I've got a MAX3232 Serial-to-TTL RS232 board which I am currently using in factory assembly lines. I don't have its picture, but here's a similar product:
This is the circuit I've managed to figure out of the board(I don't have the original schematic):
I'm using the RS-232 board to send streaming data from an electronic Weight scale to PC, where the data is grabbed by my software for display.
The problem right now, is that sometimes the board stops sending data. I used HyperTerminal to check if the weight scale is sending data or not. When it doesn't, I've tried disconnecting and reconnection the serial port connection, unplugging the serial cable and plugging again, turning off the weight scale and even the PC on/off again and such, sometimes with no results. Sometimes the weight scale (WS) stops sending data. When I left if turned off for a while, and turns it on again, the WS sends data again. I suspect the MAX3232 IC got hot, because I can see the glue I put on the board looking like it's melted off the IC. When it cools down it is operational again.
I've used an oscilloscope to check on burnt ICs - these ones clearly don't have output on pin 14 (refer to schematic), with voltage level nowhere near +- 7V.
I've searched on the internet, and also found other people with issues regarding their IC (well this is actually MAX232) heating up when connecting to PC:
So far I've done some countermeasures:
Replace the burnt/old IC with new MAX3232 ICs from element14. Since the boards were very cheap and made in China the IC were probably of low quality.
Connected the unused CMOS input (pin 10) to GND with 2.2K Ohm resistor.
Added 20 Ohm resistor in series to pin 16 (VCC).
I'm afraid that these measures wont be enough. Maybe I need to isolate my connection. Does anyone have any idea what's going on, and know what to do?