Galaxy 99v2 final bias question....

[Lkaskel]

Hey Everyone,
OK, this 99v2 is going to kill me. I now have the frequency aligned (with the help of some beez wax) and now to the final overall alignment. With the new 520's (and full power) as I set the bias I can get the driver to 50ma and the voltage is below 3.75 as specified in the 98VHP alignment specs. When I go to align the final bias I 1st turn VR10 CCW and VR 11 CW to get the bias current to 0. That doesn't seem right to me as I would expect that both VR's would be turned in the same direction to get to no current but I am unsure of it. I then adjust VR10 to 50ma and the spec says to be sure the voltage is not above 3.5vdc. At 50ma the voltage on L34 is over 4 volts. When I turn back VR10 to read 3.49vdc the current is 17ma. When I adjust VR 11 to 3.49vdc the total current is 34.

The spec says that I should be adjusting for 100ma total between both finals. Also, If I just adjust for current I can set either VR 10 or 11 to 50ma and when I adjust the other VR it will jump from 50ma to over 300ma. Its like when one FET is adjusted the other one will not balance correctly. I had the same issue with the previous FET's but with those I had about 25% power out and it was DIRTY on the scope.

Any thoughts to my issues here?

Actually, I know what my issues are and they are many..... Any thought to what the radios issues are?

Thanks so much!!!

 

[Handy Andy]

Sounds like you're doing it - "right" but you're encountering a problem I see a lot with MOSFET - you can't keep the Probe leads from "injecting" noise into your test.

So, as you check, you think you got it just right - then WHAM - some bizarre event takes place as you work thru the steps - now you're jumping all over the place.

It's the probe tips picking up IF and RF and Ambiant hum from the air and sending it into the Gate bias section - only this time it "latched" because of the noise.

Think about how those EN parts work...

• use a small trickle of RF to generate a small current, gets rectified; then POW!
  • - does not the Galaxy use a similar design for theirs?
• I mean - it uses a Zener - Zener's are diodes, right?

Check setting...

SSB mode
- RF POWER all the way up
- MIC Gain all the way down
​

So, you're in the CORRECT ballpark, but you're looking for the wrong place to find the ball.

Each radio triggers differently and as you found out - the gates are finnicky - worse than cats.

This condition is from noise, so you found the radios "trigger" at close to 34mA - run with it - if you go too high - they'll latch - as you're discovering.

To Help answer the question about "trimmers turning opposite" yes, they do - they counter rotate -​

Grounds are opposite on both - so the CCW of one - needs to be the CW of the other to match.
​

 

[Lkaskel]

Sounds like you're doing it - "right" but you're encountering a problem I see a lot with MOSFET - you can't keep the Probe leads from "injecting" noise into your test.

So, as you check, you think you got it just right - then WHAM - some bizarre event takes place as you work thru the steps - now you're jumping all over the place.

It's the probe tips picking up IF and RF and Ambiant hum from the air and sending it into the Gate bias section - only this time it "latched" because of the noise.

Think about how those EN parts work...

• use a small trickle of RF to generate a small current, gets rectified; then POW!
  • - does not the Galaxy use a similar design for theirs?
• I mean - it uses a Zener - Zener's are diodes, right?

Check setting...

SSB mode
- RF POWER all the way up
- MIC Gain all the way down
​

So, you're in the CORRECT ballpark, but you're looking for the wrong place to find the ball.

Each radio triggers differently and as you found out - the gates are finnicky - worse than cats.

This condition is from noise, so you found the radios "trigger" at close to 34mA - run with it - if you go too high - they'll latch - as you're discovering.

To Help answer the question about "trimmers turning opposite" yes, they do - they counter rotate -​

View attachment 49674

Grounds are opposite on both - so the CCW of one - needs to be the CW of the other to match.
​

Hi Andy,
1st of all, thanks for your reply!!! I do appreciate your time that you give me with your answers.

Now, I am understanding that you agree that I should just leave the bias at 34ma (or just at 3.5vdc for each final). Right? Here is the real "problem" that I am trying to solve as I know that when I return this radio to the owner it WILL be the one thing they will want to ask/talk about. The radio just does not seem to have the "punch" that I am expecting and I know that the owner is expecting. I am not looking for the crazy over driven result but a punchy one. I am testing with a stock mic so I get a reasonable result and when I compare it to other Galaxy MOSFET radios I've aligned this one seem lethargic. I just did 2 separate on air tests on AM and SSB and both operators said that the audio sounds weak or compressed. One challenge I had in the transmitter alignment was that L42 and L43 seemed to have very little effect on the output by reading the meter or the scope. I would say that L43 had no effect but that may be just shy of the truth but not far off. One other thought is that the one part I did not replace was the regulator. It has that Palomar max mod in it currently. I do have some new TIP36 and TIP42's and I was wondering if you felt like they may make a change. If I could just get this radio to have a little drive in it I could call it a day.....

Thanks so much!!!

 

[Handy Andy]

To help them understand, the "drive" and turn on are key.

When you say it sounds compressed, there are several things to consider.

One main one - to think about (how it all started), when they brought it in, was anything wrong with it and what has been done to it since then?

Palomar "Max mod" is simply an oversized part to fix a previous problem of using the undersized part to fix the problem of being the undersized part so they could sell it legally - now fixed with a bigger part.

• Similar to buying the car, them throwing away the 4-cylinder engine and dropping in a turbo;d version with a lot more spark plugs in it.

If you can understand that approach, they simply put a bigger band aid on a condition most radios face - overzealous AMC/ALC and not enough room for voltage swings because the current demands wash all those nuances away.

Flames have erupted when people start showing others how to "defeat" certain key things because they are the ones whom suffered thru the neighbor's party hut house key downs that rivaled "Worked All Neighbors" Awards -shows which were held in January, right after the Oscars - and before the Enemies - Er - Emmy awards...

"Gosh Darn It!"​

But to see / hear this, means that you might have to put it back on the table and check the output network - there are one - sometimes two, caps on the tank coupling circuit from the MOSFET to the 52-MHz trap if one failed - you'll get a difficult child to play with and the SWR meter won't show any trouble because the problem is BEFORE the SWR meter (Upstream from that riser card) The SWR only shows the conditions PART itself into the outside - not before itself.

​

But there is also some hope in listening - but also comparing - try different power Trim levels thru the AM power control trimmer inside - then look at RF power controls and AMC/ALC - and even see if the Limiter - if it's in place - take a look around here for recent threads (86V I think) has uncovered some tweaks we aren't proud to disclose, but it does help those that want the limiter in place - just not clamping their audio.

Thinking of all the directions to take this...I'll spare you the LONG list and try and post a few smaller digestible sections so you don't turn this into a gluttony of gibberish most would have to invite interpreters over to "understand".

Bear with me...
It will be a ride - in small cars, with breaks to let the kids and old-folks use facilities...

 

[Handy Andy]

To start, I'd look at listening to the PA side of things - see if the Compression distorted stuff starts back at the Mic amp...Talkback or EXT Speaker to PA jack and LISTEN at the Mic level - just have the volume turned down to listen at a comfortable level to possibly hear for those nuances they complain about.

IF you hear them, these compressed "Sounds" or weird-ed effects then the AM Regulator is not the cause - it's back at the Mic amp and its circuit. IC7 will need some TLC.
Look for mods, replace - repair - remove as needed -

​

But if not...meaning you can't seem to recreate the condition - make sure you set their mic up to do this -- verify the mic and or mic amp is not injecting its own colors into the audio.

Once you're satisfied with that, let's look at the Area Of Concern that brought you here...

There is one cap -
C214 - that normally is used to SMOOTH off audio "bass" and also be a Hi-Cut filter
- it is one last step in the audio processing line.​

D93 is not - but C214 is still used for this purpose - it also gets hammered by wild voltage swings - might want to just do a simple swap out - remove and put in a different value cap to hear the effects I mention - you'll see / hear how this particular cap affects audio - while this radio is exhibiting this condition - it can help you determine if the problem is with input drive versus the audio and bias drive instead - trimming voltages on the Main board listening to the audio - you can develop a profile from these value changes to help you troubleshoot the problem.

 

[Handy Andy]

When I mentioned "input drive" that refers to the actual amount of signal available at a given power level to begin the processing the Driver and Final take the Audio and Bias - and mixing it in with the RF.

So, take a look in the message above - I want to point out something...

Predriver section...​

So - I'm going to stop here and let you play catsup - er -ketchup - - I mean Catch Up

Because I want to know what you're doing to the radio while you're encountering these effects, they are complaining about....

​

 

[Lkaskel]

Alright... you gave me a lot to do . Here is what I've done so far.

- Tested the audio from the PA. The audio is loud and clear.
- Checked the caps at the tank coupling circuit. Both were good.
- Replaced cap C214 with various values. This had no effect that I could tell.
- I did hook up another radio in the room to hear the transmit audio and it definitely sounds like something is holding it back.

I also did a very careful exam of the board and I found a few things for discussion.

- In the place of R249 was a resistor that is not original. It is a .55ohm 1/4w. I looked at the schematic and the part is listed as CORE. I am unsure what that means. I saw a pic of a board and it looks like a resistor there but I have no idea what was in there originally.
- There is a jumper wire on the bottom of the board that I am wondering if it is supposed to be there.



Can anyone tell me what R249 is supposed to be and also tell me if that black wire should be there?

Thanks as always!!

 

[nomadradio]

R249 should be 10k. It's the base current source for the AM limiter transistor TR53 and modulation limit trimpot VR14. Making the resistance larger boosts the max modulation level.

73

 

[Handy Andy]

That is an Inductive CORE restriction - aka CORE refers to a Ferrite Bead used there.

Ferrite Core - so Bead on a Lead type of thing.

• that really is only a shorting jumper

That is not what is currently used...

Your part should be a 3.9Ω or 39Ω ohm resistor - by marking.

Look closely - Orange is 3 - White is 9 - by Resistor Color Code...

​

In the above data I showed earlier - the one they're using for R249 is 86 ohm.
Resistor right next to it, is BROWN - GREY - BROWN - being 180 ohm

• IF you notice very carefully - the Brown Green Brown or Brown GREY Brown either or, this value may change even if schematic shows one value - there may be a reason for the value change because the part Exhibits a trait that, to remain stock OEM specs, requires the value to be changed to affect performance.
• You may also have an INDUCTOR of 39uH - tough call - but having it show 0.55Ω means it very well may be the CORE as in an RF choke. - having it being a short.
  • To me it's safer to use the Resistor value than a Choke value - this is a tuned circuit yes, but you can always ADD a Ferrite Bead to the Resistor to help with RF performance, but the Resistance offers a way to keep the part from making the radio sound distorted.

​

Not too worry - just use another 39 or even 47 ohm - and it's a good catch, for this does affect the Pre-drivers ability to develop power and send the RIGHT amount of power to the next stage.

If the Resistor values isn't "right" for this part of the stage in the strip - too much power or too little RF can be generated at this spot, because this part of the stage is amplifying too much - causing a clipping distortion - which REDUCES power transferred to the next stage in the frequency you want - and it sounds distorted.

This might mean you have to rig up a 1K pot and a 100Ω ohm resistor across the fixed and wiper of the pot to make a rheostat so you can determine the CORRECT level of resistance to use. You install the pot with it's wiper to one hole and fixed to the other - the 100 ohm straddles the two at the pot - you then rotate the pot to find the correct level of power to obtain the best signal - which requires the scope or a good set of ears - and adjust to remove the distortion pinch effect - once you have it sounding good - clean no distortion, then remove power, the wires off the board, and measure the resistance across the wires of that pot to find the needed resistance and simply sub in the approximate resistor values in range to restore the proper drive level.

​

Sounds insane but they do this when parts get replaced - they have to - it can alter the radios' ability to produce RF power linearly for SSB use.

 

[Handy Andy]

When you asked about this black wire jumper?

Per my work history,
leave alone - for if it works
don't fix it.
​

 

[Lkaskel]

Things took a turn....
I did not have a lot of extra time for working on this radio but I couldn't resist hooking up a VR in place of R249. The result was interesting. I was able to "peak" the wattage reading using the VR and it turned to to read 156ohms. I did have to switch to a 500ohm pot as the setup that Andy suggested peaked out at the max adjustment and I thought there was more in it. Here is the interesting part of the result. The modulation based on the audio from the bench radio was a little improved but not a ton. I did try a different radio to test the bench radio out and it "boomed" through the bench radio with the same test mic. One last, and very frustrating result. I noticed that I had my meter set on the 5 watt scale instead of the 25 watt scale which I had been using. I remembered that I had it on the lower scale so I could verify the low power setting on the radio. For some reason, at max power (front knob and VR 14) the radio is now only putting out 3.5 watts. The sine wave is perfect on the scope, modulation shows up as clean. What have I done????? The truth is, I am tired and need to walk away. Tomorrow will be another day with a clearer head.

 

[Handy Andy]

This radio looks to be one of those "sequence of events" which means there is more than one thing wrong in any given strip in the radio.

So look for fresh solder and "type cast - compare" radios side to side, if at all possible, to narrow down the spots in the strip that need further investigation - fresh signs of previous work is a good clue to this.

You look like you found one spot, that when you "turned down" one part of the strip - it started to sound better - it's not a boomer yet, but you do have progress. So, work the next stage - onto the next stage - usually when the scope shows good, it's only to a point that it can be trusted - so the rest of the effort is in locating that (GOSH DARN) restriction - because once you see a good scope - means you cleared up a condition - but you might have to return to this spot once the problems were corrected - to restore original levels.

So far, with this progress, my experiences in "crunchy" audio effects, has been where the Pre-driver and Driver are - it's the biasing in both that if one is set too high - a lot of power has to get pushed into it, to even get anything out. IT doesn't get amplified very well either - no dynamic range.

IN the radio your next stage is the Pre-Driver so the focus then becomes; on stabilizing the driver - make sure its' area looks clean and all the caps and resistors are seated - any carbon traces or solder "hairs" in here can wreck your efforts.

Carefully measure the Pre-Drivers bias voltages - a few tenths off may signal bad parts or misaligned output core-coil (that bi-filar wind) - again, look for fresh work - I've got top and bottom of the "10" version of that board for you to review the solder mask and component side layouts in this thread. You can always "right click" on the page box numbers and open the previous pages in a separate tab on your browser so you can scroll to the area and review it as needed using CTRL+TAB to swap between the tabs.

 

[Lkaskel]

A night off did me good. Now I have a fresh head to look at this radio again. I did start by looking at the one mod I have not considered yet. The Palomar Max Mod. That is an upgraded AM regulator. The install of it was ok but I did check the voltages of it. The regulator for that radio should be +5vdc at the collector (center pin). In this radio I have 8vdc. I did change it out with a TIP36C as a test and I still had 8vdc. Does that sound right? It seems something is amiss.....

 

[Lkaskel]

One more update to this very long repair. I am checking each part in the TX chain and I have discovered that Q52 has a 2sc2059 installed. The schematic for that same part in the 98VHP (and many other radios) has a 2sc1906. I wish I had the schematic for the 99v2 with the EPT690011D to be sure what it should have. I think I will swap the 1906 from a working radio and see what I get unless someone has a different thought.

 

[144inBama]

I opened mine this morning for you, it has the 2059. Other than the swing mod, it's bone stock.