52 l85

[Angelo]

I am gonna test tomorrow. I’m just asking if that’s something that can be used in event it’s bad . 

[Geoff Weeks]

I'd just grab some diode blocks out of a Leece Neville JB2600 or JB 2800 and then the hard part, you need to assure airflow over them and they must be isolated from any other metal, and protected from wrenches etc.

 None of the silicon diodes used in modern alternators have anywhere near the surface area on the heat sink that the one you are replacing. Granted they can take the heat a little better.

 

[mrsmackpaul]

This a good point Geoff makes

Try to find components as close to what you need

But check the rectifier, it may have one crook diode that is allowing the voltage to creep up a bit 

 

Paul

[Angelo]

I definitely smelled rotten eggs when she started to die on me. Felt battery and it was warm but I don’t believe the smell was coming from that. Does the rectifier give off that kinda smell as well 

[Geoff Weeks]

Yep, when the fail, and the stuff is toxic so don't go sniffing.

Run the test and I bet you'll find a bad rectifier, but test to be sure.

[mrsmackpaul]

No, rectifier is solid state

I would think if you cooked it you would be able to tell

The battery would of been boiling prettu hard for a while and Im guessing that was the smell

Might pay to check water level in the battery if it was getting hot to touch it would of been bubbling pretty hard inside

 

Paul

[Geoff Weeks]

Selenium rectifiers had a shorter lifespan than desired. In the early stage of failure they produce a modest amount of sweet-smelling gas. Sometimes described as 'sickly-sweet'. At that point the rectification properties are almost totally gone, allowing reverse voltage to leak through the rectifier. During catastrophic failure they produced significant quantities of malodorous and highly toxic hydrogen selenide[8][9][10] that let the repair technician know what the problem was. By far the most common failure mode was a progressive increase in forward resistance, increasing forward voltage drop and reducing the rectifier's efficiency. During the 1960s they began to be superseded by silicon rectifiers, which exhibited lower forward voltage drop, lower cost, and higher reliability.[11] k

Quote from Wiki,  Also have heard and read it elsewhere. It is the prime reason, that I planned to replace mine with silicon diodes, which as you say will not smell or emit toxic fumes when they fail.

Edited October 5, 2023 by Geoff Weeks

[Angelo]

Written on my rectifier in marker says Bridgeport fire shops. 1984 replaced came off old engine 6. The old engine 6 was a late 40’s L model Mack 

[Angelo]

Mrmack my battery is few months old. Load tested perfect sealed battery 

[Geoff Weeks]

5 minutes ago, Angelo said:

Written on my rectifier in marker says Bridgeport fire shops. 1984 replaced came off old engine 6. The old engine 6 was a late 40’s L model Mack 

Looking more and more like a failed rectifier, but TEST don't guess.

READ THE ABOVE!!! HIGHLY TOXIC!!!

[Geoff Weeks]

If it come down to a failed rectifier, and it is looking that way, I would caution against looking for a replacement of the same type. I haven't checked mine, it may still be good, or it may not, but there is no way I am going to put it back in service. These selenium rectifiers were well known in small power generators of old (Onan and the like) for supplying field current. They are known to fail and are replaced when ever they are found, even if they haven't yet failed. With selenium, it is not if but when. Unlike silicon diodes which rarely fail in the life span of an alternator, selenium's are known to have a much shorter lifespan and heat tolerance. It was why the quickly disappeared when better diodes were invented.

 With silicon diodes an alternator is likely to not see a failure in the lifespan of the unit. Bushes,slip rings and bearings are now the much more common fail points. Brushes are cheap and easy to change, but when you get into slip rings and bearings it is often cheaper to replace than repair, unless there is a over riding reason to do so.

When I overhaul an alternator, if the slip rings are shot, I generally don't bother replacing, I use it for parts. It didn't take me long to switch to brushless units for my stuff, as they can take higher duty cycles than brush units. Even pushing them to max output for hours at a stretch, the only time I had a diode failure was when something internally shorted the output.

There are now air cooled alternators that exceed 300 amps, a domain that used to be exclusive to oil cooled units like the Delco DN-50.

100 amps is small by today's standards, and there are plenty of pre made diode blocks (diodes already pressed into a heat sink) that would make a fine replacement for the selenium unit, last longer and take less space and don't off gas toxic vapor when the fail.

Edited October 5, 2023 by Geoff Weeks

[Geoff Weeks]

Some more Wiki quotes:

Hydrogen selenide is an inorganic compound with the formula H₂Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H₂Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound^[3] with an exposure limit of 0.05 ppm over an 8-hour period.^[4][5] Even at extremely low concentrations, this compound has a very irritating smell resembling that of decayed horseradish or 'leaking gas', but smells of rotten eggs at higher concentrations

And:

Exposure at high concentrations, even for less than a minute, causes the gas to attack the eyes and mucous membranes; this causes cold-like symptoms for at least a few days afterwards. I

There are better rectifiers available.

"Smells like rotten eggs in higher concentrations"

 

Edited October 5, 2023 by Geoff Weeks

[Angelo]

Leaving original alternator is there anything that can go in rectifiers place. That things is way outdated and dangerous. I have seen a few rigs replace with what I was talking about a 3 phase  block rectifier that seems to work. Even if temporally till I can save some money to make better upgrades 

[mrsmackpaul]

Yes there is

 

Like the block rectifier, just find one with as close to the same values as the one you have

These plate rectifiers aren't that dangerous, I guess to me it is like all the B.S. about split rims and the like

Handled and been sensible they aren't a real issue

There would be millions of plate rectifiers still operating around the world and well into the next 100 years I would imagine

So to answer your question, yes of course you can replace it with block rectifier as you call it, find one with values a maybe 50 - 100% higher than you have as they aren't as forgiving to big back EMF surfes as a plate rectifier 

And you might need to (but unlikely to) put a capacitor across the D.C. to absorb any surges 

Remember I have no idea what other electrical stuff is on your truck, but guessing plenty of things with coils and these creat the EMF when been switched off 

But as far as I know you still haven't tested the rectifier so there is little point in changing yet

 

Paul

[Geoff Weeks]

Paul while I agree with you about lock ring wheel (I still use them, both on my antiques and up until I retired, on my linehaul stuff). I think the selenium rectifiers have plenty of drawback besides the toxic failure mode. They have a short lifespan compared to modern stuff, and for the most part any you find today are going to be at least 60 years old. At 12 volts you are running close to the limit for what one plate can safely handle in terms of PIV.

 As i mentioned before diode blocks out of a JB 2600 or JB 2800 would be fine. The spec's have already been taken care of for you as has the heat sink.  The Leece Neville JB series  today starts out at around 100 amps and goes well over 200. Initially they were made as low as 60 amps, but I haven't seen on of those in decades.

 I've included a photo of the Selenium rectifier and the JB blocks so you can get an idea of size. They would fit the bill, are nowhere near their limits (same blocks used on 24 volt and higher alternators) The black "kidney" shaped objects are the diode blocks.

[mrsmackpaul]

Geoff I agree with everything your saying 

Angelo had concerns about cost, and if changing something that isn't faulty dries up funds for what ever is faulty might not be a good outcome for him or the truck 

So testing and proving is essential to make the dollars go as far as they can for Angelo 

 

Paul 

 

[Geoff Weeks]

https://www.aspwholesale.com/index.php?route=product/product&path=71_262_274&product_id=6244

https://www.aspwholesale.com/index.php?route=product/product&path=71_262_274&product_id=6243

 There are other choices and other vendors, I just pulled these off the net.

this set is used in 130 amp Leece Neville alternators.  Because of how the mount in the case in the alternator they were designed for, there is very little heat transfer to the case, so that makes them more ideal for a retro-fit where they will not be bolted to an aluminum case and have a lot of cooling are drawn over them.

 It is a good bet that your rectifier has failed, but as Paul says, before you pull the trigger on more than $100, test them.

[Angelo]

Rectifier is gone. Also confirmed with Vineland electric in jersey. I had a feeling it was. Can’t thank you guys enough again. I take every you say into account and will use in future as well

[Geoff Weeks]

It will probably cost you the same or more to rig up some replacement rectifiers out of new diode blocks than it would to buy a used or re built modern one wire unit.

Because yours is positive ground, you either need a case neutral (Like the Leece Neviile JB series) or a positive ground unit.

[mrsmackpaul]

Well thats good news you now no what has failed 

I agree with everything Geoff has said

I guess a negtive ground rectifier could just mounted on some plastic isolators and still work fine if a positive ground unit is hard to come by

Keep us posted on how this goes

 

Paul

[Geoff Weeks]

You need both positive and negative for full wave rectification. If it is being used on a positive ground vehicle the positive rectifier can be mounted to grounded metal, but the negative would have to be isolated from any grounded metal.

[Angelo]

That’s what I was thinking. Old one is positive ground and mounted right to metal bracket on side of motor

[Geoff Weeks]

To be clear: You need BOTH positive and Negative diode sets, not one or the other. Which ever polarity the vehicle is, that diode set can be mounted to any metal, the other set has to be isolated.

Although the old one was mounted to a metal bracket, there were insulators between the fins and the metal bracket. The old one didn't have either positive or negative connected electrically to the bracket that held it.

Edited October 6, 2023 by Geoff Weeks

[Angelo]

Replaced rectifier with diode rectifier  Alternator was cleaned up and checks good, voltage regulator good, grounds good and ran a few new ones while I was up in there, still charging at 18 volts 🤦‍♂️ 

[mrsmackpaul]

Hmmmm, well back to testing then

So the rectifier wasn't faulty, the regulator isn't faulty 

 

Paul