Repair I couldn't turn down.

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Nigel Goodwin

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I don't really do repairs any more, but when an old friend's daughter contacted us we couldn't turn it down

As you can see, the selector switch is dangling - as I removed it. It had obviously had a bang on the front of the knob, as the rear of the switch was displaced, I pushed it back in place, but it still doesn't feel right - so I've ordered a new switch.

 
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Diver300 said:
It's nice to see items where the physical device and the circuit diagram probably have the same layout.
Click to expand...

I was rather disappointed to see that there's no circuit diagram in the instruction book

Not that you need one for a simple valve amp, but it would be nice if it was there.
 
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Reloadron said:
Classic hand wired chassis. Love how looking at the component layout you can see each channel of the stereo.

Ron
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Nice isn't it

I've just noticed in the picture, there's a spring in the bottom left hand corner (near the mains socket), must have fallen out of the broken switch?.
 
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The busbar wiring in the middle and the flying diodes over the caps in the lower left corner take me back -

Back in the early 70's when I was in school and building a TV station, part of it was hand-building some 24 Vdc, 10 A linear power supplies on 3U and 4 U rack panels (public TV station, no money to buy commercial units). Control transformer, big black diamond bridge, and large "computer grade" electrolytic caps. The wiring was open frame using #10 bus bar in what we called "refinery wiring" - exactly as in this amp. Lovely.

ak
 
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augustinetez said:
I've pulled plenty of those switches apart and never seen springs like that in them.
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Must admit, neither have I? - anyway, I've removed the spurious spring, and fitted the new switch - all inputs now work (on a buzz test), got to bring a phono to 3.5mm jack lead in tomorrow to stick some audio through it.

The faulty switch by the way is made by Alpha, and I can't see any kind of spring to operate a detent mechanism, so perhaps that was the spring?.

Just had a close look - there's a hole right through the switch shaft (inside the body), that spring must go through the hole, and have a ball bearing at each end?.
 
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augustinetez said:
I think I've got one or two faulty ones in the shed I can pull apart and check.
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Not the best of pictures, you can't see the detents in the body - but I've slid the spring in the hole in the shaft, and if you push it right in it's about flush with both sides, ideal for a ball bearing either end to sit in the detents.



BTW, it's playing AC/DC at the moment
 
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Turns out you're right - there should be two ball bearings somewhere.

And to think I've just been chucking these out, I could have had a nice stock of springs and ball bearings


 
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