Giuseppe,
If you are convinced that the BS170s have failed, replace them. It is not difficult.
Try to find another nearby Ham or Radio club that can help you with diagnosis and repair, if you feel insecure in doing it yourself.
JZ
On Thu, Feb 22, 2024, 7:36?PM GIUSEPPE < iw8rsb@...> wrote: John, I tried to transmit from home with QMX and listen with the Yaesu FT 817 in CW, the absorption in transmission is low but the CW tone can be heard and the signal is full, in my opinion it's the BS170 transistors that have gone up in smoke , I can't understand how it went from 6W of power to a few mW, I used a wattmeter and an LED meter and there is no RF output, I don't understand what could have happened, I sent an email to Hans but I didn't received no response, everything else about the QMX works great.? Booooòhhhh.........I don't know what to do anymore.? 73 bye
Giuseppe iu8eun
Giuseppe, that is encouraging. JZ
On Thu, Feb 22, 2024 at 4:22?PM GIUSEPPE < iw8rsb@...> wrote: Hi John, this evening I tested the QMS in cw transmission and I listened to it on another radio, the signal is very strong, and the cw dit and dat tone is excellent, I was not able to test the absorption to calculate the power outgoing and I didn't even have an antenna tuner because I was in the car doing some SSB QSOs.? If I can, I'll continue trying them from home later.? 73 bye
Giuseppe iu8eun
Hello Giuseppe,
I'm looking forward to your additional information! How well the QMX is receiving, and whether you can hear your own transmission on another radio will provide useful clues.
Usually when massive BS170 failure occurs in QDX the current draw in RX becomes highly elevated as well. In QMX, the envelope modulator hides some of that by reducing the resting voltage to the PA stage. You can change that voltage via ?"advanced settings", but the results might be concerning!
Another characteristic of large scale BS170 failure is that you can usually smell the smoke!
The few BS170 failures I have seen reported on QMX involved other unfortunate events: failure of a clock generator, for example, or a catastrophic short circuit from a bit of wire or a solder blob.
Please do look at T501. If a solder joint has opened up on the secondary, the PA will have no load on it and no power will be delivered to the antenna. Current draw will be below normal.
JZ
On Thu, Feb 22, 2024, 7:19?AM GIUSEPPE < iw8rsb@...> wrote: Hi John, I purchased the QMX already assembled, I also made the recommended modifications and everything was fine, I made several QSOs in the various bands nearby, the RF power was 6W on the major bands, the antennas I use are all monoband with swr lower than 1, then I decided to test it in WSPR transmission on 10 meters with 5 w output and swr 1, it transmitted for about 10 hours and the following morning I no longer had any reception report.? in reception absorbed 90 mA and transmission now 190 /180 mA.? John I haven't tried listening to see if anything comes out of the radio yet, I'll do it today, I don't have many tools available to do the tests.? I was thinking about transistors.? Thanks so much for your help, I'll let you know.? 73
Giuseppe iu8eun
G., one more thing: Check the solder joints on T501, especially on the output (secondary) side.? JZ
Giuseppe, IMO the problem is elsewhere. BS170 failures on QMX appear to be quite rare.
Did you assemble that QMX or purchase factory-built? What is the current draw you see in RX mode? Is RX working properly on all bands? When you attempt to transmit, can you hear your signal on a nearby receiver?? If we need to dig in more deeply, what test equipment do you have available and are familiar with?
JZ KJ4A
On Thu, Feb 22, 2024 at 5:21?AM GIUSEPPE < iw8rsb@...> wrote: hello everyone, NO POWER COMES OUT OF MY HIGH BAND QMX AFTER A 10 hour WSPR TRANSMISSION on 10 m, in cw transmission it absorbs 290 mA on all bands, could it be the bs 170 transistors that have gone up in smoke??
Giuseppe iu8eun
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