[R-390] R390a Intermittent gear alignment

[Roger L Ruszkowski]

I came across a EAC R390a that was partially disassembled. The intermittent
gear had been removed from the band switch. I have info on where the gear
itself is supposed to be aligned while in the 7+000 mHz position but I need
to know what position the band switch itself is supposed to be in also.
Luckily, I have everything back together and have good audio, good gear
movement and even static so I consider the project worthwhile to try to
complete. Any help on the band switch alignment would be appreciated.

Thanks Wally Hunt

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Wally,

Take the time to pull the FR deck to complete this alignment problem.
Remember to remove the spring from the Odham coupler on the PTO.
Once you have the deck out, you see the band switch is just a wafer
switch.

Before you drop the front panel. set the dial zero in the center
of its range. Forget the numbers on the counter the dial has a
range. Set it as close the center as you can. Remember to
loosen the dial lock before taking the front panel down.


Remember it switches as follows:
.5 - 1
2 -3
4 - 7
8 -15
16 - 32

You want to watch it as you run the MC both up and down.
Watch that the switch wiper centers in the switch contact.
watch that each switch section is making contact.
Watch that as you roll up 1-2, 3-4, 7-8, 15-16 each movement point
sets the switch into good contact on each wafer segment.
Watch that as you roll back down 1-2, 3-4, 7-8, 15-16 each movement point
sets the switch into good contact on each wafer segment.

Remember, this switch not only use to work, it use to work for years.
There is some adjustment point where it will work again.

If you remove the deck and do the adjustment by eyeball. It takes less
time.
Plus the end results are much more positive.

You may also want to inspect the 6C4 2.2K resistors for value
You may want to look at replacing brown and black caps.
Look into the CAL 5814 tubes for burnt resistors.

You know as long as you have that deck out, there is no reason to
put it back in with problems that will need fixing later.

Panic Not. Prop the front edge up on some 2x4 blocks so you can
drop the front panel flat on the bench. Remember the there is a couple of
green screws in the sides (outside right MC end) (inside under the deck
from the left (IF) end. then there are two in the front. You need to
stick the screw driver through a hole in the KC dial lock disk to get one
of them. there are two (three) green screws across the back. you need a
long skinny #1 to reach down to get those green screws. Remember to un
couple
all the cable (1 power) most are the mini RF. Watch the PTO coax as it is
strung around and needs watching as the RF deck is lifted free.

In the wafer sections you can see which section is wired to which RF
transformers. This helps you determine if the switch is set to the correct
contact as the switch changes sections. The switch change is all magic
in the gear train. A special gear there decides when to move the
band switch shaft to change the wafer section contact.

You get that gear to move the change on the MC detente to detente stop.
and the switch to center in the wafer by adjusting the switch shaft in the
switch gear clamp. These changes should not change the KC setting.
Run the KC to both ends (with the zero center) and set your counter.
remember to set the KC back to where it was so you do not rip up the PTO.
Reset your cams and PTO after you get every thing back together.

This should leave you with a good mechanical alignment on the RF deck.
Except for PTO alignment you should never need to do this again in.
Until some clamp comes loose or breaks.

Roger KC6TRU.

P.S. You do have the Y2K Manual don't you?
It really helps to have a book in one hand.