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Near as I can tell, he never hits the PTT switch to transmit. ?And the IRF510 is still heating up.

I did tell him that the gate to the IRF510 should be zero volts during receive. ? If it isn't then the next step would be to figure out why. ?The 12v TX rail that powers the LM78L05 should also be zero volts during receive. ?If that is not zero volts, I suppose there could be some sort of relay fault or a short that keeps the TX rail at 12v during receive.?

But if the gate voltage is zero and the IRF510 is heating up, then this is just a blown IRF510. ?I'd remove the IRF510, then power up the board (including the PA +12v supply into the board) and see if everything works as it should, including pressing PTT to transmit (even though it won't transmit due to the missing IRF510). ?Then adjust RV1 on the main board for zero volts on the IRF510 gate, I believe that will be fully clockwise (and thus fully counterintuitive). ?Power down, install the new IRF510, and carefully adjust RV1 for 100ma into the PA 12v connector as per the wire-up instructions on hfsignals. ?Note that the RV1 setting is very touchy, and advancing it too far could blow the new IRF510. ?The correct RV1 setting for the new IRF510 (for 100ma of drain current) could be significantly different than it was for the old IRF510.

I knew it was writing to eeprom but there is no matching call in the code to read it back. Either to apply it or pass it.? Neither does the library call it.? It can't possibly, how would it know which address it was ?? It's being assigned to a int32 but isn't called.

In the notes it is mentioned that the calibration value in eeprom be called in setup but it isn't.? It also mentioned that eeprom was used for the dual vfo's, that's not either.

I don't understand how others get it to work.? I can't unless I alter the code.

Perhaps Farhan can comment ?
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Rob G4NQX

When I got my QRP Labs VFO kit I simply removed L4 and plugged in the cable from the VFO. You can remove the trimmer cap next to L4 also but there's no need really. It made no difference for mine.

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Ryan Flowers KC7RYS?

You seem to know how to use that scope, and have a good idea of how this works. ?You'll probably figure it out. ?If you want hints, here's what I'd be looking for:

Ashhar is right, triple check that the 5v and 3.3v supplies are clean down on the Raduino. ?Yes, 12.5v should be fine going in.

Whenever the tuning pot changes the VFO frequency, the Nano will write to registers on the Si5351. ?Perhaps you have too much noise from the tuning pot into the Nano, so the Nano is continuously updating the Si5351 at 26hz? ? Look at the SDA, SCL lines from Nano to Si5351, see it there is traffic there, when things are stable those wires should be pulled high to 3.3v. ?If you do see traffic, perhaps hack the sketch so it ignores the tuning pot and updates the Si5351 once every second, always writing the same frequency. ?Perhaps somebody else out there with a Raduino and a scope can tell us if they see similar gaps in the VFO's output when the tuning pot is turned. ?I believe there have been reports of Raduino tuning causing noise in the receiver audio, though that my have been mostly noise from updates to the display. ?Look hard for cold solder joints using bright lighting and magnification.

Regarding the initial complaint of a VFO freq that is 5x lower than it should be, I only have wild guesses:

1) ?Power supply trouble on that 3.3v rail. ?This seems an unlikely cause.

2) ?Dirt on those SDA,SCL lines from the Nano, but I doubt that would give consistent results like this.

3) ?Perhaps most Si5351's power up with one of the output dividers in a particular state, your's powers up in a different state. ?And the Si5351 library has a bug, isn't initializing the register that controls that output divider?

2) The 25mhz oscillator into the Si5351 isn't operating properly. ?You might look for a 25mhz signal at the crystal with a 10x scope probe. ?It is possible the act of probing it will shut it down, but I don't think so. ?

4) Some weird failure within the Nano ? Perhaps even writing a fresh sketch to it somehow doesn't program the flash correctly, resulting in a bug where it writes to the Si5351.

3) You have a hardware failure in the Si5351

Since you had been beating your head against this for several days, I sent that post about putting in a new Si5351 in part to warn you that it might not be a trivial task. ?Ashhar says all these units get checked before shipping, an Si5351 failure should not happen very often. ?But could happen.

If you don't want to deal with it, might be worthwhile to ask hfsignals if they would take it back. ?They might want to figure this out themselves, just to make sure it does not happen on future units. ?But may only want it back if you have not been making mods to it.

It's a tough problem.

Jerry, KE7ER

I'll check rails when I get home. I'm powering the Raduino from bench-top power supply set to about 12.5 V, but that shouldn't really matter since there is 7805 to regulate, right? I'll check for ripple on that PS, and on both Nano rails (3.3 and 5). Besides being off frequency, these 'pauses' every 38 ms (~ 26 Hz) were producing nasty sound from the speaker when connected to the Bitx mixer. Now with analogue VFO Bitx sounds really clean, as it should be.

It doesn't seem that Nano is going into reset because display is fine, always showing e.g. "A: 7.1000 LSB", and it changes nicely when pot changes, although frequency is ~5 times lower than it should be. I did reprogram the Nano once, with same results, and since it's very strange problem, wanted to get to the bottom of it before doing it again and fixing it without knowing what's really going on :) Just my curiosity.

Again, I'll do more thorough testing and let you know.

Goran VE6GPO