How to tell: bad board or bad chip?

dhenshaw

Trying to determine if I have a bad carrier board, or a bad BS II microcontroller.

When I power the chip from a 9v battery, any program will run for about 40 seconds, then "freeze". If I power it from a 12v regulated power source, it runs for no more than·10 seconds and freezes (I can sense the BS II getting too warm for comfort also). If I power the chip directly via a regulated 5.0v power source, the chip won't even boot up nor can it be recognized via the "Identify" option in the development environment! In each case the power light on the board stays lit.

My suspicion is that the on-board power regulator is hosed -- a while ago my Parallax wall wart went heywire and started pumping out 19v, which possibly fried a component.

The question though, is how do I know whether a new carrier board and/or microcontroller will cure my ills? Am trying to minimize my $$ expenditure. Any ideas...?

(Also of note: I'm an experienced Stamp programmer; my program isn't simply ending. And nothing is under warranty).

Mike Green

If you unplug the BS2 from the carrier board (I assume it's a Board of Education), you should be able to check for +5V on the output of the regulator and this should remain stable for as long as you want to measure it. You should also be able to measure whatever your input voltage is on the Vin pin of the BS2 socket. It should be in the range of 6-9V. 12V won't damage the BS2, but will cause its regulator to get warm, but not really hot. A regulated 5V supply has to be connected to the Stamp's (and the board's) Vdd supply line. If you connect it to the power supply input (Vin), the chip won't work ... the voltage is too low. On the Board of Education, Vdd on the Stamp is not connected because the Stamp itself is wired to run off the Vin supply.

If you replug in the BS2 (with the power off), making sure the pins are in the right socket holes, and power the board with a 6 to 9V supply, the Stamp should work. You should be able to Identify the Stamp with the Editor and you should be able to download and run a simple "blink an LED" program from the manual.

The on-board regulator should not be damaged by hooking up to a 20V supply. It's not designed to work for any length of time that way, but should not be damaged by it.

If the BS2 runs for a while, it's unlikely to be damaged although an I/O pin can be burnt out while the rest of the chip may work fine.

dhenshaw

Thanks for the ideas, Mike. The regulator is working fine, and remains at 4.96v indefinately. I think my Stamp itself must be damaged... even with a 9v battery plugged in, the stamp freezes after less than a minute in operation (it's just a program to debug a row of "."s). I checked the pins on the stamp and they're constant at 5v also.