Author Topic: Changeover unit schematic  (Read 283 times)

Mattsepanic

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Changeover unit schematic
« on: November 04, 2017, 02:05:30 AM »
Hey guys - I'm looking to refurb our changeover unit.  One of the bridge recs is looking fried and I figured I'd replace most of the parts in there. Does anybody have a schematic they can get me ( our manual doesn't have one ) or a parts schedule would work too. That's actually all I need.  There's really not much to that thing
Thanx

waltzingbear

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Re: Changeover unit schematic
« Reply #1 on: November 04, 2017, 04:53:15 AM »
don't have the schematic, but have worked on them before.

as I recall its a diode bridge with the center tap being the output. Look at the one you suspect and try and find its EXACT replacement, it will cost more than a generic, but its "working" with the other similar unit(s) and you really want drift and voltage drop to be the same as the other pieces.

positive and negative supplies probably have different orientations as they would be inverted (cathode vs anode center tap)

There really is nothing special about the unit, it is a diode isolation between the two supplies and the board. Power supply mis-tracking can cause stress on the diode packs as they don't share current well if they aren't tracking. Making sure they are set up correctly every now and then is a good idea as well (every year or two). That keeps overheating of the power supplies down.

adding test points on the front panel for the input voltage levels is a nice touch while you are in there.

Cheers
Alan

Alan Garren
Waltzing Bear Audio