[R-390] Still deaf below 8 Mc

[Joe Foley]

If you're going to compare voltages in the radio to
voltages in the manual you NEED to get a volt meter
similar to what they used to make the manual.  Your
Fluke is a high impedance meter, they manual authors
used something with a much lower impedance like a
VTVM.  

Also, a needle-type meter will be much more useful in
tuning the coils in your radio.

Have you done the resistance checks and voltage checks
listed in the manual yet?  Just to establish a
baseline. Are the controls set to the conditions shown
in the operator's manual for testing?

Joe



--- Jim Green <jagreen3 at sbcglobal.net> wrote:

> I'm still plugging away with my R-390/URR (Not
> R-309A/URR). The main  
> struggle is the deafness below 8 Mc. I am following
> the Third Echelon  
> troubleshooting procedure in TM11-5821-357-35. I've
> made it to Signal  
> Substitution Part e IF sub-chassis tests Step 2
> where the procedure  
> is to apply a modulated 2Mc signal to E-210 with the
> receiver in  
> standby mode. I am supposed to hear a signal in the
> headphones. I  
> hear nothing. If nothing is heard the procedure is
> to:
> 
> 1) check V205 (checks good),
> 2) check V701 (checks good)
> 3) check the V701 circuit components by voltage and
> resistance  
> measurements. All voltages seem within range except
> Pin 1 at -0.46  
> VDC (should be -1 VDC to -2.3 VDC). All resistances
> are OK except Pin  
> 1 at 178K (should be 150K) and Pin 5 at 19.8K
> (should be 8.5K,  
> however the voltage at pin 5 is right on the money
> at 178 VDC).
> 
> Does anyone see any major issues with these
> readings? Note I'm using  
> a Fluke model 77 to take the measurements.
> 
> 4) Check the vfo operation by measuring the DC
> voltage at E210  
> (measured 0.000 VDC). The manual goes on to say: The
> voltage should  
> be between -3VDC and -11VDC. If the voltage outside
> these limits  
> check J223 and P723. J223 looks OK, but the cable
> P723 is connected  
> to has a kludjy splice in it. When I measure the
> voltage from the  
> center pin of P723 to ground I get 0.000 VDC.
> Perhaps this is OK  
> since it's likely an AC signal (I measured 0.01VAC).
> When I measure  
> resistance I get a dead short to ground. Are these
> measurements normal?
> 
> Jim (KG9MM)
>
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