[R-390] new member, R390A, no signal when first powered on, works after 10min but RF cutting in and out

[weekspat at imonmail.com]

Thanks for all the hints,  Couple of things I did do:  antenna relay
check, and power supply checks - I did have previous problems here too
but those were fixed.  Yes Its time for the signal generator and
scope. I got what I wanted from the forum, which is some ideas to try.
 Hopefully with these hints I'll make more progress, then I will post
back my findings or the soultion if I figure it out.  Thanks
everybody. 
73Pat 

----- Original Message -----
From: "Roger Ruszkowski" 
To:
Cc:
Sent:Thu, 26 Jun 2014 17:02:34 -0400 (EDT)
Subject:Re: [R-390] new member, R390A, no signal when first powered
on, works after 10min but RF cutting in and out

 Pat,

 Hopefully you have a signal generator that will put out 455 KHz.

 When the receiver Is not working, Look at the voltage regulator tube
to be lite.
 Measure the 150 volts on the side of the IF deck.
 Measure B+ on the fuse caps.

 This is to make sure the power supply sections are good.
 If these are good you divide the receiver in half.

 Inject 455 KHz into the If deck at 150 micro volts.
 None of this needs to be exact.

 Hopefully your receiver has a short cable from J116 on the back panel
to 
 J514 on the IF deck.

 Take the RF to IF cables off J518 and J513.
 Move the short cable from J514 to J513.
 You can then connect a BNC to the back panel and inject 455 into the
IF deck.

 Rock the signal generator into the IF center.
 Work for a peek signal in the .1 band pass.

 With the BFO off and the generator set to CW look for -7 volts DC on
the 
 diode load at the back panel.
 Adjust R519 if you have a known signal generator output level.
 Other wise just set the generator to get -7 volts DC on the diode
load.

 Turn the generator modulation on. about 30 %
 You should have about 16 volts AC on the local audio output across
600 ohms.
 A pair of 1200 ohm 1/2 watt resistors work nice.

 With the band width set a 2 KHz the IF deck and Audio deck should be
nice and stable.

 If thing are not wonderful start looking in the IF deck and Audio
deck until problem is found.
 I will hold out for bad tube or crud in tube socket pins.

 If the IF Audio decks are good then its back to the RF deck.

 Common on all bands are the antenna relay second mixer and 17 Mhz
oscillator. RF AMP 6DC6.

 Do y0u have the Y2K manual and the TM 11-5820-358-35 PDF from the
R390 web sites?
 The Y2K manual is a must read for a new R390A owner.

 Many things you need to know are well explained in the Y2K manual.

 I only had dialup for years and the Y2K in parts was a God send of
information.

 Please post and let us know how things are progressing.

 Pleas let us know what the final problems are.

 Roger AI4NI

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