John Smith wrote in message
...
Has anyone encountered fake TA7317P devices?

I've just replaced one in an Electro Voice 81PMX powered mixer but the
output relay still doesn't turn on.
Meter readings after replacement made no sense but an oscilloscope showed
high frequency oscillation at pin 6 of the replacement device which I
presume were confusing the meter.

Before anyone asks, the unit works perfectly when pin 6 is connected to
ground to turn the relay on and the output is only mV away from ground
with
no signal.

The schematic of the unit I'm trying to repair can be found by googling
ElectroVoice-61_81PMX pwrmix.pdf
And the TA7317P data sheet can be similarly found.

Before I replaced the chip I checked the voltage at all pins as follows.

1. -0.7
2. 0.7
3. 0.1
4. 0
5. -0.8
6. 76.5
7. 0
8. 0.6
9. 3.2

I concluded that The 0.7V at pin 2 must be coming from within the chip
because there is near 0V at the other end of the series resistor on that
pin.

After replacing the TA7317P, meter readings show only 1.8 V at pin 9.
There
is high (higher than my old 20MHz oscilloscope can show) frequency
oscillation at pin 6.

So I think that either the replacement TA7317P is duff or fake.

I'm going to fit some socket strip when I take the replacement out again.

I have three more TA7317P from the same source (I bought four).

I think I'll test the remaining devices with a power supply, a series
resistor to pin 9 and pin 4 grounded, and see what is on pin 9. Unless
anyone can suggests other tests to confirm whether or not the replacement
parts I bought really are TA7317P.

Thanks for any suggestions.

old guy














I was wrestling with a similar function C1237HA / uPC1237HA recently, as
falsely holding off the relays, replaced associated caps, replaced the
device , still the same