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I re-checked continuity of T501, and looks good. Then checked voltages, and all P & Secondary are zero volts with the QMX powered on in RX. But that's with L502 removed, so I'm guessing that's why (without looking at the schematic).
John, Should I reinstall L502 and see what happens? -- 73 de Roy - KI0ER Littleton, Colorado USA |
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Looks good! On Thu, Apr 4, 2024, 12:09?PM Roy - KI0ER <ki0er@...> wrote: I'm seeing 2.436 V gate to ground on the 2 BS-170's near board edge, and 2.46 V on the "lower" 2. I am running my 12V QMX at 9 V for these tests. |
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That's encouraging!? While L502 is still removed also measure the gates while TX is active. It will probably read OK but one-step-at-a-time caution is still prudent. JZ On Thu, Apr 4, 2024, 11:45?AM Roy - KI0ER <ki0er@...> wrote: Hi John. |
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Re: WSPR record DX? QCX+
Thanks Chris,
I think I'm exceptionally outgoing at times. Not one to miss an opportunity like this, to get propagation data from the far north, I got a hold of their crew and asked about at least having a WSPR beacon along. The Expedition crew got all the way to the hangar in Yellowknife without anyone asking them if they'd be carrying amateur radio of any sort along, duh!!! There is an amateur, hadn't been active in decades, on board, but not even his amateur friends suggested it. The QCX+ (not the QDX I just reported as having failed) I finished building when they showed up. The QDX, and a pre-tuned hamstick, plus the hardware and pages from the operating manual were put on our freight flight to Cambridge Bay, NU, where their crew did the final installation. The antenna was removed to get the vehicles indoors at an unmanned station, Isechen Station, and not replaced until a few days ago. This leg of the expedition should end at Iceland, I'm asking them to look into having a full HF station onboard before they start the drive to the south pole. Maybe I could suggest starting a campaign by radio amateurs to reach out to the Expedition through their contact info on their webpage to ask them to have more amateur radio activity. Such a once in a lifetime IOTA activations has been missed in the last few weeks :-( Ron VE8RT On Thu, 04 Apr 2024 07:11:26 -0700 "Chris / W2BPL" <kwaj.speedo@...> wrote: Bravo! -- Ron VE8RT <ve8rt@...> |
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Re: Something to look out for: possible cause of PA failure (QDX etc).
I have yet to start my builds (I bought one of everything), but I've been reading the posts here for a while and slowly getting prepared.? I have even bought a pack of BS170s in anticipation of possibly needing them - hopefully I don't!? I've also grabbed various inexpensive heat sinks made for rasp pi, etc, considering a possible modification to the bolt on steel washer design.
Tisha and Paul, if you have any links or pics of implementation of M2.5 copper screws/nuts, copper crush gaskets, or other heat dissipation ideas, I'd appreciate it.? A cool radio is a happy radio! Peace, Todd K4MSW |
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Roy, I strongly advise you try to figure out root cause before you replace the bad transistor. ?At a minimum, disable the power source to the PA by lifting a leg of L502, or removing it completely.? Now you can measure gate drive voltages while not risking another transistor failure. Make certain IC503 has not failed. JZ On Thu, Apr 4, 2024, 11:01?AM Roy - KI0ER <ki0er@...> wrote: On my "hot" BS-170, the Drain and Gate show a direct internal short. |
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QDX R3.2 Q7 failure
After months of operating as a WSPR beacon my QDX failed.
Q7, the reverse polarity protection, has gone open. The assembly manual tells me that it has been been replaced by a more robust component starting at Rev 4. What are my replacement options for a Rev 3.2 board? Ron VE8RT -- Ron VE8RT <ve8rt@...> |
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On my "hot" BS-170, the Drain and Gate show a direct internal short.
So the question is, if I just replace that one, am I good, or more likely, I need to find the root cause of why it went bad ... unless it's just that I over tightened the heat sink assembly? Thank you so much John and Ludwig for jumping in to help this novice EE (I'm a retired software engineer actually)! -- 73 de Roy - KI0ER Littleton, Colorado USA |
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Roy, Is IC503 warming? during RX as well? JZ On Thu, Apr 4, 2024, 10:17?AM John Z via <jdzbrozek=[email protected]> wrote:
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Ludwig, A good step towards figuring this out is to observe or measure the gate signals at each bank of BS170s. If it is not what is expected, we can begin to peel down the possibilities at that point. JZ On Thu, Apr 4, 2024, 10:02?AM <DH8WN@...> wrote: John, |
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With display removed, I powered up my QMX and watched the PA transistors with an infrared camera. One of them lit up in the camera within seconds of power up. It was the top-left PA transistor that began warming up. I'll remove it to see if it's bad, shorted internally or something.
I'll do other tests later this morning. -- 73 de Roy - KI0ER Littleton, Colorado USA |
Gary W9TD
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