Hi I have a Yamaha B2 amp I am goin through. I want to to test the health of these more than the usual Diode and Ohm reading. That is I want to use my
Leader LTC 905 curve tracer , attached file. I have a few of the same V-Fets from a Yamaha Organ amp 2 of the 2SJ26 and one 2SK76. I am feeding the outputs of the Leader to a Tektronix 2445a .
Not very familiar with either, and I was playing around with it yesterday and got some curves but they were very distorted and not useful. I feared I may have damaged the V-fets but doing the simple Diode/Ohm test they read the same as before I used the Leader 905.
SO How do I go about doing this with this equipment?
I tested the 2SJ26 , set the selector to Get, the Base Current/Gate voltage to .5ma and the Collector/Drain sweep voltage to 40 volts .
I had the Horizontal go the the CH 1 (x) on the Tek 2445 and the V go to the CH2 . but that is where I get stuck a bit. I turned the SEC/DIV knob all the way counterclockwise which I think engages the X/Y function.
But not sure what else to do. the signals are very jumpy and flashing.
Any help would be appreciated
Leader LTC 905 curve tracer , attached file. I have a few of the same V-Fets from a Yamaha Organ amp 2 of the 2SJ26 and one 2SK76. I am feeding the outputs of the Leader to a Tektronix 2445a .
Not very familiar with either, and I was playing around with it yesterday and got some curves but they were very distorted and not useful. I feared I may have damaged the V-fets but doing the simple Diode/Ohm test they read the same as before I used the Leader 905.
SO How do I go about doing this with this equipment?
I tested the 2SJ26 , set the selector to Get, the Base Current/Gate voltage to .5ma and the Collector/Drain sweep voltage to 40 volts .
I had the Horizontal go the the CH 1 (x) on the Tek 2445 and the V go to the CH2 . but that is where I get stuck a bit. I turned the SEC/DIV knob all the way counterclockwise which I think engages the X/Y function.
But not sure what else to do. the signals are very jumpy and flashing.
Any help would be appreciated
Nice tracer, it's all in 4.4. Very straightforward.
Get the specs of the 2SJ26 and 2SK76 to know the absolute maximum ratings.
Any fet is driven with voltage on the gate, and current flows between drain and source.
Try some cheap fets first to become familiar with the Leader. If they melt, you still have your jewelry save.
Get the specs of the 2SJ26 and 2SK76 to know the absolute maximum ratings.
Any fet is driven with voltage on the gate, and current flows between drain and source.
Try some cheap fets first to become familiar with the Leader. If they melt, you still have your jewelry save.
I did play with normal Power transistors to get some curves, it is pretty cool unit.
but V-Fets are another animal . Not sure if I am doing something wrong or if the V-fets are bad. I do not want to risk using the ones out of the B2 , the three I have I can spare I guess as I have no idea if they are good beyond the diode testing.
But doesn't V-Fets need a - Gate voltage? Or am I mistaken.
http://www.amplimos.it/images/2sj26_2sk76_data.jpg
One;y specs sheet I can find
Read section 4.4.4 of the leader manual . V-Fets are depletion type correct?
How do I know what polarity the voltage is coming out of the G,D,S going to the DUT?
Athanasios
30 years ago I build a manual tracer for (mainly J-) fets from scratch. Lots of fun!
Be careful with the V-fets, they're extremely rare and scarce. Hence exercising with cheap common j-fet's first.
All fets are driven with voltage on the gate.
J-fet's
N-channel: neg V on Gate, current from Drain to Source (Vd is pos, Vs is zero)
P-channel: pos V on gate, current from Source to Drain (Vd is neg, Vs is zero)
V-fet's: alike J-fet's
Mosfet's, depletion type:
Starts alike J-fet's, but may run into enhencement mode without problem.
Mosfet's, enhencement type:
N-channel: pos V on Gate, current from Drain to Source (Vd is pos, Vs is zero)
P-channel: neg V on gate, current from Source to Drain (Vd is neg, Vs is zero)
These family is more in correspondance with transistors (BJT: bipolar junction transistors), yet the difference remain: fet's are voltage driven, bjt's are current driven.
So, what I read from the datasheet is:
Vdg is | 150 | Vmax, Vds is best kept at equal value.
Vgs is | 40 | Vmax, this is the pinch off voltage (no current flows).
At Vgs is 0V, the maximum current flows, spec'd at... unreadable...
from the first graph it extends to some 6A.
Apply the proper polarities to the p- and n-ch (+ / - | value | )
Let the tracer run without a dut, measure the value of the gate (green) connector wrt the source (yellow) connector. If Vgs is neg, apply the 2SK, if pos the 2SJ.
Be careful with the V-fets, they're extremely rare and scarce. Hence exercising with cheap common j-fet's first.
All fets are driven with voltage on the gate.
J-fet's
N-channel: neg V on Gate, current from Drain to Source (Vd is pos, Vs is zero)
P-channel: pos V on gate, current from Source to Drain (Vd is neg, Vs is zero)
V-fet's: alike J-fet's
Mosfet's, depletion type:
Starts alike J-fet's, but may run into enhencement mode without problem.
Mosfet's, enhencement type:
N-channel: pos V on Gate, current from Drain to Source (Vd is pos, Vs is zero)
P-channel: neg V on gate, current from Source to Drain (Vd is neg, Vs is zero)
These family is more in correspondance with transistors (BJT: bipolar junction transistors), yet the difference remain: fet's are voltage driven, bjt's are current driven.
So, what I read from the datasheet is:
Vdg is | 150 | Vmax, Vds is best kept at equal value.
Vgs is | 40 | Vmax, this is the pinch off voltage (no current flows).
At Vgs is 0V, the maximum current flows, spec'd at... unreadable...
from the first graph it extends to some 6A.
Apply the proper polarities to the p- and n-ch (+ / - | value | )
Let the tracer run without a dut, measure the value of the gate (green) connector wrt the source (yellow) connector. If Vgs is neg, apply the 2SK, if pos the 2SJ.
Ok ' Ill set it up again and measure the voltage with no DUT.
The voltage Drain sweep knob on mine goes only to 100 , is that the Vdg spec you mention as 150?
Sorry its been a while since I remember what all those mean, Vgs, Vdc etc.
Athanasios
Voltage Drain sweep is interpreted as Vds (drain-source). Most measurements are referenced to the source for simplicity (hence my 'zero volt').
Consider Vdg is approx Vds, as the difference between G and S can become 0V, but at pinch off 40 volts 'away' from Vds. So Vdg is 40 volts 'larger' than the actual Vds which is applied by your tracer. I saw the max stepvoltage is 100V, so no worries here.
Vgs gate voltage referenced to source voltage
Vds drain ditto to ditto
Vdg drain ditto to gate voltage
It's always a relative voltage difference between two nodes.
Vdc however is Voltage from a 'direct current' source, say a battery, and Vac is from the outlet in your walls or from the load terminals of your main amp.
fet - bjt comparable nodes:
gate - base (voltage - current)
source - emitter (current - current)
drain - collector (ditto)
Long time ago scientist of those days did not yet know the real polarity of electons and made a gamble... but wrong. So the actual - physical current is not electrons (negative current), but the missing of electrons. Quiet a lot of exchanges and recombinations in those dies. Per second. Positive current called now is... 'holistic'!!! (Admitted: awful joke.)
Can't find the proper transcription of your signature.
Consider Vdg is approx Vds, as the difference between G and S can become 0V, but at pinch off 40 volts 'away' from Vds. So Vdg is 40 volts 'larger' than the actual Vds which is applied by your tracer. I saw the max stepvoltage is 100V, so no worries here.
Vgs gate voltage referenced to source voltage
Vds drain ditto to ditto
Vdg drain ditto to gate voltage
It's always a relative voltage difference between two nodes.
Vdc however is Voltage from a 'direct current' source, say a battery, and Vac is from the outlet in your walls or from the load terminals of your main amp.
fet - bjt comparable nodes:
gate - base (voltage - current)
source - emitter (current - current)
drain - collector (ditto)
Long time ago scientist of those days did not yet know the real polarity of electons and made a gamble... but wrong. So the actual - physical current is not electrons (negative current), but the missing of electrons. Quiet a lot of exchanges and recombinations in those dies. Per second. Positive current called now is... 'holistic'!!! (Admitted: awful joke.)
Can't find the proper transcription of your signature.
LOL, Posative = Holistic 😉
Ok So set Drain sweep to 80 or 100
And what about the setting for Gate voltage, I think its in steps .1,.2 or .5
Athanasios
Ok So set Drain sweep to 80 or 100
And what about the setting for Gate voltage, I think its in steps .1,.2 or .5
Athanasios
Yep, 100 is max for tracer & fet's.
Steps with .5 'cause it should run to 40... (80 steps, not sure how many will be taken) to reach max pinch off.
Have them on a moderate heat sink just in case.
Manere Domi
Steps with .5 'cause it should run to 40... (80 steps, not sure how many will be taken) to reach max pinch off.
Have them on a moderate heat sink just in case.
Manere Domi