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

[Roger Ruszkowski]

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