Can't find a diode for my TO30

[FergFan]

While rewiring my TO30 Z129...I've had an extremely difficult time locating a new diode for the wire going to my lights. I've been to four automotive stores and radio shack to no avail. Old one is operational but rest of the line is very old. I didn't recognize this line had a diode when I removed it, but I put two and two together when I attached the pos battery cable and things got a lil sparky

 

[EE_Bota]

If I remember correctly, and if I don't plenty here will, the main characteristics of a diode are their amp carrying ability, and the peak inverse voltage they will block. So are you having trouble finding a diode with those correct characteristics? It is perfectly fine to use a diode with higher current carrying ability, and higher PIV withstand, so I should think the options for a replacement diode would be pretty good. I'm not an electronics guy, but I think I am right about this for just a typical diode application. I saw a diode on Amazon with 6 amps capability, and a PIV of 1000volts for less than two dollars, but I have no idea what amperage you are looking for. Are there any numbers on the diode that will tell you anything about it?

 

[FergFan]

The only number on this diode is an 8. I'm having trouble finding a diode I can connect a 12gauge wire to, much less their amp carrying ability at this point.

 

[br1ghtnut]

Hello EE_Bota is correct... I might be able to help... Two diplomas hanging on the wall say that I am versed in Process Control & Robotics and ElectroMechanical Engineering; but you can get anything on line these days. The diode is in a wire harness to the lights of a 1953 tractor? Can you give me more details? Do you know the purpose of this diode? But, essentially anything with larger values would be okay. I got some mighty big diodes !!

 

[troutsqueezer]

I doubt if the diode needs to be huge. You can probably get away with using two legs of a full wave diode bridge which are commonly found, at least they were a few years back. Radio Shack used to sell them. Get the kind that comes in a square package with a hole in the middle for mounting to a chassis, not the TO-220 type.

Actually, a quick check on my part and I see Ray D. O'Shack still sells them. At 25 amps, you should be good. Search Result

 

[ironnut]

I am a bit puzzled by a 1953 tractor having a diode as part of its wiring. Is this diode shown in the electrical diagram for the TO30?

In 1953 transistors and diodes were in their formative years. High current semiconductor devices really didn't exist. If you bought a battery charger back then it had selenium rectifiers in it (bulky things with lots of fins). My 1967 Honda 160 had selenium rectifiers in its charging circuit. It sounds like this diode was added by a later owner. Is this a 6 volt system.? It is a bit difficult to understand the purpose of this diode in the lighting circuit. I could see a fairly large one 20 or 30 amp being put between the generator and the battery to take the place of a generator cut out.

Anybody have a wiring diagram for a TO30?

gordon

 

[ThomasH]

That diode would have to be a retrofit - possibly if the alternator was changed in order to light a light on the dash showing a charging fault or something like that. Otherwise, I have no idea what the diode is there for.

 

[banjodunn]

G'day something wrong with your wiring somewhere, it don't get much simpler than an early fergy wiring battery-switch-lights in that order alot did not even have a fuse in the circuit so a diode is definately not a factory fit. As for the sparks you got something must not be hooked up right.


Jon

 

[k0ua]

you have been given good advice about diodes and the old selenium rectifiers etc. here is an interesting paper if you are into early history of diodes and transistors.

Road to the Transistor

James K0UA

 

[EE_Bota]

I am a bit puzzled by a 1953 tractor having a diode as part of its wiring. Is this diode shown in the electrical diagram for the TO30?

In 1953 transistors and diodes were in their formative years. High current semiconductor devices really didn't exist. If you bought a battery charger back then it had selenium rectifiers in it (bulky things with lots of fins). My 1967 Honda 160 had selenium rectifiers in its charging circuit. It sounds like this diode was added by a later owner. Is this a 6 volt system.? It is a bit difficult to understand the purpose of this diode in the lighting circuit. I could see a fairly large one 20 or 30 amp being put between the generator and the battery to take the place of a generator cut out.

Anybody have a wiring diagram for a TO30?

gordon

I looked at several TO-30 diagrams online, even converted to 12 volts, but I didn't see a diode symbol anywhere.

I like Troutsqueezer's idea about using a bridge though, if he does need a diode. It will have the current, PIV, and ease of wiring necessary, and if I am thinking right, a built-in spare!

 

[Dr Dave]

No need for a diode on a lighting circuit, may want a relay though, like a Bosch 30 amp relay and 30 amp fuse.

 

[Stick895]

Or order from Mouser Electronics - Electronic Components Distributor

 

[k0ua]

I looked at several TO-30 diagrams online, even converted to 12 volts, but I didn't see a diode symbol anywhere.

I like Troutsqueezer's idea about using a bridge though, if he does need a diode. It will have the current, PIV, and ease of wiring necessary, and if I am thinking right, a built-in spare!

Not only a built in spare, but 3 spares.. and if you get the kind with a metal case and a hole thru it, you can bolt it to the chassis, for heat-sinking. I don't have a clue why the diode is in the lighting circuit though..

James K0UA

 

[EE_Bota]

Not only a built in spare, but 3 spares.. and if you get the kind with a metal case and a hole thru it, you can bolt it to the chassis, for heat-sinking. I don't have a clue why the diode is in the lighting circuit though..

James K0UA

You're right! I just sketched one up, and there are 3 spares and one for use. For some reason I was thinking of using two at a time like doing rectification of the first half cycle, but you do have direct access to each of the four diodes, and there is no reason to use more than one at a time. Thanks for the correction!

L1 to pos
Neg to L2
L2 to Pos
Neg to L1

 

[k0ua]

You're right! I just sketched one up, and there are 3 spares and one for use. For some reason I was thinking of using two at a time like doing rectification of the first half cycle, but you do have direct access to each of the four diodes, and there is no reason to use more than one at a time. Thanks for the correction!

L1 to pos
Neg to L2
L2 to Pos
Neg to L1

Yep, I used to build diode bridges, before they started packaging them in "diode bridges", out of discrete diodes. I am actually old enough to have messed with a lot of equipment that had selenium rectifiers in them.. You did NOT want to "let out the magic smoke" on one of those nasty things.!:yuck: I remember the first LED device I ever saw back about 1972 or 1973. It was a watch a friend had. I think it was about $800. It told the time in red 7 segment LED's if you pressed a button with your other hand.. I remember back in 1971 at the University, we had a centralized calculating machine called "the Wang" that had maybe 10 remote terminals off of this centralized processor that all it did was what any $5 calculator would do today(actually less). It had Nixie tubes, a type of neon gas discharge tube for a multi-segment display. I think it cost a fortune, and an entire room was devoted to it. You had to book time to get to use it to make your calculations.. Your alternative was a slide rule(yes Virginia I still know how to operate one!) with much less accuracy, or a paper and pencil. Yes it is true, I am older than dirt.

James K0UA

 

[EE_Bota]

Yep, I used to build diode bridges, before they started packaging them in "diode bridges", out of discrete diodes. I am actually old enough to have messed with a lot of equipment that had selenium rectifiers in them.. You did NOT want to "let out the magic smoke" on one of those nasty things.!:yuck: I remember the first LED device I ever saw back about 1972 or 1973. It was a watch a friend had. I think it was about $800. It told the time in red 7 segment LED's if you pressed a button with your other hand.. I remember back in 1971 at the University, we had a centralized calculating machine called "the Wang" that had maybe 10 remote terminals off of this centralized processor that all it did was what any $5 calculator would do today(actually less). It had Nixie tubes, a type of neon gas discharge tube for a multi-segment display. I think it cost a fortune, and an entire room was devoted to it. You had to book time to get to use it to make your calculations.. Your alternative was a slide rule(yes Virginia I still know how to operate one!) with much less accuracy, or a paper and pencil. Yes it is true, I am older than dirt.

James K0UA

Slide rules were slightly before my time. I have used a Wang. I had the segment LED watch, but for some reason, it wouldn't work in the hot sunshine. And it didn't last me very long. This thing had to be cheap, not expensive like $800 because my dad got me and my brother one, and said "you boys are old enough to be on time." (Actually, thinking about it, I think it was like $30 dollars, and that was a lot of money at that time, so Dad was right generous when he bought those.)

I am used to the square rectifiers mostly, but back when I hired maintenance men, one of the first test questions was "draw a full wave rectifier." It was perfectly fine if they couldn't but how they went about it mattered. If a man draws four terminals, labels them + - L1 L2 or something similar, and attaches a load to the DC, and draws a sinusoid, he will always prevail because all he has to know is what a diode does. I never has a single candidate get it right. They tried to just start stringing together diodes while remembering some rhyme (that I have never heard.)

The reason why it mattered: The utility's PF correction capacitor bank would sometimes slam across the line before the caps were discharged due to a failed time delay relay, and ruin every rectifier in our factory. There have been times where we bought up all the local supply of diodes, but ran out before the factory was fully restored due to wiring mistakes. This was in the time when DC drives were common, but before variable frequency drives were popular. I was a younger guy then, and we were a leaner factory too. I should have had rectifiers ready on the shelves. But heck, our parts room was the size of my living room...and I live in a small house!

 

[Wilky]

Yep, I used to build diode bridges, before they started packaging them in "diode bridges", out of discrete diodes. I am actually old enough to have messed with a lot of equipment that had selenium rectifiers in them.. You did NOT want to "let out the magic smoke" on one of those nasty things.!:yuck: I remember the first LED device I ever saw back about 1972 or 1973. It was a watch a friend had. I think it was about $800. It told the time in red 7 segment LED's if you pressed a button with your other hand.. I remember back in 1971 at the University, we had a centralized calculating machine called "the Wang" that had maybe 10 remote terminals off of this centralized processor that all it did was what any $5 calculator would do today(actually less). It had Nixie tubes, a type of neon gas discharge tube for a multi-segment display. I think it cost a fortune, and an entire room was devoted to it. You had to book time to get to use it to make your calculations.. Your alternative was a slide rule(yes Virginia I still know how to operate one!) with much less accuracy, or a paper and pencil. Yes it is true, I am older than dirt.

James K0UA

Careful Jim some of these youngens might think a slide rule is for measuring not calculating. Some of today's kids don't know how to figure without a calculator. I'm like everyone else not sure the purpose of a diode In a DC circuit except as a back flow prevents.
Wayne

 

[k0ua]

The deal with the LED watch was, this guy gave a girl an engagement ring, later she gave it back.. he felt he was stuck with it, and took it back to the jeweler and traded if for this high dollar gold Plated LED watch that had just come out. I can not remember the name of it, but it was quite the rage for little while. Anyway, of course in a couple of years the watch was worthless as you could buy one for $30 as pointed out. In fact I had one, and I was a poor kid. Of course the engagement ring would be worth a lot more then and now. Soon the price of every LED thing dropped like a rock, and then the LCD stuff started coming out, and off we went again. I still remember seeing my first LED calculator a friend had, and it would not even spot the decimal point. you still had to do that in your head like a slide rule. and it was 8 digits. ah, the bad old days

James K0UA

 

[k0ua]

Maybe he still got the better end of the whole deal. :laughing:

Here is the funny part, a few years later he married her. He had to buy another ring. Then they divorced after a few years..Oh well.

James K0UA

 

[EE_Bota]

Here is the funny part, a few years later he married her. He had to buy another ring. Then they divorced after a few years..Oh well.

James K0UA

Should have kept time with the watch instead.