Thread: Fidelity HF29
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Old 14th Nov 2018, 1:58 am   #21
Chris55000
Nonode
 
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
Default Re: Fidelity HF29

Hi!

Will this do with a 2M2 added across the ends of the track?

https://www.ebay.co.uk/itm/Vintage-E...UAAOSwSKtaf371

A single transistor amplifying stage could easily be added to your HF29 amplidier chassis on a piece of tagstrip, use a BC557 with upper base resistor 22k to supply –ve, a collector resistor of about 4k7 to supply –ve, a 6k8 from base to chassis, with an emitter stabilising resistor of 1k5, bypassed by 10uF to chasses (+ pole of cap to chassis – the foregoing assumes your amplifier is +ve earthed to chassis which will almost certainly be the case in a 1960s unit!

I/P and O/P couplers of 2.2uF (input cap –ve pole to base and O/P cap –ve pole to collector) will be fine!

The values suggested will give about three times voltage–gain which should be enough for most of the replacement ceramic cartridges you can find nowadays!

Chris Williams

PS!

If you run into bother with that tiny mains transformer, a 9–0–9V one with a 250mA secondary with a 115V primary (use a dual–primary one with primaries in PARALLEL) fed from the 90V taps and neutral of the original motor will give just about the right voltage!
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Last edited by Chris55000; 14th Nov 2018 at 2:09 am.
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