Hello all,
I purchased an Agilent E3620A power supply from our favorite auction site recently. I'm looking for the schematic diagram of the voltmeter/ammeter display assembly for this unit. I've found the schematic for the power supply in a few spots on the web (including this site!)....but I haven't found a schematic for the voltmeter/ammeter assembly. Does anyone know where I might find this?
The unit works fine with the exception of the voltmeter display. The voltmeter works fine from 0V up to 19.99V, but once it switches to the higher range above 20.0V it goes wonky. Once it goes above 20.0V, the voltmeter fluctuates between the low range and high range, and flashes back and forth. Once the voltage is above ~21.5V or so the high range finally locks and the it works okay. But right around 20.0V - 21.0V the display is not usable. The power supply output is actually fine, no oscillations or anything weird if you look at it on a scope or if you connect a multimeter to the output. When lowering the voltage from high voltage (say 25V) downward, the range switch takes place right at 18V like it is supposed to and works good. But the range switch going up has a problem.
I suspect that the TC14433 voltmeter IC is faulty, but I'd like to find a schematic of the display section to verify this. I have found sample schematics for that IC on the Microchip website, but all of the sample schematics I've found do not have the autoranging feature.
Anyone know where I might find a schematic?