POWER FUSES ON i100 and i200 HARDWARE MANUFACTURED BEFORE 1998 TROUBLESHOOTING > i100 DEVICE >
This note is ONLY relevant to i200 and i100 products manufactured prior to 1998.
If the instruNet devices are plugged in while power is applied, it is possible for some pins in the connector to make contact while other do not (for several milliseconds). This can cause power to be applied incorrectly, which can lead to a short circuit, which can cause an internal fuse to blow. To check for a blown fuse, measure the voltages at the -12V, +12V, and +5V screw terminals on the instruNet 100. For example, to measure the +5V voltage, place one voltmeter lead on the "+5V" screw terminal and the other lead on the "GND" screw terminal. If the voltage is off by more than ±1V, a fuse is probably blown in either the instruNet 100 (if manufactured before 8/97 and are pre Rev 3) or the controller card (if manufactured before 1/98). These fuses (they are actually resistors) can be replaced by the instruNet supplier, or by the end user (this requires de-soldering / soldering small chip resistors). For extra fuses, please contact your supplier -- they are available free of charge. To check if a fuse is blown, measure its resistance with a dvm. The iNet-100's manufactured after 7/97 and the iNet-200's manufactured after 1/98 contain resettable fuses, that automatically close after they blow; and they therefore never require replacing.
R9 1, 3
R8 1, 3
R14 2, 3
R15 2, 3
11206 chip resistor, 1/4Watt, .39ohms, 5% 21206 chip resistor, 1/8Watt, 5.1ohms, 5% 3Currently manufactured units use resettable fuses in these positions, and they never need replacing.
The easiest way to fix a fuse is to tack a leaded resistor (or resettable fuse) on top (i.e. in parallel) of a surface mount resistor (i.e. fuse) that blew (e.g. tack a 5ohm leaded 1/4W resistor onto iNet-200 R9 chip resistor, in parallel). This "tacking" is easily done with a regular soldering iron by placing a bead of solder on one side of the surface mount part, let it cool, place a bead of solder onto the other side, let it cool, heat one side, attach the resistor lead, let it cool, head the other side, attach the other resistor lead, and then let that cool. Make sure you keep one side of the surface mount resistor cool, else the part might lift from the board. Also, instead of tacking down a leaded resistor in parallel, one could tack down a resettable fuse instead. These look like disk capacitors, yet are not. They are fuses that automatically reset after the power is taken off (i.e. they never need replacing). This are available for free, from your instruNet supplier (Part #RXE-017 for iNet-100 ±12V and Part #RXE-065 for iNet-100 +5V and iNet-200 ±12V).