First of all, get ahold of the owner's manual............this is available
as a free download at a few sites. Google will find them for you.
You mentioned that the display works.........does the display stay locked on
the frequency that you are tuned to, or does it run in a free-run mode. If
the display doesn't give a stable reading, odds are that the electrolytic
caps in the 24V power supply that supplies the VCO tune voltage are bad.
If the display works, tune the receiver to 8888.8kHz; this way, you can see
if any of the display segments are burned out (a common problem, since Drake
ran these devices at too high of a current).
Next, do some internet research and find out what frequencies are in use at
the time of year. As a quick and dirty test, tune the radio to the MW band
and see if you can clearly hear any stations.
I could go on and on and on........................but, if you really want
to check it out, send it to John Kriner, over at R.L. Drake and have hime
check it out. I don't have the time to do this kind of stuff
anymore..........too many projects of my own. I think his rate is about 100
dollars per hour.
If the receiver has all of the optional I.F. filters and it works properly
on all ranges, it is worth about 1200 dollars, plus or minus market demand.
Basically, it is the same receiver as the later versions of the R7 receiver,
with the exception that it adds a CW filter, a noise blanker, and a resistor
across one of the unused filter slots so the the bandwidth is determined by
the roofing filter.
Electrically, they are the same. Now, the older R7 receivers used eight
1N4148 diodes in a ring for the 2nd mixer, while later R7s (including this
one) used four 1N4148s, with a resistor in series with each of the diodes.
This configuration gives slightly better IMD response, but the NF is
slightly degraded.
Better to dump those 1N4148s and replace them with 1N5711 hot carrier
diodes.
Not a bad receiver, as long as you know how to repair them.
Now, if you have a good RF signal generator with an accurate calibrated
output attenuator, you will be able to measure the sensitivity. If the
receiver is working properly, you should be able to easily hear a -127dBm
signal across the whole tuning range.
I have had mine for a couple of years, and after upgrading the 1st and 2nd
mixers, mine is a keeper!

Pete

Pete
wrote in message
...
Hi experts,

I was able to buy a Drake R7A in the market near by.
I don’t have any knowledge about this (I don’t have any understating
in Radio).
I simply bought it because I assumed it might be worth more than I
paid.

Anyway, when connecting it to power I see the display (I guess it’s a
good indication…).

How can I tell if it really works? Do I need to hear some noise?
Anything else I can do to check that it is working?

I would appreciate any tip you can give me.
I might try to sell it later on when I better understand the condition
of the unit I have.

Thank you!