[Premium-Rx] Racal RA 3701

[Danny Higgins]

Hi Pat.

I agree about the Schaffner IEC inlets.  I've had 2 go on me, and the smell
is not very nice.  It seems that it is the EMC filter section that fails and
produces some smoke and brown oily goo.  Fortunately I was in the shack both
times and was able to switch things off quickly, although they filters were
still smoking.  I don't know what would have happened if they had been
unattended when they failed.  I had heard other reports of these filters
disintegrating in Racal equipments (one of mine was an RA3702 and the other
was the MA3752 Drive Unit which uses the same chassis).  I spoke to
Schaffner who denied all knowledge of batch problems.  I replaced one with
the same Schaffner part at a cost of about £28, but when the second one went
I took a hacksaw and removed the EMC filter section and replaced it with
another (non-Schaffner) and put it back together with some Araldite.  I'll
do this to the rest of my units before I start using them in earnest.

Danny, G3XVR

-----Original Message-----
From: premium-rx-bounces at mailman.qth.net
[mailto:premium-rx-bounces at mailman.qth.net] On Behalf Of Pat1McA at aol.com
Sent: 10 September 2011 16:30
To: clemenso at gmail.com
Cc: premium-rx at mailman.qth.net
Subject: Re: [Premium-Rx] Racal RA 3701

Hello Clemens.
 
RA3701. Serial Numbers. Do not take much notice of the S/Ns. A lot  more 
remote control receivers with a blank front panel were made so the  fewer 
Manual Operator Front panels will have lower S/Ns.
 
To my knowledge very few Preselectors were ever produced, they were a very  
expensive option.
 
The RA3701 displays are totally different to the ones used in the RA1792.  
As I recall and it is a few years ago, only the Right Hand Side Mode display

was  adjustable for viewing angle the others were adjustable for brightness 
 only.
 
I may be mistaken and getting mixed up with the RA3791!  Memory is  
failing.....now where was I ?......
 
The RA3701 is very well made. The BITE is quite amazing.
 
The let down is the "made to a price" IF Filters in the Filter Unit. These  
have rather poor ultimate skirt attenuation. 
 
If you can ever get hold of the Optional IF Filter Unit it takes the  
"Standard size" larger STC/ITT Filters and gives better selectivity and
easier  
to find Filters.
 
The main RA3701 fault is the Schaffner IEC Mains Filter. These regularly go 
 short circuit. Whether this is because the normal supply voltage here is 
240v  a.c. or whether a lot of the RA3701s used a faulty batch is
debateable.
 
The RA3791 is a lower quality "made to a beancounter's price" receiver  
than the RA3790 but it is a much better performer.
 
It is the ONLY DSP receiver that I have been able to test to specification  
using exactly the same techniques as those used for an analogue receiver  
like the RA3701.
 
73 de Pat G3YFK
 
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