[Premium-Rx] WJ-8615D Issues.

[Steve Pappin]

Hi David,

Your precision reference could be off frequency or other alignment issue. Is
it on both side bands? The reference should measure 10 MHz exactly after
warm up. Older radios are usually off. Remove the cable interconnect between
the 1st LO and 2nd LO to measure this.

The power supply could also be introducing switching harmonics at several
stages.

The pre-selector will introduce attenuation loss, but your problem may be
partially due to an alignment issue.

Best Regards,
Steve

----- Original Message ----- 
From: "David Schofield" <davesc50 at tiscali.co.uk>
To: <Premium-Rx at mailman.qth.net>
Sent: Saturday, July 20, 2013 10:08 AM
Subject: [Premium-Rx] WJ-8615D Issues.


> Hi All,
>
> I've just acquired a WJ-8615D which to the most part is working very well
> indeed.
> When it first arrived the PSU had failed spectacularly, and after a couple
> of atempts at rebuilding it I decided it was beyond salvation....
> To that end I brought a more up to date, better spec'd PSU and made up a
> set of adaptor leads, and a plate to fit the new module so an original
> unit could be fitted should I ever find one, or actually succesfully fix
> the original.
>
> The receiver is now functioning well, apart from the fact that the SSB
> demodulator has a loud hum of approx 50Hz superimposed on the output.
> Before I start to investigate this, I was wondering if their are any known
> issues that can cause this. I suspect a bad earth, or possibly a failed
> decoupling capacitor on the SSB module. The new PSU seems to be performing
> 100% ok, so I think this is a secondary fault.
> SSB seems to be working OK underneath the hum, so it would be nice to get
> it working 100% ok.
>
> The other thing is that this unit is fitted with the optional oreselector,
> which appears to be making it pretty deaf, although it does seem to be
> doing it"s job and improving intermodulation Etc. especially on HF.
> If I bypass the preselector the gain is far better, but full of harmonics
> Etc, is this normal for these receivers?
> If it is I can live with it, I have plenty of other "hotter" receivers,
> and would rather have reduced gain than spurious images, but though I'd
> ask in case their are any known issues in this area either.
>
> Thanks in advance,
> Dave. S.
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