Help with transformers

[Mattlee0037]

Ok, so after reading and thinking I understand transformers I realized I only very lightly understand them. Ok so take a power transformer for example. It has a primary and many secondaries I understand. In the case of a regular tube rectified amp it would have 120v primaries and 6.3v, 5v and around the high 200's for secondaries (I think). Each secondary consists of two wires. So is one of these wires ground and one carrying the stepped up/down voltage? Also how are these wires identified visually is there normally a color chart? I ask because I was looking into making a geofex spyder power suppply and it requires this transformer https://taweber.powweb.com/store/pdlxfmr.gif

If I understand correctly the black wires would be connected to Neutral and Line of a power inlet (ground would be grounded to the chassis?) with a fuse between the line and its primary? Then the green wires could be used for a 9v AC signal and each pair of the brown wires could be full-wave rectified, filtered, and then supply the correct voltage?

[Phil_S]

... Also how are these wires identified visually is there normally a color chart? I ask because I was looking into making a geofex spyder power suppply and it requires this transformer https://taweber.powweb.com/store/pdlxfmr.gif

In the picture of the item, there are only brown wires for the 11V windings, of which there are 8 pairs. Your meter set to Ohms will confirm continuity. For each brown wire, there will only be one choice that shows continuity. The rest will read open. You can get a multipack of colored heatshrink tubing to place some markers on the pairs if you really feel the need.

As for your other questions, a transformer is a relatively straight forward device. It is a set of wire coils wrapped around a core that is placed inside a stack of metal plates (laminations or "lams".) In general, there is one primary and yes, the hot leg gets fused. Some transformers are made for US and EU voltage supply and may have multiple primary windings to accommodate that, but let's not complicate things. Secondary windings may or may not be center tapped. The center tap (CT) is drawn out half way between the two ends and it is usually grounded. The high voltage winding nearly always consists of three wires because it includes a CT. A CT is needed for many kinds of rectifiers (tube, full wave bridge), but not for simple full wave. The 5V winding is the filament supply for a 5V rectifier tube and rarely would have a CT and if used with a tube rectifier, you'd insulate the end of the CT and leave it unused. The 6.3V filament supply is a toss up -- a CT is nice to have but not necessary. Find some diagrams (Hammond has nice ones) and study them. It will start to make sense sooner or later.

[Mattlee0037]

Thanks, I'll have a look at those diagrams. Not to mention we'll cover transformers in physics in a few weeks I'm assuming as well.

[guitardude57]

If you used a solid state recto... you would heat shrink the 5V taps...unless you needed them for a different regulator, for channel switching relays... etc.