F0810NH thyristor

[John Woodgate]

The F0810NH thyristor seems to be a well-known unobtainable. Does anyone
know a suitable substitute.

It's a 'fast switching' device and it's used in an electric fence
controller. The gate firing pulse is very short and will not trigger a
TYN812, although it seems plenty big enough.

 

[Spehro Pefhany]

The F0810NH thyristor seems to be a well-known unobtainable. Does anyone
know a suitable substitute.

It's a 'fast switching' device and it's used in an electric fence
controller. The gate firing pulse is very short and will not trigger a
TYN812, although it seems plenty big enough.

I didn't see a data sheet for the F0810NH, at least not easily, so the
only thing I have to go on is a (correct?) 5.1A rating (and an
extortionate GBP18.50 price, beside the "out of stock" notice), and
that it has to be faster than the ST TYN812 (tgt = 2usec typical).

Based on (only) that perhaps you could look at the IR 10TTS08
which has a tgt of 800ns (typical).

http://www.irf.com/product-info/datasheets/data/10tts08.pdf

Hopefully you have a bit more information to compare. The IR parts are
cheap (about 1.50 US one-off) and in stock (in TO220) at Digikey.


Best regards,
Spehro Pefhany

 

[John Woodgate]

<[email protected]>) about 'F0810NH thyristor',

I didn't see a data sheet for the F0810NH, at least not easily, so the
only thing I have to go on is a (correct?) 5.1A rating (and an
extortionate GBP18.50 price, beside the "out of stock" notice), and
that it has to be faster than the ST TYN812 (tgt = 2usec typical).

I found a data sheet at: http://www.alldatasheet.com/

tgt is typically 2 us, but the TYN812 doesn't trigger; ITrms is 8 A and
VDRM is 800V. So the 10TTS08 is a good substitute.

Based on (only) that perhaps you could look at the IR 10TTS08 which has
a tgt of 800ns (typical).

http://www.irf.com/product-info/datasheets/data/10tts08.pdf

Hopefully you have a bit more information to compare. The IR parts are
cheap (about 1.50 US one-off) and in stock (in TO220) at Digikey.

Yes, I now have the data. Thank you very much. Maybe there is another
fault. So far, I've replaced a 7556, a PNP small-signal transistor and
the thyristor. This suggests to me a surge picked up by the fence, due
to a fairly distant lightning strike, and there are several diodes in
the circuit that might be damaged. The trigger pulse is reaching the
gate, but its duration may be very short indeed; since it happens only
about once every two seconds, it's a bit difficult to tell.

 

[Spehro Pefhany]

<[email protected]>) about 'F0810NH thyristor',


I found a data sheet at: http://www.alldatasheet.com/

tgt is typically 2 us, but the TYN812 doesn't trigger; ITrms is 8 A and
VDRM is 800V. So the 10TTS08 is a good substitute.

Yes, I now have the data. Thank you very much. Maybe there is another
fault. So far, I've replaced a 7556, a PNP small-signal transistor and
the thyristor. This suggests to me a surge picked up by the fence, due
to a fairly distant lightning strike, and there are several diodes in
the circuit that might be damaged. The trigger pulse is reaching the
gate, but its duration may be very short indeed; since it happens only
about once every two seconds, it's a bit difficult to tell.

Are you sure it's not the gate *current*? The TYN812 needs 15mA at
25°C, and the tgt is specified at 40mA.


Best regards,
Spehro Pefhany

 

[John Woodgate]

<[email protected]>) about 'F0810NH thyristor',

Are you sure it's not the gate *current*? The TYN812 needs 15mA at
25°C, and the tgt is specified at 40mA.

No, I'm not sure of much about this. The F0810NH IGT spec is min 10 mA,
max 25 mA. The gate is driven like this (use Courier font):

--+--|<|-- + V 6 V to 12 V
|
[1k]
+-[100nF]----+
| |
Gnd |
/c
+pulse in----| ZTX450
\e
|
[10R]
+-----> gate; source is grounded.
|
[1k]
|
Gnd

The charge dump from the 100 nF is presumably limited to about 1 A(!)
with a 12 V supply. I can look at the voltage across the 10 ohm with a
DB scope to see what current is actually flowing, if any.

 

[Spehro Pefhany]

<[email protected]>) about 'F0810NH thyristor',

Are you sure it's not the gate *current*? The TYN812 needs 15mA at
25°C, and the tgt is specified at 40mA.

No, I'm not sure of much about this. The F0810NH IGT spec is min 10 mA,
max 25 mA. The gate is driven like this (use Courier font):

--+--|<|-- + V 6 V to 12 V
|
[1k]
+-[100nF]----+
| |
Gnd |
/c
+pulse in----| ZTX450
\e
|
[10R]
+-----> gate; source is grounded.
|
[1k]
|
Gnd

The charge dump from the 100 nF is presumably limited to about 1 A(!)
with a 12 V supply. I can look at the voltage across the 10 ohm with a
DB scope to see what current is actually flowing, if any.

I wonder if the Zetex xistor or the 10R could be damaged. Maybe
measure the latter in-circuit and pull the ZTX450 and check hFE in
your multimeter? This would be more plausible if the SCR failed with
an open to the cathode, thus allowing current to flow back to the
drive circuit.


Best regards,
Spehro Pefhany

 

[John Woodgate]

<[email protected]>) about 'F0810NH thyristor',

I wonder if the Zetex xistor or the 10R could be damaged. Maybe measure
the latter in-circuit and pull the ZTX450 and check hFE in your
multimeter? This would be more plausible if the SCR failed with an
open to the cathode, thus allowing current to flow back to the drive
circuit.

I checked the transistor. But I found why the thyristor wasn't firing;
the gate wasn't in contact with its pad, which is very small. I should
learn to solder, or rather see, better. Now it fires, but at about 34 V
on the storage capacitor, and I suspect that should happen at about 200
V.

The plot thickens.

 

[legg]

<[email protected]>) about 'F0810NH thyristor',


I checked the transistor. But I found why the thyristor wasn't firing;
the gate wasn't in contact with its pad, which is very small. I should
learn to solder, or rather see, better. Now it fires, but at about 34 V
on the storage capacitor, and I suspect that should happen at about 200
V.

The plot thickens.

Limitations are also due to input pulse amplitude, as this is an
emitter-follower.

RL

 

[John Woodgate]

<[email protected]>) about 'F0810NH thyristor',

Limitations are also due to input pulse amplitude, as this is an
emitter-follower.

It was firing at 34 V because the 1 ohm resistor that senses the storage
capacitor charging current was open-circuit. It all works now.

Thanks to all for help and interest. I'm leaving this NG now, because I
can't spare the time to keep up, but I may be back one day.