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Old 18th April 2012, 12:43 PM   #12211
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you can always use an LM317 / LM337 set up as 400mA current limiters for the initial testing -- once you get the amp to this level it's easy to remove the current limiters and keep climbing up to the bias you want. Make sure to heat sink the regulators.

It's always helpful to make a note of which direction of the trimpot moves the bias current up or down.

And with the F5, patience in adjusting the bias is its own reward.
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Old 18th April 2012, 02:07 PM   #12212
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better check one by one Jfet,Mosfet by using matching circuit to confirm material work in order.
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Old 18th April 2012, 02:15 PM   #12213
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Speaking of matching: I ordered some matching transistors from another forum member.

I received:
2x IRFP9240 - 4,034
2x IRFP240 - 4,111

I am surprised to see this, I would think to minimize distortion you want to match N-channel with P-channel, no??
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Old 18th April 2012, 02:58 PM   #12214
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also can check working V,I of them when you change with each value voltage of matchinh circuit.
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Old 18th April 2012, 03:17 PM   #12215
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Default fully check

Quote:
Originally Posted by studiostevus View Post
Speaking of matching: I ordered some matching transistors from another forum member.

I received:
2x IRFP9240 - 4,034
2x IRFP240 - 4,111

I am surprised to see this, I would think to minimize distortion you want to match N-channel with P-channel, no??
check 02 jfet Ids --will decide Vgs of IRF
check 02 IRF Ids bothside when Vgs changing also temp changing ..
and IRFP9240 seem too high Amp no need can change by other,because circuit only run whith 2,6A ..cut off by protection circuit.
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Old 18th April 2012, 03:53 PM   #12216
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Just in case you missed this.

Mighty Zen F5 bias setting doc
Attached Files
File Type: doc Bias Setting.doc (21.5 KB, 127 views)
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Old 18th April 2012, 04:19 PM   #12217
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Quote:
Originally Posted by studiostevus View Post
surprised to see this, match N-channel with P-channel
IRFP240 and IRFP9240 are not complementary devices.
These were likely matched at a drain current of ~250mA, at a little above 1A they'd have close to identical Vgs.

The "matched" part refers to Vgs difference between the two IRFP240, or between an IRFP9240 and the second one.
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Old 19th April 2012, 01:22 AM   #12218
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Default check all

Because you want to make high quality amp.I suggess to you need check all part for build up in your amp ( resistance, jfet,mosfet,power.) with changing of V,I,Temp (should be fix mosfet on heatsink actually testing for try with some degree of temp).everything can happend.
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Old 19th April 2012, 10:36 AM   #12219
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Quote:
Originally Posted by wengtech View Post
primary 0-220-250
secondary 0-36-55 0-36-55
addition 18-0-18

shown on my toroidal transformer.
You could use 36V and 55V outputs and get 19V, providing there is sufficient current from them.
That is just these two (pairs of) wires, nothing else.
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Old 19th April 2012, 10:36 AM   #12220
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Thanks for all your advice.

What still confuses me is the bulb tester. I know it functions as a current limiter. But what exactly am i testing with it?
And what should i be looking at when i power up with the tester (aside from smoke, fire & explosions) ?
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