[Elecraft] 2T Gen problem

Don Wilhelm donwilh at embarqmail.com
Tue Oct 31 23:50:48 EDT 2017


Jeremy,

Those voltages seem to be OK.

I have obtained information from Elecraft support that C2 may be the 
problem.
The capacitor may be too low in value.
Replace C2 with a .01uF capacitor and see if that fixes the 1900kHz 
oscillator.

73,
Don W3FPR

On 10/31/2017 9:14 PM, Jeremy Jones wrote:
> Don,
>
> Q2 Gate = 5.20v
> Q2 Drain = 4.66v
>
> Jeremy
>
>> On Oct 31, 2017, at 6:37 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>>
>> Jeremy,
>>
>> What is the voltage at the gate of Q2?  And what is the voltage at the drain?
>> Those two points should control the level of the 1900Hz tone.
>>
>> Likely possibility is that Q2 was damaged by static when installed.
>>
>> You should have the JP2 jumper set for the "T" position.
>>
>> 73,
>> Don W3FPR
>>
>> On 10/31/2017 6:01 PM, Jeremy Jones wrote:
>>> Hi Don,
>>>
>>> I have the 700Hz tone, but not the 1900Hz.  Here is the quote from the original post.  I measured similar voltages.  I’ve also included your response to him.  It seems like a pretty simple device, and I’ve double checked the components and soldering.  My 12 year old daughter did most of the soldering, so the only thing I can think of is her leaving the heat on too long and damaging a component, but there are no burn marks on the circuit board.
>>>
>>> The 700 Hz generator works and produces a max 150 mVolt peak signal, but the
>>> 1.900 Hz generator does not work. I noticed that Base of 2N3904-Q1 (1.900
>>> Hz) shows 0 V, while Base of 2N3904-Q3 (700 Hz) shows 2,1 mV. With a 8.9
>>> Volts Vcc, Collector Q1 shows 8,1 Volts while Collector Q3 shows 6.7 Volts.
>>> Drains Q2 and Q4 (2N7000) show both 4.4 V (= Vcc/2). The voltages of pins
>>> 1,2,3,5,6,7 of U1 (LMC6482) are all 4.4 Volts. Replacing Q1 with an
>>> available spare didn't help and didn't change the voltages.
>>>
>>>
>>>
>



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