Scope of board pin 15 with -24 strapped to edge 12
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Okay, so you've now got your 7.6kHz at pin 15. A quick favour to ask - can you turn on the bandwidth limit on the scope, please?
You'll probably now see a signal on the collector of TR9 but you will most likely need to fit C15, as per the adjustment instructions.
You should be able to progress this by following the adjustment instructions; just ignore any reference to an ATM/1. By the way - the output level will be quite low at pins 7 and 8, only about 400mV peak to peak.
But why is the waveform such a fluctuating mess
edit
Hold
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Excellent, step 5 has improved things massively, RV1 had been twiddled to the wrong end.
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Wow, that's one heck of an improvement!! So what are you seeing at pins 7&8 now?
Still the weird waveform I had at the start
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That looks like something going in to bursts of instability.
What signal can you see at either side of C14 and at the collector of TR9 now, assuming you've fitted a 39nF and 2.2nF cap in the positions of C15 and C15A?
There's nothing recognisable on any of those
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On one side of C14 it looks like a lopt ring !!
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@crustytv Okay, experiment time.
TR6 and TR8 exists to mute the tones going into the output stage: remove that link between pin 12 on the edge connector and the -24V supply and also, temporarily remove TR6 and TR8. Then let's see what we get.
Sine wave on all three test points now
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@crustytv Right, so most likely TR6 was muting it despite us strapping pin 12 to the -24V supply.
What does the signal look like at pins 7 and 8 of the edge connector now?
Sine wave now
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Just shy of 400mV
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Not good!
That was before removing TR6 & TR8, now all waveforms are sine
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Just nipping out to drop my sone off at work, back in 15-mins
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Exactly what the book says - good, but I'm a little worried by all that spiky rubbish on the waveform.
Now, I wonder if we can reduce the frequency of the oscillator to something more usable?
