[Boatanchors] NC-109 Help Needed

[Garey Barrell]

I have a "cleaned up" PDF of the NC-109 schematic.  Can attach for 
anyone interested.

73, Garey - K4OAH
Atlanta

Drake 2-B, 4-B & C-Line Service CDs
<www.k4oah.com>



John Marshall wrote:
> Joe,
>
> The individual page schematic on the BAMA mirror is a lot clearer than 
> the PDF version.  I have no trouble making it out on my 'puter.  It's 
> on two pages:
> http://bama.edebris.com/download/national/nc109/12.gif
> http://bama.edebris.com/download/national/nc109/13.gif .
>
> The NC-109 didn't have any provision for external muting so you don't 
> need any jumpers in the accessory socket unless the set was modified.  
> According to the schematic, pins 1, 2 and 3 on the accessory socket 
> should be unused, so if you see connections there it might indicate a 
> mod.
>
> Assuming you tried swapping out the 12AT7 and 6AQ5.  I don't recall 
> exact values from my 109 but look for full B plus (200V or whatever 
> your PS puts out) on the 6AQ5 plate (pin 5) and 180V or so on the 
> screen (pin 6).  The cathode (pin 2) should probably be around 10V 
> give or take.  No voltage on the screen would indicate a problem with 
> the Receive/Standby switch.  If those voltages are good, you might be 
> able to hear a click by probing the 6AQ5 grid (pin 1).  The Tone 
> switch shunts a capacitor from grid to ground so check to make sure it 
> or the capacitor is not shorted.  The 12AT7 first audio will have a 
> pretty low plate voltage but it also comes thru the Standby switch.
>
> GL troubleshooting!  This makes a nice receiver for SWLing and the 
> sharp crystal filter makes it pretty good for CW on the low bands.  I 
> used mine on 80 last year for SKN and had a great time.
>
> John, KU4AF
> Pittsboro, NC
>
>
> On Tue, 26 Sep 2006 22:53:37 -0400, Carole White-Connor 
> <carolew at bellatlantic.net> wrote:
>
>> Hello, all. I just picked up a National NC-109. It was sold to me as a
>> basket case but it actually does not look too bad. It should be a fun
>> project.
>>
>> 1.  Does anyone have a voltage chart? The manual I downloaded from 
>> BAMA does
>> not have one.
>>
>> 2.  Does anyone have a legible schematic. The BAMA one is tough to read.
>> Surprisingly, Sams does not list a service packet for this set.
>>
>> 3. My problem appears to be in the audio section. The voltages coming 
>> out of
>> the power supply are good. However, there is no audio and no response 
>> when I
>> stick a soldering iron on the volume control. The output transformer 
>> tests
>> good.  Does anyone know what the voltages should be on the audio output
>> (6AQ5) and the AF amp (12AT7)?
>>
>> As always, thank you in advance.
>>
>> Joe Connor