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Old 2nd Jun 2021, 7:36 pm   #54
dazzlevision
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Join Date: Sep 2003
Location: Near Swindon, North Wiltshire, UK.
Posts: 3,596
Default Re: Murphy V659/759 restoration

Quote:
Originally Posted by Niechcial,Steve View Post
As a matter of interest Dave, I'm curious why are you after the full manual for the converter? I have not had to do any serious work on mine, but the layout is very simple and straightforward in a way which makes me think it would be very easy to find anything- vision valves all in a row on one board, sound valves in a row on another.
Hello Steve,

I always like to have the full manufacturer's service information for anything I work on.

With Murphy Radio products, I'd expect a circuit diagram, modifications list, detailed parts list, drive cord stringing diagram, component layout diagrams (often photos with component references added), circuit description and alignment details - as per their full TV service manuals. In the case of their UHF converters, this was promised, but (it would appear) never issued.

I can manage with a circuit, but to have all the rest is really helpful and speeds up any work, especially alignment, as Murphy loved to use "damping units" in their TV alignment processes.

Bush Radio published full service manuals of all their UHF/625 conversion kits, so I'm surprised Murphy didn't. I expect it was an "economy measure", as Murphy sold out to Rank in 1962, due to increasing annual losses.

It does seem strange that Murphy didn't use a vari-mu valve as the first common vision and sound IF amplifier in the Astra (and previous chassis, IIRC). Setmakers in the Mullard camp would be using either an EF85 or EF183 (in later designs). Although it is now a long time ago, I do seem to recall that, when these sets were in everyday use, changing a 6F23 in a Murphy Astra did cause a noticeable change in IF alignment. Of course, there are three 6F23s in the vision IF strip of the UHF converter!

Last edited by dazzlevision; 2nd Jun 2021 at 7:45 pm.
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