[Premium-Rx] WJ-8718/MFP Questions

[pviappiani at tin.it]

Hello Greg:

I post my reply to your questions to all the list members as maybe the following infos are useful to other 
people too.

In my opinion the Preselector is a very useful option for the WJ-8718 receiver and it can really improve the 
performances of the radio. I guess the presence of such an option increases the receiver price of about $ 
200-300.

About the differences between the non-A and A version of the receivers, there are rumours that the "A" 
version is capable of better VLF performances than the "non-A", but it is seems not to be true: really some improvements 
of the performances in the lowest part of the RF spectrum were obtained through a change in the A2 (Input 
Filter) subchassis. A new version (791616/280093) of the RF Input Filter,
provided with adjustable and shielded coils, replaced the older one (that had fixed toroidal coils instead). 

But this improvement involved both the "non-A" and the "A" versions of the receivers and it depended upon 

the manufacturing date only.
Incidentally, other product improvements involving small circuit changes affected in time also the A3 (Input 
Converter) subchassis and some A4 Filter Switch Boards, but it happened for almost all the receivers of the 

Series.
The real differences between the "non-A" and the "A" versions of the receivers consist in the following 
details:
1) While in the "non-A" version of the radios, when the ISB mode is selected, one of the two channels of the 
phones jack carries the USB signal (jack tip) and the other one the LSB signal (jack ring) simultaneously, 
in the "A" and in the "-9" versions both the phones output channels carry the same audio signal (USB or LSB, 
depending upon the choice made by two pushbutton selectors that had been added in the front panel of the 
receivers just to the left of the RF Gain Control).
Please note that in all the MFP versions of the radios the phones output signal is not selectable anyway 
and, when in ISB mode, the USB and LSB discrete signals are always applied to each section of the
stereo jack in the front panel at the same time.
2) The "A" and the "-9"versions of the receivers are provided with an additional +12V regulator (U4, uA7812) 
for the A4A10 Audio Amplifier board (746001-X), whilst in the "non-A" version an unregulated +22V voltage 
reaches the A4A10 Audio Amplifier board directly.
In this case a different A4A10 Audio Amplifier board (7459) is used, it includes a voltage/current regulator 
(Q2, TIP29) for the Line Audio output stage.
Further changes came in the course of production of this successful series; among them it's worth to mention 
the adoption of a larger power transformer and of a new metal tuning knob (the first radios
had a black plastic tuning knob with an aluminium front cover).
About the differences between the WJ-8718/MFP and the WJ-8718A/MFP, some other details have to be added to 
what has been specified at the point (2) above, i.e.:
a) The Front Panel of the WJ-8718/MFP receivers has wider keys in the numeric keypad, in the WJ-8718A/MFP 
all the keys have the same size;

b) There are some significant board differences between the "non-A" and the "A" MFP versions. 
In more details: 
-The "non-A" MFP version makes use of a 796013-X Card for the Front Panel Switch/Encode MB (MFP-A1), while 
the "A" version employs a 794310-X Card;
-The "non-A" MFP version makes use of a 796057-X Card for the Front Panel Switch Board (MFP-A1A2), while in 
the "A" version a 794309-X Card is employed;    
-The "non-A" MFP version makes use of a 796032 Card for the IF interface Board (MFP-A3), while the "A" 
version employs a 794308 Card;
-The "non-A" MFP version employs a 796029-X Card for the Synthesizer Inteface Board (MFP-A4), while the "A" 
version uses a 794275-X Card.

Incidentally both the versions make use of the same Front Panel Encode Board 796056-1 (MFP-A1A1).

Other differences between the receivers reside in their BITE software: while the WJ-8718/MFP is provided 
with a simple "Panel Test" only (access by pressing the keys 17 and *), normally the WJ-8718A/MFP has also 
the seven-test function (access by pressing the keys 18 and *).

The performances of both receivers are unchanged anyway.
Hope this can be of some help, best 73

Paolo Viappiani