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Can I go to radio shack and ask for a 680 ohm resistor and get what is on my board? Sorry Chuck. .my stupidity Is starting to show through.

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Can I go to radio shack and ask for a 680 ohm resistor and get what is on my board? Sorry Chuck. .my stupidity Is starting to show through.

 

Yes, but be prepared for a blank stare - or at best, "What's that ?"

 

!5 years ago I would say absolutely yes, they would have that value. These days, it would be best to call the store with a part number from their website and see if they have them is stock.

 

From what I can see from Andy's post, you will likely need

 

680 ohms

1000 ohms

470 ohms  (yellow violet brown) located in the lower right corner of the board. I am fairly confident the first color band is yellow. 470 ohms is a VERY common value used in electronics.

 

All these values make sense as they represent appropriate values which would be used in this family of diode based logic circuits.

Edited by Save Old Iron

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Noticed another post on another thread where the gentleman had a pic of a board that looked exactly like mine. .if I can get good pics of his board. .and the color bands. .can I just replace the parts we think are bad? Most I assume are cheap.

Or..I can send it to you if You want to look at it

If you wish, yes, you can send the board to me and I will be happy to look at it and make the repairs free of charge.

 

There are several considerations if you send me the board.

 

1) I would not have a tractor to place the board into to check the proper operation. I could accomplish the same check on a "test bed" which I would have to create. This is a project I was thinking about a few years back and maybe now is the time to take it on.

 

2) Reverse engineering the circuit, creating a test bed and repairing / checking the boards function involves a time factor. If you don't mind being without the circuit board for a month or more, I would be happy to make this a winter project.

 

3) Ultimately, the problem you have experienced with the indicator lights could be due to issues in the tractor wiring or safety switch circuits. You may receive the board back fully functional but yet still have issues in the tractor.

 

Let me know what you first impressions are of how you would like to proceed.

Edited by Save Old Iron

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By the way ...... I never asked and I don't believe you ever mentioned

 

 

What the original problem was that prompted you to start investigating the indicator pcb ?

 

Are all the safety switches and safety features currently working on the tractor?

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All,

 

Great topic and it's got me wondering if there is a practical way to simplify the circuit board.  It seems to me that it would be possible to run a wire from each switch through one of the indicator lights, so that when the switch is closed the light comes on.

 

Now I realize that there may be multiple switches that have to closed for the lights to come on and perhaps the oil sensor circuit might need to have resistors and diodes but is the rest of what we see really necessary?

 

I think I have 5 lights on my 418's and things like the parking brake and PTO seem to be prime examples of when the switch is closed the light comes on.

 

I suspect that I am over simplifing things but these boards seem rather fragile over time and while I wouldn't have a problem funding Chuck to redo mine, a board/light combination that any layman could repair would be greatly appreciated.

 

Cod

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Chuck

I first started digging into the board soon after I bought it. .last week. ..because the lights didn't come on. After investigating I noticed two of the bulbs had broken leads. Those are the ones I replaced. I now have bulbs on order. I have been able to test the park brake switch light and just replaced the pto switches. ..they were crusty. You're correct I might have issues after you look at it but I guess at least id know the board was sound.

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. wondering if there is a practical way to simplify the circuit board.  It seems to me that it would be possible to run a wire from each switch through one of the indicator lights, so that when the switch is closed the light comes on.

 

Good question Cod,

 

I have wondered that myself. I do know there are "logic" decisions being made by the diode based electronics. At a minimum, each indicator light must respond to 2 inputs. One input is from the switch associated with the safety function and a second input would be from the TEST switch. So the electronics would be configured in an "OR" logic - the safety switch in the incorrect state OR the TEST switch engaged would light the indicator bulb.

 

Beyond that simple arrangement, I simply have not put pen to paper to try to figure out why there would be any other "logic" needed to make a decision to light or extinguish the indicator lamps. Given the size of the circuit board and the real estate available on the board, modern electronics could easily fill the space with a fully functional "command center" based on very inexpensive microprocessor circuits.

 

I am very much interested in seeing why a dual OP AMP circuit is needed on the newer style board. The wonderful thing about electronics is there are many different ways to skin the cat. I would very much like to understand the reason for this circuit configuration. Diode logic is very robust and is highly immune to voltage spikes, etc that are commonplace on mobile equipment.

 

This post will allow us all the opportunity to learn more about the electronics pcb and possibly fix a defective circuit board or two. If you gentlemen can do without your boards for a month or two, I am willing to take this on as a winter project. There will be no repair cost associated with fixing your board BUT I MUST STRESS THIS PROJECT IS NOT #1 ON MY TO DO LIST.

 

I will bump it up above this bucket list item

 

129098738589219441.jpg

 

but I still anticipate a few months will go by before I can fully reverse engineer, secure parts and put together a test bed to confirm the board operation. If you are willing to participate on the time table of a few months, then I will be happy to look at the boards.

Edited by Save Old Iron
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Chuck-hard at work trying repair old circuit boards at 1:00 a.m. :rolleyes:

 

2985419-7081243885-Squir_zps70dbb9ff.jpg

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Good question Cod,

 

I have wondered that myself. I do know there are "logic" decisions being made by the diode based electronics. At a minimum, each indicator light must respond to 2 inputs. One input is from the switch associated with the safety function and a second input would be from the TEST switch. So the electronics would be configured in an "OR" logic - the safety switch in the incorrect state OR the TEST switch engaged would light the indicator bulb.

 

Beyond that simple arrangement, I simply have not put pen to paper to try to figure out why there would be any other "logic" needed to make a decision to light or extinguish the indicator lamps. Given the size of the circuit board and the real estate available on the board, modern electronics could easily fill the space with a fully functional "command center" based on very inexpensive microprocessor circuits.

 

I am very much interested in seeing why a dual OP AMP circuit is needed on the newer style board. The wonderful thing about electronics is there are many different ways to skin the cat. I would very much like to understand the reason for this circuit configuration. Diode logic is very robust and is highly immune to voltage spikes, etc that are commonplace on mobile equipment.

 

This post will allow us all the opportunity to learn more about the electronics pcb and possibly fix a defective circuit board or two. If you gentlemen can do without your boards for a month or two, I am willing to take this on as a winter project. There will be no repair cost associated with fixing your board BUT I MUST STRESS THIS PROJECT IS NOT #1 ON MY TO DO LIST. I anticipate a few months will go by before I can fully reverse engineer, secure parts and put together a test bed to confirm the board operation. If you are willing to participate on the time table of a few months, then I will be happy to look at the boards.

Ah ha!!!  It's my logic circuit that's shorted, just don't tell the my wife... ;-)

 

After reading your post I realized that the main function of the board and the lights is safety and just running one side of the light to ground only turns the light on, it won't kiil the engine if you have the PTO engaged and get out of the seat.  So now having the resistors and such, makes more sense.  I'm game on the board repair as I've got two but it might be a week or two before I get to pulling it out of the 418, so I'll be in touch.

 

Cod

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Chuck-hard at work trying repair old circuit boards at 1:00 a.m. :rolleyes:

 

2985419-7081243885-Squir_zps70dbb9ff.jpg

 

 

Ain't that the truth.

 

SquirrelHaX0R.jpg

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Ah ha!!!  It's my logic circuit that's shorted, just don't tell the my wife... ;-)

 

After reading your post I realized that the main function of the board and the lights is safety and just running one side of the light to ground only turns the light on, it won't kiil the engine if you have the PTO engaged and get out of the seat.  So now having the resistors and such, makes more sense.  I'm game on the board repair as I've got two but it might be a week or two before I get to pulling it out of the 418, so I'll be in touch.

 

Cod

 

 

Very important to remember the indicator board only INDICATES - it DOES NOT CONTROL any function of the tractor. You can remove the board from the tractor and it will function without issues.

 

I'll wait for your response when you are ready to send out the board. I'm sure the outcome will be several repaired boards and maybe 3 or 4 more people worldwide who understand how (and give two hoots) about this board works.

 

p.s - I started preliminary work on reverse engineering the components on the top 1/4 of the pcb. Most of the components are there solely to flash the oil light - fascinating, as there were simpler alternatives available when this design was conceived.

Edited by Save Old Iron
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I rally am interested in this post. Chuck I have one of the old boards with a broken circuit where it makes connection with the push on connector. I saw where you mentioned the glue on strips. Where do you get them?

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I use copper foil for stained glass panels or crafting.

 

http://www.walmart.com/ip/24626739?wmlspartner=wlpa&adid=22222222227000000000&wl0=&wl1=g&wl2=c&wl3=42423897272&wl4=&wl5=pla&wl6=51320962143&veh=sem

 

is one example from a google search.

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So I got my new led bulbs in the mail today but I don't see a way to tell polarity on them side to side they look the same.

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I won't. . To scared! But I know what side is positive and negative. Just no idea how to match to the board.

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Nothing to be scared about

 

BUT

 

LED's operate off current and not voltage. I won't belabor the point only to say if you hook an LED DIRECTLY ACROSS a voltage source, mega current flows and blows out the LED in fractions of a second. The circuit board contains resistors that limit the current able to flow thru the LED to a level below its maximum current rating.

 

For orientation of the replacements, look at the lower left corner of the circuit board and you see the schematic symbol of the LED. On the board, I see the flat line oriented to the top of the board. This means the row of LED's should have their cathode (flat on body, or shorter lead from body) oriented toward the top of the circuit board. If they are inserted incorrectly, no damage will occur but the LED will not function properly.

 

If you want to check out the LED's before mounting them , to make sure they function, grab some 680 ohm resistors we spoke about last week and wire them up to the diagram shown below. When you touch the leads to the tractor 12 volt battery, the LED should light up a bright red.

 

Remember, cathode (flat on body, or shorter lead from body) goes to battery [-]. You will not do any damage to the LED as long as you use the 680 ohm resistor (or even a 1000 ohm resistor) wired in series ass shown below.

post-1689-0-96295900-1414642865.png

Edited by Save Old Iron

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Andy, as luck would have it, I have access to a 312-8. When my friend stores the tractor for the winter [ 2-3 weeks], I will have the ability to check the connector for the pcb and gain some information to allow construction of a test jig. At least we will be able to help out 300 and possibly 400 series owners in need of board repairs. Stay tuned and send an update on your progress with the LED replacements.

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Andy, as luck would have it, I have access to a 312-8. When my friend stores the tractor for the winter [ 2-3 weeks], I will have the ability to check the connector for the pcb and gain some information to allow construction of a test jig. At least we will be able to help out 300 and possibly 400 series owners in need of board repairs. Stay tuned and send an update on your progress with the LED replacements.

I know of no one who goes to the trouble you do to help our members. This has been a great thread and a learning experience for us all. Thanks.

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Been out of the loop for a while. .old iron..you still willing to look at my board..ill send you the board, leds ..what would you charge?

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Yours is a third generation board, much less expensive to fix component wise, but still still susceptible to contact corrosion. Since I have not seen a third gen yet, I would need some patience on your part until I can reverse engineer it. If you have a few weeks, I'll give it a go.

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Been out of the loop for a while. .old iron..you still willing to look at my board..ill send you the board, leds ..what would you charge?

 

I am still trying to finalize my test jig wiring. If you send the board, either take a picture of the wiring on the top of the board connector or draw out a small diagram on paper indicating the color of the wire on each pin of the connector.

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