[R-390] More On Low Audio Problem

[Jim M.]

Ask yourself, what could have happened when the front panel was removed and 
replaced.  There are large cable bundles that get flexed when you remove the 
panel.  I have broken many wires going to gain pots in the process of 
removing the panel.  Something could have happened to a wire on the audio 
pot of wide/narrow switch.  Sometimes the twi multipin connectors to the AF 
module work loose.  Hopefully a wire wasn't crimped under the panel when you 
replaced it.
JM
----- Original Message ----- 
From: "Cecil Acuff" <chacuff at cableone.net>
To: <r-390 at mailman.qth.net>
Sent: Saturday, December 17, 2005 1:28 PM
Subject: Re: [R-390] More On Low Audio Problem


> Got a bit crosseyed....should have said 1 and 7 not 1 and 6....
>
> Cecil...
> ----- Original Message ----- 
> From: "Cecil Acuff" <chacuff at cableone.net>
> To: "Frederick Bray" <fwbray at mminternet.com>; <r-390 at mailman.qth.net>
> Sent: Saturday, December 17, 2005 11:53 AM
> Subject: Re: [R-390] More On Low Audio Problem
>
>
>> Fred,
>>
>>    In the wide position the response switch S-104 should be already 
>> shorting pin 1 to pin 6.  If you are using a clip lead to connect pins 1 
>> and 6 and it restores audio you have a bad contact on S-104 or a broken 
>> wire between pins 3 and 9.
>>
>> Looks like you are close...
>>
>> I didn't have a schematic for the 390A from the shop but used the pull 
>> out in the TM11-4000 that was already on my desk here in the house.  I 
>> hope the designations are correct...I believe the schmatic to be.
>>
>> Cecil....
>> ----- Original Message ----- 
>> From: "Frederick Bray" <fwbray at mminternet.com>
>> To: <r-390 at mailman.qth.net>
>> Sent: Saturday, December 17, 2005 11:40 AM
>> Subject: [R-390] More On Low Audio Problem
>>
>>
>>> First, let me thank everyone who has replied -- both on and off list.
>>>
>>> I think I have narrowed the problem down to the first AF amp/cathode 
>>> follower.  I would appreciate it if those who are more experienced that 
>>> I with the 390A can confirm that I am on the right track.
>>>
>>> I used an audio signal generator to ascertain that a signal injected at 
>>> the local and line level controls seems to produce a normal audio 
>>> output.
>>>
>>> Using a VTVM, I confirmed that on there is an AC voltage on terminal 1 
>>> of the wide/sharp switch and that I can trace this voltage through the 
>>> switch.  Jumpering this voltage to terminal 6 on the switch seems to 
>>> restore the audio level to approximately normal, or at least much closer 
>>> to normal.
>>>
>>> From looking at the schematic, I think that what I am doing is bypassing 
>>> the first AF/cathode follower and going directly to the local and line 
>>> AF amps.
>>>
>>> Does this make sense?
>>>
>>> Thanks,
>>>
>>> Fred Bray
>>> KE6CD
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>>
>>
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