That confirms my earlier thoughts, hard to say what the fitted output valve is, KT61, E元3 or maybe a 6P25 or 6V6g. At the moment, there are several of these on Ebay for quite high prices!
So far, I have just brushed all the surface grime off it. I will probably remove the whole of the power supply, and get it working from an external source before thinking of making a new safe supply! The mains appears to go straight the chassis and the metal rectifier. The orange transformer just seems to supply the heaters, and the wires from it, to the heaters are just poked through two very small holes drilled in the chassis without any pretence at insulation beyond the covering on the wires (cracked and brittle). The E元3 could be used in push pull to deliver 8 Watts, but the normal use was in domestic radio receivers as a single ended stage.
Mullard describe this valve as a high sensitivity output pentode for use in AC mains equipment. So the first two match up, so it looks like the unmarked output valve in an E元3! These have been recently tested, gm 7.0mA/V and 7.5 mA/V (spec is 6.0mA/V). The E元3 audio output valve is the little brother of the E元7 with which it shares pin connections. Please see the substitutes at the top of the page for more details. The BVA valve equivalents are:īVA273 = ECH35, BVA243 = EF39, BVA264 = E元3. KT61 Data sheet links: National Valve Museum: KT61: html, html2: Frank Philipse (Wildcat mirror - Jörg Jan Münter) KT61: KT61Radiotron.pdf (932028 bytes) Bold designators are close or identical, Italic designators are different ratings, different pinouts or different filament voltages. (07-02-2017, 03:17 PM)Sparks Wrote: I have looked into it a bit more, and got a circuit from online.
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