Bridge rectifier

B

Bus Driver

501 Club
Quick question: Will an encapsulated/potted bridge rectifier rated at 1000 volts function properly at just 6 volts?
No need to read further unless you wish to do so.
I have a Dayton (Grainger) battery charger that did not work yesterday. Never an indication of problems before. The transformer hums, no indication of overheating, no unusual noises. I opened the case and all looks well. The circuit breaker shows continuity. Further testing will follow.
Grainger offers no diagrams or parts for this charger. Appears to be made by Century from other photos I found online of the interior working parts. No diagram or parts for the Century either.
Two diodes on the heat sink, not yet tested. So the transformer must be center-tapped if the DC output is full wave.
My electronics knowledge is from the days of vacuum tubes. If the original diodes, either or both, should prove to be faulty, the bridge is my cheapest and quickest repair.
If the bridge rectifier I found (of adequate amperage rating) rated at 1000 volts will work OK at 6 and 12 volts, it will be mounted on the heat sink plate with compound and just the positive output terminal should be used for my purposes. Does that sound right?
 
Short answer: yes. Long answer: maybe or maybe not. It takes 0.6 volts to activate a diode, if for some reason the bridge is really many diodes in series to get the 1000 volt rating then it may not work. Can't think of a reason they would make a bridge like that but possible. I made a few like that over the years to get to the 25K volt range. You likely have a standard 4 diode bridge and it should work on 12 volts. Radio shack and others sell a 30 A? bridge that I have used in the past with good results.
 
Check for output voltage from the transformer, prior to the diodes.

Small, individual diodes are available from sources such as Radio Shack. Larger individual diodes are available from industrial supply stores. If the diodes are pressed into the heat sink, individual diode may be the way to go.

Check your capacitor(s), providing the battery charger has a capacitor(s).
 
Hectic day. Little time for any particular project. The transformer output is 14.9 VAC with no load. Looks good to me.
I want a 50 amp rectifier minimum and all I find from convenient, low-priced sources, are rated 1000volts. Apparently Radio Shack has pared back their offerings and no longer offers anything near 30 amps, per the results of my search. No capacitors or other smoothing filters in this charger.
 
Bus Driver if you can post how you’re going to repair your charger .I have a Century charger that quit working a few weeks ago and I’m trying to figure out what to do. I’m getting A/C voltage to the rectifier. The rectifier has no markings on it and nobody has any info.

Thanks Jack
 
Jim stated:
Diodes for a car alternator. If you can't find any, I can probably find something
Click to expand...
.

Jim and Landreo; I wonder if you can wire in a rectifier from a Delco-Remy type 10Si Series alternator?
 
JackF":7h9c5vow said:
I wonder if you can wire in a rectifier from a Delco-Remy type 10Si Series alternator?
Click to expand...
Don't see why it wouldn't work. You will only need to use two of the three input terminals, leaving one blank/empty.

Might see if you can find the bridge from a non functioning alternator. Lot of times one pair of diodes ceases to function, leaving two functioning pairs.
 
http://moparforums.com/forums/f7/can-i- ... arger-881/

This link shows one that looks like mine inside. The second photo item "what is this" is the circuit breaker. I think that the nut on the circuit breaker is the only thing that holds the heat sink/diode assembly in the charger. The charger is in the shop building some distance away. I think the heat sink plate is also the conductor from the diodes to the circuit breaker. Don't short it to the charger housing. For JackF, if you can wait a couple of weeks or so, I will try to post the latest on my attempts to get this one repaired. The 50 amp bridge costs less, part plus postage, shipped directly from Hong Kong than the cost of the gas for me to drive to Radio Shack. So I am going to try that. They may take 2-3 weeks to arrive.
More questions: Using just three of the terminals on the bridge means that just two of the internal diodes will be in use but the center-tapped transformer will give full-wave rectification. Does that mean that the bridge will heat less than if all 4 diodes were being used? And if a failure occurs, is it likely that the other two diodes would still be useful by switching a few leads to get the output polarity correct?
My charger is 6 volts, 12 volts 2 amps, 12 volts 10 amps/50 amp boost. I do not recall using the boost feature.
Thanks for the help. Interesting thread.

I used to take the 6 volt radios from junked cars, the filament transformer from junked TVs and eliminate the vibrator, feeding the 6 volt AC to the radio. Wonderful radios with amazing static supression. The OZ4 gas rectifier was the weak link. And most of the radios were AM only. Made a great shop radio, especially if fluorescent lights were in use.
 
Eugene,
After I posted I started confusing myself how I could make this work. What two terminals on the rectifier would I attach and how do I incorporate the diode trio and do I need the diode trio? One side of the rectifier is the positive side and the other is the negative. I’m looking for some old books on how this thing works… I just can’t remember this stuff anymore.
Thanks for your help!
Jack

ALT.jpg

ALT1.jpg
 
Using the diagram of the Delco 10SI. Alternating current from the stator is supplied to the 3 terminals on the bottom of the bridge. Direct current out put is the single terminal at the top in the photo, positive voltage.

Check the forward bias with a multimeter, Ohms setting. You should get a reading in one direction. Reverse the leads and no reading. This check will also disclose an open pair of diodes. No current flow in either direction.

Depending on how the output side of the transformer is wired, you may only need one or perhaps two of the terminals on the bottom of the bridge for your battery charger.
 
I just added then deleted a post that was mostly wrong. If you saw it, forget it. Here is my second try. I hope it makes sense this time.

The AC produced by the alternator is 3-phase. The output from your transformer is single phase. You should be able to turn your single phase into DC using the connections as shown in the schematic for 2 of the 3 connections from the stator. You will end up using 2 of the 3 portions of both the diode trio and the rectifier bridge.
 
To avoid embarrassing myself, I could have just let this thread play out. My charger is working again. This morning I tested everything about the charger- eventually. The 9 volt battery died in my tester during the process, so that introduced a delay.
The diodes tested good. The heat sink plate does mount to the circuit breaker as I assumed earlier. Could find no problem inside the charger housing.
So I tested the DC leads for continuity and the Positive tested open. When I pulled back the red sleeve on the battery clamp, the solder had pulled loose allowing the conductor to just float touching nothing. The clamp around the insulation was holding well. The soldering on the negative clamp was holding but did not look to be well done. Resoldered both of them, put it all back together and it works fine.
So I was too hasty to buy the bridge rectifiers.
 
Since the problem is solved just a few comments that may help others.

The 10 si diode trio is for the field current and likely would not survive in a battery charger due to the higher current. The rectifier bridge should work. A center tapped transformer is actually 2 phase current and needs only 2 diodes for full wave, if you use a bridge then do not use the center tap.

Some of the old auto radios used rectifier tubes such as the OZ4 but others used a mechanical rectifier in the form of a sychronous vibrator. The primary side vibrator was linked mechanically to a second set of points on the secondary which switch the polarity of the current on the secondary in synch with the primary. Mechanically rectified the current and no other rectifier needed. Interesting solution.

When checking a diode use an analog multimeter or a digital with a diode setting. Modern digital meters may not put out .6 volts and the diode will measure open both ways. An analog meter or digital with a diode setting will put out enough volts to activate the diode.
 
This was a worthwhile discussion anyway. I large percentage of charger failures are probably diode failures. I had a charger fail in a way very similar to what you finally found. The solder at the clip was holding, but the wire broke just off the end of the clip and inside the insulation. All the handling those leads get is eventually going to take a toll somewhere.
 
Not to be a ****** but the name of the condition Jim Becker encountered was called a cracked wire in my telco days. That is broken under the insulation.

Edited to add Bus Driver you are a real man. I always enjoyed your posts ans found great wisdom in them. To continue on and tell us what really happened is precious

.
 
Bus Driver, Landreo, Eugene and Jim

Sorry for being a pain in the*%$@! but, I’m confused when Landreo stated “the 10 SI diode trio is for the field current and likely would not survive in a battery charger due to the higher current”. This particular generator weakness was the diode trio and back in the day I replace a lot of them. I know how to test and diagnose this generator and probably when I was trained on it I was taught the operation of the diode trio function and rectifier, but have since forgotten. When you stated; diode trio is for the field current it seems as though the diode trio only operates low amperage part of the generator. This part confuses me because it’s attached to the rectifier and what I can see in the diagram is; the voltage regulator grounds the diode trio when current is required.

This is how the generator operates

With the generator operating, AC voltages are generated in the stator windings, and the stator supplies DC field current through the diode trio, the field, TR1, and then through the grounded diodes in the rectifier bridge back to the stator. Also, the six diodes in the bridge rectifier change the stator AC voltages to a DC voltage which appears between ground and the generator "BAT" terminal which is connected to the storage cell. (Battery)
 
Hoping my memory is correct, Chevrolets started using alternators in the 1963 model year. External regulator. Delco 10DN. The largest of those I ever saw was rated 63 amps and many were 37 amps. I do not know if all of them used the same diodes. Chevy started using the internal regulator in 1974. Delco 10SI. Some of those were just 37 amps also.

Added: The reason I mentioned Chevrolet, some of the higher end GM products (Cadillac, Buick) used alternators earlier. Some of those were oddball items that were produced for only a short time and evidently were made obsolete by rapid advances in design and construction of alternators. By the time Chevy got them, the design was well established and volume production was in progress.

I have a Delco 15SI as a conversion on a Farmall 140. Electrical hookup identical to the 10SI. It is from a Buick, 70 amp, $18.00 at the wrecking yard. Overkill on the amperage! Slightly larger than a 10SI, but plenty of room for it on that tractor. Shop-made mount to hold it in close to the engine on that tractor was a challenge, for me at least. Alternators tucked in close are much less subject to damage.
I am getting too far off subject.
 
That is about what I remember on the externally regulated Delco alternators as well. I think they were common until about 1970. The change to internal regulation was probably not done all at once. Delco evidently had several different diodes with different current capabilities. They no doubt shared a size/shape. Some of the aftermarket suppliers had a single replacement that was cross listed to several Delco numbers (example SMP's D1P and D1N). They were probably sized for the highest capacity they crossed to. Check this page (and the following):
http://www.gmpartswiki.com/getpage?pageid=18675
It appears the one I pointed at was used up to 52 amps and only in '62. I know that the Corvair alternator (used diodes 1959829 and 1959830) came standard at 37 amps and was changed to 47 amps by only changing the rotor. The same diodes are listed as high as 61 amps. By the way, if you start chasing any of these numbers, the page I pointed at above has an important typo. The group number should be 2.319, not 3.219.
 
You must log in or register to reply here.
Back
Top