Murphy A242 VHF IF Alignment - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Steve_P · 26th May 2009, 4:49 pm

At the time, Murphy were not allowed to use the VHF valves that Mullard had, as they had an agreement with Mazda. Also, in those days, VHF was for home only use and an external antenna was needed.

Align the whole of the VHF chain and put new valves in the VHF section. Check C1 and C2. Check the HT voltages to the valves and the cathode voltages.

Cheers,

Steve P.

JimMac53 · 26th May 2009, 7:10 pm

Thanks for the advice Steve. Interesting note about the valves Murphy was allowed to use. Concerning alignment, I pretty much plan to do that. I already know the voltages are where they should be (both anode and cathode). I have some other tubes I can sub-in. I also just acquired a Murphy A252, which is working and even though it's a later model (and different valve set), it does give me something to compare it to. Which makes me wonder: "How much variation in performance was there from set to set as it came off the factory floor? (this could be its own thread)" It would be nice to know how much gain each stage had, bandwidths, etc.

26th May 2009, 4:49 pm	#41
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Murphy A242 VHF IF Alignment At the time, Murphy were not allowed to use the VHF valves that Mullard had, as they had an agreement with Mazda. Also, in those days, VHF was for home only use and an external antenna was needed. Align the whole of the VHF chain and put new valves in the VHF section. Check C1 and C2. Check the HT voltages to the valves and the cathode voltages. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

26th May 2009, 7:10 pm	#42
JimMac53 Hexode Join Date: Apr 2009 Location: Naples, Florida, USA Posts: 255	Re: Murphy A242 VHF IF Alignment Thanks for the advice Steve. Interesting note about the valves Murphy was allowed to use. Concerning alignment, I pretty much plan to do that. I already know the voltages are where they should be (both anode and cathode). I have some other tubes I can sub-in. I also just acquired a Murphy A252, which is working and even though it's a later model (and different valve set), it does give me something to compare it to. Which makes me wonder: "How much variation in performance was there from set to set as it came off the factory floor? (this could be its own thread)" It would be nice to know how much gain each stage had, bandwidths, etc. __________________ Jim Mac