Back to square 1

General discussion and support for the Peaberry SDR V2.

Back to square 1

Postby k1qn » Tue Jul 21, 2015 11:14 pm

So, it wasn't the PCM3060.

After running a full day, with plenty of transmit time, I get slowly diminishing TX output power, chopping of the 4 audio outputs at 1kHz rate. See previous posts for waveform. Duration of the off-time increases over about 8 minutes to the full 1msec, then it goes back to full operation.

I can reset it by removing / returning the 12 volt power.

Demonic posession?
Al Gerheim, K1QN
Celebrating 50 years in ham radio!
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Re: Back to square 1

Postby W4MMP » Wed Jul 22, 2015 3:16 am

Al,
Do you have another computer to test with? That rig ran key down for at least 30 minutes.

(Duration of the off-time increases over about 8 minutes to the full 1msec, then it goes back to full operation. )


I'm not sure I know what that means.
73
Ron / W4MMP
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Re: Back to square 1

Postby k1qn » Thu Jul 23, 2015 3:26 pm

It doesn't seem to be thermal. Going key-down for long duration doesn't seem to upset it. Also, I have another Peaberry that's been working flawlessly for a year or so. Then again, it's for 80/160, so it doesn't get as much use as the 60-20 rig. :-)

Yes, I have a junk XP laptop I can run it with. May take some setup. :-)

What I meant was, it'll show about 90%, then about 80% power for no apparent reason. The power will drop slowly and continuously. After about 8 minutes, it'll be at 0 RF output, then go back to 100% suddenly.

The other "outward signs" are that I can restart the PC with no effect, but if I physically disconnect the USB cable or 12 volt power, it'll reset itself instantly.

I wish I knew more about the conversion from USB signals to analog output. The 1 kHz chopping rate is only seen in the USB part of the board. (I have some very old degrees in EE, but not current on USB protocol.)
Al Gerheim, K1QN
Celebrating 50 years in ham radio!
k1qn
 
Posts: 90
Joined: Sun Oct 20, 2013 9:42 pm

Re: Back to square 1

Postby W4MMP » Thu Jul 23, 2015 3:39 pm

Al,
OK, this what I really want you to do:

The idea is to use a test environment that we can both visualize (particularly for me since I'm not able to see your setup)

1) Attach your dummy load.
2) Start HDSDR and may sure everything is configured properly.
3) Set HDSDR 20M and FM mode. Make sure the "output power" slider is set to Maximum. The Mic Gain slider is irrelevant for purposes of this test.
4) Click the TX button.
5) Measure the power output. (I don't remember how you measuring power output)
6) Let this burn until the problem appears.

Them we will go from there. The idea is to have a clean test environment as a base we can both work from.
73
Ron / W4MMP
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Re: Back to square 1

Postby k1qn » Thu Jul 23, 2015 5:45 pm

1) I don't have a dummy load I use a longwire with a tuner. I'm confident it's 50 ohms, resistive.
2) I measure power with an MFJ QRP swr/wattmeter.
3) I use PowerSDR - Might consider HDSDR, but I don't think it's software-related.
5) There's a problem here because tests indicate it may take hours-to-days for the problem to start.

I traced the issue back to the audio. I posted a screenshot (attached) showing the PCM3060 side of R20. This is what I saw on the hot sides of R17-R20. The drive audio is roughly 1kHz just so I could see that the waveform is preserved part of the time. The chopping happens at 1kHz rate regardless of the input audio frequency. The duration of the chop increases slowly till it goes to the full 1msec. Then it suddenly goes to zero, and the rig functions perfectly again.

scopetrace.jpg
scopetrace.jpg (185.05 KiB) Viewed 2406 times


During a failure, I used freeze spray until the entire board got a bath, with no change in RF output,

It's not a fault in the RF portion. The problem is somewhere between the USB input and the output of the PCM3060.
Al Gerheim, K1QN
Celebrating 50 years in ham radio!
k1qn
 
Posts: 90
Joined: Sun Oct 20, 2013 9:42 pm


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