959 has low modulation

[Robb]

Please excuse my ignorance but why if I key the mice with the freq counter in antenna center pin, and speak, the counter goes from 27.205 to 23.XXX and 28.XXX and anywhere it feels like going. Is it just because of my voice?

Surprised you didn't pop your freq counter doing that.
Yes; speaking changes the freq.

 

[Jdb0367]

Surprised you didn't pop your freq counter doing that.
Yes; speaking changes the freq.

Something is soon gonna pop Robb!
I'm learning something new everyday.

Thanks for the info on over peaking coils using a wattmeter.
I have been using my scope and adjusting it to see a good clean wave and then adjusting until the wave doesn't get taller or shorter.
I hope that's the correct way

 

[loosecannon]

it is indeed in that radio.

at this point i dont see much point in having you go through any antenna testing, as you have just stated the cause of your problem!

your radio is going off frequency when you speak into the mic.

no this is not normal, and your RF frequency should not change when you speak into the mic.
that is known as FM (frequency modulation).

there is a chance that speaking into the mic causes your freq counter to read erratically even though the actual carrier frequency is not changing, but with the problems you are having, it seems more likely that the frequency is actually changing.

so, lets eliminate the possibility of the freq counter getting freaked out by your modulation.

i know you said that the VCO seems to be working properly, but i want you to try something for me in order to illustrate the point im making.

get both of your 959's on the bench with the bottom covers off in order to do some A/B testing.

first, connect your freq counter to TP3 of the WORKING 959, mirror board removed.

once again, ch. 20, AM mode, clarifier centered, but this time with the mic gain up.

once you have the counter connected and are reading 16.5100mhz in receive; key the mic, and speak in to it.

did the VCO frequency change when you spoke?
it should not.

now do the exact same thing to the NON-WORKING 959.
did the VCO freq change when you spoke?
my guess is that it did, base upon your earlier statement.

if this all worked the way i think it will, you have just found your problem.

something inside your radio is causing the VCO to deviate off freq. when you are modulating.

the bad news is that there could be quite a few causes for something like this.
biggest possibility is that the voltage feeding the VCO is dropping with modulation.

so, first test would be to connect your DC voltmeter to TP2.
if your radio is still on channel 20, you should be reading pretty close to 3 VDC here.

now, key the mic and talk into it with the DC meter still connected to TP2.
did the voltage change?

if it did, we need to find out why.
if it didn't, you need to find out which signal/ voltage is dropping out on the VCO chip.

put the DC meter on each pin of the VCO chip, and try to find the one that is dropping out or freaking out with modulation.

right now i am thinking that with the dual finals, there is something in the radio that can't keep up with the additional current requirement of your modulated audio, and is in turn causing an unstable voltage at the VCO.

this would cause the problem you are having.

so next step is to find out where this dropping voltage is sourced from.
well, it's definitely going to come from a voltage regulator seeing as it's the PLL and voltage stability is critical here.

one example: your radio pulls so much current on modulated TX that the input voltage to the regulator is dropping so low as to cause the output to be erratic.
this is where my mind is at right now.

we are getting closer!
don't give up, your tenacity is admirable.
let me know what you find, and take full advantage of having a working radio to compar against.
any time you measure something that you don't understand; check the same thing in the working radio.
LC

 

[Jdb0367]

it is indeed in that radio.

at this point i dont see much point in having you go through any antenna testing, as you have just stated the cause of your problem!

your radio is going off frequency when you speak into the mic.

no this is not normal, and your RF frequency should not change when you speak into the mic.
that is known as FM (frequency modulation).

there is a chance that speaking into the mic causes your freq counter to read erratically even though the actual carrier frequency is not changing, but with the problems you are having, it seems more likely that the frequency is actually changing.

so, lets eliminate the possibility of the freq counter getting freaked out by your modulation.

i know you said that the VCO seems to be working properly, but i want you to try something for me in order to illustrate the point im making.

get both of your 959's on the bench with the bottom covers off in order to do some A/B testing.

first, connect your freq counter to TP3 of the WORKING 959, mirror board removed.

once again, ch. 20, AM mode, clarifier centered, but this time with the mic gain up.

once you have the counter connected and are reading 16.5100mhz in receive; key the mic, and speak in to it.

did the VCO frequency change when you spoke?
it should not.

now do the exact same thing to the NON-WORKING 959.
did the VCO freq change when you spoke?
my guess is that it did, base upon your earlier statement.

if this all worked the way i think it will, you have just found your problem.

something inside your radio is causing the VCO to deviate off freq. when you are modulating.

the bad news is that there could be quite a few causes for something like this.
biggest possibility is that the voltage feeding the VCO is dropping with modulation.

so, first test would be to connect your DC voltmeter to TP2.
if your radio is still on channel 20, you should be reading pretty close to 3 VDC here.

now, key the mic and talk into it with the DC meter still connected to TP2.
did the voltage change?

if it did, we need to find out why.
if it didn't, you need to find out which signal/ voltage is dropping out on the VCO chip.

put the DC meter on each pin of the VCO chip, and try to find the one that is dropping out or freaking out with modulation.

right now i am thinking that with the dual finals, there is something in the radio that can't keep up with the additional current requirement of your modulated audio, and is in turn causing an unstable voltage at the VCO.

this would cause the problem you are having.

so next step is to find out where this dropping voltage is sourced from.
well, it's definitely going to come from a voltage regulator seeing as it's the PLL and voltage stability is critical here.

one example: your radio pulls so much current on modulated TX that the input voltage to the regulator is dropping so low as to cause the output to be erratic.
this is where my mind is at right now.

we are getting closer!
don't give up, your tenacity is admirable.
let me know what you find, and take full advantage of having a working radio to compar against.
any time you measure something that you don't understand; check the same thing in the working radio.
LC

Thanks LC!
For the help and inspiration. I want to conquer this fix.
I will post back my results

 

[Jdb0367]

Ok LC.... Latest tests

Good radio:
Freq cnt TP3, channel 20AM, mirror board removed
16.51000 on RX. -16.51001 on TX. -16.51000/16.50999 when I'd speak

Bad radio:
Freq cnt TP3, channel 20AM, mirror board removed
16.51000 on RX - 16.51006 on TX - 16.51006/16.51005 when I'd speak

Good radio:
V meter to TP2 - 2.908v - No change on TX and speaking

Bad Radio:
V meter to TP2 - 2.986v - 2.985/2.986 on TX when speaking

Both radios - VCO pins

Pins 4,6,8,9,10,11,12 and 13 show 1.2 to 1.3mV on RX
All move to 1.8mV with the mic keyed
All pins fluctuate from 1.5 to 2.0mV while I speak
**Note** these pins would drop at the start of my voice, hold steady at the 1.8mV and rise to 2.0mV as I stopped speaking. Then fall back to the 1.8mV

I only tested these pins because the others did not show any change.

I think this test get a passing grade???

Thank you for your help and patients!

 

[loosecannon]

ok,

now we know that the VCO section works normally without the mirror board in.

the reason i had you do it this way was to eliminate a few possible voltage paths.

next test is to put the mirror board back in, and do the exact same tests on both radios.

if the VCO freq does start drifting around with the mic gain up, or when you speak into the mic; then we know that you are pulling the supply voltage down, and causing this issue.

the first place i would look is the collector of Q37. its the TO-220 style transistor mounted to the chassis toward the front of the radio from the audio chip.

put your DC voltmeter on the collector, mirror board in, key the radio, talk into the mic, and see if this voltage drops or fluctuates.

if it doesn't then i need to start over and re-assess my advice.

if it does act strangely, then move the positive lead over to the emitter leg, and see if that voltage drops or fluctuates with modulation.

if only the output of Q37 drops, then it is your culprit and might benefit from an upgrade.
(check to see if they used a different part in the "bad" radio, as opposed to the "good" radio)

if the input to Q37 drops also, then either T1, or the power switch isn't up to the task.

if this is the case, then there are a couple of things you can try, but it may end up being a case of that radio just not being able to handle the increase output.

just out of curiosity, what are you running the deadkey at?
LC

 

[Jdb0367]

ok,

now we know that the VCO section works normally without the mirror board in.

the reason i had you do it this way was to eliminate a few possible voltage paths.

next test is to put the mirror board back in, and do the exact same tests on both radios.

if the VCO freq does start drifting around with the mic gain up, or when you speak into the mic; then we know that you are pulling the supply voltage down, and causing this issue.

the first place i would look is the collector of Q37. its the TO-220 style transistor mounted to the chassis toward the front of the radio from the audio chip.

put your DC voltmeter on the collector, mirror board in, key the radio, talk into the mic, and see if this voltage drops or fluctuates.

if it doesn't then i need to start over and re-assess my advice.

if it does act strangely, then move the positive lead over to the emitter leg, and see if that voltage drops or fluctuates with modulation.

if only the output of Q37 drops, then it is your culprit and might benefit from an upgrade.
(check to see if they used a different part in the "bad" radio, as opposed to the "good" radio)

if the input to Q37 drops also, then either T1, or the power switch isn't up to the task.

if this is the case, then there are a couple of things you can try, but it may end up being a case of that radio just not being able to handle the increase output.

just out of curiosity, what are you running the deadkey at?
LC

Final report for tonight LC

Good radio:
Mirror board in, channel 20AM, freq cnt TP3
16.50993 RX - 16.50999 mic keyed - 16.50998 talking

V meter TP2
2.899v RX - 2.900 talking

Bad radio:
Mirror board in, channel 20AM, feq cnt TP3
16.51002 RX - 16.51003 mic keyed - *16.51638 talking.*


V meter TP2
2.985 RX - 2.992 keyed - 2.992 talking

Q37 pin voltages:
Bad radio
B=13.89v RX - 13.10v keyed - 13.31v talking
C=8.65v RX, keyed and talking
E=13.21v RX - 12.35v keyed - 12.56v talking

Good radio
B=13.87v RX - 13.25v keyed - 13.23v talking
C=8.59v RX, keyed and talking
E=13.22v RX - 12.47v keyed - 12.48v talking

Thank you for you help and patients with me tonight!!

Oh and for the dead key....
I've tried it anywhere from .5 watt to 15 watts

 

[Jdb0367]

LC, Robb, Waverider.....
I would first like to thank you all for the guidance and suggestions you gave me over the past few days!
Especially you LC. Your patients is amazing.

The good news is, the little 959 is FIXED!!

I'm not sure if I should be embarrassed, pissed off, or just be thankful that it works.

I removed the TRB2 echo board.
That was it. Plain and simple.

Radio is putting out 60 watts. Made a contact tonight 30 miles out and he said the radio sounded amazing.

Just for shits and giggles, I put the echo board in my Cobra 29. It works perfect.
I also have the same board in my other 959 and it works perfect.

Went back thru and checked my original installation and it was done correctly.

I'm gonna chalk it up to gremlins and try and put it outta my mind. Lol

Just ordered a Stryker SR-497.
That shall be my next experiment. Just kidding. I need to convert it and then I'll probably just run it awhile and see how it does. I hear good things about them.

If any of you have a quick insight on the conversion, or just opinions on the radio itself...... I'd love to hear em.

So glad I found this forum and I plan on staying here to absorb as much knowledge as possible.
Thanks again guys,
Joel

 

[wavrider]

Glad you got it going,

Members here have a wealth of information, and humor at times

 

[loosecannon]

well i am glad to hear it!

i guess it would have been helpful to know that the radio had an echo board. they do tend to make quite a racket when they are not working right.


i hope you were able to glean a little radio troubleshooting understanding from this thread, as it sounds like you are set up to repair and mod future radios.

oh, and welcome to the forum. don't drift away just because your radio works now!
LC

 

[Jdb0367]

well i am glad to hear it!

i guess it would have been helpful to know that the radio had an echo board. they do tend to make quite a racket when they are not working right.


i hope you were able to glean a little radio troubleshooting understanding from this thread, as it sounds like you are set up to repair and mod future radios.

oh, and welcome to the forum. don't drift away just because your radio works now!
LC

I thought about that LC.
I guess I didn't really think it would factor in because I tried trouble shooting the problem with the echo board turned off and also with it unmounted from the chassis ( just hanging by the wires).
Lesson learned.
Still don't fully understand why the same board works fine in two other chassis.
Don't worry about me leaving the group as I am here to stay and learn.
I just purchased a Stryker SR-497 and I must say.....it's a little powerhouse.
I haven't seen much on here about the radio and I'm thinking of doing a small post about it.
Looks like it should be a real performer at over 100 watts pep outta the box.
Thanks for the welcoming and for your help.

Joel

 

[loosecannon]

I'll tell you JDB, and im sure you know this from being an auto mechanic; that it's ALWAYS that one thing that you keep looking at, and saying, "no, don't waste time considering this, it can't be the problem". LOL

Some pictures of that stryker in a thread that had the radio's name in the title would be a very cool addition to the forum.

they keep making radios, but the service info is getting harder to come by.
heck, uniden didnt even bother releasing any schematics of their new radios.

a good quality picture that can be zoomed in, of both sides of the PC board is a great resource.
most likely that radio is built upon the same chassis design as the RCI-2970N2, which you can find info on.
take a look and compare them. if they are the same, this is good info to put out there too.

A WORD OF CAUTION! these new SMT chassis do not like swing mods, even though you will find people out there doing them.

i have personally taken in more than 10 of these types of radios, all of them having strange performance issues, and the installed swing kit was the culprit.

the good news here is that you really don't need one. turn up the modulation pot inside the radio, set the deadkey range where you want it, and they will swing up pretty darn well with no mods at all.

i also discourage people from attempting mods and repairs on their SMT radios, as they are so easily ruined by the wrong soldering equipment.

another word of caution on these chassis is that because the tuning coils are so broadbanded, you can have a hard time finding a peak on some of them.

best advice is to put the thing on frequency, and just adjust the pots for the performance you want. then just leave it alone.

glad to hear you are sticking around.
LC

 

[Jdb0367]

I'll tell you JDB, and im sure you know this from being an auto mechanic; that it's ALWAYS that one thing that you keep looking at, and saying, "no, don't waste time considering this, it can't be the problem". LOL

Some pictures of that stryker in a thread that had the radio's name in the title would be a very cool addition to the forum.

they keep making radios, but the service info is getting harder to come by.
heck, uniden didnt even bother releasing any schematics of their new radios.

a good quality picture that can be zoomed in, of both sides of the PC board is a great resource.
most likely that radio is built upon the same chassis design as the RCI-2970N2, which you can find info on.
take a look and compare them. if they are the same, this is good info to put out there too.

A WORD OF CAUTION! these new SMT chassis do not like swing mods, even though you will find people out there doing them.

i have personally taken in more than 10 of these types of radios, all of them having strange performance issues, and the installed swing kit was the culprit.

the good news here is that you really don't need one. turn up the modulation pot inside the radio, set the deadkey range where you want it, and they will swing up pretty darn well with no mods at all.

i also discourage people from attempting mods and repairs on their SMT radios, as they are so easily ruined by the wrong soldering equipment.

another word of caution on these chassis is that because the tuning coils are so broadbanded, you can have a hard time finding a peak on some of them.

best advice is to put the thing on frequency, and just adjust the pots for the performance you want. then just leave it alone.

glad to hear you are sticking around.
LC

Yeah..... I chalk that 959 up to a lesson learned for sure!
I couldn't resist popping the covers off of this 497 this evening and running a couple checks on it just to satisfy my curiosity.
One thing is for sure......it's a completely different animal to me.
All and I do mean all components are surface mount.
The four mosfets are fastened to a 1/4in thick aluminum block and also full shielded.
A nice feature is that all of the VR pots are labeled on the board.

The lack of info is def going to be a problem for some but I will tell ya this...
Frequency was right on the money out of the box.
The conversion took a whopping three seconds.
Modulation was already as high is it could go without flat topping.
Low power is 3 watts and high power is 60 watts.
The first "helllllllooooo aaauuuuddddiiioo" showed 110 watts pep.
I marked the high power VR with a fine tipped pen and moving it just the thickness of the pen line, gave me just over 130 watts pep.

I honestly done see any reason for this radio to need anything else touched.
I'm stuffing my RK56 mic in it and running it!

This thing is a keeper for sure.
It most certainly wouldn't be "all that" to some folks who have been around radios all their lives but it is the best radio I have ever owned. We'll see how it holds up in the long run.

I'm definitely putting some good photos together, and I will post more about it.

One lesson I learned is...... The factory sure can make power a lot cheaper and less frustrating that I can. Lol!

But for me.... experimenting and learning new things are worth their wait in gold.

Joel

 

[9C1Driver]

I would think a 60 watt dead key is just a bit too much for 110-130 peak wattage. Too bad there is no alignment information out there to double check with.

 

[loosecannon]

9C1driver has a point.

if the maximum PEP out of the radio is 130 watts, then you should set your maximum deadkey at 1/4 of that, or 32.5 watts. (i would set it at 30 watts)

the reason is that if measuring power using Peak Envelope Power, 100% modulation equals four times the carrier power. (1.5x for average)

so there is no use in having a 60 watt deadkey if your radio cant modulate it to 240 watts.
LC