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Faulty Mosfet?
Faulty Mosfet?
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Old 15th August 2017, 10:38 PM   #11
nigelwright7557 is offline nigelwright7557  United Kingdom
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ECX10N20
ECX20N20
ECX10P20
ECX20P20

Not sure if they are the same package.
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Old 15th August 2017, 10:48 PM   #12
DiyGazza is offline DiyGazza  United Kingdom
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Great, Thank you, A quick read and it appears the ECF10N20 is a suitable replacement for the 2SK135, and the ECF10P20 is the complimentary part, Not a bad price either.
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Old 15th August 2017, 11:24 PM   #13
JMFahey is offline JMFahey  Argentina
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Not sure about your bare finger touching *very* high impedance gates test or what you intend to prove with that.

Try them in this simple gig which is designed for matching but as a side job will tell you bias voltage to pass about 11-14mA .
That alone confirms whether you have a functional MosFet or a blob of molten silicon, whether itīs a Lateral or Vertical MosFet, etc.

Click the image to open in full size.

Here device is properly polarized, biased and connected; open gate or noise injection into an open gate mean little, if anything at all.

So measure what you have today and post results.
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Old 16th August 2017, 09:28 PM   #14
DiyGazza is offline DiyGazza  United Kingdom
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Hi, Thanks for your reply, I am unable to open your attachment / Image so can't comment at the moment.

What I can tell you is that I powered up the module today on a 15v - 0 - 15v supply with the suspect Transistor in place, and the amp seems to work just fine, the only thing I did notice is a slight overshoot on the Rising Edges of a 1khz Square Wave, will have to wait and see how it compares to the other module once re - capped and the thermal compound replaced under the Mosfets, and of course on it's correct power supply.
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Old 16th August 2017, 10:18 PM   #15
KatieandDad is offline KatieandDad  United Kingdom
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I've two of these that are faulty if anyone wants them for parts.
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Old 18th August 2017, 02:36 PM   #16
DiyGazza is offline DiyGazza  United Kingdom
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Quote:
Originally Posted by KatieandDad View Post
I've two of these that are faulty if anyone wants them for parts.
Pm'd you.
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Old 18th August 2017, 04:43 PM   #17
DiyGazza is offline DiyGazza  United Kingdom
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Quote:
Originally Posted by JMFahey View Post

Try them in this simple gig which is designed for matching but as a side job will tell you bias voltage to pass about 11-14mA .
That alone confirms whether you have a functional MosFet or a blob of molten silicon, whether itīs a Lateral or Vertical MosFet, etc.
R1 is a 1k Pot?
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Old 29th August 2017, 08:55 AM   #18
JMFahey is offline JMFahey  Argentina
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Posting here what I answered to your PM

Quote:
Re: Mosfet Matcher
Quote:
Originally Posted by DiyGazza
Hi There
Thank you for posting the circuit for your MosFet Matcher, although I am still a little unclear on a few points.

R1 - Is this a 1k Pot?
No, R1 is a fixed 1k resistor.
Quote:
Quote:
What is the Gate connected to?
That is Ground Symbol.
Quote:
Quote:
Red Probe to "Ground", and Black Probe to "Measure", When you say "Ground, do you mean the 0v of the + / - 15v supplies.
Yes.
To have + and - voltage, it is measured relative to ground.
There are no "single" voltages on their own, they are always measured relative to some point, in this case Ground.
Quote:
Quote:
Measure, what exactly are we measuring here, the Current 11 - 14ma, or the Typical value of around 3.5 v.
Whe are measuring the Gate-to-Source voltage, also called Bias Voltage, needed to pass current around 1mA through the power MosFet.
Exact value will vary depending on individual transistor, and is exactly why we build and use this matcher in the first place: we get a batch of transistors, **they will be all different** because thatīs a reality of life, we measure and label all, I suggest you attach a small sticky label to each, writing the value found, which is usually around 3.5V in VFets (IRFPxxx), around 0.6V in Lateral Fets (2SK/2SJxxx) , etc. and when building/repairing an amplifier you choose those with as-close-as-possible Vgs ensuring they will pass basically same current and share load equally.
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Old 29th August 2017, 11:40 AM   #19
DiyGazza is offline DiyGazza  United Kingdom
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Thank you for explaining that.
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Old 29th August 2017, 02:03 PM   #20
KatieandDad is offline KatieandDad  United Kingdom
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