[ARC5] BC-348Q CW Oscillator Question

[WA5CAB at cs.com]

No.  If you are measuring the resistance to ground at the right end of the 
80K resistor (which is the B+ buss), you should have somewhere between 500 
and 1000 ohms if the dynamotor is installed and 100K if it isn't.  

If you are measuring at the junction of the 20K pot and the 80K resistor, 
you should get something around 16K, which is 20K in parallel with 80.5 K to 
81K.

This is based on the schematics for the BC-348-J and BC-348-Q.  The other 
models are slightly different but not seriously.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480


> 
> 
> Thank you for your comments.  I agree if measuring resistance through the 
> wiper.   However, measuring the resistance form the end of the 80K resistor 
> should give you the sum of the 80K resistor and the Volume Pot.   At max 
> volume the pot should be 0 (ideally), so the total resistance should be 80K. 
>   But, it's not and I'm still not sure why.
> 
> 
> Mark K3MSB
> 
> 
> 
> 
> 
> On Sun, Jan 17, 2016 at 1:03 AM, WA5CAB--- via ARC5 <arc5 at mailman.qth.net> 
> wrote:
> >> Mark,
>> 
>> The table calls for rotating the Volume/Sensitivity knob fully CW.  The 
>> fully CW ends of the two pots are at the bottom, not the top.  With the 20K 
>> pot fully CW, the wiper is at the grounded end.  So the 80K resistor has 
>> no effect.
>> 
>> In a message dated 01/16/2016 18:57:08 PM Central Standard Time, 
>> mark.k3msb at gmail.com writes: 
>> >>> My Question.  Resistor 94-2 is the 80K resistor connected to the 
>>> ungrounded terminal of the volume pot.  With this in the circuit, a great 
>>> many of the values in the table should be much higher.  My measured values 
>>> agree with all the table values.   How can that be?  The 80K resistor is 
>>> in series with the volume pot!  80K Isn't insignificant in this 
>>> context....   It's easy to isolate this resistor;  it's there and it measures near 
>>> 80K.
>>> 
>>> 
>>> 73 Mark K3MSb
>> 
>> Robert &Susan Downs - Houston
>> wa5cab dot com (Web Store)
>> MVPA 9480
>> 
> 
> 
> 
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