[R-390] R-390a Image problem?

[Tony Casorso]

Aha! The 1st RF tube is correct (6DC6) but when I remove the tube and put a 
small cap from pin1 to pin 5 (grid to plate), the receiver works fine and NO 
image. I'm going to check the AGC to that stage.

Tony
----- Original Message ----- 
From: "Bob Camp" <ham at cq.nu>
To: "Tony Casorso" <canthony15 at msn.com>
Cc: <R-390 at mailman.qth.net>
Sent: Friday, October 19, 2007 7:13 PM
Subject: Re: [R-390] R-390a Image problem?


> Hi
>
> I'd check the grounds as Jon suggested. The R390 can pick up "stuff"  from 
> the power line pretty easily. The AC line filter works both ways  with a 
> loose ground ...
>
> Next up would be to start swapping front end tubes. You may find that  you 
> simply have a defective tube. You may also find that somebody  "improved" 
> the design by putting in a tube that didn't belong there.
>
> Bob
>
> On Oct 19, 2007, at 8:58 PM, Tony Casorso wrote:
>
>> Hi Bob, I'm using the balanced input. I bought a twinax to BNC  adapter 
>> so one side of the balanced input is grounded.
>>
>> Same antenna doesn't bother the R-392.
>>
>> Tony
>>
>>
>> ----- Original Message ----- From: "Bob Camp" <ham at cq.nu>
>> To: "Tony Casorso" <canthony15 at msn.com>
>> Cc: <R-390 at mailman.qth.net>
>> Sent: Friday, October 19, 2007 6:52 PM
>> Subject: Re: [R-390] R-390a Image problem?
>>
>>
>>> Hi
>>>
>>> Which antenna input are you running into? The situation you  describe 
>>> would be pretty typical if you run a long antenna into  the 
>>> "unbalanced" input.
>>>
>>> Bob
>>>
>>>
>>> On Oct 19, 2007, at 8:31 PM, Tony Casorso wrote:
>>>
>>>> Hi everyone. This is my first post to the list although I've been 
>>>> following it for a long time now. A few months back I bought a  67  EAC 
>>>> R-390a. The only problem I had was an open Z-503 AGC  coil. I  replaced 
>>>> that and did an alignment and the radio seemed  to be  working real 
>>>> well. Sensitivity was very good on all bands.  Recently  I've noticed 
>>>> broadcast stations coming through in the  3Mhz band. A  local station 
>>>> on 1650KHz is about 40db at 3300KHz  on the R-390a. I  don't hear it on 
>>>> my R-392. Even moving the  2-4MHz RF slug rack by  hand, I still hear 
>>>> the station (although  it does get a bit  quieter). There are several 
>>>> other stations  coming through as well  on other frequencies. I didn't 
>>>> notice  anything odd when I aligned  it, everything seemed to peak like 
>>>> it should. Looking around at  other frequencies with my signal 
>>>> generator, I started noticing all  kinds of harmonic responses,  but 
>>>> that is probably (at least to some degree) just my signal  generator (a 
>>>> Boonton 102C). I'm pretty sure something is wrong  here but I'm 
>>>> scratching my head trying to think  of a good  explanation. If the BC 
>>>> station harmonic was that bad, I'd  hear  it in my other radios I would 
>>>> think.
>>>>
>>>> Ideas anyone? How do I track this one down?
>>>>
>>>> Thanks,
>>>>
>>>> Tony
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>>
>