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Old 12th Apr 2010, 10:25 pm   #10
Sideband
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Join Date: Oct 2003
Location: Croydon, Surrey, UK.
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Default Re: Philips Hi-Z record player

No I think the UL84 is right. It's heater is run from a separate winding on the mains transformer. It's called 'Hi Z' because it uses an 800 ohm speaker. The EL84 and UL84 are run in a transformerless circuit (the UL84 drives the speaker). The cathode of the UL84 is connected directly to the anode of the EL84 so therefore the cathode of the UL84 is running at a high voltage...probably about 150V. Therefore the heater/cathode insulation needs to be good hence the use of the UL84. Effectively they are 'in series' across the HT rail. I think it's called 'cascode'.

It's a bit like the 'Bi-Ampli' designs of the continental sets. Only ever seen one and it worked very well.

I'm sure the circuit is in the Newnes servicing books but I've no idea what year...guess between 57 and 59.
Rich.
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