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Old 15th Feb 2019, 1:59 pm   #34
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,161
Default Re: Ferrograph 4A: Restoration advice needed

...C3 is marked as 0.02mFd 360V, but in the unit it is bypassed by a resistor and a 3100pF(? - value half illegible) 'Suflex' (picture attached). What is the reason for this not being on the circuit diagram? Is it a pre-calculated snubber circuit for the speed control switch?
From memory these are for calibrating the repro (playback) response for which components had to be individually selected in production, possibly because the tolerances on the record/play head couldn't be made tight enough to use standardised resistors and capacitors.

I think the Suflex caps are polyester and as I recall, unlike electrolytics were long lasting and reliable. I wouldn't be changing them without a good reason.
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