[Premium-Rx] WJ 8709

[Ahmet Gundes]

Hello,

Wishing you good luck with your repairs and most importantly
enjoy your nice set.

I do not have the 8709 but know a little about the 8718. Certainly it would be hard to know exactly what the problem is or where it might be coming from, but it might be worth a shot at the following:

( of course first and foremost is to make sure every module/card is properly inserted, the contacts are clean, there is no battery leakage, all leads are connected properly in the right connectors
and are clean.... all the basic precautions... )

1) I had a similar display issue and I cleaned the inside of the
Rotary Encoder ( the large circular unit that is used to change frequency by turning the dial ).  It is a delicate unit so you must be very careful.  But I was able to open it, clean it, close it right away.  This might be causing freq display problems.

2) Try to cool the set with a fan and see if this helps to cure the problem. It would be good idea to see if cooling especially the card where the Reference Oscillator is located would help. I had a similar situation when the set was getting hot there were some locking problems.  I am now always using a fan with this set.  Eventhough my problem is now gone !...

In regards to the line audio, I think most of the 8718s have this
problem. I checked some and I believe it is poor isolation of control circuits.  Also LED Display Drivers leak substantial noise into the Audio amplifiers I think via power lines. If you place 100uF Caps at the DC input of the two drivers you will get rid of some of the Audio Noise. This does not fully cure the Audio problem but I did not get to the bottom of it yet.

Hope this helps you a bit.

Enjoy and all the best.
Ahmet Gundes



> 
> Greetings to all list members,
>                                               I have just been 
> accepted into this list, being a recent purchaser of a WJ 8709. 
>  From my experience, WJ receivers are not all that common here in 
> Australia.  My set, S/N 183, came via the Royal Australian Navy. 
> There seems to be a reasonable amount of information regarding WJ 
> sets on the internet, which I have read over, and also many 
> interesting past posts to this list. However, I still have some 
> questions/ thoughts that I would like to put to this list.
> 1)    It seems that the 8709 is a "no frills" or basic half rack 
> version of the 8718 or similar variants.  I have had no success in 
> tracking down a full manual for the 8709, although I have 
> photocopies of a fair number of the schematics and the first few 
> pages of the manual with brief description and specifications. I 
> suspect that the 8718 manual circuitry would be the same  for the 
> 8709 also. Fair Radio does sell a 8718 manual, but I see from some 
> earlier posts that their version of the manual may be incomplete. 
> At the moment, I  am mainly interested in the circuitry description 
> part of the manual.
> 2)    My 8709 performs very well, but seems to have 2 areas where 
> problems could be occurring-
>         a)   After the set has been on for a few hours, and is 
> warm,  when I change frequency from say 5020KHz DOWN to 5019 KHz,
>               there seems to be a long period where something loses 
> lock, and I just receive noise, until lock suddenly occurs. This 
> only
>               happens going down in frequency from multiples of 10. 
> It does not occur tuning up, or tuning down from numbers that are
>               not multiples of 10. And it only happens when the set 
> has warmed up . This doesn't really cause me any trouble at this 
> stage,
>               but I am wondering whether this could be an early 
> sign of a developing fault?
> 
>         b)   The  line output audio seems to suffer from hum.  
> Again , this does not cause me any real trouble because I use a 
> speaker
>                driven by a 600/8 ohm transformer from the phones 
> output, and this output shows no sign of hum.
> 
> 3)    Since finding this list,  it has been very interesting 
> reading the past posts, not only about WJ equipment, but about  
> receiver topics in general. I congratulate the moderators and list 
> members on some very interesting and informative posts.
> 
>                                                                     
>                                          Best Regards from 
> Downunder!
>                                                                     
>                                                                     
>                              Eric.
> 

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