[TMC] SBE-3 question

[Meir Ben-Dror WF2U]

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

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On Feb 1, 2022, 12:55 PM, 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
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