Electrical – Broken Photodiode – how to find a replacement

infraredphotodiodereceiver

I have nearly no knowledge at all in electronics – but maybe you can help me 🙂

I got here a vintage moving message LED sign (brand: litek lmr 6002) and it seems that its controller is broken. The sign itself works, I can confirm that the IR leds on the remote are flashing (by pointing a digital camera on it) but the sign itself doesnt react on any command.

So I startet looking for the receiver but all I found was an unexpected solid looking diode – maybe a photoresistor. It seems to be connected to a TDA stereo amplifier chip (huh?).

I unsoldered that mysterious 2-pin diode and there is a high resistance between both legs – and its not changing when I point a flashlight, laser or the IR sender to it. So I think that diode is gone. Maybe – if I am lucky – I can bring life to that controller again by replacing this diode?

Is there anyone who can give me some advice how to identify that diode?

There are no marks or letters on it and it doesnt seem to be very transparent. It has a mark ("cut corner") on top but thats pretty much all.

I can supply some pictures of the small controller board – I marked the diode and its soldering points:

http://www.directupload.net/file/d/4523/iuyyurf5_jpg.htm
http://www.directupload.net/file/d/4523/rqfmcu8d_jpg.htm
http://www.directupload.net/file/d/4523/43n26du8_jpg.htm
http://www.directupload.net/file/d/4523/8333hzop_jpg.htm

Any hints are highly appreciated – and sorry for my lack of electronic knowledge again!

Best Answer

Any IR PD will work as they all have similar characteristics, except this is radial with daylight blocking dark plastic filter.

keywords for search...

PIN photodiode IR radial side view digikey (or RS or Mouser etc)

The 1st likely match I found was,

http://www.digikey.ca/product-detail/en/lite-on-inc/LTR-516AD/160-1032-ND/121725

enter image description here

Looks very good - but isnt it necessary to take care what wavelength, resistor values etc? - Peter Dudikoff

  • maybe , but I have some confidence it will work well from tons of research in these products in the past, the chip size is pretty standard and the RESPONSIVITY is typically 0.4A/W or 0.4uA/uW, wide IR spectrum, low speed app.

    • there are others to choose that may be better or worse, as long it is stock , pick 2 types , if you like, (cheap) enter image description here

http://www.digikey.ca/product-search/en/sensors-transducers/optical-sensors-photodiodes/1967048?k=&pkeyword=&pv16=10757&FV=17840001%2C17880004%2C17880006%2C17880007%2C17880008%2C1788000a%2C1788000d%2C17880013%2C17880014%2C17880015%2C17880017%2C17880019%2C1788001f%2C17880022%2C17880023%2C17880024%2C17880026%2C1788002a%2C1788002c%2C1788002f%2C17880032%2C17880039%2C1788003d%2C17880043%2C17880048%2C17880049%2C1788004e%2Cfff4001e%2Cfff803c8%2C1f140000&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

2nd option above 0.55 A/W spec http://www.excelitas.com/Downloads/DTS_vtp7840.pdf

Check Anode pin.