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

[Bob Camp]

Hi

I'd swap it for another tube just in case.

With no input to the radio, there should be pretty much no AGC to the  
front end. It may be the problem, but only indirectly.

If the radio is fine with no front end tube, you probably have one  
very large antenna.....

Bob


On Oct 19, 2007, at 10:17 PM, Tony Casorso wrote:

> 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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>>>
>