What kind of diode is this?

[Leggyownz]

So I have a diode that appears to need replaced. This board mounts up to a block with a motor for a lid lock within that block. So the screw is driven over by the motor and this diode is in the only window the block has to identify whether the lid properly locked. My question then becomes, what type of diode is this? There are no identifying marks on it.







[mod note: images resized]

 

[HellasTechn]

It looks like a dual diode package but without marking or some service manual then it will not be easy finding a replacement.

 

[Minder]

Check to see if there is AC in to one pair, if so it is most likely a small Bridge.
They typically are set up with the DC and the AC diagonal from each other as that appears to show.
M.

 

[Leggyownz]

Only DC going in to the diodes. no AC present.

 

[Minder]

How did you arrive that it needed replacing?
M.

 

[Bluejets]

Except for thinking the diode needs replacing, I for one have no idea what you are describing.

 

[dave9]

Yeah the description of what this board is supposed to do is not very useful.

Try to draw a schematic of the board and what is upstream and downstream of it.

As for what type, probably some variant of a photodiode. Is it only sensing ambient light or is there an emitter on the other side, producing infrared or something? If so then you need one filtered or otherwise optimal for that spectrum and light level.

Since I'm still making a wild guess about what this device is, it might end up being more fruitful to add a mechanical switch to sense when the mechanism is closed to turn the motor off, just do without the function of that board completely, or with a complete enough schematic someone could possibly recreate a new emitter-sensor combo that would work if you can't find the right photodiode to work with what else is there.

 

[HellasTechn]

Except for thinking the diode needs replacing, I for one have no idea what you are describing.

If you have a multi meter then you can set it to diode test and see if it will conduct one way side and block the other.

 

[Leggyownz]

The reason I came up with this being bad is that I never get a different reading on it whether I have it covered from light or a piece of metal on top of it. In diode mode it reads from pin to pin in all combinations forward or reverse. The machine gives an error that the lock is not being sensed. This is a color gram stainer for preparing slides for examination. Being a third party in this field means nobody supports us. I've been here two years and seen schematics for maybe three instruments out of 5000 or so. If we call for parts they tell us they won't support us and they leave it at that.

As for its function, I've uploaded a few more pictures below to help you understand. In the locked position the lock would be in the window shown (on the left side of the block, I know its dark). The board sits up against that block with the diode poking through the window. Pictures aren't of the highest quality because I just grabbed my cellphone for these ones.

 

[Leggyownz]

Yeah the description of what this board is supposed to do is not very useful.

Try to draw a schematic of the board and what is upstream and downstream of it.

As for what type, probably some variant of a photodiode. Is it only sensing ambient light or is there an emitter on the other side, producing infrared or something? If so then you need one filtered or otherwise optimal for that spectrum and light level.

Since I'm still making a wild guess about what this device is, it might end up being more fruitful to add a mechanical switch to sense when the mechanism is closed to turn the motor off, just do without the function of that board completely, or with a complete enough schematic someone could possibly recreate a new emitter-sensor combo that would work if you can't find the right photodiode to work with what else is there.

As far as creating schematics, that would be difficult as nothing on the board is marked other than the chip on the left, but it only has "k 503" on it which turns up empty on any of my searches to identify that. The only other thing I could do was attempting a schematic with the use of my multimeter and reading the actual values on them.

There also is no emitter on the other side of the block. Mechanical switch may end up being what I have to do. I don't necessarily prefer that method but if there's not a way to come up with a suitable fix for my problem, that may be the road I end up taking.

 

[Minder]

I see now that looks like a retro-reflector, there are several versions out there, QRE1113, CNY70 just to name a couple.
One side is a LED emitter, the other the receiver.
M.

 

[Leggyownz]

Well, I do believe you are correct. Thank you Minder.

 

[dave9]

There is only so much I can suggest without having the equipment in hand and of course not having any vested interest in it, so if I blew it up, it's no loss to me.

I might try to determine which line going to the board (connector) is power, ground, and signal, and see if the signal problem is it's staying low or high, which state it needs to switch to to signal closed (probably high), then try to trace back the schematic you made to see where that is going wrong... or you could just start throwing matching pairs of emitter/receiver diodes in to see if you have any luck.

 

[Leggyownz]

There is only so much I can suggest without having the equipment in hand and of course not having any vested interest in it, so if I blew it up, it's no loss to me.

I might try to determine which line going to the board (connector) is power, ground, and signal, and see if the signal problem is it's staying low or high which it should switch state, then try to trace back the schematic you made to see where that is going wrong... or you could just start throwing matching pairs of emitter/receiver diodes in to see if you have any luck.

Well a lot of the instruments we get in use custom parts with no markings. I've got one board in with PSI repair to replace a diode that had a marking nobody could recognize. These are the problems I've constantly run into. I'm completely self taught other than the help I can get from you guys here on this forum. Sadly, a lot of the science behind things are interestingly difficult to teach yourself and with no prior knowledge and no mentors, It's hard to learn some of the more difficult things.

Here at the company I work for, we are a small company that deals in refurbishment and resale of medical and lab instruments. Mostly Lab. There are four technicians (one being my boss) and around 15 of us total here. Out of all of us, nobody understand circuitry better than I do here. If ever, any of us break anything, the boss shrugs it off and we sell the machine for parts. It's really nice actually to not be under any pressure like that. Your on the job training is very minimal as the training you receive is what you teach yourself and obviously we all help each other out when we can. I get every board that's bad, and every machine with an electrical issue. I've had surprisingly good luck with all of it. A few on the back burner sitting in the corner of my area that I'm struggling with but not much.

With that knowledge being given. Going by looks, there are only two that I can find that look exactly like this one. I went ahead and ordered the ON Semiconductor QRE1113. The other I found was the Everlight EAITRCA6. Looks as though the QRE1113 has been around longer and the EAITRCA6 hasn't been around long enough to have been around during the initial production of this machine. I know looks aren't the best to go on but it is a fairly unique design.

 

[Minder]

The retro-reflectors such as the ones I quoted are all one piece unit, they are easy to trouble shoot if you use such as a white reflector you should detect a change at the transistor side output, usually a 10k pull up (or down) resistor.
You may have to investigate as to the same pin out for the QRE/CNY.
M.

 

[73's de Edd]

Sir Leggyownz . . . . .

Referencing to your Photo #1 and in reading the board, it looks like power +5vdc ? feeds from R1 to power up the light emitter LED on the " D1 " unit and the photo transistor feeds back to U1 then the U1 logic output goes up to pin 1 of your 3 pin connector.
Just reassemble the unit up to its housing ***** and initially check for power at the pin 3 as refeenced to the center pin 2 ground and then move over to monitor pin 1 for DC voltage state and then . . . . . repetetively open and close the door to see if you get repetitive and coincident logic state changes of the pin 1 test point..

***** (So that any high ambient room lighting will not be falling on the sensor and swamping it . . . . . if attempting an out of environs testing. )

Thassssit.
73's de Edd
.....

 

[Minder]

Interestingly in testing the QRE1113 it appeared impervious to fairly bright ambient light,
M.

 

[73's de Edd]

M . . . . on powering up the LED emitter . . . . . does it seem to be generating visible or IR light . . . .without me consulting its data sheet . . . . since you already have one out ?
Pause . . . . . . . . quickly confirmed as being I.R.