How could I go about a simple test for this.

[killivolt]

SN74LS86AN

Data sheet
https://www.sierraic.info/datasheets/TI/001348.pdf

This is in a duplicator and I'm not sure if it's bad.

Do I just replace it or test it somehow.

I have slot type sensors that are connected to it when I tested them they are high until I cover the slot and then go low.

kv

 

[vne147]

You want to test it without removing it from the circuit?

 

[killivolt]

Already pulled it I'm to inexperienced to test while in the machine. I was hoping maybe just diode check or something.

 

[killivolt]

Plus I have no schematics. The manufacture has been spoon feeding me.

I did come up with a test for the sensors though I haven't checked them all but I don't think their any trouble has to be here or deeper.

If I can't get it here then I'll have to ship it back to the manufacture.

kv

 

[vne147]

I'm not sure if this fits your definition of simple but I'd just throw it in a bread board with a DIP switch to toggle the inputs and use a DMM on the outputs. I'm not sure about the diode check, sorry.

 

[killivolt]

I thought about that I have breadboard doing similar thing I'm passing voltage through the sensors to an LED and turning it off and on.

 

[killivolt]

dip 1A and 1B read 1Y to ground for output voltage hi or low. Repeat. 2A and 2B

 

[vne147]

If I understand what you're saying, that's how it's supposed to work

A B Y
L L L
H L H
L H H
H H L

 

[killivolt]

If I understand what you're saying, that's how it's supposed to work

A B Y
L L L
H L H
L H H
H H L

Yes, Thank you.

I tried sending PM but I'm sure if you got it ? Seem to hang like didn't do anything.

kv

 

[vne147]

No PM, sorry.

 

[killivolt]

I figure if I can supply the Vcc / GND and the 5v / GND to it with all four sensors in place I should be able to test it out of the machine here are the resistors on the board for the emitter and the sensor goes directly into the A/B the Y is going off the board into a connector and down into the machine originally but I have it out of the machine and on the bench.

PINS connected are...

1-2-3- (7 GND) and ( 14 Vcc ) 13-12-11 the other pins not used on this circuit board.

What setting should I have my DMM set to amps or volt where should I reference +/-

 

[WolfGang]

stumbled across this thread and just wondering...what brand/model duplicator are you working on? also why do u suspect this chip is bad?

 

[killivolt]

stumbled across this thread and just wondering...what brand/model duplicator are you working on? also why do u suspect this chip is bad?

Vinpowerdigital / Titan series.

I don't suspect, just easier next stop on the trouble train.

When I began the first step they said was replace the sensor this was before I learn how to test them. Next easiest on the list is the receiving board which passes it onto the load arm board after that "down inside " to the processor.

The Senors of 4 slot type mounted on the loading arm the bottom one is giving an error code indicating out of disk's ( But, they say still could be on the same side on the top but checks good.

No schematics nothing. No dis-assemble instructions either and if it's not here I'm forced to send it back.

The worse part of this, when I did replaced the bottom sensor it worked. Loaded the source disk and moved onto load following 2 drives. I aborted it. The next day nothing right back again?

Having those weeks. A little success a little failure.

Ah'em, Oh yea

kv

 

[vne147]

I can't really make heads or tails of your schematic but if you want to test the 74LS86 you can do the following:

Connect pin 7 to ground
Connect pin 14 to +5V

You are going to test 1 gate at a time.

For the first gate:

Connect input 1A to +5V through a 10 kΩ resistor.
Connect input 1B to +5V through another 10 kΩ resistor.
Connect output 1Y to ground through a third 10 kΩ resistor.

Connect all the remaining inputs to ground (2A,2B,3A,3B,4A and 4B).
Leave the remaining outputs unconnected.

Set your DMM to measure DC voltage and connect the positive lead to the 1Y output (pin 3). Connect the negative lead to ground.

At this point you can connect the voltage souce.

Now if everything is hooked up correctly at this point, both inputs (1A and 1B) will be high so the output (1Y) should be low (≈ 0V). Check your DMM to make sure.

A=H, B=H, Y=L

Next, connect 1A to ground and then check your DMM. It should be ≈ 5V.

A=L, B=H, Y=H

Disconnect 1A from gound and connect 1B to ground. Check your DMM, it should be ≈ 5V.

A=H, B=L, Y=H

Next, leaving 1B connected to ground, reconnect 1A to ground and check your DMM. It should be ≈ 0V.

A=L, B=L, Y=L

That's it. You just tested every possible state of the 2-input XOR gate.

Repeat the above steps for the other 3 gates making sure to ground the unused inputs.

I hope this makes sense.

 

[killivolt]

I was thinking I would not have to pull the Chip from the board. But, maybe it will be easier.

I did some correcting to the drawing in order to represent the way it' mounted and used in the circuit board with the sensors.

I used your Idea instead.

Thank you.

kv

 

[vne147]

I was thinking I would not have to pull the Chip from the board. But, maybe it will be easier.

I thought you said you already pulled it way back at the begining of this thread???

I did some correcting to the drawing in order to represent the way it' mounted and used in the circuit board with the sensors.

I don't really understand how the sensors you have in your schemtic work. It looks like when there is no object in the slot, the NPN is on which causes the inputs to go low. But when there is an object there, the light path gets blocked, the NPN turns off and then the pin is floating. Are you sure that the NPN's collecter is not connected to anything other than the input pin on the 74LS86?

I used your Idea instead.

Which idea did you use?

 

[killivolt]

I thought you said you already pulled it way back at the begining of this thread???

Pulled the circuit board from the machine. Chip is still mounted in the board. Sorry about that.

I don't really understand how the sensors you have in your schemtic work. It looks like when there is no object in the slot, the NPN is on which causes the inputs to go low.

I suppose. But, the test on the sensors resulted in lighting an LED with slot open and off with slot blocked.

I used this diagram to light it.

http://www.fignoggle.com/workshop/media/optoSwitch/figNoggle_optoSwitchWiring1PS.GIF

But when there is an object there, the light path gets blocked, the NPN turns off and then the pin is floating. Are you sure that the NPN's collecter is not connected to anything other than the input pin on the 74LS86?

The traces are visible from each sensor collector and goes straight 1A-4A / 1B-4B all points are verified. I've taken my Dmm and couldn't find any other connections, all collectors lead to intputs indicated.

Which idea did you use?

Post #14 The only one suggested. If you still think I should follow it.

Thanks again.

kv

Edit: I am preparing the connections now.

 

[vne147]

I suppose. But, the test on the sensors resulted in lighting an LED with slot open and off with slot blocked.

I used this diagram to light it.

http://www.fignoggle.com/workshop/media/optoSwitch/figNoggle_optoSwitchWiring1PS.GIF

The diagram in the link makes more sense. It shows the collector of the NPN connected to +5V through a light bulb and a 1 KΩ current limiting resistor. When the slot is blocked the NPN turns off, no current flows through the light bulb and it goes out. When the slot is not blocked the LED turns on the NPN, current is allowed to flow and the light bulb turns on. This is how I would expect the circuit to work and that is how you said the sensor behaved even though it is the opposite of what is stated in the caption of the diagram.

The traces are visible from each sensor collector and goes straight 1A-4A / 1B-4B all points are verified. I've taken my Dmm and couldn't find any other connections, all collectors lead to intputs indicated.

If you say that the collectors of the NPNs are connected to the inputs of the 74LS86 and nothing else, I believe you but it just doesn't make sense to me and that's not how the diagram would lead me to believe the sensor should work and interface with the 74LS86.

Post #14 The only one suggested. If you still think I should follow it.

You used the past tense when you wrote "I used your Idea instead". I thought that meant you had already done the test but you also said that you hadn't pulled the 74LS86 yet. It was confusing.

As far as whether or not I think you should follow the instructions in post #14, that's up to you. I can't tell you what's wrong with your device, if the sensors are working properly or even if you should suspect the 74LS86. I was just answering the original question of this thread which was how do you test the 74LS86.

So in answer to your original question, if you follow post #14, that should tell you whether or not the 74LS86 is still good.

 

[killivolt]

Should Vcc and Ground on the chip be connected in this test or left out ?

Edit: I see the first instruction. Yes to my own question.

One last check for all points. Working ............

 

[killivolt]

Ok. Test Resulted. Vcc 4.5 my small power supply will only do (3v-4.5v-6v-7.5v-12v) I don't have a five volt regulator. I think the data sheet was showing a little more for this Chip.

Anyhow I'm not sure what the value's should be based on the supply should I try 6v.



1A_H / 1B_H = 1Y_ 0.165v

1A_L / 1B_H = 1Y_3.069v

1A_H / 1B_L = 1Y_3.069v

1A_L / 1B_L = 1Y_ 0.159v