First, it doesn't matter which orientation of the spade lug (the tab) is facing. Diodes conduct current in one direction and block it in the opposite.

I was talking about the orientation of the diode, not the spade.

 

This is why I always say "Fully diagnose the problem before beginning repairs." If you can - put it back together and get it on a known good battery and see if the charge is going up. Watch the voltage AND watch the amperage. A nearly fully charged battery will only draw a few amps. A weak battery will draw much more current. A bad battery may never draw any amps no matter what.

Put it back together if you can. Then test it. KNOW what you're doing before you start.

I can’t. Two of the diodes broke when taking the wires off.

 

From the odd bits of information that you have provided I think the windings have a center tap which is the negative output. All 8 diodes will have the cathode end connected to the heat sink. If you find pairs of windings with the same voltage reading with respect to the negative output and then measure the voltage between those two points then you will get a reading equal to twice the reading of each winding end and the negative output. ( These winding ends are the wires that go from the transformer to the anode ends of the diodes.)
The spread sheet in post #25 is usless as you have not identified the wire ends in the left hand columns on the pictures. also for 3 of the 4 sections with the comment black, blue or yellow wires connected. You don't say where thes wires come from and what they are connected to.

Les.

 

From the odd bits of information that you have provided I think the windings have a center tap which is the negative output. All 8 diodes will have the cathode end connected to the heat sink. If you find pairs of windings with the same voltage reading with respect to the negative output and then measure the voltage between those two points then you will get a reading equal to twice the reading of each winding end and the negative output. ( These winding ends are the wires that go from the transformer to the anode ends of the diodes.)
The spread sheet in post #25 is usless as you have not identified the wire ends in the left hand columns on the pictures. also for 3 of the 4 sections with the comment black, blue or yellow wires connected. You don't say where thes wires come from and what they are connected to.

Les.

Those colored wires go from the amperage selector switch to the transformer. A white wire and a black wire go together to the input of the switch and the colored wires are the output. Not all the button diodes on the plate have the same orientation. Some are upside down and some are righ side up
How can I go about using a bridge rectifier

 

I have been following this discussion with some interest. The information provided is in many small comments and pictures with very little to information that can tie them together into an overall picture. It is like looking at the pieces of a complex jigsaw puzzle.
I realize that the TS has limited electronic knowledge but that should not stop us from helping him in a very positive way. Before we make anymore assumptions and suggestions, I think a block diagram would be very helpful if it showed each component as a block, with the color coded wires shown connecting the blocks together. The normal convention would be power input on the left and charging output on the right.

 

I have been following this discussion with some interest. The information provided is in many small comments and pictures with very little to information that can tie them together into an overall picture. It is like looking at the pieces of a complex jigsaw puzzle.
I realize that the TS has limited electronic knowledge but that should not stop us from helping him in a very positive way. Before we make anymore assumptions and suggestions, I think a block diagram would be very helpful if it showed each component as a block, with the color coded wires shown connecting the blocks together. The normal convention would be power input on the left and charging output on the right.

Thanks for the help what pictures or information do I need to provide to get an idea of how to get this to operate correctly with a bridge rectifier?

 

Now my guess is sort of verified. AND FIRST, the direction of the tabs on the diodes probably indicates the polarity they connected with. SO IT MAY MATTER A LOT!!! OR maybe not???

What it looks like to me is like none of Tony's drawings, but similar to the one with 8 windings and one end of each tied to that black wire, EXCEPT that the polarity of half of the windings are reversed.
So functionally there are four center tapped windings with the center taps all tied to the black wire. THAT would explain the voltages quite well.
Consider that such a transformer today would sell for at least $300, or more than $500 if it had industrial quality terminals added.
And consider also that such a transformer can live despite a total short circuit for probably 15 to 30 seconds, plenty of time for a fuse to pop, while the modern switches charger will either shut down or be destroyed in much less than a second.
The real benefit of such ancient iron is it's thermal inertia. It does not overheat in milliseconds and fail.
So I suggest, now that the end to end voltage is measured, to check the voltages relative to that heavy black wire.

 

I logged on today to post my GUESS only to find thet my GUESS is the same as MisterBill2s post #47.
I do not agree that the diodes may not be all the same polarity. They all MUST have the cathode end connected to the heat sink.
Here is my GUESS as to the basic schematic of the charger


The TS has NOT posted any pictures of the switch either from the front or the back. I don't understand why only three wires (Black, blue and yellow) shown connected to taps on the transformer primary. (It needs 4 for the 4 voltage tables.)
I suspect that a picture showing one item that I think will be a solid state relay (SSR) switches the power to the transformer primary. I think the control signal for the SSR comes from the timer. All the SSRs that I have seen require a low voltge dc control signal. I dont know where ths low DC voltage comes from unless it comes from the battery that is being charge. If this is the case then it would ensure that a battery that was not totaly flat was connected befor the charger could switch on.
All thes guesses need to be verifide by someone that is capable of doing so.

Les.

 

Put it back together if you can.

I can’t. Two of the diodes broke when taking the wires off.

Well, now you have no choice. Full wave rectification is not necessary for a battery charger. But you're going to need high amperage diodes that can be mounted to a heatsink.

 

I do not agree that the diodes may not be all the same polarity. They all MUST have the cathode end connected to the heat sink.

I am attaching a picture as to why I was questioning it. The orientation the diodes are soldered to the metal are different. I am not sure on these diodes which end is cathode and which is a node, but their orientation appears different.

 

The TS has NOT posted any pictures of the switch either from the front or the back. I don't understand why only three wires (Black, blue and yellow) shown connected to taps on the transformer primary. (It needs 4 for the 4 voltage tables.)

There are 4 wires to the switch: red, blue, black, and yellow. (The black may actually be brown it’s hard to tell. There is a white and black wire combined on the same spade terminal that I assume is the input of the switch. I am attaching a picture of the front and back of the switch area. The front picture is with the switch removed. I also will attach a picture of the switch with spec numbers on its side.

 

Well, now you have no choice. Full wave rectification is not necessary for a battery charger. But you're going to need high amperage diodes that can be mounted to a heatsink.

What about using a 200 amp bridge rectifier? I ordered one that should be here today. Or are you saying it would be better just solder 2 new diodes to replace the ones that broke?

 

The third picture is what I thought was a solid state relay. So maybe the contacts on the time switch do handle the full mains current. To emulate the existing rectification system you would need to use 4 bridge rectifiers but you would only be using half of the diodes in each bridge. (These 4 bridge recifiers would only need to be rated a 50 amps each.) To use a single 200 amp bridge you would have to parallel all 4 centre tapped secondary windings. I would NOT advise doing this as the windings may not be wll enoug matched to share the load. (If you do try this you will have to make sure the ends of the windings that you connect togeter are in phase wit each other.) Have you looked up the specification of the existing diodes. (This may be dificult as they are so old.)
You can identify the anode and cathode of the diodes using your meter set to the diode test range.

Les.

 

The third picture is what I thought was a solid state relay. So maybe the contacts on the time switch do handle the full mains current. To emulate the existing rectification system you would need to use 4 bridge rectifiers but you would only be using half of the diodes in each bridge. (These 4 bridge recifiers would only need to be rated a 50 amps each.) To use a single 200 amp bridge you would have to parallel all 4 centre tapped secondary windings. I would NOT advise doing this as the windings may not be wll enoug matched to share the load. (If you do try this you will have to make sure the ends of the windings that you connect togeter are in phase wit each other.) Have you looked up the specification of the existing diodes. (This may be dificult as they are so old.)
You can identify the anode and cathode of the diodes using your meter set to the diode test range.

Les.

Thanks so much for the help! I did look up the number, but could not find anything on it. How would I connect the 4 bridge rectifiers?
How would you insure the phase of the windings are the same if using a single bridge rectifier?

 

So I suggest, now that the end to end voltage is measured, to check the voltages relative to that heavy black wire.

Checking each of the 8 wires compared to the heavy black ground wire, each has 7.6 volts ac. Interestingly, when I attach the negative lead to that ground and do not connect the positive lead of the volt meter I get 3.6 volts roughlyThose are with the yellow wire attached to the switch.
With the red wire connected have 13.2 volts ac.
Withe the blue wire connected at the switch, all 8 wires have 9.8 v ac.
With the brown/ black wire connected, all 8 wires have 10.7

 

Checking each of the 8 wires compared to the heavy black ground wire, each has 7.6 volts ac. Interestingly, when I attach the negative lead to that ground and do not connect the positive lead of the volt meter I get 3.6 volts roughlyThose are with the yellow wire attached to the switch.
With the red wire connected have 13.2 volts ac.
Withe the blue wire connected at the switch, all 8 wires have 9.8 v ac.
With the brown/ black wire connected, all 8 wires have 10.7

You should also check the diameter of the wires used for the coils on the transformer itself. This will tell you (and us) something about the current ratings of each wire. You have to get to the transformer terminals to see the diameter of the actual transformer wires, not the wires coming off of the transformer, unless they are the same enamel coated type wire.

There is such a thing sometimes called a full wave rectifier, which is not a bridge rectifier but still supplies full wave rectification through the use of a center tapped wire. That's just two diodes connected either with both anodes or both cathodes together, and sometimes in a single package. The two diodes provide the rectification.
You also have to be aware of the power handling ability of the transformer. If you randomly stick in bridge rectifiers, you may end up drawing more current from a wire if it originally only conducted half the time (with that full wave, 2 diode rectifier).

To understand how the transformer is wired, you might have to measure several voltages and compare them to each other. You also might have to apply a small load resistor like 100 Ohms to each measurement so that you are not measuring a "ghost" voltage, which is the voltage that might appear due to some small leakage current. Measure the voltage without the resistor first though so that you don't end up burning up the resistor. If the voltage is less than 20 volts you can get away with a 100 Ohm 5 watt resistor for short, quick measurements. If you have something like 200 Ohms that could work too, maybe even 500 Ohms.

In general, doing this is not as simple as it might sound. Several measurements and close inspection are the requirements, but if you could get a manufacturers data sheet that would tell the entire story. This being 30 years old though getting that is doubtful.

Just so you know, new battery chargers for automobiles are not super expensive unless you need really high current, but then even $100 USD will get you a pretty good one. They also have advanced features like boost starting. Some of them are a bit shy on metering though, but then you don't need it if the device works properly.
They also make really good battery 'maintainers', that can try to get the battery working better than it was before, and also they use 4 stage charging which is more modern. That gets the battery up to a better operating condition.
I assume you are talking about lead acid batteries for charging.

 

Can anyone advise a way to use a bridge rectifier or multiple bridge rectifiers that would work?

 

By the way, the diodes all have the positive on the blade terminals that plug into the 8 transformer wires and the negative on the plate. They measured ,40 to .48 with my diode tester.

 

Thanks so much for the help! I did look up the number, but could not find anything on it. How would I connect the 4 bridge rectifiers?
How would you insure the phase of the windings are the same if using a single bridge rectifier?

That picture looks to me like a push-button reset-able circuit breaker, rated at 25 amps. A closer examination should reveal the number of connections. An SSR will have four connections, a circuit breaker only needs two connections.
Those diodes look a lot like the ones marketed by Motorola for use in Mopar alternators about 35 years ago. With pigtail leads they were rated about 15 amps, soldered to a heat sink with forced-air cooling they were good for 60+ amps. But I recently soldered to some of them and THAT WAS A PAIN, so I recommend stud mounted diodes with an adequate heat sink and a small fan/blower.

I have used a part of a bridge rectifier as a full-wave, NOT BRIDGE rectifier in a much smaller battery charger and it has performed well for over 20 years of fairly hard use. The scheme is the two ends of the transformer connect to the two AC terminals of the bridge, and the positive output comes from the "+" terminal. The "-" terminal is left open. The negative output connection is from the center tap of the transformer.
Rather than the expense of four bridge rectifiers, eight stud mount rectifiers attached to a heavy aluminum, brass, or copper plate as a heat sink might cost less, and be simpler to wire.
As for the enameled wires from the transformer, they are most certainly the same wire as the actual winding. The wires are brought out like that because it is cheaper than attaching it to a more flexible wire.
The diode manufacturers have some rather detailed instructions about correctly mounting stud-mount diodes to a heat sink, and certainly doing it correctly makes a great difference, and is the only way to achieve meeting the ratings.

 

That picture looks to me like a push-button reset-able circuit breaker, rated at 25 amps. A closer examination should reveal the number of connections. An SSR will have four connections, a circuit breaker only needs two connections.
Those diodes look a lot like the ones marketed by Motorola for use in Mopar alternators about 35 years ago. With pigtail leads they were rated about 15 amps, soldered to a heat sink with forced-air cooling they were good for 60+ amps. But I recently soldered to some of them and THAT WAS A PAIN, so I recommend stud mounted diodes with an adequate heat sink and a small fan/blower.

I have used a part of a bridge rectifier as a full-wave, NOT BRIDGE rectifier in a much smaller battery charger and it has performed well for over 20 years of fairly hard use. The scheme is the two ends of the transformer connect to the two AC terminals of the bridge, and the positive output comes from the "+" terminal. The "-" terminal is left open. The negative output connection is from the center tap of the transformer.
Rather than the expense of four bridge rectifiers, eight stud mount rectifiers attached to a heavy aluminum, brass, or copper plate as a heat sink might cost less, and be simpler to wire.
As for the enameled wires from the transformer, they are most certainly the same wire as the actual winding. The wires are brought out like that because it is cheaper than attaching it to a more flexible wire.
The diode manufacturers have some rather detailed instructions about correctly mounting stud-mount diodes to a heat sink, and certainly doing it correctly makes a great difference, and is the only way to achieve meeting the ratings.

Which wires would you attach to each side of the bridge rectifier?