[R-390] I got my R-390/URR

[Jim Green]

OK,

I finally got my R-390/URR. I put it on the bench and follows is a  
list of the problems I discovered:
1)    The function switch:

1a: When the function switch is in the off position and the receiver  
is plugged in the receiver is actually in standby mode. In other  
words, the dial light is on and so are all the filaments. When I  
switch the function switch to standby, there is no change.

1b: The receiver behaves the same when the function switch is in AGC  
as it does when it is in MGC. In other words, AGC does not function.

2)    The Mc tuning knob:

2a: some fool cut away the skirt of the tuning knob to gain better  
access to the binding ring.

2b: When I turn on the crystal calibrator and step through all the  
bands they all work except form 3Mc to 4Mc. I suspect a weak crystal  
in the crystal ocelator sub-chassis. Probably Y404 (12.6 Mc).



3)    The kc tuning knob:

The kc tuning knob is a complete un-original replacement.



4)    The bandwidth switch:

The band width switch seems to function ok, but there is a very  
narrow step between 8 and 16. All the other clicks are evenly spaced.



5)    The Power Supply:

V801 and V802 (both 26Z5W tubes) are missing. There are 2 each 100  
ohm resistors wired in series with the leads passing through the  
center hole of the tube sockets. I haven’t taken a close look, but I  
suspect a previous owner replaced V801 and V802 with solid-state  
diodes and replaced the ballast tubes with the two 100 ohm resistors.  
I’m not a complete tube purist so the solid-state diodes don’t bother  
me all that much. However, I don’t like the idea of the resistors  
replacing the ballast tubes. I think I will undo that mod.

6)    The manufacturers tag:

The tag is missing. I don’t know why people felt the need to remove  
these, but there it isn’t. There enough parts inside that say Collins  
on them that I suspect this one was manufactured by Collins not  
Motorolla.



7) the green gear is missing.


Cosmetically the receiver is quite good. It’s clean inside and the  
tuning dials turn freely. The best thing about it is it came in a  
genuine shock mounted cabnet. On the whole I think it’s worth fixing.  
I have a few questions:


1)    How does one go about removing the crystal oscillator sub- 
chassis? I need to do this to check out the crystals.

2)    Where can I get the following parts:

2a: The green gear

2b: replacement tuning knobs

2c: a replacement manufacturers tag

3)    Does anyone know what could be going on with the function  
switch? And/or the AGC?

4)    Is the small step between the 8 and 16 position on the  
bandwidth switch normal? Can it be adjusted or repaired?

5)    Is it safe to remove the front panel without the green gear?  
Any other things I should be aware of?