Clean solder joints are not necessarily good solder joints. Pretty on the
outside, ugly on the inside...
I have found more solder issues on that board than any other Omni 6 board,
ever. Of course it’s no comparison to the solder work on the enigmatic Paragon
synthesizer boards, but still pretty awful.
Desolder, using Solderwick if you have it. Otherwise a good vacuum solder
remover works well.
I tend to not use the spring loaded “Solderpult" devices here because they
shear across the small and marginally held bond pads and peel them unless you
are really a lot more steady than I.
Be careful though, only unsolder one pin at a time on two terminal devices or
they will fall off the board, often inside the shield cans. Don’t ask me how I
know...
When working on this board, if you have the option, use a very sharp tip solder
pen. That will save you a lot of grief and will limit the amount of heat you
couple into the adjustable cans.
Gary
W0DVN
> On Feb 4, 2019, at 9:13 PM, Phil Erickson <phil.erickson@gmail.com> wrote:
>
> Hi all,
>
> The saga of the deaf Omni VI+ continues. As a reminder, the rig had a
> repair to the post-mixer amplifier on the BPF/front end board and then I
> found it was deaf on RX for four low bands (160 through 30 meters). LO
> drive coming from the crystal board was verified as low on these bands
> (only +7 dBm or so into 50 ohms; should be +17 dBm to match the Synergy
> level 17 mixer requirement).
>
> Today, Will KD4FOV and I did an experiment. With some external cables
> cobbled together, we patched in a Minicircuits amp with some padding here
> and there using cable 26 from the XO/LO board (carrying the LO) as input to
> temporarily increase the LO level to about 15 dBm, and reinjected that
> level at connector 26. Sure enough, this restored full receive on the
> bands with the problem. This confirms the problem is indeed in low LO
> drive on these bands coming out of the XO/LO board, causing the mixer to
> not turn on.
>
> But I can't leave this patched mess in-circuit, and the external amp is
> distorting the LO clean waveform when I amplify it externally. The whole
> point of a clean receiver in any case is to have a pure LO tone going in.
>
> So now we get to wade into the crystal oscillator / LO mixer board to see
> why the LO output is different on different bands. I will start probing
> around in there but has anyone been through that board and might know where
> to look? Somewhere around Q1, Q2, and Q3 is probably right. I notice
> there is one electrolytic cap on that board (C19) - maybe it now is leaky
> and is messing up the crystal oscillator amplification before the mix at
> U1? Or something else? Solder joints look clean in that area.
>
> 73
> Phil W1PJE
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