TA7317P output protection

[John Smith]

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

 

[N_Cook]

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

 

[Tim Schwartz]

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

Good Morning,

I've usually seen these IC's in NAD receivers. I've certainly had
issues with both the capacitors and resistors going bad, even though
they seem to measure OK in circuit. I'm going from my memory (bad idea)
but 150K, 180K, 220K 15K, 18K and 22K stick in my mind.

Best of luck,
Tim Schwartz
Bristol Electronics

 

[N_Cook]

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

For a Panasonic SA313 use of TA7317P, p1 to p9
-.7,0,0,0,-.7,1.3,0,1.3,3.1 V dc

 

[Franc Zabkar]

The schematic of the unit I'm trying to repair can be found by googling ...

It would have been nice for you to have made it easy for us ...

ElectroVoice-61_81PMX pwrmix.pdf
http://www.eserviceinfo.com/download.php?fileid=46360
http://elektrotanya.com/electro-voice_61_81pmx_sm.pdf/download.html

And the TA7317P data sheet can be similarly found.
http://www.portes.cz/data/integrovane_obvody/TA7317P.pdf

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.

AISI, the maximum voltage at this point would be equivalent to the
voltage drop across 4 forward biased diodes. Simlarly, the voltage
drop at pin 5 should be equal to a single forward biased diode.

If the voltage drop is taken to be 0.8V, then this is consistent with
both measurements.

What voltage do you see at pin 5 of the replacement? Do pins 1,2,3 and
7 of the replacement part now show the expected voltages?

Does pin 9's series resistor (R372) measure correctly (22K)?

- Franc Zabkar

 

[Franc Zabkar]

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

6. 76.5
9. 3.2

AISI, the voltage across R372 (22K) must be 73.3V.

Therefore its power dissipation would be ...

73.3 ^ 2 / 22K = 244mW

However, the parts list rates it for 1/5W.

- Franc Zabkar

 

[John Smith]

AISI, the voltage across R372 (22K) must be 73.3V.

Therefore its power dissipation would be ...

73.3 ^ 2 / 22K = 244mW

However, the parts list rates it for 1/5W.

Thanks but this is one of the first things I checked before replacing the
device.
R372 does measure 22K.
I actually cut one of its legs to test it out of circuit because it's a pain
to get the board off the heatsink (all output FETs have to be unsoldered) I
then soldered its leg together again.

I spotted another potential design error.
Compare the TA7317 Vcc max with what I measured. This only affects pin 6.

I'll find out more when I get back to it on Monday.

old guy

 

[John Smith]

It would have been nice for you to have made it easy for us ...

Sorry, I didn't think a quick cut & paste into Google was hard.

I'll be able to answer your other questions on Monday.

old guy
....

 

[John Smith]

....

For a Panasonic SA313 use of TA7317P, p1 to p9
-.7,0,0,0,-.7,1.3,0,1.3,3.1 V dc

Useful information. Thanks.

 

[Mark Zacharias]

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

At a glance, 0.6 volts at pin 8 is wrong - capacitor C312 should charge up
through R364.

If it is held low, the thing will never turn on. The voltage at pin 9 looks
like may be low - R372 could be way high in value.

Mark Z.

 

[Franc Zabkar]

Sorry, I didn't think a quick cut & paste into Google was hard.

No harder than a quick cut & paste into a newsreader ...

BTW, I notice that the voltage rating of the filter capacitors (C401 /
C402) on the amp's positive and negative supplies is 80V. Are you sure
the AC mains voltage selector is in the correct position?

- Franc Zabkar

 

[John Smith]

At a glance, 0.6 volts at pin 8 is wrong - capacitor C312 should charge up
through R364.

I'll check R364/C312 tomorrow.
R362 measured 22K out of circuit. I might replace it anyway.

 

[John Smith]

No harder than a quick cut & paste into a newsreader ...

BTW, I notice that the voltage rating of the filter capacitors (C401 /
C402) on the amp's positive and negative supplies is 80V. Are you sure
the AC mains voltage selector is in the correct position?

I'll check it on Monday. I'm in a 115V 60Hz area.

 

[Franc Zabkar]

At a glance, 0.6 volts at pin 8 is wrong - capacitor C312 should charge up
through R364.

If it is held low, the thing will never turn on.

AISI, pin #8 should go low if either pin #1 or pin #7 are high, or if
either pin #2 or pin #3 are outside the range of -0.7V to +0.7V.

If there is a fault condition, one or more of Q6, Q18, and Q19 will be
on. This means that Q10 will be off and Q11 will be on. This in turn
means that Q12 and Q13 will be off and the relay will be open.

- Franc Zabkar

 

[John Smith]

It took me a little longer than expected to get back to this but here's the
story so far.

The mains voltage selector is set correctly for the area I'm working in. So
+75V and -75V rails seem to be correct.

I removed the replacement TA7317P and fitted socket strip.

With no chip fitted R372 = 21.6K and R364 = 220K.

All other resistance checks made sense and no adjacent socket pins are
shoreted together.

I then connected pin 6 to pin 4 of the socket to turn the relay on and also
connected four 1N4148 dioded in series from pin 9 to pin 4 of the socket.

With the power on, here are the voltage readings I now get. Note that no
chip is fitted, just the diodes mentioned above.

1. -15V
2. 8.8mV
3. 0.17V
4. 0V
5. -75V
6. 0V
7. 0V
8. 2.67V
9. 2.7V

The voltage on C314 is varying between -42 and -49V, presumably due to
ripple. I'll scope it tomorrow. The voltage at pin 1 of the socket is also
varying a bit too.

Thanks for any further suggestions.

My next move will be to test the remaining TA7317P I bought, with a 22K
resistor to pin 9 and pin 4 grounded with no other pins connected and see
what I get on pin 9.

Old guy

 

[Franc Zabkar]

The mains voltage selector is set correctly for the area I'm working in. So
+75V and -75V rails seem to be correct.

That means that quite a few components are operating close to spec or
slightly in excess of spec.

I removed the replacement TA7317P and fitted socket strip.

With the power on, here are the voltage readings I now get. Note that no
chip is fitted, just the diodes mentioned above.

1. -15V
2. 8.8mV
3. 0.17V
4. 0V
5. -75V
6. 0V
7. 0V
8. 2.67V
9. 2.7V

The voltage on C314 is varying between -42 and -49V, presumably due to
ripple. I'll scope it tomorrow. The voltage at pin 1 of the socket is also
varying a bit too.

I'd change the capacitor, but I don't believe that level of ripple
would be enough to influence the circuit.

AISI, pin #1 senses the current in the 0.33 ohm load sharing/sensing
resistors R33, R34, R35, and R36. It would require about 2A to turn on
Q324. Q325 would then turn on after a delay determined by C311 and
R357, sending pin #1 of the TA7317P high and causing the relay to
open.

My next move will be to test the remaining TA7317P I bought, with a 22K
resistor to pin 9 and pin 4 grounded with no other pins connected and see
what I get on pin 9.

I suspect that your replacement parts may have a string of 3 diodes on
pin #9. If the voltage at pin #5 is -0.6V, then this would tend to
confirm it.

I notice that the datasheet identifies each diode as a Q rather than a
D, so I suspect that the original part uses diode-connected
transistors rather than actual diodes. Perhaps your replacement part
uses the latter?

- Franc Zabkar

 

[Franc Zabkar]

Has anyone encountered fake TA7317P devices?

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.

I believe pin #3 is being used to provide thermal overload protection.
That said, I can't see how it could possibly work, even with the
"correct" supply voltage at pin #9.

Here is the relevant section of the circuit:

pin #3
o
|
pin #9 o-|-- R366, 15K -- TH301 --|-- R367, 3K --o pin #4, Ground
| |
|-- R365, 180K ----------|


TH301 is an NTC thermistor, Panasonic p/n ERT-D2FHL503S:
http://www.panasonic.com/industrial/components/pdf/arg0000ce2.pdf

It's resistance at 25C is 50K.

AISI, in order for the thermal overload to activate, pin #3 would have
to exceed 0.6V (the B-E voltage of Q15 in the datasheet). However,
even if we allow the resistance of TH301 to fall to 0, then the
voltage at pin #3 is still only 0.57V, assuming a voltage of 3.2V at
pin #9. At 1.8V, the voltage at pin #3 would be only 0.32V.

C316, R371 and R374 appear to provide a dethump delay at switch-on.

- Franc Zabkar

 

[John Smith]

.....

I believe pin #3 is being used to provide thermal overload protection.
That said, I can't see how it could possibly work, even with the
"correct" supply voltage at pin #9.

Here is the relevant section of the circuit:

pin #3
o
|
pin #9 o-|-- R366, 15K -- TH301 --|-- R367, 3K --o pin #4, Ground
| |
|-- R365, 180K ----------|


TH301 is an NTC thermistor, Panasonic p/n ERT-D2FHL503S:
http://www.panasonic.com/industrial/components/pdf/arg0000ce2.pdf

It's resistance at 25C is 50K.

AISI, in order for the thermal overload to activate, pin #3 would have
to exceed 0.6V (the B-E voltage of Q15 in the datasheet). However,
even if we allow the resistance of TH301 to fall to 0, then the
voltage at pin #3 is still only 0.57V, assuming a voltage of 3.2V at
pin #9. At 1.8V, the voltage at pin #3 would be only 0.32V.

C316, R371 and R374 appear to provide a dethump delay at switch-on.

Thanks Franc

I haven't checked your analysis but in my time as a circuit designer (not
saying how many years or what I worked on) I encountered many situations
where pleasing management was the most important thing.

So a thermal overload test may have been done on one unit and it may well
have passed.
And then it may have been assumed that...

The unit has a very big heat sink, actually I don't recall many that were
bigger.
So I'm not too concerned if thermal overload doesn't work.
No one is going to be injured by a FET going pop, well except the speaker if
the relay doesn't turn off, so my risk assessment is that it doesn't matter
as long as I can get the relay to turn on when the output isn't stuck at a
rail.

If I can't do that then I won't get paid for the repair

Old guy

 

[Franc Zabkar]

The unit has a very big heat sink, actually I don't recall many that were
bigger.
So I'm not too concerned if thermal overload doesn't work.
No one is going to be injured by a FET going pop, well except the speaker if
the relay doesn't turn off, so my risk assessment is that it doesn't matter
as long as I can get the relay to turn on when the output isn't stuck at a
rail.

I pointed it out because it looked wrong. In fact the design seems to
have too many oddities.

That said, the 4 protection inputs look OK to me, so there does appear
to be a problem with the IC.

There is one thing you might like to try. The TA7317P datasheet
specifies a maximum current of 5mA into pin #9. The circuit as it
stands draws about 3mA through R372. Perhaps you could add a 47K
resistor in parallel with R372. If the voltage on pin #9 rises, then
this would point to an internal regulation problem.

- Franc Zabkar

 

[John Smith]

Thanks Franc,

Here are the results of todays experiments.

I took another of the TA7317P I bought and carefully bent most pins so that
when I put it in the socket only pins 4,5 and 9 are in the socket.

Here's what I get:

Socket pin V, Chip pin V.

1 -16.5, -1.04
2 0.01, -1.98
3 0.01, -0.66
4 0, 0
5 -2.39 -2.39
6 76.6 -2.38
7 0, -1.29
8 0.3 0.122
9 0.3 0.3

Something tells me that this can't be a TA7317P despite its markings.

Maybe the manufacturer got it reversed in the package.
I think it should be safe to try one backwards.

Old guy