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

[ANTHONY CASORSO]

Checking the injection levels is a good idea. I'll try that tomorrow.

Tony


>From: Bob Camp <ham at cq.nu>
>To: Tony Casorso <canthony15 at msn.com>
>CC: <R-390 at mailman.qth.net>
>Subject: Re: [R-390] R-390a Image problem?
>Date: Fri, 19 Oct 2007 23:06:32 -0400
>
>Hi
>
>Stage voltages are a good idea if you have a VTVM. With an RF probe  you 
>can also check the injection levels at the mixers. Low drive to a  mixer 
>can cause all sorts of odd things. Your 17 MHz crystal  oscillator may be a 
>bit "sick" for instance ....
>
>Another stupid thing to check - did somebody put a couple of diodes  up in 
>the antenna relay to "overload protect" the radio?
>
>Bob
>
>
>On Oct 19, 2007, at 10:48 PM, Tony Casorso wrote:
>
>>I see what you mean about AGC.  I checked it anyway. -11 volts on a  
>>strong local station. I swapped tubes with no improvement. I wonder  if 
>>the stage bias could be wrong? I guess I should measure the  voltages just 
>>to be sure.
>>
>>When I said 1st RF stage, I guess I forgot this was an R-390a. Part  of 
>>the cost reduction removed one of the RF stages didn't it? There  is only 
>>one.
>>
>>The antenna is a 100 foot longwire.
>>
>>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 8:36 PM
>>Subject: Re: [R-390] R-390a Image problem?
>>
>>
>>>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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>>>>>>
>>>>
>>
>