Posted by
JeremyJones on
Oct 31, 2017; 10:01pm
URL: http://elecraft.85.s1.nabble.com/2T-Gen-problem-tp452848p7635565.html
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.
With the scope, I get a 689 Hz sinusoidal signal on U1 pin 7 (570 mV peak),
but nothing on U1 - pin 1.
There is a "saw teeth" signal on collector Q3, nothing on collector Q1.
Raymond,
I believe the oscillator should oscillate even with Q1 removed. Look
carefully at the feedback loop around U1A particularly C2, C4, R1, R2
and R6. Be certain the jumper blocks are in the 'T' position.
The most likely problem is soldering or a misplaced component. Use a
magnifier to check for any tiny slivers of solder between adjacent pins.
73 and good luck with it,
Don W3FPR
Thanks,
Jeremy
> On Oct 31, 2017, at 5:56 PM, Don Wilhelm <
[hidden email]> wrote:
>
> Jeremy,
>
> I don't do Nabble, so I don't know about that 10 year old post.
> What is your problem with your 2T-Gen?
> Note that this is one of the 2 Elecraft products that use a hyphen in the model designation! The N-Gen is the other one.
>
> 73,
> Don W3FPR
>
> On 10/31/2017 5:39 PM, JeremyJones wrote:
>> Well this post is 10 years old, but I am having the exact same problem. I
>> have checked with a magnifying glass for any solder bridges or poor solder
>> joints. Everything looks fine. I'd appreciate any further troubleshooting
>> ideas.
>> 73,
>> Jeremy
>> VA3ZTF
>> --
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