Re: QMX(+) Build experience, Poor Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test and resolution with new PCM1804
Hi Hans,
?
Yes, the problem is very strange.
In my case the PCM1804 worked almost correctly. The fault was only in the unequal amplitude of the I and Q signals. If I had not used the diagnostic tools in the terminal I would not have noticed the problem immediately.
What is common in all cases is that the problem is present from the first power up, and fault never appears later. That is why I suspect a fault in the PCM1804 manufacturing process.
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73 de Zrinko Ivan, 9A7AM
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Re: QMX(+) Build experience, Poor Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test and resolution with new PCM1804
Wow - a 15% failure rate sounds exceedingly high.
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On Jan 1, 2025, at 7:48?AM, Hans Summers via groups.io <hans.summers@...> wrote:
Hi Zrinko Ivan
My assumption is that the Chinese manufacturer does not install original chips, but copies that in many cases do not work well.
It isn't how it works. While the PCBs are manufactured and SMD assembly is in China, we don't use a Chinese manufacturer in the way that people submit a PCB and BOM to JCLPCB or someone (not saying there's anything wrong with JCLPCB per se).?
I have a trusted colleague in Shenzhen, a sub-contractor who I have worked closely with since 2014. Many of the parts are ordered direct from the manufacturers e.g. NXP Semiconductor, or Analog devices or from US distributors such as Digikey, Mouser and Arrow. Other parts like resistors and capacitors are sourced locally in Shenzhen from reliable sources but all the parts are tested by me and then the same suppliers used in all manufacturing batches. Everything is traceable and documented.?
Over the years there have occasionally been problems, things were particularly difficult during the global semiconductor shortage post Cv19. We've been able for the most part to quickly identify and resolve any issues that arise.?
The PCM1804 problem is a rather unique one that so far remains a mystery. Progress is being made. On QDX and on current Rev 2 QMX+ PCBs, we're able to test the board INCLUDiNG PCM1804 before shipment and I think we have a very high success rate at detecting failed chips. There was about a 15% failure rate in the batch, which were rejected here and not shipped to kit constructors. I don't think it's an ESD problem caused by the kit constructors.
So I think I'm making progress on the problem and hope to solve it finally got the QMX which is the remaining issue.?
73 Hans G0UPL
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Re: How to smooth QMX+ heatsink area
#QMXplus
Hi Evan,
You could run solder wick across the area with your iron to soak up most of the excess solder. A thin layer of thermal paste would then smooth out the small hills and valleys.
Tony AC9QY
Hi Chris,
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Thank you for your input.? I have read the posts on what kills the BS170s.? I believe it is more complicated than just a single condition.? As the temperature of the BS170 goes up, the possibility of breakdown seems to increase.? ?This would lead me to believe that providing the best heat transfer, managing power out, SWR, and working voltage are required.
?
I am looking for a way to smooth the pad area.? I am hesitant to reflow the solder, which could worsen the problem.? I was hoping someone could give me tips on how to redo the area.
?
73
Evan
AC9TU
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Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp)
#ABS
#ATU
#PSU
#QMXplus
I’d love to participate with one unit
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Jacob
N3JU
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Re: Beginning New Year with a Original QCX Bang
Your old CPU's a goner, but great results!
?
HNY!
--
73, Dan? NM3A
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Re: How to smooth QMX+ heatsink area
#QMXplus
Hi Chris,
?
Thank you for your input.? I have read the posts on what kills the BS170s.? I believe it is more complicated than just a single condition.? As the temperature of the BS170 goes up, the possibility of breakdown seems to increase.? ?This would lead me to believe that providing the best heat transfer, managing power out, SWR, and working voltage are required.
?
I am looking for a way to smooth the pad area.? I am hesitant to reflow the solder, which could worsen the problem.? I was hoping someone could give me tips on how to redo the area.
?
73
Evan
AC9TU
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Hi,
?
Would it be difficult to change BS170 final transistors to LDMOS ones??
?
Regards
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Re: QMX(+) Build experience, Poor Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test and resolution with new PCM1804
Hi Zrinko Ivan
My assumption is that the Chinese manufacturer does not install original chips, but copies that in many cases do not work well.
It isn't how it works. While the PCBs are manufactured and SMD assembly is in China, we don't use a Chinese manufacturer in the way that people submit a PCB and BOM to JCLPCB or someone (not saying there's anything wrong with JCLPCB per se).?
I have a trusted colleague in Shenzhen, a sub-contractor who I have worked closely with since 2014. Many of the parts are ordered direct from the manufacturers e.g. NXP Semiconductor, or Analog devices or from US distributors such as Digikey, Mouser and Arrow. Other parts like resistors and capacitors are sourced locally in Shenzhen from reliable sources but all the parts are tested by me and then the same suppliers used in all manufacturing batches. Everything is traceable and documented.?
Over the years there have occasionally been problems, things were particularly difficult during the global semiconductor shortage post Cv19. We've been able for the most part to quickly identify and resolve any issues that arise.?
The PCM1804 problem is a rather unique one that so far remains a mystery. Progress is being made. On QDX and on current Rev 2 QMX+ PCBs, we're able to test the board INCLUDiNG PCM1804 before shipment and I think we have a very high success rate at detecting failed chips. There was about a 15% failure rate in the batch, which were rejected here and not shipped to kit constructors. I don't think it's an ESD problem caused by the kit constructors.
So I think I'm making progress on the problem and hope to solve it finally got the QMX which is the remaining issue.?
73 Hans G0UPL
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Re: How to smooth QMX+ heatsink area
#QMXplus
I have built 6 QRP Class D/E type of PA kits (QCX, QDX, and QMX) that use the board as a heatsink and did not see this excess solder on the board.? I was surprised, as the quality has been much higher in the past.
?
I will use some paste and see what happens.? I have another QMX+ on order in case it has problems.
?
73
Evan
AC9TU
?
?
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Re: How to smooth QMX+ heatsink area
#QMXplus
There have been many threads on "what kills the BS170s" including my own.??
It appears that over temperature is unlikely.? Much more likely is voltage transients, particularly on the 160m and 80m bands where the voltage across the BS170s may exceed the manufacturers rating (Hans knows and plans to reduce the PA voltage on these bands in future software).? I suggest on 80M and 160M using 10V supply.
The peak BS 170 voltage becomes worse with Poor SWR.? Never use higher than 12V (or 9V with that model).? Use an ATU with extremes caution since while searching for a match the SWR can be >10
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Re: How to smooth QMX+ heatsink area
#QMXplus
Hi
1- don't use termal paste, your QMX won't work
2- use termal paste, it will improve heat transfer drastically
both are wrong
73 & HNY DE muhsin TA1MHS
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Re: How to smooth QMX+ heatsink area
#QMXplus
That sounds like it could work as well as anything else. Someone here, which link I couldn't find, did some tests that showed the leads dissipate a lot of the heat, so I always add more solder to the leads at the top of the board. Another thing you could try is to stick on a small square of copper tape over the heatsink area.?
--
73, Dan - W2DLC
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Re: QMX(+) Build experience, Poor Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test and resolution with new PCM1804
My assumption is that the Chinese manufacturer does not install original chips, but copies that in many cases do not work well.
?
73, Zrinko Ivan, 9A7AM
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How to smooth QMX+ heatsink area
#QMXplus
Given the excess solder in my QMX+ heatsink area, does anyone have suggestions on improving the heat transfer?? My best guess is to use thermal paste.
?
?
73
Evan
AC9TU
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Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp)
#ABS
#ATU
#PSU
#QMXplus
Sorry if it has been said but how much is it per person?
I would like to be included as well.
Rhett -KB4HG I would like to be added to the group buy list for one of the ABS kits.
?
Thanks,
Howard Cripe - N0AZ
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Re: There is no RX and TX in QMX+.
Hi Halil.
Did you remember to install the jumper behind the BNC? See page 37 of the assembly manual. It is easy to miss.
73
Roger
8P6RX
Get
Hi Daniel;
?
I shared the measurements again by providing Dummy Load.
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Thank you for your support.
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Re: There is no RX and TX in QMX+.
Hi Daniel;
?
I shared the measurements again by providing Dummy Load.
?
Thank you for your support.
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Re: QMX(+) Build experience, Poor Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test and resolution with new PCM1804
It's remarkable that you have had three PCM1804 failures even while using antistatic procedures. I built a QMX and a QMX+ without using any precautions, and did not have a chip failure. The PCM1804 mystery continues.
--
73, Dan - W2DLC
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Re: There is no RX and TX in QMX+.
Halil,
You need a dummy load to properly begin analyzing the problem. Your SWR protection has been triggered, so the radio won't transmit until that is reset.?
--
73, Dan - W2DLC
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There is no RX and TX in QMX+.
I have assembled my QMX + device, all visual functions are working. but SWR is almost above 10 on all bands. I can not listen at all. There is no dummy load at the moment, it is only connected to the antenna, I think the antenna is working properly (Diamond RHM12)
I have very little technical knowledge here. Where can I start to solve the error.
I am very sorry for my bad English.
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Kaufman, Matt - N3AR
Daniel Conklin