hifonics output driverboard help


2011-09-03 11:43 am
im only getting output on 1 of the 4 banks. Ive already replaced both 21844s chips and all of the d2 transistors. the arrows on the picture are the pins that are supposed to have output to the banks. the green arrow is the only one with signal on it.


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Yes, the two low-side banks, if the rectifiers are in the circuit.

Read the 9v section and supply the high-side with B+ to see if you get high side.

I've damaged those 21844s installing them. They're easy to damage. The failures have been all sorts... low impedance on the input dragging the signal down, high-side no output (even with applied 9v) but the low side was OK...
The 21844 is an easy chip to diagnose with outputs installed. There are 3 main questions to ask yourself while troubleshooting these. Pay attention to your scope assuming you are using one.
1- Do you have an input signal on pin 1? If yes go to 2, if no then back up to the 211/311
2- Do you have the low drive on pin 6? If yes go to 3, if no chip is bad (this will ride the negative rail)
3- Do you have the high drive on pin 12? If yes the chip is good and move to output resistors, no chip is bad.

As Perry said these chips are finicky! All the way to ESD damage. I hang my wrist strap on my rework stations just for these chips.