio is the problem. Going to replace the driver transistor and not run it until the new radio arrives.
 
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My recommendation would be to bypass the single-transistor driver stage altogether and drive the four transistors directly. Might take more than just a jumper wire to get the input SWR right.

But it would sound better. Just can't see how a single 2879 can soak up all the drive power of a two-final radio, let alone a single final.

You would sacrifice some wattmeter-bragging rights, but odds are it will sound a lot better than it can with a one-transistor driver stage.

73
 
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Nomadradio, I may give that a try as well. The 1X (as I'm sure you already know, I'm just saying for others that may find this post) is best for low powered radios, like a stock, peaked 29LTD (my original use), and the 959 I have coming that's putting out 15-25 watts max. It was great on the 148GTL which was only putting out 13-18 PEP. Once you get into higher output xmitters, you have to pad the input (reduce the amount of power going in) so you don't blow the driver, which if you're having to pad it, you don't need it. I'm pretty sure if it was padded even more it would do fine with the 99v2, but again, if it's being padded, why do I need it? Now with that said, the 959 doing 25 max into a padded 1X4 "should" last forever as NOTHING is getting driven close to it's max....
Now that I've said all that, feel free to shoot hole in it as this is just "my" understanding of it and I have ZERO problems being taught new things or corrected on things I "think" I know.
 
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OK.....My 99v2 has the Ranger EPT690011D board in it, I can not find a VR7 in it.... The component layout is very similar to the 959 as far as location of identified parts. The VR6 on the 99v2 is in the same place, as are the other VRs on the 959, so is it possibly the VR6?
 
nomadradio said:
My recommendation would be to bypass the single-transistor driver stage altogether and drive the four transistors directly.
Click to expand...

That is what I used to do with my own personal Texas Star 667 amps, bypass the driver. I was using either a RCI-2950 (first gen) or an HR2510 for a radio. Which sort of made the amp into a 500. I made it so I could put it back to stock if/when I sold it later. This was back in the Toshiba days, before 2000.
 
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It is indeed VR6.....a micro mini tweak dropped the SSB carrier almost completely out, the needle only twitches on key and doesn't activate the amp. It does however hold a 100 watt dead key after modulation ends. I noticed it has a swing mod in it so that could have something to do with it? But anyway....VR6 is the carrier balance for the 99v2.
 
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Sorry, but got busy...Glad you found it!

This is a "tiki-twiki" issue, for the USB and LSB filter coils, their band pass - one rises, the other falls - against the inductive effects of their slugs and their position, or aspect, in the inner form of the slugs' core..

What does this mean - it means you may / should - tweak the USB Slug of remove some of the lower "Bass" the coil can reach down for in where it is positioned in it's core. It sounds by symptom, to me (IMHO) that the USB slug needs tweaking - in which direction, listen to the tone from the speaker, you need to raise it's tone slightly higher to offset the bass part (shift the bandpass of audio up slightly more up in tone - more to treble - like you're adjusting tone control on Dads' old Car Radio.

Which one? The one that affects the USB vocal bandpass...L26 -which heads off to the Balanced Modulator (TP5)
 
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