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2T Gen problem

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Raymond METZGER

2T Gen problem

Hi,

I am in the final alignment and tests of my K2/SSB/PA100, which seems to be
going very well, . but I am facing my first real problem with an Elecraft
kit, the 2 T GEN.

This is rather frustrating, since there are only a few components, no
toroid, etc.

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.

I have of course inspected carefully the soldering and the component
placement.

Thanks for your suggestions,

Raymond METZGER

F4FNT

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Don Wilhelm-4

Re: 2T Gen problem

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

Raymond METZGER wrote:

>
>
> Hi,
>
>
>
> I am in the final alignment and tests of my K2/SSB/PA100, which seems to be
> going very well, . but I am facing my first real problem with an Elecraft
> kit, the 2 T GEN.
>
> This is rather frustrating, since there are only a few components, no
> toroid, etc.
>
>
>
> 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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JeremyJones

Re: 2T Gen problem

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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Don Wilhelm

Re: 2T Gen problem

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
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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JeremyJones

Re: 2T Gen problem

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
>> --
>> Sent from: http://elecraft.365791.n2.nabble.com/
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]

Don Wilhelm

Re: 2T Gen problem

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.
>
>
>

JeremyJones

Re: 2T Gen problem

Don,

Q2 Gate = 5.20v
Q2 Drain = 4.66v

Jeremy

> On Oct 31, 2017, at 6:37 PM, Don Wilhelm <[hidden email]> 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.
>>
>>
>>
>

Don Wilhelm

Re: 2T Gen problem

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 <[hidden email]> 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.
>>>
>>>
>>>
>

JeremyJones

Re: 2T Gen problem

Don,

C2 is already .01uF. Are you suggesting I try a .1uF?

Jeremy

> On Oct 31, 2017, at 11:50 PM, Don Wilhelm <[hidden email]> wrote:
>
> 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 <[hidden email]> 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.
>>>>
>>>>
>>>>
>>
>

Don Wilhelm

Re: 2T Gen problem

Jeremy,

No, I am saying replace it with another 0.01uF.
What is suspected is that the one in your 2T-Gen is on the low side of
tolerance, and putting in one closer to the nominal value or slightly
higher may make it oscillate.

73,
Don W3FPR

On 11/1/2017 11:45 AM, Jeremy Jones wrote:
> Don,
>
> C2 is already .01uF. Are you suggesting I try a .1uF?
>

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JeremyJones

Re: 2T Gen problem

Hi Don,

I didn’t have a .01uf capacitor on hand, so I swapped C2 and C6. The 700Hz tone continued to work, while 1900Hz still had nothing.

Jeremy

> On Nov 1, 2017, at 2:50 PM, Don Wilhelm <[hidden email]> wrote:
>
> Jeremy,
>
> No, I am saying replace it with another 0.01uF.
> What is suspected is that the one in your 2T-Gen is on the low side of tolerance, and putting in one closer to the nominal value or slightly higher may make it oscillate.
>
> 73,
> Don W3FPR
>
> On 11/1/2017 11:45 AM, Jeremy Jones wrote:
>> Don,
>>
>> C2 is already .01uF. Are you suggesting I try a .1uF?
>>
>