[R-390] Newbie looking for Calibration Instrument(s)

[Perry Sandeen]

Yo Bubba Dudes!
Dave,

There has certainly been a wide range of opinions on this subject. Here'a mine:
You are standing at the junction of to paths to take.
One is you can nickle and dime keeping your radio running - sort of.  The problem with this approach is that at some time your radio is going to fail very badly and you won't be able to fix it with your present approach.  To repair it properly you'll need to send it someone who repairs/restores these for a living.  The cost with shipping could easily be as much or more than you paid for your radio.
Some people on this list keep forgetting: THERE IS NO SUCH THING AS A FREE LUNCH.
That said, a URM 25 unless it has been rebuilt will not give you the accurate RF output one needs to properly calibrate your radio.  As an example:  several years ago a list member reported that he achieved the 20 to 30 dB test as shown in the TM manuals with .1 micro-volt from his signal generator.  While the dials he read said that, it just ain't so.
If you are seriously into your receivers health and well being there are a number of items you need.  The most expensive is a good used HP signal generator. Shopping with care one can by a guaranteed operating digital unit for under $400 including shipping.
You need to D/L from the R390 FAQ site the Almost ultimate R-390A schematic as it has marked on it the high failure parts as well as a Chuck Ripple cap fix.  Acquire over time two each of the different tubes used in the receiver.  Also a $50 or so DVM for measurements. While nice to have a VTVM is not necessary for the -7 volt setting.  However if so inclined they can be had from $20 on up all day long on ebay.
If you make up a parts list of the likely - to - be - bad caps they can be bought from Mouser for less than $20.
If you are planning for the long run some simple mods are very helpful.  See the above mentioned ski and peruse the Y2KR3 manual.
All this said what you spend will be a lot less than a set of good golf clubs w/accessories.
One gets out of ones radio what one puts into it.
For any of the wise guys who like just take pot shots, I have over 500 B/A receiver tubes, every resistor and capacitor needed for at least 5 R3XX and SP600 receivers. I rewrote the Y2KR3 manual adding four new chapters, authored the SP 600 anthology and have had 3 articles on B/A receivers published in ER magazine. I've digitized the R390A, SP600 and R620 schematics so one can get large no-smear prints at Kinko's or use them on ones computer.
There's lots I still don't know but at least I've tried to make positive changes for our hobby.
So to any of my critics I say: What have you done to help?
Regards,
A 78 year old worn out Perrier