US transformer in a UK amp

[BadDave]

Howdy everyone,

I just got a little 5w Hayden High Five off eBay, which seems to be a Valve Jr clone, with an EL84 and a 12AX7.  I was a bit surprised to see the transformer primary marked 115v and the secondary at 240v, but I figured probably somebody put the wrong sticker on it at the factory, since the chassis is marked 240.  However, my EL84 plate measures about 750v, and using the same ratio as 115:240 and then multiplying by 1.414, that's right in the neighborhood of what I would expect for a 115v transformer run at 240v. I really hope I've made a mistake, but otherwise it's this something you've ever heard of before? What the heck do I do about it?!

[sluckey]

First off... I'm surprised that someone has cloned a $99 valve jr! 

Your PT has two primary windings. They can be connected in parallel to operate on 115V mains, or you can connect the two windings in series to operate on 240V mains. Your PT will quickly fail if you don't correct the primary wiring.

[PRR]

You gotta love a seller who posts a bag of compost in the ad.

https://www.ebay.co.uk/itm/326045735800   -- scroll down, the pre-sale ad is there for  a few days

Yup, does say "220V" on the tin, but clearly wired 115-ish. And sold from UK? So how is it tested? (Hint: a UK construction-site transformer will convert but hum may be horrid.) Obviously the same product is sold 120 or 240, and jumpers are likely, if you can suss them out without smoke.

(Jealous here. My wall voltage has been flat zero for hours, storm. An excuse to wire batteries and cell-tethers; this was so much easier on my old Chromebook and cheap phone than on the spiffy Moto and Ultrabook.)