After a failed attempt to "win" what looked to be a valve-less Mullard
5-10 chassis in the hope of getting a replacement output transformer for my 5-10
at a reasonable price I did a bit more googling on the topic of transformer rewinds. Somewhere in the many forum posts I found a mention of checking for failures
where the transformer windings are joined to the connecting
leads. Given the style of transformer I've got, this seemed worth a check. So I opened it up carefully removed the outer layers of tape. In the picture you might be able to make out that the connections to the yellow wires are good but all four strands that should have been connected to the red centre-tap had failed. There was some charring and a little
bit further away from where the connection had been some green traces. Further poking around and I had all four strands again. A little shorter than originally, but by scraping off the enamel I was able to test for continuity. Three of the four windings were OK. I don't know enough about transformer winding to know why each half of the primary was made up of two parallel windings
, or why for the half that still had two good windings (I presume
they were both good) one had a higher resistance than the other. Anyway I decided to use the two of the three good windings with the nearest resistances. Put it back together, and hey presto, a working "five - ten" with its original transformer returned. It probably can no longer safely deliver the full ten watts, but that's not really a problem.
With that job being easier and more successful than I'd expected I decided to keep going and "re-cap" my workshop Leak Stereo 30. This was bought very cheaply on ebay - "spares or repair". With the view that it would provide
spare parts for another that I have in the house. I'd ordered the capacitors from RS and decided to get axials, as originally used, so I spent a couple of hours pulling out the old, and bending and fitting the new. The left channel was always a bit weak, so I did that first and checked at the 1/3 and 2/3 count.
After the first third through the left channel it still wasn't great, but by 2/3rds it was as good as the right channel and with all replaced it was better. So then I did the right channel. Then checked the voltages and currents at the test points and all done. Now it sounds better than the good one in the house. So now I guess I'll have to do that one too. But for now I'll just swap them over :-)
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