Unstable DIY R*S Serge NTO

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teezdalien
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Unstable DIY R*S Serge NTO

Post by teezdalien » Fri Mar 13, 2020 3:40 am

Hi everyone, I've got a bit of a stability issue that's just cropped up with one of my NTO modules. It's only a couple of years old and has been great up until very recently. I highly doubt it's power related, my case has a good supply and my other NTO and oscillators seem fine.. I've also tried going back through the callibrating procedures and isn't making any difference.

I guess my question is what most likely causing this and is it likely to be an easy fix? What might cause an oscillator to suddenly become unstable in frequency?

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cygmu
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Re: Unstable DIY R*S Serge NTO

Post by cygmu » Fri Mar 13, 2020 3:57 am

I once had an oscillator whose frequency suddenly went wobbly. The issue in my case was a potentiometer that had somehow gone bad. I think it was the main frequency pot. Replacing it fixed the issue immediately.

Diagnosing might be difficult but if you have a scope and can probe the lugs of the pots you may be able to spot wobbliness.

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teezdalien
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Re: Unstable DIY R*S Serge NTO

Post by teezdalien » Fri Mar 13, 2020 4:06 am

Thanks for the advice. I'll dig out my multimeter and go over it thoroughly tomorrow. That actually seems a likely culprit. :tu:

Will report back with my findings.

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cygmu
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Re: Unstable DIY R*S Serge NTO

Post by cygmu » Fri Mar 13, 2020 8:45 am

teezdalien wrote:
Fri Mar 13, 2020 4:06 am
Thanks for the advice. I'll dig out my multimeter and go over it thoroughly tomorrow.
It might be tricky to see much on a meter as opposed to a scope but you should use what you have of course! If the meter has an AC voltage mode, that would let you see how much a given voltage is varying, which is what you want I think.

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yghartsyrt
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Re: Unstable DIY R*S Serge NTO

Post by yghartsyrt » Tue Sep 08, 2020 11:16 am

teezdalien wrote:
Fri Mar 13, 2020 4:06 am
Thanks for the advice. I'll dig out my multimeter and go over it thoroughly tomorrow. That actually seems a likely culprit. :tu:

Will report back with my findings.
Did you find the solution? My NTO started to get unstable today. Since I have no scope nor multimeter around, it is hard to check....

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teezdalien
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Re: Unstable DIY R*S Serge NTO

Post by teezdalien » Fri Sep 11, 2020 7:36 pm

Sorry for the late response.

It turned out to be a bad potentiometer as cygmu suspected, which was easy enough to address. Ended up buying a whole bunch for spares as I also had some similar problems with other modules. I've read from a few others here having similar wonky NTO issues, so I don't hold great confidence in these particular alpha pots.

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yghartsyrt
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Re: Unstable DIY R*S Serge NTO

Post by yghartsyrt » Mon Sep 14, 2020 1:32 am

cool. thanks.

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yghartsyrt
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Re: Unstable DIY R*S Serge NTO

Post by yghartsyrt » Fri Sep 18, 2020 2:39 am

mine was also a malfunctioning potentiometer

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