The L50C is a PC diagnostic card, which displays Power on Self Test (POST) error codes. This card receives the error codes through the parallel port and displays them on a four-digit 7-segment LED display. The card operates on 5 V and takes its power from the female USB socket
Based on the Atmel AT89C51 microcontroller, it is fast and displays the BIOS error codes straight away. In addition, an accompanying booklet lists the codes and their meanings. Hence, once you have the code, you simply look it up in the booklet to find out what it means.
There are many diagnostic cards available on the market, and I think I must have used many of them over the years. This one is the cheapest one I bought on eBay for 3.00 including postage and it came from China. Amazingly, it works fine!
Manufactured to a high standard, the Atmel chip is one of the best parts of it that seems to work well in this application.
A card that connects through a parallel port is useful because it is ideal for use when you have a laptop that does not make any BIOS beep sounds and appears to be dead. This card is likely to give some indication as to what might be happening.
The Atmel AT89C51 is an 8-bit microcontroller with a 4 K reprogrammable flash memory. The square pads are the connections for programming the chip. It is interesting to note that if one were to make this by buying the parts separately it would cost more.
According to the PC architecture originally specified by IBM, error codes sent to the parallel port provide engineers with useful diagnostic information. Hence, if you have a dead laptop, or a PC showing nothing on the display, chances are that this card will indicate what the fault is.
This card arrived with a cable for the USB port.
You also get this pocket sized manual with fonts so small that you need a large magnifying glass to read, but it does appear thorough.