Quote:
Originally Posted by Lloyd 1985
A very interesting post, and a lovely little set saved! I’ve still not got one of these, but maybe I’ll pick one up at next years NVCF.
I never thought of making an adapter with diodes in the base to fit a more easily available valve. I e got an Ekco U29 that would benefit from such an adapter.
Regards
Lloyd
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https://www.vintage-radio.net/forum/...ad.php?t=44574
At the link above, the second pic shows the adaptor I made, which incorporates a couple of OA91 diodes built into an Octal valvebase removed from a duff Octal donor valve and cross wired to a B9A valveholder.
This adaptor enables an EL84 valve to be plugged into the adaptor, and in turn, the adaptor to be plugged into the octal valveholder on the radio chassis without any alterations to the original valveholder wiring, thus enabling the EL84 to be used as a substitute until perhaps an EBL31 comes along.
There was another post here:
https://www.vintage-radio.net/forum/...ad.php?t=44574
It was also covered in an article in Summer 2010 BVWS Bulletin.
As the EBL31 has a top cap and the EL84 doesn’t, it was necessary to provide a “top cap” on the adaptor onto which the top-cap clip could be clipped. I then cross-wired the pins from the octal valve base to the correct pins on the B9A valve-holder, housing the two OA91 diodes inside the adaptor.
The EBL31, being a double diode pentode with a top cap, was a bit more involved than the he FB10 adaptor, (6X5GT - 6V4 rectifier), but I'm sure there are many valves that lend themselves to this treatment, particularly if the original valve is rare or expensive and a more common/cheaper valve is available. An adaptor has the merit of not requiring a re-wire of the valve-holder on the chassis. Where rectifier valves are concerned, there's also the option of making an adaptor by using silicon diodes, and I'm sure I won't have been the first to mention that.