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Evan: The BS170 breakdown voltage actually increases with temperature. Before wasting too much time on marginal thermal improvement you should measure the thermal increase with key down.? Many VOMs

Hi all HNY! I was wondering if there had been any further investigation into this one or whether it's a matter of either accepting the noise or fitting a toggle switch (the latter is something I'm

To be clear again: I'm saying 15% of the batch of 1000 QMX+ Rev 2 PCBs was rejected during our testing here. The percentage of Rev 2 QMX+ with faulty PCM1804 that reach actual kit builders should be

Yes, remarkable that the PCM1804 saga continues. I built 4 QMX and one QMX+. Only one had an 1804 failure. First Rev 1 and Rev 3 (mini) had/have no failures. Second Rev 1 had SMPS (5V), then Mplx chip

A 15% failure rate for any semiconductor device is extremely high. Googling PCM1804 failures shows posts about high-level audio noise that randomly occurs and goes

Hi Mateusz, Gate input capacitance and output capacitance of any replacement transistor must be in the same neighborhood as the BS170. The closest match I’ve found is TN0110 which some here have

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

Wow - a 15% failure rate sounds exceedingly high. 73 -- Matt N3AR

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

I’d love to participate with one unit Jacob N3JU

Your old CPU's a goner, but great results! HNY! -- 73, Dan? NM3A

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

Hi, Would it be difficult to change BS170 final transistors to LDMOS ones? Regards

Hi Zrinko Ivan My assumption is that the Chinese manufacturer does not install original It isn't how it works. While the PCBs are manufactured and SMD assembly is in China, we don't use a Chinese

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

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

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

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

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

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