[R-390] Initial progress and Questions

[Dennis L. Wade]

Gentlemen ?	

	Over the last week or so I've had my Motorola R-390A with EAC SSB 
mod running and baking.  I've been getting acquainted with it again 
and getting a feel for its performance in preparation for installing 
Dave's re-cap kit. 

	Some observations:  First thing I did was test the tubes on an 
emission tester.  Several were clearly weak, namely V 601, 602, 604, 
the 6U8 in the product det. module, V509 and V206.  

	Mechanically the radio feels very nice, although a bit dry.  I 
dabbed a little oil in some critical places which helped things until 
I drop the panel and have more room to work.  No binding or sticking 
of slug racks were noted.   Everything turns nicely.  

	The LSB (only) side of the BFO in the SSB mod doesn't oscillate.  
USB works fine.  ( I pulled it to take some pics for a couple of 
listmembers, so it could be a broken wire from handling or the 
crystal..not much else in there).

	And now, some questions:  Having not identified any critical 
problems (other than the SSB module), I'd like to take some baseline 
measurements of sensitivity so I can make comparisons of before and 
after re-capping.  My objective is to make repeatable measurements 
that are comparable to what others have done.  What is the preferred 
method of getting the generator signal into the balanced input of the 
radio?  I can build a pi network with a 50 ohm input and a 125 ohm 
output and a balun to balance it to the radio, but it this necessary 
or overkill?  The generator is a Measurements Model 80 with 
calibrated attenuator and 50 ohm output.

	Re-capping:  There are three caps in the RF deck that are in the re 
cap kit:  C256, C275 and C309.  256 and 309 are part of the crystal 
oven and seem to bypass the heater.  C 275 bypasses the regulated 
+150.  I'm very leary of pulling the RF deck especially since there 
doesn't seem to be any other reason except to replace those caps.  
How important are these guys in the scheme of things?

	VFO endpoint:  Where is the best place to put a frequency counter to 
check endpoint and linearity?  And while we're on the topic of 
counters..where is the best place to pick off the BFO frequency?

	And finally..the requisite silly question:  When I drop the front 
panel and check that the cams line up with their respective marks..am 
I going to be able to see everything I need to without further 
disassembly?  Front and rear?

	Although I've been tinkering around for longer than I care to 
admit..this is the first radio I'll be getting into so deeply.  I'm 
sure I'll have other questions as things pop up.  

	Thanks in advance!

		Dennis  

	-----------------
"If you can remain calm, you just don't have all the facts"

Dennis Wade
KG6ZI
Carmichael, CA