Re: Philips 2514
Had a bit of try with ferrites on the HT line, RF stage drain and Det drain.
regen is much smoother now and hum is maybe a bit better. My house is incredibly bad for RF pollution and the wide bandwith really makes it worse.
I tried the phones on the Interstage tranny and there was hum there too. The quality of the audio was better though. The Gain of the O/P bottle I would guess at about 4. Very dodgy running this without the O/P bottle HT goes from 155V to 243V. Something a bit weird? The 2.7Ks after the 1N4007s drop 15V, About 5.5mA so the total HT I is about 11 mA. Need to check it on Duncan's PSU calc.
O/P stage I is about right as my 2 MOSFET valves only take about 1mA.
I will try and knock up an O/P valve with a 2n3819 and a BF47*. I tried a horn speaker, volume was a bit low and it was pretty poor quality. Another possibility is to use a small 220/12V toroid and an 8R speaker. I have some excellent sounding 3" Grundig units. I looked at the O/P transformer, It doesn't appear to be gapped and the distortion is LF, maybe the 10mA is saturating the core.
So 3 things to sort, Volume, Quality and Hum.
Here is a pic E415 PCB is a bit messy, will tidy later
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