[Premium-Rx] WJ advice needed.

[GandalfG8 at aol.com]

Hi All
 
First, a thanks to Jan for getting us back on the air.
Secondly, whilst I know this will be a bit off topic I doubt  there's 
anywhere else I can ask for help/advice on WJ kit so apologies in  advance for that 
but any advice would be much appreciated.
 
I have a couple of problems with a DMS 107, 0.1 to 10  MHz, demodulator.
 
First problem, a definite problem this one, is mechanical offset in  the 
meters, the meters being similar to those used in many WJ receivers.
Both meters, signal and tuning, have significant mechanical offsets,  ie 
about 1/4 inch off zero and centre respectively.
Although there are no meter adjustment screws, and the access  holes have 
been taped over, it is possible to access the mechanical  adjustment by removing 
the meters.
However, trying to adjust them in this was is pushing the movement to the  
limit and still not quite getting there.
Neither pointer looks bent, and both meters work fine electrically, but the  
plastic housing on both, behind the metal body of the meter, does look to  be 
misaligned.
Both resist any attempt to realign them, they seem locked solid and not  sure 
if they can be shifted anyway, perhaps an initial setting that is fixed,  but 
it does seem to me that if only that part of the meter housing was rotated  
slightly it would solve the problem.
Does this make sense? Any advice would be appreciated.
 
Second problem may not be a problem as such, just that I don't know what to  
expect.
 
With the signal level control set to maximum, and using the "set"  marker on 
the signal level meter as a reference, the CW sensitivity is fairly  
consistent across the frequency range at around 83 db UV, which I estimate as  
approximately 15 mV.
In itself that doesn't seem unreasonable for an add on demodulator but I  
also have a DMS-105A, covering up to 1.6 MHz,  and this has sensitivity in  the 
microvolt region.

I don't want to go looking for a fault that may not exist, especially with  
no documentation, so if anyone can tell me what order of sensitivity I should  
expect I would be grateful.
If there is a problem it's likely to be in the front end somewhere, as the  
sensitivity is reasonably consistent at all IF bandwidths and each bandwidth 
has  it's own amplifier chain, but I'm reluctant to disturb the front end/mixer 
until  I know for sure there is a fault.
 
If anybody has any documentation, even just a specification, on either or  
both the DMS-105A and DMS 107, or can point me in the right direction, that  
would also be most helpful.
 
regards
 
Nigel
G8PZR


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