[Premium-Rx] WJ 8709

[Carcia, Francis A HS]

Oh WJ does a divide by 4 which explains the quieter phase noise. I wondered
why it worked
so well.  fc

-----Original Message-----
From: Karl-Arne Markström [mailto:sm0aom at telia.com]
Sent: Tuesday, March 01, 2005 2:05 AM
To: premium-rx at ml.skirrow.org; Eric Gauja
Subject: Re: [Premium-Rx] WJ 8709


Dear Eric,

It appears that your problem is in the 1st LO synthesizer.
The tuning step in this PLL is 40 kHz, which then is divided by 4 to get 10
kHz steps,
and to improve close-in phase noise.

It is very likely that you have a heat- or component-ageing related trouble 
in the phase detector or loop filter.
To help diagnose this problem, look at the "1st LO UNLOCK" indication LED
(CR4). 
If this  LED flickers on and off, you have verified a PLL locking problem.

Before "digging into" the synthesizer, first check that all supply voltages
to the LO
cards are ripple-free and within specifications (5V +/- 0,1V and 15 V +/-
0,5 V), 
as the 1st LO PLL contains ECL IC's  which are "fussy" about proper
voltages.

Possible other causes may be:

Bad loop filter op-amp U7 (741HC)
Bad phase detector U5 (MC4044P)
Bad count decade U8 (74LS190)

And/or components around these IC's.

Hope this helps and 73/

Karl-Arne
SM0AOM


----- Original Message ----- 
From: "Eric Gauja" <e.gauja at unsw.edu.au>
To: <premium-rx at ml.skirrow.org>
Sent: Monday, February 28, 2005 6:22 AM
Subject: [Premium-Rx] WJ 8709


> 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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