I have a Leader LSG-245 RF frequency generator
that has a weird keyboard response issue..
It's a micro-processor based test equipment.
On the front panel you can set the gen frequency,
modulation percentage and its output level value in dBu.
Well that's where my problem starts..
According to the specs this generator can deliver -10 to +120dBu
(in 1dBu steps) on a 50 ohms load using +/-10dB and +/-1db buttons
on the keyboard. that is 131 steps overall.
My problem is that the display shows a max of +114dBu
and a minimum of -16dBu.
You can see there is a -6dBu offset there on all the readings !!!!
I cannot see what is causing that -6dBu offset..
http://www.arcenson.com/public/Leade...ice_Manual.pdf
http://www.arcenson.com/public/Leade...ion_Manual.pdf
The keyboard buttons are 'scanned matrix' type
read from a micro-processor and seem to do what they should.
There are 131 steps read from -16 to +114dBu.
The 3 x '7 segments output levels digits' are displayed through CD4511
BCD to 7 segments drivers also driven from the micro.
The micro uses 27C64 and 27C128 eeproms program memories.
I'm beginning to suspect the actual program could be
altered and inserts a -6dBu offset on the output scale
keeping the keyboard from going any further than +114dBu.
This generator also accepts external bytes from
a parallel rear external connector. I'm about to try to
'inject' external dBu value bytes and see what the micro
accepts as min/max..
If anybody sees somethnig I did not see
feel free to reply .. I'd be very happy
to see your comments..
Thanks.
J-Pierre