12v50a 385 246-386-000

Thread Starter

Gdrumm

Joined Aug 29, 2008
684
I'm working on a different problem with a car battery charger.
I've replaced all of the button diodes, and I still only get 11.3 volts.
I think the transformer is good, and all of my readings at various switches, etc., make sense.

There are two other parts that I cannot ID, and they are linked together.
The only identifying marks on them are 12V50A 385 246-386-000.

What are they, and might they be the source of my problem?

Thanks,
Gary
 

beenthere

Joined Apr 20, 2004
15,808
The markings might be for a circuit breaker. It could be a thermal type with no operating lever.

What is the AC output from the transformer?
 

beenthere

Joined Apr 20, 2004
15,808
That is hard to understand. Assuming you are in the States, line voltage should be in the close order of 120 VAC. A secondary output of around 16 - 18 VAC is more than enough for a battery charger.
 

Thread Starter

Gdrumm

Joined Aug 29, 2008
684
I guess I don't understand the question.
I took readings of what I believed to be the the transformer output at the switch that controls 6 volts vs 12 volts. When switched to 6 volts, the yellow wire (coming from the transformer) reads 91 volts; when switched to 12 volts the red wire (coming from the transformer) reads 148 volts.

When reading after the diodes, I am only getting 11.3 volts when the High/Start switch is engaged, and when it is switched to the Low (normal charge) mode, the output is around 9 volts.

Thanks,
Gary
 

Thread Starter

Gdrumm

Joined Aug 29, 2008
684
Here is a bitmap of the charger.
I believe I had the other lead on one side of the 110V input, where it attaches to the timer.

Thanks,
Gary
 

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Thread Starter

Gdrumm

Joined Aug 29, 2008
684
Okay,
I found the schematic (attached), and the parts list, so I know that the parts I was trying to identify are indeed circuit breakers, and I've narrowed my list of suspicions down to the transformer itself.

It has two negative outputs (that go to the dual diode daisy wheels that make up rectifier), and one positive output. The in-feed comes from two selector switches, they are the Low:High/Start switch (2 wires going into the transformer), and the 6V / 12V switch (also has 2 wires going into the transformer).

Given these parameters, what / how should I check the transformer (power disconnected) to check for a short or open?

What should I check for, power on?

I have a similar transformer from another device, do they have to be an exact match to fix the battery charger? I could live with 12 volt only.

This is all just learning for me, no rush, no crisis,

Thanks,
Gary
 

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Last edited:

BillB3857

Joined Feb 28, 2009
2,493
If you had one lead of the voltmeter connected to the line side of the transformer and the other connected to the rectifier side of the transformer, your reading is rather meaningless. Think of the transformer as an isolation between the line and your battery (because that is what it does.) From the schematic, it looks as though you have either a tapped primary or multiple primaries (probably tapped.) If you connect your AC voltmeter between the studs on the rectifiers, you should read the double the RMS voltage available to charge the battery since you have a Full Wave rectifier with Center Tapped transformer. Changing the switches for VOLTAGE and RATE, you should see that voltage change. THE USUAL CAUTION HERE. WITH POWER ON THE UNIT, POSSIBLY FATAL VOLTAGES ARE PRESENT AND CAN GET YOU WITHOUT FULL ATTENTION AND CAUTION!!!!
 

Thread Starter

Gdrumm

Joined Aug 29, 2008
684
I tried that, by accident, and didn't see any appreciable difference.

Might I have put diodes in that were rated too high?

I used (12) 6K ohms diodes.

if I used 5K, or 4K, would that increase the voltage output?
 

BillB3857

Joined Feb 28, 2009
2,493
Can you be more specific on the diodes you used? I never heard of diodes rated in ohms!
 

Thread Starter

Gdrumm

Joined Aug 29, 2008
684
I read up on how to test a transformer, and I think I may have found something.
I put an ohm meter across several of the wires coming out of the transformer, and found that I had resistance (possibly a short), between two sets the wires.

Does that make sense?
If so, how do they short out?

The steel core is fairly rusty, perhaps it had standing water inside the case at one time.
Would that cause it to short out the transformer?

Thanks,
Gary
 

Thread Starter

Gdrumm

Joined Aug 29, 2008
684
They are called button diodes, and if you test them neg-pos, they should have no resistance, but if you test them pos-neg, they do show resistance in the ranges I've listed below.

I may not be testing them correctly, but using that method, I found that I had several reading in the 3K range, a few in 4K and 5K range, and several in the 6K range.
I replaced all 12 in the 6K range, with 12 in the 3K range, and it made no difference in the voltage output. That's why I now believe the transformer is the problem.


How should I test the diodes?
Thanks,
Gary
 
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