Old AC DC power supply with mechanical rectifier ?

[OffGrid-on-Rocker]

I have this old AC- DC transformer that is not working. I believe it has a mechanical rectifier but I could be way off base.

It does work on AC. Readings taking are about 12V AC between two taps and 7V AC & 5V AC between the other two.{center tapped}

There is a rotary switch that switches between AC an DC.

There is a drawer with coils that seem to operate points{contacts} .The metal bars that are at the top of this drawer contact brass tabs when the drawer is in place. It would seem to me this is what would make pulsating DC as the coils draw the contacts together and than release as the AC voltage returns to 0v. It looks as though someone has replaced some wires in this so I am not sure if it is wired correctly. It could also be missing some wires. In one of the pictures I labeled where 120Volts input{primary} is. I can take some more pictures if it would help. Does any one know how this should be wired?


Thanks

 

[Minder]

The only mechanical rectifier I am aware of is the synchronous vibrator used in vintage car radio etc.
This does not appear to be a version of this however, but a proper drawn schematic may show more info.
Obviously appears to be some home built device.
M.

 

[Old Steve]

Wow, this looks like it belongs in a museum. What a beauty.
It looks like it must be a half-wave rectifier, since there are no change-over contacts. Just the one set.

I wonder if it ever really worked properly, or if it was an experiment. Apparently, vibrator type rectifiers were only used in low-current applications, radios as Minder says, and also in motorcycles, but this looks a bit bigger than that.
I can't help with the wiring, but thanks for showing it.

 

[Old Steve]

This is a similar unit, used to charge batteries in the 1920s:-

 

[Minder]

The way the synchronous rectifier works is where the primary of a step up transformer is fed from a DC supply and the primary is switched in polarity very rapidly by a set of contacts, the secondary is also switched in synchronism with the primary and the resultant secondary DC voltage is used for the high voltage tube circuit in a radio.
No rectifier required.
See synchronous version. fig4.
http://www.radioremembered.org/vpwrsup.htm
M.

 

[OffGrid-on-Rocker]

Here are a few more pictures of the outside.
The way that it is wired now, the relay coils are being driven by 120V AC. This does not seem right to me. It seems like the secondaries from the transformer should be feeding the coils. Any thoughts?

 

[duke37]

The relay seems to contain a magnet so that the armature will move in one direction when the input is positive and the other direction when negative. The contacts can therefore be connected in a way which will give a unidirectional output.

Cunning!