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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 19th Nov 2019, 9:26 pm   #1
Martin G7MRV
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Default Deaf single transistor super-regenerative - where to start?

I have two self-quenching super-regenerative receivers (part of the SARBE-5 im working on), the two are identical, except that one is deaf!

Ive attached the circuit. The two transistors and resistors in the middle are part of the switching between the two.

Im wondering, other than a bad transistor, what would be the most likely cause of one of these receivers to be deaf? Its not that it doesnt receive, so it isnt that its not working as in not oscillating/quenching, I wouldnt have thought, but it needs 10x the signal than the other good receiver!

Im hoping theres a likely suspect - as the circuit is incredibly cramped, so not easy to work on!



Cheers
Martin
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Old 19th Nov 2019, 10:11 pm   #2
kalee20
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Default Re: Deaf single transistor super-regenerative - where to start?

Can you 'scope on C46 and C56? I'd guess that the output would appear across these, coloured with a lot of quench-frequency component. Comparing quench frequencies might tell a lot.
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Old 19th Nov 2019, 10:28 pm   #3
Martin G7MRV
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Default Re: Deaf single transistor super-regenerative - where to start?

Quote:
Originally Posted by kalee20 View Post
Can you 'scope on C46 and C56? I'd guess that the output would appear across these, coloured with a lot of quench-frequency component. Comparing quench frequencies might tell a lot.
I 'might' be able to - its incredibly tight in there, but there might be a bit of leg showing that I can get the probe onto. I'd have no idea what any difference in trace between the two would signify though!

Im far more used to superhets!

The transistors a SMT on the other side of the PCB, trouble is, if I take the PCB out, i'd need to rig up an elaborate arrangement of magnets to put all the reed switches into the correct state! (everything in this is controlled by reeds with external magnets)
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