Quote:
Originally Posted by Jon F
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Well, no components wasted there.
In general, you expect a direct triggered circuit to be much more noise sensitive compared to an AFC circuit. If L42/R38 through R39 and C44 is the source of sync, then L42 may be rolling off some high frequency noise depending on its size. Probably they experimented with the roll-off but couldn't get reliable triggering with it rolled off more.
Since there is more than one example in existence, I'd guess this is a design limitation that won't be fixed reliably without changing the circuit somehow.
Meanwhile, my guess is to try to eliminate possible sources of noise, as others have suggested.