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.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
