[Premium-Rx] WJ-8615D Issues.

[Bob Betts]

Hi Dave and Group:
You didn't mention if the PS is a linear one or switched mode. I have all but abandoned switchers for their noisy output and (even) radiated hash. Although, if that's your problem, I'd expect to hear a buzz and not hum. You may want to scope the output of the PS for noise. Even a few mV can get into the system and be noticeable. I had built a linear supply, with regulators and extensive output filtering and never looked back.
http://bobsamerica.com/instrument-PS.html
 
As far as the preselector goes, I don't use one since the bandpass filters seem to be fine and there's no nearby channel problems here. I did find that the feed from my discone and yagi antennas needs a bit of a boost. I currently use about 15dB of boost from a broadband preamp. I went kind'a crazy with the first preamp (that's how I have fun), but I found that a simple CATV "drop amplifier" with appropriate freq response will do nicely as well.
http://bobsamerica.com/vua-preamp.html
 
If you are using a linear supply, I hope you can isolate the problem. I love my 8615D and can attest to the rather involved procedure for removing the PS from the radio...much less trying to isolate a bad cap somewhere.
http://bobsamerica.com/wj8615.html
 
 
Good luck with the project,
Let us know how it goes.
 
Bob

http://www.bobsamerica.com
http://www.youtube.com/n1kpr


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From: David Schofield <davesc50 at tiscali.co.uk>
To: Premium-Rx at mailman.qth.net 
Sent: Saturday, July 20, 2013 1:08 PM
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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