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Old 25th Oct 2020, 2:53 pm   #4
Sideband
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Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 5,917
Default Re: Philips 274A - ugly duckling!

Hi Keith. Yes I rebuilt the wet electrolytics and in fact restuffed all the others including the big can. Mine has May 1934 stamped on the side so they are of similar age.

Interesting that you have a PM24A in yours. Mine has a PM24M (which ties in with the valve diagram on the back cover) which in fact I have recently replaced due to failure of part of the filament in the original. I was lucky to find a very good replacement on eBay which gives a huge improvement over the original. As an experiment some time ago I tried a PM24A since I already had a good one of those. Less volume although the quality seemed about the same. One thing that does notice on these....the anode bend detector doesn't like the high modulation levels of some of the local MW stations, (in this area, Gold) which shows noticeable distortion whereas R4 is clear and clean as is Talk Sport. Not sure about the regen. I was told by an older engineer (no longer with us) that the gain and selectivity was purely down to the design of the coils, hence Superinductance. These are apparently wound in a special way on glass formers but I haven't dared open one to have a look.
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