UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Techman · 21st Jan 2023, 1:18 am

I agree regarding the UU5.

I've got data books, but you can look up all you need to know about most valves on-line.

Here's a link to the valve museum, where there's data on thousands of valves, including your MU14 which I've linked to...
http://www.r-type.org/exhib/aaa0703.htm

You can probably glean from the writeup on that page that it wasn't the best of valves, being a re-badged MU12 that happened to just meet the specifications. Another thing is that the UU5 is a lower heater current, so less stress on the base pin connections and the transformer. You can see all the equivalents listed at the top of that page and click on them to see their specifications, including heater current and peak anode voltage etc. I quite like using the Brimar R3, not for any other reason than I happened on a stash of them a few years ago. They seem to be a good valve with 500 volts anode rating. However, they do draw 2.5 amps heater current, so perhaps not ideal for your set. Although the R3 is shown in the equivalents list on that web page, there's no on-line data for it, so I had to use one of my data books to check the exact specifications.

It's worth noting that the original valve being a UU4 only has a 2.2 amp heater, so your set has had its transformer slightly overloaded with that MU14 with its 2.5 amp heater.

21st Jan 2023, 1:18 am	#31
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: What did I get myself into? Murphy A40C. I agree regarding the UU5. I've got data books, but you can look up all you need to know about most valves on-line. Here's a link to the valve museum, where there's data on thousands of valves, including your MU14 which I've linked to... http://www.r-type.org/exhib/aaa0703.htm You can probably glean from the writeup on that page that it wasn't the best of valves, being a re-badged MU12 that happened to just meet the specifications. Another thing is that the UU5 is a lower heater current, so less stress on the base pin connections and the transformer. You can see all the equivalents listed at the top of that page and click on them to see their specifications, including heater current and peak anode voltage etc. I quite like using the Brimar R3, not for any other reason than I happened on a stash of them a few years ago. They seem to be a good valve with 500 volts anode rating. However, they do draw 2.5 amps heater current, so perhaps not ideal for your set. Although the R3 is shown in the equivalents list on that web page, there's no on-line data for it, so I had to use one of my data books to check the exact specifications. It's worth noting that the original valve being a UU4 only has a 2.2 amp heater, so your set has had its transformer slightly overloaded with that MU14 with its 2.5 amp heater.