Tony,
Thanks for the input. I can't do what you say until tomorrow and I don't have a scope. I'll report back what I see tomorrow.
Another bit of info, I replaced the PS#1 board with one from another QMX. It worked ok, but the voltage varied quite a bit just sitting there, like .3 or .4 volts. Back in the original QMX it only varies slightly. Seems as if something in the "bad" QMX is causing a varying load. Very odd, IMO.
toggle quoted message
Show quoted text
On May 29, 2024, at 16:11, Tony Scaminaci via < tonyscam@...> wrote:
Your initial thoughts that Vcc was too high at 6V are confirmed and this is likely why the original 6.3V cap blew.
I think Ludwig is correct, the feedback control loop isn’t working properly. If you have a scope, check the waveform duty cycle at the PWM_5V test point. Also check the DC voltage at the ADC_5V test point which should be 2.5 V. My guess is the ADC test point is 3V or higher. The duty cycle at the PWM test point should be no higher than 56% and most likely, less than 50% because the output voltage exceeds 5V. If the duty cycle is within spec (also shown on the SMPS screen), then there is another faulty component in the switcher circuit.
Tony AC9QY Cliff,
it looks like a problem in the control loop.
How and where did you measure VCC?
If really 6 V and more D108 on board #1 must be broken or disconnected. But this isn't the reason for the high VCC. It's only a lack of protection.
Please show a screen shot of Terminal - Hardware tests - Diagnostics. But use only around 7 V input to protect the QMX. And what is VCC in this situation.
73, Ludwig
|
Ludwig,
The QMX will not boot at 7V. 9V will let it boot so the screen shot if with 9V.
As it sits there the 5V varies up and dow a little. If I go to 10V in it varies up 5.8 or so.
toggle quoted message
Show quoted text
On May 29, 2024, at 15:59, DH8WN via < DH8WN@...> wrote:
Cliff,
it looks like a problem in the control loop.
How and where did you measure VCC?
If really 6 V and more D108 on board #1 must be broken or disconnected. But this isn't the reason for the high VCC. It's only a lack of protection.
Please show a screen shot of Terminal - Hardware tests - Diagnostics. But use only around 7 V input to protect the QMX. And what is VCC in this situation.
73, Ludwig
|
Re: Wall warts can be fatal to QMX :-(
This is why I prefer supply nomenclature on schematics be specific such as 3V3 and 5V rather than Vcc and Vdd which are too easily confused.
On Tue, May 28, 2024 at 11:29?PM Hans Summers via <hans.summers= [email protected]> wrote: Hi Reg
I should make it clear, somewhere... - Vcc = 5V
- Vdd = 3.3V
- Vin = the voltage right at the power connector input
- +12V = the voltage downstream of the reverse polarity protection and soft on/off power switch. Though identified as?+12V it could of course be other than that, depending on what your Vin is.
This Vcc/Vdd nomenclature appears to be most commonly associated with the 74-series logic in which on the 74xx and 74LSxx TTL (bipolar transistors) logic chips, Vcc was the supply voltage?(c = collector) and was always 5V. On the 74HCxx chips (MOSFETs), Vdd was the supply voltage (d = drain), and was not necessarily 3.3V; but the subsequent most common supply voltage on many digital IC's (MOSFET-based) is now 3.3V so this is what Vdd commonly means. It does all get a bit confusing and even controversial.?
On Wed, May 29, 2024 at 3:40?AM Reginald Beardsley via <pulaskite= [email protected]> wrote: Chris,
Thanks.? ? Neither of the #1? boards shows 5 V on +12? after grounding power on.? The voltage is 1-2 V max.? ?Happily, I have two unbuilt QMX kits I can borrow replacements from.
Is Vcc = Vin?? I've not seen it stated anywhere in the schematics.
Have Fun!,
Reg
|
Your initial thoughts that Vcc was too high at 6V are confirmed and this is likely why the original 6.3V cap blew.
I think Ludwig is correct, the feedback control loop isn’t working properly. If you have a scope, check the waveform duty cycle at the PWM_5V test point. Also check the DC voltage at the ADC_5V test point which should be 2.5 V. My guess is the ADC test point is 3V or higher. The duty cycle at the PWM test point should be no higher than 56% and most likely, less than 50% because the output voltage exceeds 5V. If the duty cycle is within spec (also shown on the SMPS screen), then there is another faulty component in the switcher circuit.
Tony AC9QY
Cliff,
it looks like a problem in the control loop.
How and where did you measure VCC?
If really 6 V and more D108 on board #1 must be broken or disconnected. But this isn't the reason for the high VCC. It's only a lack of protection.
Please show a screen shot of Terminal - Hardware tests - Diagnostics. But use only around 7 V input to protect the QMX. And what is VCC in this situation.
73, Ludwig
|
Cliff,
it looks like a problem in the control loop.
How and where did you measure VCC?
If really 6 V and more D108 on board #1 must be broken or disconnected. But this isn't the reason for the high VCC. It's only a lack of protection.
Please show a screen shot of Terminal - Hardware tests - Diagnostics. But use only around 7 V input to protect the QMX. And what is VCC in this situation.
73, Ludwig
|
Re: Question about the Max voltage operation for QMX
The problem with 13.8V (the normal 12V in a car or shack) comes when transmitting. Limiting the voltage to 12V protects the finals. If you have a perfect antenna 50ohm 0z you may get away with 13.8 volts forever. Since I never have that perfect antenna, I lower to 12V. I blew up a QDX when I was running a big mismatch at 13.8, I forgot to change the tuner when changing bands. The repair took about 30 minutes and cost about $3 in parts. I was running 5w of WSPR for two minutes of key down and two minutes of break and it took quite a few cycles to blow.?
--
Colin - K6JTH?
|
Re: Question about the Max voltage operation for QMX
I use a Buck Boost DC from Aliexpress, Input 8 to 36V output 12V between the battery and the QMX.
|
Re: #qmx wrong inductances for LPF?
#qmx
Start with Zout is not 100 ohms its 50, the antenna.
Steve why add 10 ohms at the input?? ?ELSIE can set the source and
load impedance to the desired value.? All the 10 ohms adds is
insertion loss and will distort the filter.
Generally with Elsie if I use real values and Qs I get result remarkably
close to reality.? By remarkably close if I use 10% caps, and measured
inductance I get what was modeled.? When they differ its due to strays
or component tolerance (or the selected filter is intolerant!) .
I find the TUNE function useful. With that I can inject some manual
Monte Carlo to see how it behaves with part variation.?
To move the cutoff up start with the base filter and trim the value
by a percentage of the original base frequency and the target.
That's only a starting point.?
So software simulation is as much how the user drives it can influence
the result.? GIGO!
RE: FERRITE over the years I've used a metric boat load of it for all manner?
of designs.? ?EVERY TIME I had an error that didn't measure there was an
error either not uniformly wound or under count (+1 turn).
FYI:? if you pinch the winding close rather than uniform a variation of
more than 10% is easily had and I've seen as much as 18% measured
from close to as wide as possible.
Tools that measure I have, AADE LCII (very accurate), ACE LCR,
NanoVNA (I have three), HP4191A impedance analyzer, Daton M250?
LCR bridge.? When they all agree, then the error is elsewhere.
Its very easy to create your own errors.
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
|
Re: Wall warts can be fatal to QMX :-(
FYI: This device allows one to adjust the voltage (down only) and clean the power coming from various wall warts or computer power supplies. However, the output voltage will be at minimum 2V lower than the input voltage to the device.
see:
--
73
de Roy - KI0ER
Littleton, Colorado USA
|
Re: QMX 170mA draw at 7V with first application of power
This seems like a good addition to the QMX wiki. I also was confused by ~130mA current draw at 7 volts, when there's mention made of "Receive current 80mA". Of course, I now know better, thanks to this group....
de va3rr
|
QMX AF Filter Sweep Problem
New Rev 4 QMX. Receiver was working fine. Transmitter needed some LPF tweaking. Transmitter now fine, but receiver has no sensitivity.
The AF Filter and RF Filter sweeps now look terrible (60-80 dB attenuation).? No obvious solder issues.? I traced through the RF path with an RF signal generator and scope. Looks okay from antenna connector to pins 7 and 9 of IC403.
I think I need to start with the AF sweep problem.? I don't really understand the ADC and audio chain after T401 . I would appreciate advice on how to proceed. As mentioned previously, I have an RF signal generator and a scope. Could easily rig up an AF signal generator.
Thanks and 73,
Steve, N2IC
|
Re: #qmx wrong inductances for LPF?
#qmx
As was mentioned, you need to add the missing capacitor in parallel. 47pf in the QDX HB. IIRC this is all the parts Hans shows in his example of the LPF modeling in the QDX manual. I did my modeling for 50 ohm impedances, but knowing that it's not what happens in reality. But using the "tune part" function in Elsie, I could easily see what the relative effect was of changing inductances or capacitor values.?
I modeled this LPF for the QDX using values that Hans put in the manual for inductance. (Which, is what it was modeled with I believe, probably using the earlier T37-10 toroids.)? ?That one used 290 and 250nh for inductor values for the 15/17m LPF. If I leave the one at 290, and shift the other to less ,like 220nh, my -3db frequency increases by about 1 Mhz.
For this LPF, try reducing the inductance on Part #4 in your model.??
If you mess around with the inductance of part 2, you'll see in the plots it wildly affects the SWR...which is another component of filter design that makes it more tricky! Reducing Part #4 inductance seems to be favorable, SWR wise, and still moves the cutoff frequency up.?
-Nate
N8BTR
?
|
QRP Labs friends,
I am repairing a friends QMX that blew C107. Replaced the CAP with a 10V version. Checking the voltage out of power supply board #1 with 10V input to the QMX I see about 6 V on VCC, should be 5V. Pushing the input to 12V gives 6.8V on the 5V buss. Any ideas what to check? One of the Zener diodes?
I hope someone that understands the power supply circuit board #1 more than I can point me to where to look.
73,
Cliff, AE5ZA
|
Re: #qmx wrong inductances for LPF?
#qmx
Steve, also you missed C522 which is in parallel with L512.?
Ron
On Wed, May 29, 2024 at 09:51 Tisha Hayes, AA4HA via <Tisha.Hayes= [email protected]> wrote: Steve,
Agreed, those input/output impedances have bitten me in the behind before; I had an engineering manager who believed that the software model was 'more accurate' than what we built on the bench and if the results were different it was because we were incompetent at actually building a circuit. Thankfully he was not long for the engineering-world and was quickly "promoted" to sales.
Like Hans had indicated, a model is a reasonable starting point but it eventually turns in to an exercise where the designer is hand picking components that are close in value and inserting them in to the circuit to come up with the accurate values.
You should look up the reference to something called a "gimmick capacitor". Sometimes I work on old radios and find one left behind; It is humorous when some other restorer either cuts it out or just solders the two ends together.
--
Tisha, AA4HA
|
On Wed, May 29, 2024 at 04:54 PM, Reinhard Gr?nz wrote:
The processor should have 3.3V when the band is blocked. I found that Q510 always has 3.3V on G regardless of the band and the other FETs always have 0V.
Hi Reinhard, I think there is a missunderstanding. 3.3 V at G opens the channel and pulls the D voltage down. So the LPF is active. Which LPF for which band is configurabel. Please check Terminal - Configuration - Band configuration. Maybe for all bands the same LPF is configured. After a Factory reset the default values should be set. 73 Ludwig
|
Re: QMX 170mA draw at 7V with first application of power
RESOLVED
Hey everyone thank you very much for the detailed explanations of how the power works on the QMX.? It turns out it was a false alarm.? I finally got back around to checking out this build and everything was just fine. Applied power at 7V and 0.1A and the QMX drew no power.? After checking everything one more time, I gave it the full juice and pushed the left encoder.? Everything fired right up and I was able to load FW, no problem.? So far so good!
Thanks again for all your help!
Yet another QMX that should be on the air soon.
Corbin
N7SNS
|
Re: QMX: having CW and I/Q output at the same time?
I'm so glad to see others asking for KY support!
Hopefully it raises its priority on Hans' to-do list.? : )
73, Mike KK7ER
|
Re: #qmx wrong inductances for LPF?
#qmx
Steve,
Agreed, those input/output impedances have bitten me in the behind before; I had an engineering manager who believed that the software model was 'more accurate' than what we built on the bench and if the results were different it was because we were incompetent at actually building a circuit. Thankfully he was not long for the engineering-world and was quickly "promoted" to sales.
Like Hans had indicated, a model is a reasonable starting point but it eventually turns in to an exercise where the designer is hand picking components that are close in value and inserting them in to the circuit to come up with the accurate values.
You should look up the reference to something called a "gimmick capacitor". Sometimes I work on old radios and find one left behind; It is humorous when some other restorer either cuts it out or just solders the two ends together.
--
Tisha, AA4HA
|
Re: Question about the Max voltage operation for QMX
Thanks Danny, I looked on Thomas K4SWL's blog because I know he had used the QMX and mentioned that he needed a different battery with a lower max volt of 12V. He had a link to the battery he used with the QMX so I ordered one. Thanks very much for your help. Joy N6GO
|
I have no issues transmitting more than once.
|
Colin Kaminski
va3rr
Ronald Taylor
Tisha Hayes, AA4HA