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Lost power

 

Qmx power issue.
Everything was good for about a year.
I always transmit into a resonant ?antenna ?through an Elecraft?tuner.
Walked up to it this morning and made a test transmission and had almost no power on all bands.
I tried my other radios and they were fine.
Where do I start troubleshooting and is this a common issue?
thank you everyone.
N2HHH
 

Have you been using the same power source for the last year?
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What is/was the voltage supplied on last use?
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I ask this as the BS-170. tend to be 'sensitive' to high input voltages.? ?This is common min many rigs that use this device for a PA section....? A web search will show this as a common topic on many boards.
 

I’ve been running it on a regulated 12 V through a ?buck converter.
on an Astron power supply.
 

On Wed, Jul 17, 2024 at 06:47 AM, Howard Lamhut wrote:
and had almost no power on all bands.
Howard,
some question:
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  1. Which mode did you use, CW or digi? If digi could you check CW?
  2. Is the receiver working well?
  3. Which FW version is in use?
  4. Did you see a letter "P" or "S" in the first row right from the frequency? If yes please check the operation manual for practice mode or SWR protection.
  5. Did you check by an external rf power meter or only via the internal? If only internal please check by an external meter.
  6. What is the supply current in RX mode and in TX mode, much higher or nearly the same. If much higher then the PA is consuming current.
  7. Did you check via terminal - Diagnostics? All voltages are ok? What PA voltage when pressing no key, pressing "P" and "T"?
    Please use a dummy load for this.
These are some steps.
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73, Ludwig
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1 cw
2 receiver good
3 firmware version 19
4 no
5 both external and internal.
6 I have not checked current in Rx vs tx.
7 have not checked via terminal diagnostics yet.
 

I had power output loss on a qdx (same architecture) when txing into a resonant antenna via a tuner.? Sometimes my at-10 would decide to do a tune cycle if it detected the swr creating up over 2:1.? ?It then temporarily presents repeated high swr to the radio, albeit briefly. I think this repeated mini abuse of the finals was enough for them to eventually give out.?
I ordered a bag of about 20 bs170's for next to nothing and just replaced them. On testing them one had gone os.??
Knowing that antenna never strays above about 2.5:1 I removed the tuner and haven't had any issues since.? Replacement was quite a simple job with a de-soldering iron.?
 

Hi Samantha. ?
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Not quite the original posted situation I think but yes this is a regular peril where some auto ATUs and their ?‘just try all the possibilities’ first stage algorithms meet ‘running at the limits with limited or no SWR protection’ radios
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If the auto ATU range can match 10:1 SWR to 1:1 it can also make a 1:1 load look like 10:1 at the rig. ? ?
By contrast my beacon antenna ( fed directly NOT via ATU ) came down in the garden after high wind but was still only presenting 3:1 to the rig which waited patiently to be noticed/rescued (still working) next day. ??

Where I have to use an auto ATU on these rigs it’s a ‘latching relay’ type so I tune it using another rig or via a 3dB attenuator ?and then turn it off to lock the setting.
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A QRP auto ATU with a less brutal tuning cycle and automatic input attenuator on tune would still be a good addition to the QRP labs line up?
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Howard?
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I’ve been running it on a regulated 12 V through a ?buck converter.
on an Astron power supply.
?
Thus may be part of the problem. - Though not the fault you’re now trying to identify
?
When you’ve completed the other test steps can you describe this set/up in more detail?
 

On Thu, Jul 18, 2024 at 04:12 AM, Bruce Akhurst wrote:
Not quite the original posted situation I think but yes this is a regular peril where some auto ATUs and their ?‘just try all the possibilities’ first stage algorithms meet ‘running at the limits with limited or no SWR protection’ radios
Most if not all of those tuners have a relay to reverse the input and output connections to accommodate high- or low-Z loads.? While that switchover is occurring there is a practically-infinite open-circuit VSWR spike presented to the transmitter.? Though the switchover takes milliseconds, a semiconductor can fail even faster.
Then there are the lesser but more frequent tuning mismatches.
I use a resistive bridge when tuning, and so far so good.
73, Don N2VGU
 

I I I I I ? ? I finally learned how to use puddy.
I changed all four bs170’s with no improvement… So it’s not the finals.
I checked all the obvious things. if everything was correct it should be transmitted in CW, but unfortunately it is not.
 

Just out of curiosity, did you press Capital 'P' and/or Capital 'T' in the hardware test Putty screen??
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You can and should hold down either of those two keys for a few seconds and see what is shown on the PTT signal, RF Output, Power and SWR values on the screen.
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Be sure to have a good dummy load connected.?
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Greg. KI4NVX?
 

 

Ah.?

Just checked both my QMX high band and QMX+ and both show approx 30ma Bias Current and 15-16% Bias Duty Cycle on the Transmit tests.
Both are powered from a 12 V source.?

Now... Having said that, I'm not knowledgeable enough of the circuitry or components involved in the power tests to figure out why yours shows twice the Bias Current,? Zero Bias Duty Cycle, Zero TX Power Out and yet does show a value for the transmitted SWR.?

Have you / can you run the suite of Sweep Tests and the new ADC I/Q test??

Hopefully Ludwig and/or perhaps Jeff Moore can weigh in on what to check next.?

Greg KI4NVX?



On Sat, Jul 20, 2024 at 4:44 AM, Howard Lamhut
<Howardlam@...> wrote:
 

Hello Howard,
Q502 and the things around are a SMPS to drive the bias current through the switching PIN diodes.
The bias current is flowing through the diodes in state ON (active LPF).
The shown high bias current maybe real or the measurement is wrong.
To decide we need to know the voltage at TX_BIAS and the other side of R514 and of R516 (see schematics page 5) in TX mode or better you use terminal - Diagnostics pressing key "P".
Using "P" is lowering the danger for the PA.
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73, Ludwig
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