[TMC] SBE-3 question

[Chris Bolkan]

Thank you Meir!
That makes sense to me and is what I needed to know. On to the next
oscillators, then onto other circuit blocks one by one!
I will probably have lots of questions as I go. :-)
Warm regards,
Chris
KI7NXY

On Tue, Feb 1, 2022 at 12:27 PM Meir Ben-Dror WF2U <wf2u at ws19ops.com> wrote:

> Chris,
>
> The waveform out of an oscillator without a resonant circuit in the output
> is going to look pretty weird and dirty, as it is full of harmonics.
> Look at the output of V126 (6AH6) as it feeds T127, which is a tuned
> circuit for 250 kHz.
> What you want to do, is to turn the two audio input channels OFF and turn
> the carrier insertion up, until you have a decent amount of 250 kHz signal
> visible at the plate of V126.
> You should see a reasonably clean sinewave there.
>
> Let me know how that worked out.
>
> 73, Meir WF2U
> Landrum, SC
>
> Get BlueMail for Android <https://bluemail.me>
> On Feb 1, 2022, at 12:55 PM, Chris Bolkan <bolkyboats at gmail.com> wrote:
>>
>> Hi TMC lovers!
>>
>> I am currently trying to bring up a rough SBE-3 to operational condition
>> and need some help. I have no experience to pull on so I am hoping someone
>> on here has "been there and done that". I am starting by looking for the
>> most basic functionality...are the oscillators oscillating? The first
>> oscillator I am troubleshooting is the 250Khz sideband carrier (Z-103,
>> Z-108). It seems to me that this oscillator should be outputting a pure
>> looking sine wave. Mine is oscillating at the right frequency, and I
>> believe the final amplitude out of the cathode follower is approximately
>> correct, but the waveform is horrendous. Should it be a clean sine wave
>> like I think it should be or is it OK that it looks like $h1t?
>>
>> I've looked the circuit over, checked component values and believe there
>> are no out of tolerance resistors or leaky caps, but something just doesn't
>> seem right.
>>
>> It seems to me that if this oscillator is creating the (re)inserted carrier
>> it should be a pretty clean waveform. Any thoughts?
>>
>> Best regards,
>>
>> Chris
>> KI7NXY
>>
>>