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Just completed mods to U3s and mistakenly applied 12v supply to 5 v bus. Pinned the ammeter, hard.

Replaced synthesizer and eprom. ?QLG1 GPS not flashing.

Only thing not replaced is the display board. ?Shows ? most signs of life but won't tx. ?

Any hope of recovery? ?What components likely damaged? ?Maybe start with a new U3s?

Another less dangerous hobby perhaps?

Thanks,
Tom ?KJ6MKI

Just completed mods to U3s and mistakenly applied 12v supply to 5 v bus. Pinned the ammeter, hard.
Replaced synthesizer and eprom. ?QLG1 GPS not flashing.
Only thing not replaced is the display board. ?Shows ? most signs of life but won't tx.
Any hope of recovery? ?What components likely damaged? ?Maybe start with a new U3s?

Tom
It has been done before

73 Alan G4ZFQ

I've done this. OMG so frustrating.
But, have found that these are avalible?from a popular online shop: $10USD with next day delivery! Just search for GPS module.

Here is the exact unit, better than a three-week wait:
MakerHawk GPS Module 51 Microcontroller GPS Compatible NEO-6M STM32 Arduino Navigation Satellite Positioning GT-U7
I hope that helps.

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Best regards,
Chris
M0XFL

Hi,
Would anybody know where I could buy a replacement?GPS?chip: YIC51612. Or an alternative?

I'd like to resurrect the standard GPS board (QLG1) for fun, but am unable to find a source?

#gps #YIC51612
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Best regards,
Chris
M0XFL

I worked on?a U3S that had been connected to +12V and I found two traces had become brittle and finally broke away from the board while closely inspecting them. One of them was the supply voltage to the microcontroller and the other might have fed the synth board. I was able to repair the missing traces using some fine gauge wire-wrap wire I've had for a long time.?

I had to repair the synth module and replace the microcontroller. It was a learning experience working on the surface mounted Si5351a as well as flashing a new non-programmed chip. But, all very do-able!?

Good luck with your repair!

--Al?
WD4AH

...also, it's much easier to mount the Amazon purchased GPS antenna and decoder. The decoder is tiny, the GPS antenna is a separate?device connected by a lead which can be poked through a hole in the lid!

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Here it is working, it's so small you can't see it on this photo. Works right off the bat:


I've also able?been able to connect the GPS board to my PC using free software:


But, it's not as sensitive as the QRP-Labs one so I have purchased a bigger GPS antenna?(on it's way).

Best regards,
Chris
M0XFL

...also, it's much easier to mount the Amazon purchased GPS antenna and decoder.

Chris,

One thing to consider when using a non-QLG1 is whether the NMEA messages are compatible with the U3S.
I use a uBlox (LEA-5S?) and had to disable the checksum to get the U3 to see it. Then from time to time it gave the wrong locator for a while before going back to the correct one.
I got over this by fitting a proper backup battery and configuring it, disabling the NMEA GLL sentence with the uBlox utility.

73 Alan G4ZFQ

Chris M0XFL?
Hello, did you just connect 4 wires to U3S and didn’t do anything else? Please give a direct link to this module, which will work exactly with U3S without additional manipulations.

Hello,
I just connected the wires and it burst into life.

However, I did end up logging in?to the GPS using the free software to switch some things off that we're not needed. I also?set it to UTC instead of GPS time.

But I do have one issue, the frequency offset is set wrong. With this GPS connected, it gets pushed up too high. Maybe this is to do with the 1pps signal? But I wouldn't have thought?that the 1PPS could be wrong? I'm still trying to get to the bottom of this issue. I don't know if anybody else has had this issue? I've searched the forum but did not find anything.




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Best regards,
Chris
M0XFL

the frequency offset is set wrong. With this GPS connected, it gets pushed up too high. Maybe this is to do with the 1pps signal?

Chris,

How far off is it?
Does it stabilise?I'd think just about any PPS would work fairly well, it gets smoothed.
I'm not sure about how pulse width and polarity will affect it. You have read the operating manual?

73 Alan G4ZFQ

Hello Alan,
Thanks for your reply.?I have the GPS pulse set to +1 edge. I have the U3S set to GPS Mode 2: From?the manual:"2 The kit triggers on the rising (positive) edge of the 1pps signal. This is appropriate for most GPS modules, where the pulse width is 100ms for example. "
The calibration?sequence forces the Ref. Freq to: 27,005,3555 , which pushes the transmissions about?1.4 khz?too high (I think).

Here is?a screenshot of my GPS settings below:



It's odd, isn't it? What am I doing wrong?
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Best regards,
Chris
M0XFL

Hello Hans,
Thank you for your reply. I'm tuning in using WSJT-X on another rig, +attenuator +another 10m dipole.

When the offset is set to 27,004,000, I can see and hear the signal in the waterfall display. But when the offset rises?to 27,005,3555, I do not see the Tx in the waterfall, all I hear is a low rumbling noise.

I am assuming the transmission is being pushed to high? Or maybe it's something else?

This is certainly?keeping me entertained. I have learned a lot about PPS signals and GPS modules this weekend :-)
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Best regards,
Chris
M0XFL

Thank you for your reply. I'm tuning in using WSJT-X on another rig, +attenuator +another 10m dipole.

Chris,

This is on 10m?
Are you actually seeing other signals there to confirm your RX is correct?

73 Alan G4ZFQ

When the offset is set to 27,004,000, I can see and hear the signal in the waterfall display. But when the offset rises?to 27,005,3555, I do not see the Tx in the waterfall, all I hear is a low rumbling noise.

Hi Alan,
Oh sorry, should have clarified that. I'm trying to work 40 and 20 meters though the U3S. I'm using the 10m dipole to attenuate the signal further.

Yes, I'm picking up spots from other people through WSJT-X on 20 and 40m.

Best regards,
Chris
M0XFL

Oh dear, I think I have it.?
I was tuning?to the WSJT frequency of 14.095.600 for example. I should have been turning to the frequency suggested in the manual. 14.097.100 for example.

I feel a bit foolish. As my Nan used to say, always read the instructions.

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Best regards,
Chris
M0XFL

I was tuning?to the WSJT frequency of 14.095.600 for example. I should have been turning to the frequency suggested in the manual. 14.097.100

Chris
Ah yes, it takes a little thought, USB RX of WSPR is 1400-1600Hz above Dial frequency. The U3 frequency is true TX frequency.
So the PPS is working correctly.

73 Alan G4ZFQ

Just completed mods to U3s and mistakenly applied 12v supply to 5 v bus. Pinned the ammeter, hard.
Replaced synthesizer and eprom. ?QLG1 GPS not flashing.
Only thing not replaced is the display board. ?Shows ? most signs of life but won't tx.
Any hope of recovery? ?What components likely damaged? ?Maybe start with a new U3s?

Tom
It has been done before

Tom:

Did you ever get your ?U3 going? ?


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73, Bernie, VE3FWF