[R-390] R-390 alignment question

Tue Jul 29 21:50:46 EDT 2014

Frank,

Bob's response is just a clear as can be.

You are looking to set the .1 hertz cap to a minimum response.
But that filter is so wide you can not just dial the cap in.
You look for two skirt points that can be found.
Then you set the cap to a mid point between these two marks.

Before washing your IF deck, the Z501 can may have had six marks around the cap.
You would have hoped it had three on the can and one on the cap.

When you are done you will have six marks on the Z501 can and 1 mark on the cap.
Use a # 2 pencil for a marker.

Make a mark on the cap usually in line with the tool slot and only on one side of the slot.
Every cap in the R390 should have two peak points.
If the cap has only one peak point you may have a circuit problem.
The cap is reaching the max mesh or minimum mesh and you do not know it the capacitance
value is sufficient (min or max) to bring the circuit to peak alignment.

So each cap should have two peak points as you rotate it through 360 degrees.

So as you do the alignment procedure you should first get two minimum points for the cap on the low frequency side.
And two minimum points for the cap on the high frequency side.
Now you have four marks in two pairs. with a high side point and low side point in each pair.
This is a demonstration and witness mark that the circuit was working the last time it was performed.
Do this procedure once on your R390 and be happy for life.

Then you eye ball the mid point between the high frequency and low frequency marks and place a third line at the mid point.

Now you have six marks on the top of the can.
The two mid point marks are equal alignment points.
Align the cap mark with either of these two mid points and the cap for the Z501 filter is set to optimum setting.

Set the AN/URM25 to 455 KHz at 150 micro volts coupled into E210 on the RF deck so you can align T207
and all of the IF deck to 455. As the third mixer in the RF deck will give gain at 455 the AN/URM output should be well below 150 
micro volts. dial the out put of the generator down to a level that is - 6 volts on the diode load using CW on the generator.

Pop the output level on the generator up three switch positions. (that's times 10 time 100 time 1000 [three positions])
Dial the AN/URM off 455 until the diode load drops back on to the meter scale.
Spin the cap on Z501 and find two points where the diode load read minimum. 
Mark these two points as H H or L L depending on which way you went with the generator.

Dial the AN/URM back across 455 and move along until the diode load voltage drops back onto the meter scale.
Spin the cap on Z501 and find two points where the diode load read minimum. 
Mark these two points as what ever you did not mark the first pair as.

Eye ball a mid point between a H and an L Make a mark.
Eye ball the mid point on the other pair and make a mark.

Set the mark on the cap to align with one of the two mid point marks.
Procedure is complete.
Find a beverage of choice and grin.

Forever and ever just set the cap mark to align with the mark on the can top.
The cap is aligned.

This setting is broad and the cap will be good enough for the alignment of the receiver.

If you have a frequency counter than set the generator to 455 + 8 = 463 and 455 - 8 447
up the gain on the generator to get the diode load voltage at mid scale on the meter and spin the cap to minimum.
Mark the points up as above and eye ball the mid point to set the cap too.

A good receiver has six ticks as L C H L C H and one tick on the cap.
You set the cap tick to a C tick and go on with life.

Roger 33C4H 68 - 75  

Hi,
I am trying to do my first alignment on the "tailgate" R-390, so as to perk
up the performance.

Using this manual:
http://i180.photobucket.com/albums/x257/fish1_07/R-390/r390TMcover_zps1455706b.jpg

R-390A alignments in the past have been no issue, but the R-390 is a little
different, and I am baffled by one procedure.

All was going well, peaking coils, watching the HP 410C meter increment a
tiny bit more with every pass.

Then I hit paragraph "K".
OK, I am old, and cognitive functions are more limited - most of my brain
cells are dedicated for looking for my glasses.

Thus I would be MOST appreciative if anyone can explain in language I could
understand what they are trying to tell me in paragraphs "K" - "N". I just
don't get it.
TEXT:
http://i180.photobucket.com/albums/x257/fish1_07/R-390/r390text_zps4f6aeefc.jpg

TEST SETUP:
http://i180.photobucket.com/albums/x257/fish1_07/R-390/r390_test_setup_zpsfeee93f8.jpg

THE DREADED Z501:
http://i180.photobucket.com/albums/x257/fish1_07/R-390/Z501_zps5acd2b93.jpg

73
Frank
KJ4OLL
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