Marquette Battery Charger

TroyHog

New User
I have an old Marquette Battery Charger that I have used forever. I love the old thing but yesterday it decided to trip the breaker when I tried to use it. I can not find any schematic for it anywhere and was wondering if anybody could help me trouble shoot the old girl. I have background in electromagnetic theory and transformers as I am an engineer for the electric coop (I know I shouldn't have told ya all that! ha). Any help would be greatly appreciated. Thanks! Right now if you turn it on it grunts and slowly turns the fan and then trips the 20Amp breaker.
 
Open it up and unhook the fan and see if ti trips the breaker. If it does then do some simple trouble shooting on the diodes and see if any are shorted to ground etc. Also look for burnt wires or a simple short
 
Solid state rectifier of selenium? Depends upon how "old."

If selenium, it will not be cost effective to repair as selenium rectifiers are NLS.

Dean
 
Thanks guys - the fan was my first thought too, but it spins freely and so I tried to help it by pre-spinning it when I turned it on - it didn't change anything - the first time I did it I spun it the wrong direction and it stopped and changed direction before the breaker tripped. Am I thinking right that it is probably not a shorted transformer since it tries to run?
a238235.jpg
 
Abraded/broken insulation on wires is good place to start looking. You can carefully (so as not to damage transformer) unbolt the braided wires connected to the two large diodes and see if it will turn on without tripping breaker. If it does, that likely rules out transformer and points to the diodes (at least one of them).
 
It's solid state.

Check the diodes with an ohmmeter.

Marquette built good stuff and they do not build them like that anymore.

Dean
 
I've done the ohm meter thing and some times find they read bad but if you use a 12 volt battery and alight bulb the same ones tested good. I don't know why they did but they did
 
Sorry, not true.

Opens and shorts in diodes can be conclusively checked with a good ohmmeter if done properly.

Dean
 
I have to disagree with you because I have run into it more then once. I have a whole of schooling in electronic and understand all that but I have found a meter does not tell the truth but a battery and light bulb do. I have a battery charger that work just fine but the diodes did not pass with a meter but did with the light bulb test. I repair computers in the Navy so I understand meter and o-scope and all. But the common home meter which I have is not calibrated and is nothing like the Shimpson 260 I used in the navy
 
The two silver-colored devices that look like bolts are diodes. Since it's throwing the breaker, my first guess is one or both diodes are shorted. If you disconnect the shorted diode it will limp along, putting out only half-wave rectified ac.

Two test the diodes, you'll need to disconnect them from the circuit. The easiest way to do that is to unbolt them from the heat sink. Then you can check them for continuity in each direction with a multimeter. Note that digital multimeters have a "diode/continuity check" scale separate from the ohms scale; it will be marked with the schematic symbol for a diode. The diode check scale actually reads volts, not ohms. A good diode will measure about 0.6 or 0.7 volts when forward-biased, and will be an open circuit when reverse-biased. Most multimeters will generate a constant tone across a shorted diode, but just a "chirp" across a forward-biased diode.

Since your charger uses readily-available stud-style diodes, you should be able to find replacements online. If you can't find a part number to cross-reference, just get a diode that will fit, at least 50 volts peak reverse voltage and as high of forward current rating as you get (or afford).

If the diodes check OK, isolate them from the circuit (e.g. wrap the disconnected diodes in electrical tape) and try turning on the charger. If it still throws the breaker, there's a good chance the transformer is shorted, which would most likely be cost-prohibitive to fix.
 
(quoted from post at 21:28:16 09/23/16) I have to disagree with you because I have run into it more then once. I have a whole of schooling in electronic and understand all that but I have found a meter does not tell the truth but a battery and light bulb do. I have a battery charger that work just fine but the diodes did not pass with a meter but did with the light bulb test. I repair computers in the Navy so I understand meter and o-scope and all. But the common home meter which I have is not calibrated and is nothing like the Shimpson 260 I used in the navy

Has to do with the volt meter... some will not use enough voltage in the ohm mode.... to bias the diode on.. most better meters will have a special setting for checking diodes.. this setting simply uses more voltage, to bias diodes and transistors on...along with the meter resistance and the other resistors in the meter circuit. it takes aleast ,7 volts to bias a pn junction forwards and some cases as in high current devices, it can take almost 1.2 volts.. this can put a bit more current through the meter than the designers want.. so its not available on all meters.. Also meter that use a 1.5 volt power source... will usually NOT work as opposed to meters using a 9 volt power source.


And meter with extreme high impedance... which are desired for most measurements will not do well where low impedance is needed. So sometimes a very good high impedance meter will bite you in the butt.
 
These are high amp diodes and to get a reading on the ohm meter you have to use to 2M setting and you get a pretty high ohm reading but the light bulb test works very well. I know all the diodes I have are good just with the cheap meters the common man has the readings do not come up like one would think they should.

Yesterday after reading Deans post I tried it again and had to go to the 2M setting and got .785 reading and tha twas to only scale that would read any ohms one way and of course infinite the other way
 
Read what I just told Mark. These cheap meter the common man has do not work real well. Sorry when you have to use the 2M scale to read and ohm value in a diode it is by far easier to use the battery and light bulb test
 
Read what I initially posted.

"Opens and shorts in diodes can be conclusively checked with a good ohmmeter if done properly."

You disagreed with that statement.

What is inaccurate in the statement above?

Dean
 
And note what I say who now days have a good meter not the common man so the light bulb test work far batter for the common Joe. I know I sure as heck am not going to go out and spend $250 on a S-260. I have 3 meters and all of them on the high amp diodes need to use the highest scale to get a reading and even then they all read in the high end of things so again the common man would think the diode is bad but in fact it is good. So you think the common man should spend that type of $$ to check a simple diode for his $100 battery charger??????????
 
You don't know much about diodes if you're trying to test them on your meter's 2 megohm range. If a diode really had 800 kilohms of resistance when forward-biased IT WOULD NOT WORK! Do the math: 10 amps through 784 kilohms is 7.84 MILLION volts!

Any digital multimeter made in the past 30 years has a diode check range. When you use the diode check range, the meter will apply enough voltage to forward-bias the diode under test. The readout will then be in volts; a silicon diode junction typically has a 0.7 volt drop when forward-biased.
 
Yes I does have a diode test setting but you both are so close minded your missing the whole point

Most people if they even have a meter do not know how to use them so the simple NO BRIAN battery test works well for any common Joe.
Open your minds to the simple way ANY CAVE MAN can do test

I.E. what I said about diode test is for the COMMON man not ones who have the training. I learned many years ago to KISS
Keep it simple stupid or your are being stupid open your mind
 
Yes I does have a diode test setting but you both are so close minded your missing the whole point

Most people if they even have a meter do not know how to use them so the simple NO BRIAN battery test works well for any common Joe.
Open your minds to the simple way ANY CAVE MAN can do test

I.E. what I said about diode test is for the COMMON man not ones who have the training. I learned many years ago to KISS
Keep it simple stupid or your are being stupid open your mind

Oh and do not bother to answer this post I'll not read any more of your attack to simple ways of doing things
 
Have it your way, Old.

I can check diodes with my $12.99 Craftsman DVM or with my free HF DVMs.

Perhaps you cannot.

Dean
 
No one here has said or even implied that you cannot drag out a battery, some test leads and a light bulb to check a diode.

That said, I find it far easier to simply hook up my free HF DVM.

I too like to keep it simple.

Dean
 
Hello Dean,

Here is the free HF meter. I just use the diode check function,

Guido.
a238318.jpg
 
Bingo, Guido.

I've probably gotten 20 or 25 of those "free" in the past few years.

I was giving them away as stocking stuffers until all of my friends had one or two. I still have 10 or 12 sitting on my desk unopened.

Dean
 
Hello Dean,

I have a couple of flyers from HF, guess what free coupon I am going to redeem!...later

Guido.
 

couple of years back.. when on sale, I would buy 10 at a time.. when the 9 volt battery dies, its cheaper to just grab a new meter. And as Old said,,, they make good stocking stuffers,,, also the 19.99 angle grinders when on sale in the past.
 

If the voltage is not high enough to fully bias the pn junction on... the resistance will be very high.. .very high.... so again,, the meter is not applying enough voltage to fully turn on the diode...and you have it partially turned on.. and yes.. you read very high resistance...
 
Hello TroyHog,

I would take a close look at the AC . there is may be a bare wire touching the case. Look at the AC cord where it enters the case, you might get luckY. Post back if you get it to charge. Inquiring minds like to know,


Guido.
 
So if I isolate the diodes and do the light test with a 12v battery - how do I ground the diode? Thanks guys!
 
(quoted from post at 11:16:57 09/26/16) So if I isolate the diodes and do the light test with a 12v battery - how do I ground the diode? Thanks guys!
iode onny has 2 terminals...........mounting stud is 1 and the other is big braided wire on opposite end. Could only be simpler if it had one terminal.
 
I think the mounting stud is at terminal output voltage and the braided line is connected to the transformer coil - so I don't think it's quite that simple - unless I'm looking at it wrong. The diode may not have a common - I'm not sure.
 
The studs of the two diodes are bolted to a metal plate (conductor & heat sink). At that point, they are common to each other and no doubt to either the pos or neg cable that you connect to the battery. What exactly is it that you want to know?
 
What you are seeing is a typical full-wave bridge rectifier on a center-tapped transformer. The center tap will be at "ground" potential (i.e. the charger's negative lead), and the heat sink will be "hot" (going, eventually, to the positive lead).

If either diode is shorted, it will result in a short-circuit path back to the transformer for the other diode when the good diode is forward-biased.

Remove each diode from the heat sink and isolate them from each other and everything else (e.g. wrap with electrical tape). Then turn on the charger. If the breaker doesn't trip, you probably have a shorted diode; you'll then have to figure out which one it is (maybe both).
 
(quoted from post at 15:43:03 09/26/16) What you are seeing is a typical full-wave bridge rectifier on a center-tapped transformer. The center tap will be at "ground" potential (i.e. the charger's negative lead), and the heat sink will be "hot" (going, eventually, to the positive lead).

If either diode is shorted, it will result in a short-circuit path back to the transformer for the other diode when the good diode is forward-biased.

Remove each diode from the heat sink and isolate them from each other and everything else (e.g. wrap with electrical tape). Then turn on the charger. If the breaker doesn't trip, you probably have a shorted diode; you'll then have to figure out which one it is (maybe both).
xactly, Mark! He was told that 3 days ago, but then many other "helpful?" posters inserted all kinds of tangents, so he probably missed the point and needed telling again. As teachers know, "tell them what you are going to tell them, tell them, then tell them what you told them". :wink:
 
Simplified schematic upper right does not show the other devices in path, such as reverse polarity protection, ammeter, etc.
 
It's been my experience that you don't need to worry about biasing a suspected shorted diode to prove it's shorted. There's no longer a PN junction to bias, so it will read a dead short in either direction, zero volts.

It is necessary to bias a suspected open diode, of course.
 
(quoted from post at 19:51:45 09/26/16) It's been my experience that you don't need to worry about biasing a suspected shorted diode to prove it's shorted. There's no longer a PN junction to bias, so it will read a dead short in either direction, zero volts.

It is necessary to bias a suspected open diode, of course.
But you and I know how to use an Ohmmeter.
 
With the light bulb test - one diode is still working the other is shorted. Can we get these diodes anymore? They look like old Westinghouse.
 
Westinghouse Semiconductor Co. is long gone. Maybe some old stock somewhere, but several companies still manufacture large stud mount diodes. Probably have to make educated guess as to voltage & current ratings, but I would go for 100amp plus current rating and 100 volt rating just to be safe.
If lucky, you might find out what that Westinghouse rectifier was rated at, but it may take a lot of looking. I have a different model of that charger & I substituted a 1N3293 (100amp, 600v) rectifier in mine over 15 years ago and it is still doing fine. Stud is 3/8 (smaller than yours), but heat sink grease & washers has done fine. There are many to choose from. Finding a source to buy small quantity of one or two may be a hurdle.
 
Here is a 200 volt, 150 amp diode with a 3/8" stud. 24 bucks each plus shipping.

If you're going to fix the charger, you might as well replace both diodes. No doubt the good diode is near its end-of-life.
GeneSiC 150KR20A
 
Thanks for all the help - two new diodes later that old Marquette is charging batteries once more. And to all the people at work that told me to throw it in the dumpster................. HA
 
(quoted from post at 17:03:11 10/06/16) Thanks for all the help - two new diodes later that old Marquette is charging batteries once more. And to all the people at work that told me to throw it in the dumpster................. HA
e love success, don't we! Congrats!
 
Hello, First time posting. I have the Marquette charger being discussed here. I suddenly quit, no spark when I strike the clamps together. No interior bulbs come on. I think it may be a simple fix but as I don't have alot of knowledge on this. Any ideas what it is.
 
striking the clamps together probably shorted either the diodes, transformer, or took out the fuse. NOT supposed to short the clamps together.
 
I can remember when these diodes first came on the market.. They were SURPLUS submarine diodes and were over $100 a piece... iirc... was in the early 70s.. but its pretty fuzzy.. we were trying to put them on our tombstone welders to try to go to dc.
 

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