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Ok put a mic on the bulb. ....4.87.

So 5mm? What volt and ma do I need? Anyone out there with a New style board and shoot me a pic? Mine is an 89. I need to see what value my resistors are. Thank you all for the support. .I couldn't do it without you.

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Run a pencil eraser across the gold plated fingers on the board to remove additional buildup.

 

Remove the buildup shown below and check the gold contacts are still connected to the copper traces (green) leading away from them.

post-1689-0-03134900-1413948229_thumb.jp

Edited by Save Old Iron
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Ok put a mic on the bulb. ....4.87.

So 5mm? What volt and ma do I need? Anyone out there with a New style board and shoot me a pic? Mine is an 89. I need to see what value my resistors are. Thank you all for the support. .I couldn't do it without you.

 

So you need to order a few 5mm red LED's. The body may be clear but the element inside the body will glow red. The newer LED's will probably be much brighter than those available in the late 1980's, so if the difference bothers you, replace all the LED's on the board.

 

Make sure you have LEADED solder - not LEAD FREE solder. Lead free solder is very difficult for the hobbyist to use. I'm assuming you have a soldering iron and are familiar with how to use it ??

 

The reason I asked about the multimeter is to possibly be able to identify the resistors without color bands by actually measuring the resistor(s) and comparing with other resistors already on the board. There are essentially 5 identical circuits on this board and will probably use identical sets of resistors. If you are familiar with how to use the multimeter as an ohmmeter, I can point out the spots on the board to connect the meter to measure the resistors.

 

Let me know what level of confidence you have with using the multimeter to measure resistance.

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Andy,

 

a high resolution picture of the back side of the circuit board would be helpful.

 

Thanks

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In regard to the led..the link you sent me to..are they red led? What about volt rating? I bought a better iron specifically for working on boards. .its pretty easy. I understand resistance. ..Just was unsure what to trace. Also, hooking up to a bad resistor went tell me what I want. ..so I'd have to find a matching resistor somewhere else on the board. ..right? If I knew what to trace I could do it. I'll get I pic of the back of the board tonight. By the way. .the 12v stab in connector isnt the best. .any idea if I can buy a new edge connector?

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The edge connector is Molex WMLX-213. I was able to get mine at Baynsville Electronic here in Baltimore County. The should be available on line. If you are talking about the connector that you push the wires in and they automatically make a connection, this is not the one. This one comes with the Moles pins. I have a large supply of pins so I did not need to purchase any extras but I recommend that you get some extra pins in case you ruin one. They are cheap.

 

This is an extremely good topic as the step by step procedures you are following will be very helpful to the other members who may have these same problems.   

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Ok here is the back of the board. .still has sealing mat residue around the edge. .hope that's ok. .

post-10371-141402418406_thumb.jpg

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Looks like it is in good shape.

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Ya..but the resistors on the front are the issue...I think. .but don't understand how they work

a453b583b3f5092c98817c81b393d44b.jpg

Residue cleans up. .but look at tab 2 and 4 from the right. .corrosion?

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Could b e corrosion or just the clear coat worn off. Ohm it out using you meter

 

You said earlier that the diodes you bought were dim? How did you test them. Did you fire up the board and the lights came on?

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The two I replaced are not diodes. .I thought I had grain of wheat bulbs. Tested by plugging in yes. ..however I have an for leds where they put a resistor inline on a test lead and hook to the diode.

I have since ordered red leds from eBay. ..link from save old iron

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Andy,

 

thanks for the update. The corrosion you still have near the gold contacts appears to be a deposit of some sort. The green circuit board material is fiberglass and therefore not subject to corrosion as such. Poking at the deposit with a toothpick or other small pointed object will likely release the deposit from the board. You may need to clean the board more aggressively with alcohol and a toothbrush once again. Don't be afraid to go in between components on the board to clear out the deposits. Isopropyl alcohol will not degrade the board in any way.

 

Take a pencil eraser to the gold contacts until they are shiny. You will not harm the gold pads with a more aggressive action.

 

I have included a web link to allow you to calculate resistor values by selecting color codes into the web program.

 

http://www.dannyg.com/examples/res2/resistor.htm

 

I have labeled the resistors below with their marked values. The ones with ?? marks are not marked clearly enough to be certain. We will have to use the multimeter set on ohms to check across the resistors marked with ??. DO NOT expect the values to be exactly what the color codes show them to be. The gold band on the resistor body designates the values should be with +/- 5% of their marked value (when they were new). Some variances are also introduced when you measure resistors on the board vs. removed from the board.

 

Check out the 2 marked resistors on the pic below and see what we get.

post-1689-0-37247900-1414059095_thumb.gi

Edited by Save Old Iron

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p.s. please take a high res photo of the rear of the board. 

 

I understand the components are on the top side but we need to inspect the solder joints and copper traces on the backside of the board also. Having a view of the rear side of the board may also give me a better idea of how the components are interconnected and how they function.

 

Thanks

Chuck

 

Nevermind - I saw you did post the image earlier - thanks again

Edited by Save Old Iron

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Ok what I'm I Doing wrong. .meter reads 178 peak. .then settles to .51..im testing one you labeled as 1000

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measure the same resistor but reverse the black and red probes at the resistor

 

see if the readings change.

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Nope. .high number spike then settles to .50 .51..I and an older fluke multi meter..maybe it's the meter?

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Probably not the meter Andy. This scenario is very typical of electronics troubleshooting. In a circuit with many alternative current paths, the resistance you measure is not just the one component you attach meter leads to. If there is another pathway thru another resistor, the meter cannot isolate the reading to just one component but shows the equivalent resistance of the two or more pathways.

 

The reason I had you swap the leads is to determine if there was a diode in parallel with the resistor. Diodes conduct well in one direction but do not conduct at all in the opposite direction. So if there was a diode in the circuit with your 1000 ohm resistor, you would have received different readings with the meter leads swapped. Diodes on the circuit board are the black cylinders with the band marked at one end. Most of yours are marked 1N4005. Try to measure the resistance across several of those diodes. First with meter leads in one orientation then swapping the leads red for black, A properly functioning diode should show large differences in the ohmmeter reading one lead orientation to the other.

 

The "spike" you saw is probably due to the action of the capacitor (little yellow tube" in the upper left portion of the circuit board).

The capacitor acts as a electronic reservoir to store small amounts of energy to release into the circuit when needed. The spike on the ohmmeter represents a surge of current from the meter into the capacitor. When the capacitor discharges or charges to the meters test voltage, the spike settles out and you get the value of the resistor (or resistors in this case).

 

Here is where my head is at right now. To fully and accurately troubleshoot this circuit board, you will need some understanding of electronics and certainly an understanding of diode logic circuits. The designers apparently gave up on using transistors from previous designs and started to use  more tolerant DIODE RESISTOR logic design. I would have to have an example of this board in my hand to trace out the circuit design in order to understand EXACTLY how it works. Without having a similar board at my disposal, I could not accurately and efficiently coach you to check the board function.

 

Going forward, I would ask you to replace the red LED's back onto the board and check all the solder joints for cracks or "dry joints". Good solder joints have a shiny silver coloration and dry joints look dull and - well - "dry". If you were to touch up all the dry joints with fresh LEADED ROSIN CORE solder, you may be able to fix any issues with solder joints causing board malfunction. Please also note the LED lights are polarized. They must be inserted into the board in a certain orientation. The base of the LED will have a flat spot and the flat must be oriented as the others are oriented on the circuit board. If they are inserted incorrectly, they will not lite under any circumstances.

 

I have two 416's and one of them has the old style board. I have not checked the other 416 yet to see if they differ. I'll try to wade back in the barn this weekend to see what style is in the 2nd one.

 

Let me know what your level of understanding is for troubleshooting electronics. Maybe everything I said you already know.

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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

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Does this photo help / answer the question?

 

post-4509-0-24558600-1414178902_thumb.jp

 

It's the best I have - the two resistors in Chuck's pic with multimeter attached to the unknown one ppear to be the same i.e. 680 ohm.

 

Hope this is helpful.

 

Andy

 

ps - the resistors on this board are less chunky so lower wattage. I guess the manufacturer used whatever could be bought in cheapest maybe.

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I think it Does. .I might have a few more I need cross referenced. Do you still have the board.

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Sorry to disappoint but I've not had a horse with the later type board. The photo was submitted to Chuck's very first thread on repairing these boards by another member. I checked the thread but the photo which was hosted on Photobucket has since been deleted. I've doubled the original size of the copy I kept and sharpened it as best I can but it is what it is I'm afraid.

 

I think I can can make out most of the resistor values which I'm sure Chuck will have a go at too.

 

Andy

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