[R-390] Re: R-390 Digest, Vol 6, Issue 26

[Chuck]

Check the 3TF7 ballast tube
Chuck

r-390-request at mailman.qth.net wrote:

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>Today's Topics:
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>   1. R-390 Problems (David C. Hallam)
>   2. Re: R-390 Problems (Bob Camp)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Sat, 30 Oct 2004 14:07:55 -0400
>From: "David C. Hallam" <dhallam at rapidsys.com>
>Subject: [R-390] R-390 Problems
>To: "R-390 List" <r-390 at mailman.qth.net>
>Message-ID: <NFBBJDPKCPDDNNAFOPDGEEBDDBAA.dhallam at rapidsys.com>
>Content-Type: text/plain;	charset="iso-8859-1"
>
>I have a problem with my R-390 nonA and don't know exactly where to start.
>The radio went dead.  I suspected a B+ problem and found that one of the
>26Z5W rectifiers had gone bad.  I replace both and now can measure 180 VDC
>at the test point for regulated B+.  The radio still is dead.
>
>Symptoms;
>
>No movement in either the line audio or carrier level meters on any band
>with either manual or automatic gain
>
>No noise on the local audio output at any setting of the audio gain control
>
>455 kHz signal from my URM-25D applied to test point E210 (grid of the 3rd
>mixer) produces the expected output measured with the 410B at the diode load
>terminal until the pass band is increased to 8 kHz or 16kHz.  Then it's like
>something breaks into oscillation as the diode load voltage increases to
>something like 100 or more volts.
>
>I guess the next step is to start checking the voltages at each tube, but I
>wondered if someone might have an idea as to a specific location to
>concentrate on.
>
>David C. Hallam
>KC2JD
>
>
>
>
>------------------------------
>
>Message: 2
>Date: Sat, 30 Oct 2004 14:50:16 -0400
>From: Bob Camp <ham at cq.nu>
>Subject: Re: [R-390] R-390 Problems
>To: dhallam at rapidsys.com,	R-390 HF Receiver List
>	<r-390 at mailman.qth.net>
>Message-ID: <8A64AE8E-2AA4-11D9-A751-000A95C4FE54 at cq.nu>
>Content-Type: text/plain; charset=US-ASCII; format=flowed
>
>Hi
>
>Well the first thing to *always* be sure of any time you see IF filters 
>involved is to be sure that the "magic" B+ blocking capacitor is in 
>series with the filters. I see no reason why that would be your problem 
>but it never hurts to be sure.
>
>The 26ZW5 can get pretty dead and the radio will still work. I suspect 
>yours has been dead for a while and you just found the problem when the 
>second issue started up.
>
>As you may have guessed the problem is likely to be an IF stage going 
>into oscillation. Since it changes with the filters it probably is one 
>of the stages ahead of the mechanical filters. I would also do a 
>resistance check on the filters just to be sure the two wide band 
>filters are still ok.
>
>	Enjoy!
>
>		Bob Camp
>		KB8TQ
>
>
>On Oct 30, 2004, at 2:07 PM, David C. Hallam wrote:
>
>  
>
>>I have a problem with my R-390 nonA and don't know exactly where to 
>>start.
>>The radio went dead.  I suspected a B+ problem and found that one of 
>>the
>>26Z5W rectifiers had gone bad.  I replace both and now can measure 180 
>>VDC
>>at the test point for regulated B+.  The radio still is dead.
>>
>>Symptoms;
>>
>>No movement in either the line audio or carrier level meters on any 
>>band
>>with either manual or automatic gain
>>
>>No noise on the local audio output at any setting of the audio gain 
>>control
>>
>>455 kHz signal from my URM-25D applied to test point E210 (grid of the 
>>3rd
>>mixer) produces the expected output measured with the 410B at the 
>>diode load
>>terminal until the pass band is increased to 8 kHz or 16kHz.  Then 
>>it's like
>>something breaks into oscillation as the diode load voltage increases 
>>to
>>something like 100 or more volts.
>>
>>I guess the next step is to start checking the voltages at each tube, 
>>but I
>>wondered if someone might have an idea as to a specific location to
>>concentrate on.
>>
>>David C. Hallam
>>KC2JD
>>
>>
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>>    
>>
>
>
>
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>End of R-390 Digest, Vol 6, Issue 26
>************************************
>
>  
>