ABFAB Builders Club - building The eSCAPEd Goat Mk I

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#41
naah

I didn't meant to knock down your sand castle ........ probably more to accentuate something on which we obviously agree on - it seems we forgot way more than we know today ......... sort of

pretty much worthy , when it's hard to invent something really new, is to un-dust old tricks and try them in new environment , often in spite of common beliefs ......

so , go for it , I'm always rooting for Dodossess :clown: , good chance for moi to learn something (so having more to forget later :rofl: )

btw. - if that's not danger for you to answer - what screen name you had , prior to 2013 ? (judging by your writings , you were member .......... )**

** you can PM that
 
#42
Zen Mod said:
naah

I didn't meant to knock down your sand castle ........ probably more to accentuate something on which we obviously agree on - it seems we forgot way more than we know today ......... sort of

pretty much worthy , when it's hard to invent something really new, is to un-dust old tricks and try them in new environment , often in spite of common beliefs ......

so , go for it , I'm always rooting for Dodossess :clown: , good chance for moi to learn something (so having more to forget later :rofl: )

btw. - if that's not danger for you to answer - what screen name you had , prior to 2013 ? (judging by your writings , you were member .......... )**

** you can PM that
Click to expand...

Jacco still remembers me. Hahahaha
 
#46
Wakoo Dodossesss
 

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#48
After biasing up and checking dc offset.
I have removed trimpots and replaced with the appropriate jfet drain resistors

Circuit now looks like this.

I'll see if I can successfully remove gate resistors next
 

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#50
Zen Mod said:
why should you ?

I see them (always) as integral part of mosfet

except if you going to make exceptionally fast iteration of Lightsaber ..... but , hey , Yoda was good even with most dreky one .......

:devilr:
Click to expand...

You are right, it will add absolutely nothing to the amp, but I am curious to see what can be achieved, or at least determine at which point the devices start oscillating.

I've started with 1k gate resistors and will start lowering the value to determine where they become unstable. It's really just an exercise in curiosity.
 
#51
Hi.
Intresting project and very Nice PCB.

I tried about the same with 2SJ55 & 2SK175 a week ago.
But I kept the current limiters in F5 cirquit, in case of...

May be that was the reason that bias suddenly dropped from 1 amp to 0.04 amp.
I decided to sleep on it for a while, then we'll se...

Figge.
 
#53
Finally put a sine and square wave through it.
Getting a nice clean sine wave but getting overshoot with a little ringing (but not oscillation) on 10kHz square wave.

This was predicted in simulation, I just chose to ignore/disbelieve it (dumb bastard). Hahahaha


20160104_224546.jpg




20160104_224820.jpg


According to simulation I can lower the overshoot by lowering the resistance but to get rid of it completely I need to go the other way (obviously) and increase it to around 5k.

I'll try lowering the resistance first since that doesn't require soldering anything and will be quick.
 
#59
Before I start soldering new resistors, is it possible a linear regulated lab power supply could potentially cause overshoot issues with 10kHz square wave (measurements were done using lab power supply)

I might try the CRC supply to confirm result
 
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