Re: QDX finals modification, imbalanced heating
Thanks Tony! Grateful to you for pointing out the?TN0110! I see discussion also of TN0106, but I suppose there's no?reason to prefer that over TN0110 other than price/availability? I received the TO-92 hat heat sinks; they're not great, but I'll try attaching them with thermal glue.
On the imbalance... I went ahead and ordered a new IC5 74ACT08 and plan to try that. But if there are other things I can check first it would be good to know. I have a tinySA on the way, which seems worth at least a quick look if it arrives in good time. I wonder if there's any suggestion about why I also see imbalance at the IC5 input. Could it be the IC5 damage shows up as bad input impedance? If it turns out I have problems further upstream?I will probably go to plan B of building a new QDX with the extra kit I have on the shelf...
On Sat, Dec 30, 2023 at 10:39?PM Tony Scaminaci < tonyscam@...> wrote: Hi Peter,
I like what you¡¯ve done so far. Keeping the TN0110 leads as short as possible is in line with many comments that the leads conduct most of the heat away from plastic TO-92 packages. The Raspi black-finned heat sink is also a good idea to help improve heat transfer from the board itself. Finally, the metal transistor hats will be a plus but likely marginal. Still, I¡¯d do this too. There are copper finned heat sinks in the Raspi form factor that would be better than black aluminum so you might want to look into these as well.
Using black paint will not help at all and will probably decrease heat transfer. Not a good idea, I¡¯d scrape off that paint.
The TN0110 will produce a larger voltage kick at turn off than the BS170 but TN0110 is a 100V device compared to 60V for the BS170 so you have considerably more safety margin. However, the lower gate threshold of the TN0110 will produce a higher drain current which is why you get a higher voltage kick at turn off. I¡¯d go with one of the diode bypass methods offered in this forum for a better safety margin even though it¡¯s probably not necessary.
Some here have experimented with cranking the gate driver AND¡¯s up to 6V. While this will help drive the BS170 to be a better switch, I doubt this would help at all with the TN0110 so don¡¯t bother with that mod. The TN0110 is already a better switch since its gate threshold is lower.
Finally, the imbalance you¡¯re seeing could be due to mismatched transistors with different thresholds. I intend to match my TN0110¡¯s with a DC threshold measurement using a superstrip breadboard. But investigate the other possibilities suggested here first. A scope on those gates would be very useful for troubleshooting this if you can get your hands on one.
Overall, you¡¯re doing great with these mods and keep up the feedback. We¡¯re rooting for you!
Tony - AC9QY Thanks Bruce! Once I have the finals imbalance sorted out I will try adding the hats and report back if I have anything useful to add.
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I have completed my Mid-Band build and got tested and tweaked.? ?I was targeting 40-15 but it turned out that 60 was a go as well.? ?I'm happy enough with everything but the receive side of 15M.? That is not as good as I would like but it has surpassed my threshold of? desire to continue futzing with it for the time being.? ?The attached PDF is what I ended up doing minus some of the iterations in the middle of the process.? ?I also have a low-band QMX (REV1 PCBs) all built up that I may tinker with at some point to switch to a mid band as well.?
73,
Bill, N6MTB?
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Sorry, it is a QCX mini. ? -KB9HV
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On Dec 31, 2023, at 2:34 PM, Ronald Taylor <wa7gil@...> wrote:
? Check the voltages on ICs 8 and 9. Look for wrong capacitors or resistors in that area as well (assuming you are talking about a QCX Classic or QCX+). If it's a mini, then all that is pre-soldered SMD and probably correct but you can still check the voltages around the two ICs, and look for any SMD parts that may have been dislodged during construction. Typically, you should?see fairly strong stations drop off almost completely with only one or two 100 Hz tuning steps either way of center.
Ron On Sun, Dec 31, 2023 at 1:24?PM Mike McCarty < mmccarty@...> wrote: I built a QCX for 20 meters the other day. It went well.? I powered it up, aligned it, and immediately made a QSO.? It put out 5 watts at 13.8 volts without any adjustment.?
I¡¯ve noticed that the CW filter isn¡¯t very tight though.? I can hear strong stations from 100 Hz to 1800 Hz as I tune up and down the band, although largely diminished when off of the 700 Hz center frequency, but not quite gone.? I¡¯ve looked at that portion of the board and can¡¯t find anything obvious.? Any ideas?
Mac, KB9HV
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Check the voltages on ICs 8 and 9. Look for wrong capacitors or resistors in that area as well (assuming you are talking about a QCX Classic or QCX+). If it's a mini, then all that is pre-soldered SMD and probably correct but you can still check the voltages around the two ICs, and look for any SMD parts that may have been dislodged during construction. Typically, you should?see fairly strong stations drop off almost completely with only one or two 100 Hz tuning steps either way of center.
Ron
On Sun, Dec 31, 2023 at 1:24?PM Mike McCarty < mmccarty@...> wrote: I built a QCX for 20 meters the other day. It went well.? I powered it up, aligned it, and immediately made a QSO.? It put out 5 watts at 13.8 volts without any adjustment.?
I¡¯ve noticed that the CW filter isn¡¯t very tight though.? I can hear strong stations from 100 Hz to 1800 Hz as I tune up and down the band, although largely diminished when off of the 700 Hz center frequency, but not quite gone.? I¡¯ve looked at that portion of the board and can¡¯t find anything obvious.? Any ideas?
Mac, KB9HV
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I built a QCX for 20 meters the other day. It went well. I powered it up, aligned it, and immediately made a QSO. It put out 5 watts at 13.8 volts without any adjustment.
I¡¯ve noticed that the CW filter isn¡¯t very tight though. I can hear strong stations from 100 Hz to 1800 Hz as I tune up and down the band, although largely diminished when off of the 700 Hz center frequency, but not quite gone. I¡¯ve looked at that portion of the board and can¡¯t find anything obvious. Any ideas?
Mac, KB9HV
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Re: QMX HI Band Rev 2. Immediate current limit on startup
Seems like there are a lot of occasions where it turns out that
the MPU is fried. I've encountered it what, two or three times?
The MPU had to be working to put in the boot loader; what could
subsequently damage the MPU in a normal turn-on? Is it always
over-voltage on VDD, or is it exposing some other connection to
the MPU to over-voltage?
And I suppose importantly: are there design changes that would
better protect the MPU? (Not critiquing Hans' design, he's done
more than I would've!)
73, Paul -- AI7JR
On 12/31/23 09:19, Evan Hand wrote:
Hello Ken,
I suggest you separate all the boards and measure the resistance
on the Vdd line of the main board.? If that is zero, you can do
little other than check for shorts.? In my case, it was the MPU
that shorted out.? The chip needs the QRP-Labs boot loader program
to work, so replacing the chip is not yet an option, even if you
can replace a large SMD device.
If the mainboard Vdd is not shorted, Check the other boards to see
which one is the culprit.? I hope this is your case, as those are
repairable.
73
Evan
AC9TU
--
Paul -- AI7JR
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Lun,
Keep in mind that the noise level and signals on 80 meters tend to be pretty strong. If you had switched in a 15 db attenuator to any good communications receiver you would not notice much of a difference at all. You can up the gain in the Band Configuration if it seems too low. If you wanted you could add some parallel capacitance to C402 to bring the resonance lower but I wouldn't bother.
73, Jim AJ8S
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Re: QDX: WSJT-X indicates that QDX resides at COM3 but I'm still getting Hamlib errors when I try to test CAT there.
Evan and group.
I have something intermittent going on here. Sometimes, QDX Digital XCVR shows up in audio and as COM3 in Device manager. But, sometimes one or both will disappear. When either is absent, or course, test CAT fails with plenty of Hamlib messages. This rig has worked great in the past and this is a recent issue.
Perhaps a defective USB cable or PC port. BTW, to complicate things, I also use the same PC and WSJT-X 2.6.1 with a second configuration for a Yaesu FT-450D permanently set for 5 watts out which works consistently well. More experimentation to follow.
Thanks and 73,
Bill, WB4HIO
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If I understand you correctly, you have already fixed the error, that's great, congratulations?
In the training documents from moltrecht, there are a few probes that can be set up quickly in the measurement technology class A section, for example:
I myself always have an antenna tuner with power display (ATU-100) at the output of my qdx because otherwise I would be a bit worried about my finals.
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Re: QMX HI Band Rev 2. Immediate current limit on startup
Hello Evan, and thanks for the reply.? Yes, the test I mentioned above was on the main board alone.? There is a direct short from the vdd connection for the 3.3 volt switching supply board to ground.? Other than start pulling parts I don't see anything indicating a short so it may very well be the processor. I was afraid of that after reading some other threads here.
I had some hobby money in paypal so I've ordered another kit and will keep looking this one over.?
Thanks again and 72/73
Ken
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Re: QDX: WSJT-X indicates that QDX resides at COM3 but I'm still getting Hamlib errors when I try to test CAT there.
wb4hio,
Have you set up the audio?? I had the same issue until I got the audio set correctly.? Both need to be set up for Hamlib to be happy.
73
Evan
AC9TU
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Re: QDX: WSJT-X indicates that QDX resides at COM3 but I'm still getting Hamlib errors when I try to test CAT there.
On 31/12/2023 17:03, wb4hio via groups.io wrote: QDX does show up in Device Manager at COM3. BTW,? Baud rate is set for 38400 and rig set for TS-440S. Have also tried rig for QRPLabs QCX/QDX.
That doesn't work either. Maybe an issue inside rig? Maybe. Does the "Test CAT" work? Can you connect by the terminal? What is the Hamlib error message? 73 Alan G4ZFQ
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Re: QMX HI Band Rev 2. Immediate current limit on startup
Hello Ken,
I suggest you separate all the boards and measure the resistance on the Vdd line of the main board.? If that is zero, you can do little other than check for shorts.? In my case, it was the MPU that shorted out.? The chip needs the QRP-Labs boot loader program to work, so replacing the chip is not yet an option, even if you can replace a large SMD device.
If the mainboard Vdd is not shorted, Check the other boards to see which one is the culprit.? I hope this is your case, as those are repairable.
73
Evan
AC9TU
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Re: QMX rev 2 build dead and does not boot
Ouch, Evan. Yes that could do it.
JZ
On Sun, Dec 31, 2023, 9:07?AM Evan Hand < elhandjr@...> wrote: John,
I interpret that pins 1 and 3 of the MOSFETs are source and gate.? That would indicate that Q103 and Q105 turn on when holding down the left encoder.?
You are correct in that Q102 is not turning on.? That is likely because the "LIN_REG_EN" is low from the MPU.? That should start High, and then when ready, the MPU will set it low.? That could be measured as well.
This is the third or fourth post with this type of issue.? In those cases, it came down to a blown MPU.
Franz,
I would still suggest that you measure the resistance on the Vdd line, as your symptoms are identical to mine.??
You could also confirm the voltage on the input to the 3.3-volt regulator while the encoder is pressed and the gate voltage on Q102.
73
Evan
AC9TU
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Re: QMX rev 2 build dead and does not boot
John,
I interpret that pins 1 and 3 of the MOSFETs are source and gate.? That would indicate that Q103 and Q105 turn on when holding down the left encoder.?
You are correct in that Q102 is not turning on.? That is likely because the "LIN_REG_EN" is low from the MPU.? That should start High, and then when ready, the MPU will set it low.? That could be measured as well.
This is the third or fourth post with this type of issue.? In those cases, it came down to a blown MPU.
Franz,
I would still suggest that you measure the resistance on the Vdd line, as your symptoms are identical to mine.??
You could also confirm the voltage on the input to the 3.3-volt regulator while the encoder is pressed and the gate voltage on Q102.
73
Evan
AC9TU
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QMX HI Band Rev 2. Immediate current limit on startup
Hello,
QMX? Ver. 2
12 volt build
After complete success with my low bands unit I built the hi band over Christmas.? Every connection was inspected with a loop during the build and everything was re-inspected before attempting to power up.? I used a current limiting supply set for 7volts and 250ma.? Upon pushing the left encoder I noticed immediate current limiting and the voltage pulled down to about 5.5 volts.? I let go of the encoder and current went back to zero.? There was no smoke or smell.
I've since been over the board several more times and can find no shorts I may have created.? The 3.3 volt rail on the main board now measures a direct short to ground.
Any pointers as to what I might check next would be greatly appreciated.
Thanks,
Ken, W4KAC
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I have been using the low band QDX for a couple months and it seems to be reaching out when I try (can usually get at least one heartbeat on JS8Call).? I could swear that the last time I checked (about a month ago), I was getting around 4 watts out.? I finally got the QRP-Guys SWR/Power meter and it seemed to be showing .5 watts.? I double checked this morning and put a Rig Experts SWR meter and confirmed I had 1.2/1.3 to the QDX, and a Bird power meter showed just over 1 watt.? Current draw for the radio is about .3A receive and about .83A on transmit.? All this at about 8.5V.? Is this normal, or should I start testing components, and if the later, which ones?
Bob
KG5GTE
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Re: QDX: WSJT-X indicates that QDX resides at COM3 but I'm still getting Hamlib errors when I try to test CAT there.
Thanks, Alan. QDX does show up in Device Manager at COM3. BTW,? Baud rate is set for 38400 and rig set for TS-440S. Have also tried rig for QRPLabs QCX/QDX.
That doesn't work either. Maybe an issue inside rig?
73,
WB4HIO
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Re: Clock with QLD2 - Voltage Regulator
#clock
Without taking my QLQ2 apart I can¡¯t measure the current on the 5V line, but the overall current with 13.5V supply is only around 90mA. So there¡¯s not very much power being dissipated. It has been on for about 20 minutes now and I can¡¯t feel any difference in temperature where the regulator bolts to the die cast box.
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Re: Clock with QLD2 - Voltage Regulator
#clock
Likely bad part they usually shut down rather than smoke.??
FYI the 7805/LM3xx series is a very old part, I started using them back in
the mid 70s.
That said its about power, not amps.? The 7805 can dissipate maybe a few
Watts?on a good large heatsink.? Since the tab is ground no need for insulator.
How is power determined?? Input Voltage minus output voltage or for?
the 12V case 12-5= 7volts across the regulator. At 150mA that means?
.15*7 or 1.05W as heat!? However if the current was 1A that would be 7W
and demands a larger heatsink.? FYI the max current is not universal
I have 7805 parts from many vendors and their max current across the
set is anywhere from 1A to 2.5A but they all get hot at the same power
dissipated.
The peak current spec is the limit where it will stop regulating, but usually?
it requires a large heatsink and its more a momentary value rather than?
continuous due to heating.??
If you need substantial current its better and more efficient to go
switch mode (buck converter).
--
Allison
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Post online only,?
direct email will go to a bit bucket.
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Ronald Taylor
Paul - AI7JR
Jim AJ8S
Bill, N4QA/QRP