[Premium-Rx] Alignment test points in Racal 6790

[Paul]

Hi Group,

I think I have determined that the RA6790 first mixer FETS are actually ok.
I turned on the radio the other day and had a good listen to it and it was
right in there with the 6793. Maybe only 1/2 and LCD segment lower than the
6793 for a given station. I don't know why it was way down 2 weeks ago. Mood
swings? 

Anyway, I would like to do a proper alignment on the A1 filter and A2 mixer
as I have played with the slugs. Question is, am I correct in assuming when
testing the levels in the various modules, I should be using a high
impedance RF probe when on the internal test points, and a terminated 50 ohm
RF probe when measuring at the SMB output connectors like J2 etc.?
Also when measuring relative levels as in figure 5-2 in the receiver block
diagram in the manual, would those levels indicated, like -21dBm out of A2,
assume using a 50 terminated RF probe as well?

Finally, when I put in -50dBm, which I think is about 300uV, out of my
IFR-1500 or 8640B into the antenna input of the RX, I don't see any LCD
segments lit up on the 6790, but I see about 5 or 6 on the 6793. Then as
mentioned above, if I connect to an antenna and listen to a station, they
actually read the same RF level. Is there an alignment for the D/A driver
for the LCD? I didn't see anything in the schematics or alignment manual.

Thanks again boys for your help.

Kind regards

Paul
VE7KHz