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[help] Only noise being seen while IQ balance / phase lo / phase hi.

Jose Tent
 

Hi. I'm pretty new to electronics.  I bought QCX not only to get on 40m CW, but to learn how this thing is working. I'd appreciate anyones' help as I'm at wit ends to get my QCX working.  

I was able to align the BPF at 8.xxx , but I'm not getting any thing but noise trying to align IQ balance / phase lo / phase hi.  My measurement for those are just bars jumping around randomly with "0" on the top right of the LCD.  I suspect I'm not getting any input from I nor the Q channels to adjust. 

So far, I tested with my mutimeter: 
-Proper soldering/connection of 4 windings for T1. 
-Proper soldering/connection of 4 other toroids. 
-Checked voltage 
    junction of R1 and R2. 2.5V 
   test pins 7 and 9 of IC4, 2.5V
   Pins 2,3,5,6 IC5 around 2.5
-Volume pots are soldered well and have good connections.
-Checked my soldering and for any shorts.   Can't find any problems.

Couple of symptoms observations: 
-LCD screens, center knob, and buttons seem to work fine. 
-I was able to aligning the BPF at 8.xxxx.  But, I noted that volume know doesn't work in a linear fashion.  The tone volume increases exponentially.  That is, the volume goes from zero to 100 some where in the middle really fast.   (normal ?? not sure) 
-Going in to  IQ balance / phase lo / phase hi menu item, I do not hear any tone.  Even with the volume turned all the way up. 

As a next steps, I'm going to check my voltage at various places indicated in the manual to trouble shoot further.   That's quite a list show in the manual, so that should take me most of the time I have tomorrow. I'm not past getting a cheap oscilloscope to troubleshoot this thing.  I think that might be kind of fun, if I wasn't so frustrated.  

Having said all of the above, If you have any guidance or advise on any direction I should look at, I surely would appreciate it. 

P.S. This is a QCX 1.05 purchased  May 22nd.  (Probably one of the last batch before it went to QCX+)

ed.j.tink@...
 

Hi Jose,

I built the same kit on 40m band just recently and had a very similar problem.

Yes, there is a checklist of voltage readings to measure using a DVM on pages 133 and 134. I found a cold solder joint on IC10 (ground pin) that fixed the problem I had.

Please read and carefully heed the instructions on pages 132 and do not attempt to probe the surface mount IC pins directly.

Hold off on the oscilloscope.

Ed

Jose Tent
 

Thanks.   I read your thread.  I was encouraged by you finding your problem.  But no such luck with mine yet.   I'll keep trying, but I'm also a bit frustrated at this point, I might need to put it away for few days, which may allow me to come back with a fresh outlook. 

BTW, a difference from your case is that I'm not hearing ANY tones when I do  "IQ balance / phase lo / phase hi." is that I'm hearing no tone even at maximum volume. 

Daniel Conklin
 

Just to mention that that is not normal volume control behaviour. Maybe there is an issue between that and IC10B.
--
73, Dan - W2DLC

Jose Tent
 

Daniel, 

thanks. I didn't think it was.   I tested the volume pot and it dials up smoothly from 5k to zero.  So, it's not the pot.

Don VE3IDS
 

I would recommend checking the volume pot solder joints again. They can be tricky as the leads aren't long enough to reach through. You may have to solder them from the pot body side. The volume control should lower the volume to almost nothing and smoothly come up. With headphones I usual only have to run the volume up at 9 o'clock if the control is against the stop at 8 o'clock. Also before doing the 3 blue multi turn trim pot adjustments, turn them many times one way and then turn them about 10 turns the other way so they aren't at one end of their adjustment. 

73 Don ve3ids

On Wed., May 27, 2020, 11:49 a.m. Jose Tent, <ksaito2@...> wrote:
Daniel, 

thanks. I didn't think it was.   I tested the volume pot and it dials up smoothly from 5k to zero.  So, it's not the pot.

Jose Tent
 

Don,

Volume pots have been checked at least three times. The soldering points have been filled in from the top and re-heated to ensure good connection as well. They do dial up from zero to 5k smoothly as measured on the contact points on the board from the top. 

Thanks for the tip on the blue miti turn pot. I did gently crank them untill I heard it start making a small popping/clicking noise.  I believe that it reached an limit at one end at that point.  I then dialed back about ten full turns the other way. These things seem to have a lot of turns.  

Ronald Taylor
 

Jose, since you got a good setting of the BPF, that means the signal is getting as far as the IQ balance control/CW filter input area of the board. The BPF tone measuring point is in that location. The monitoring point for the balancing and nulling adjustments is at the input of the last audio stage, IC10A. So the signal is being lost somewhere between the input of the CW filter and the output of IC 10B. 

I couldn't tell from the thread but if you haven't yet measured all the DC voltages around ICs8, 9 and 10, you should do that next. Expect the approximately 2.5 volts on1,2,3,5,6 and 7 of IC8 and 5,6 and 7 of IC9. I,2 and 3 of IC9 might be a little different as it is no longer part of the DC coupled circuitry like all the opamps  preceding it. But its still somewhere in that range I think. Pins 1,2,3,5,6 and 7 of IC10 will be somewhere around half the supply voltage.

If any of those are off, re-check connections in that area. If all is right, then you need to find a way to trace the signal through those stages. With the unit in the alignment mode (test tone present), flow it back from the last stage, output, input, next to last stage output, input etc till you find where it stops. Don't replace an opamp until you are certain it's not something else... Hope this helps

73 ... Ron

Jose Tent
 

I want to thank everyone for their inputs so far !. 

News 1:  THE DETOUR
I followed the official "Debugging QCX issues ~~" video, parts of it follows through the IC's looking at the voltage as Ron suggested.  (Thank you Ron)  Doing this I found IC9 Pin 1 is 5 volts.   According to the video at 16:58, it should be 2.5v !   BUTTTTTTTTT..... I go back to my Rev5e manual and page 139 indicates IC9 Pin 1 *SHOULD* indeed be 5 Volts ???   So I guess the video is wrong OR the design has been updated.

News 2:   PAYDIRT ?
I decided to measure voltage at all the pins of all the IC and compare against the manual. (Vs. Youtube)  I'm finding some voltages that are competely off....

Here are some voltage at the IC that isn't jiving with the manual :  Input volitage is 12.36 volts btw. 
IC6       Pin #3,5 measures around 2.5v  [manual indicates lower at 1.x v)
IC7       Pin #3,5 measures around 2.5v  [Manual = 2v]     *within tolerance ??*
IC8       Pin #5 measures around 2.37v  [Manual = 0.67v]
IC9       Pin #3,5 measures around 2.5v [Manual = 0.65v]
IC10     
     Pin #1,2,3,7 measures 12 volts [Manual = 5.83v]      ??!!??!! 
     Pin #4,5 is measuring 3.02 and 2.31v  [manual = 4.21 and 3.94 ]     *within tolerance ??*
     
 So perhaps I have a inadvertant jump in connections somewhere......  I have to think about this a bit more to figure what is wrong.  

Jose Tent
 

Hmmm... I'm looking at my own information, but I have no idea where to start looking other than perhaps being mindful of my soldering jumping in advertantly to a 12v path......

I'm looking at the circuit track/traces and seeing where the 12v paths are.  But, I definitely could use an elmer to throw me a hint or two. 

dl8lrz
 

Hi Jose,
i think:
first: IC10
PIN4 - connected to ground, must be 0V. Check why no 0V (bad solder joint, conductor path interrupted, measured correctly ??)
IC9:
PIN3 is 5V over 750k (r35). If PIN1 is roughly 5V, everything is ok.
IC9B, IC8, IC7, IC6, IC5:
The voltages depend on the voltage of the FST3153 (IC4, PIN7,9). It is best to measure whether IC5/IC7 PIN1 and IC9/PIN7 are ok. I think 2.5V is ok.
Conclusion:
The QCX noises, the volume can be adjusted with volume - So IC8-10 works first.
The voltages at IC6.7 suggest that IC5.6.7 also work (2,5V).
Align 8.1: Here about 7030kHz 8.2: 700Hz 8.3: 600Hz 8.4: 800Hz
8.7 Peak BPF: Press Select - loud tone must be generated. If only noise, then the path SI5351 - IC3C - filter T1 - FST3253 or CLK0 / CLK1 is disturbed
(many have faults on the connections T1). Only if a maximum is found with C1, then:
IQ balance: adjust with R27. If there is no minimum, the path BPF (T1) - FST3253 - IC5,6,7 or CLK0 / CLK1 is strongly asymmetrical or defective

If no balance tone is produced, check:
- Is the transmitter working? (use dummy!) -> test for IC1 and IC3
- Connect antenna, change frequency. Is some (weak) reception or just noise?

vy 73 Reiner DL8LRZ

Jose Tent
 

Dl8lrz, 

  WHAT I WROTE IN MY PREVIOUS EMAIL : 
     "IC10     
     Pin #1,2,3,7 measures 12 volts [Manual = 5.83v]      ??!!??!! 
     Pin #4,5 is measuring 3.02 and 2.31v  [manual = 4.21 and 3.94 ]     *within tolerance ??* "

I TYPO'ED the above.   I meant to say  Pin 5,6 for IC10.    Pin 4 is indeed grounded and 0volts. 

Jose Tent
 

So just to kind of gather my thoughts.......and summarize for the benefit of those trying to help me. 

Symptom: 
  • No tone for IQ balance / phase lo / phase hi even with volume pot turned to the right. 
  • value at IQ balance / phase lo / phase hi is zero with graph jumping up/down randomly.  (Assumed to be just noise)
  • While doing BPF adjustment, the volume of the tone goes up suddenly from near zero to almost 100% in a very small range around the middle. 

Things Checked and thought to be validated:
  • All torroids and its continuity.    (T1 has been checked at least 5 times thoroughly now) 
  • Proper install of Volume pot.  (value slides smoothly from 5k to zero as measured on the board)
Items found to be inconsistent with spec outlined in the manual:   Few items that are way out of spec in RED.  Input voltage is 12.36V.
  • IC6       Pin #3,5 measures around 2.5v  [manual = 1.5ish v) *within tolerance ??*
  • IC7       Pin #3,5 measures around 2.5v  [Manual = 2v]     *within tolerance ??*
  • IC8       Pin #5 measures around 2.37v  [Manual = 0.67v]
  • IC9       Pin #3,5 measures around 2.5v [Manual = 0.65v]
  • IC10     Pin #1,2,3,7 measures 12 volts [Manual = 5.83v]      ??!!??!! 
  • IC10      Pin #4,5 is measuring 3.02 and 2.31v  [manual = 4.21 and 3.94 ]     *within tolerance ??*

Summary: 
The excessive voltage in IC8, 9, 10 shows issues.  Just not sure how that is happening. Continuing to troubleshoot. 

Don VE3IDS
 

Is IC10 pin 4 at 3.02 or is that a typo and it is pin 6 at 3.02?

Don ve3ids


On Thu., May 28, 2020, 11:50 a.m. Jose Tent, <ksaito2@...> wrote:
So just to kind of gather my thoughts.......and summarize for the benefit of those trying to help me. 

Symptom: 
  • No tone for IQ balance / phase lo / phase hi even with volume pot turned to the right. 
  • value at IQ balance / phase lo / phase hi is zero with graph jumping up/down randomly.  (Assumed to be just noise)
  • While doing BPF adjustment, the volume of the tone goes up suddenly from near zero to almost 100% in a very small range around the middle. 

Things Checked and thought to be validated:
  • All torroids and its continuity.    (T1 has been checked at least 5 times thoroughly now) 
  • Proper install of Volume pot.  (value slides smoothly from 5k to zero as measured on the board)
Items found to be inconsistent with spec outlined in the manual:   Few items that are way out of spec in RED.  Input voltage is 12.36V.
  • IC6       Pin #3,5 measures around 2.5v  [manual = 1.5ish v) *within tolerance ??*
  • IC7       Pin #3,5 measures around 2.5v  [Manual = 2v]     *within tolerance ??*
  • IC8       Pin #5 measures around 2.37v  [Manual = 0.67v]
  • IC9       Pin #3,5 measures around 2.5v [Manual = 0.65v]
  • IC10     Pin #1,2,3,7 measures 12 volts [Manual = 5.83v]      ??!!??!! 
  • IC10      Pin #4,5 is measuring 3.02 and 2.31v  [manual = 4.21 and 3.94 ]     *within tolerance ??*

Summary: 
The excessive voltage in IC8, 9, 10 shows issues.  Just not sure how that is happening. Continuing to troubleshoot. 

Jose Tent
 

AW daing it. Copied over the typo again.   Yes.   i meant pin 5 and 6.... not pin 4,5.

Don VE3IDS
 

Jose
Let's start somewhere. IC 10 pin 5 is an input with a simple voltage divider to set the level. It should be about 4.21 and you are much lower? With power off, check the resistance of each of the 10k resistors, R39&40. Also you could check the voltage of the 12 volt side of R40, the junction of R39&40 and the ground side of R39. This is with your meter negative lead on power supply negative. We want to see if the supply lines are good to that area as well as determining if the resistors are correct. If you need to check the resistor out of circuit, I would suggest rather than trying to unsolder the resistor, clip the lead at the top with a tiny set of cutters so you can solder it back together afterwards. 
Did you use an ohmmeter to identify the resistors or did you go by the color bands?

73 Don ve3ids

On Thu., May 28, 2020, 1:29 p.m. Jose Tent, <ksaito2@...> wrote:
AW daing it. Copied over the typo again.   Yes.   i meant pin 5 and 6.... not pin 4,5.

dl8lrz
 

hi,
I think IC10 / PIN7 12V is not correct.
My thoughts:
- R38 120k is defective / faulty solder joint
- C22 is defective (poor insulation) or installed incorrectly
- IC10 is faulty (or installed incorrectly?)
The voltage at IC10 / PIN5 is somewhat low, but unlikely to be the cause of the 12V in the PINs.

    "While doing BPF adjustment, the volume of the tone goes up suddenly from near zero to almost 100% in a very small range around the middle."  -
that is correct, good sign
Reiner DL8LRZ

Jose Tent
 

Don VE3IDS, 

  • 10k resistors, R39&40. =    10k confirmed.  solder continuity good.
  • 12 volt side of R40, =       11.9v
  • the junction of R39&40 =   3.32v
  • ground side of R39. =      zero
          I believe everything looks good here.   Thanks for the advise about clipping the top wire! Very helpful. 


DL8LRZ, 
  • R38 is 120k.  (Took it off the board and confirmed)
  • C22  .....not sure... (no equipment to properly test) 
  • IC10..... not sure....(no equipment to properly test) 

After I checked the above I stared at the circuit diagram for about an hour. and marked where the wrong voltage was being detected.  I also looked up specs on LM4562IC.  I didn't have any revelations, but I'm really starting to understand a lot about this circuit.  

I'm really tempted to buy an oscilloscope so I can trace the tone through the circuit. it's only 38$.  I figured the knowlege that I pickup going through the circuit with that would be worth it. 

dl8lrz
 

Hi,
short test for IC10
Check again whether the marking on the circuit shows the display (ok, already done 100 times)
Use a protective resistor Rp approx. 220 Ohm (against unwanted short circuit), do not connect voltages directly to the PINs.
Connect voltmeter to PIN7
+ 12V via Rp at PIN5 -> PIN7 high, about 12V
+ 12V via Rp at PIN6 -> PIN7 low, about 0V
0V via Rp at PIN6 -> PIN7 high, about 12V
0V via Rp at PIN5 -> PIN7 low, about 0V
Remove Rp

Connect PIN7 and PIN6 directly (analog IC10A) -> PIN7 5V +/- (approximately equal to PIN5); if 12V -> IC defective?
remove the wire PIN7 - PIN6
if no 5V +/- at PIN7:
remove R37
if 5V +/- at PIN7 -> C22 defective ???
if further 12V -> IC10 defective ???

The voltages at PIN7 and PIN1 should be approximately the same.


  • "10k resistors, R39&40. =    10k confirmed.  solder continuity good.
  • 12 volt side of R40, =       11.9v
  • the junction of R39&40 =   3.32v
  • ground side of R39. =      zero"
The voltage should be about 4.2V (Manual), 3.32V is little. If C24 is installed with the correct polarity, this can indicate a defective IC10 ??

vy 73 Reiner

Jose Tent
 

On Fri, May 29, 2020 at 05:40 AM, dl8lrz wrote:
  • the junction of R39&40 =   3.32v
The voltage should be about 4.2V (Manual), 3.32V is little. If C24 is installed with the correct polarity, this can indicate a defective IC10 ??
R39&40 junction is pin 5, +input for 10B.  I'm getting very suspcious of the IC10.   All voltage except pin 4 & 8 (V- in & V+ in)  is wrong.  

Measured voltage for IC10 are:   pin  1  ~ 8   :   11.7  / 11.7 / 11.7 / 0  ==  3.3 / 2.31 / 11.7 / 11.7    (Volts) 
Manual indicates :                        pin  1  ~ 8   :   5.8   / 5.8   / 5.8  / 0   ==  4.2 / 3.94 / 5.83 / 11.67    (Volts) 

I tried to suspect that I've done something wrong instead of suspecting a component.  But, perhaps I should just replace the IC rather than wondering if it's good or NG.   Wonder if I can source this IC locally.