I have an older transformer with a rectifier circuit what I managed to backtrace and looks like this:

enter image description here

I could not find a lot of details about this online but it seems the transformer can supply 2x2x24V.

Can someone explain this rectifier circuit? It looks to me this is 2x half way rectifiers on both end but what is the diode in between the two serves for?

Is it safe to connect the 2 32V outputs in series to maximize the voltage?


  • \$\begingroup\$ This looks most unlikely. It would help if you figure out what transformer taps are connected to each other. If you can measure the secondary voltages that would be useful too. \$\endgroup\$ – Transistor Jan 8 at 22:23
  • \$\begingroup\$ are you sure that pin3 and pin5 on the transformer are bridged with a wire? \$\endgroup\$ – jsotola Jan 8 at 22:24
  • \$\begingroup\$ I have updated it because the measurements with cable tester were misleading I backtraced the wires. It turns out that this transformer not just a center tap but it looks like this is a double center tap. \$\endgroup\$ – hedon Jan 9 at 15:57


simulate this circuit – Schematic created using CircuitLab

Figure 1. Redrawn schematic.

It looks like you have two centre-tapped secondaries with full wave rectification on each. This wouldn't be unusual other than winding 'b' has a lower output voltage so I've marked the lower DC output '32 L' and the higher one as '32 H'. This in turn makes D3 very unusual.

The only reason for this that comes to mind is that D3 will prevent a high load on 32 H from stealing power from the 32 L line but can supply the 32 L line when power is available.


simulate this circuit

Figure 2. The simplest way.


simulate this circuit

Figure 3. A more elegant way.

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