Gallien Krueger 250ML overdrive.. (J406/J412???)

sm3000 · 16th May 2009, 07:08 AM

Hello everyone,
I'm starting a project about building a pedal that would capture the overdrive of a Gallien Krueger 250ML. As you can see in this thread http://www.diystompboxes.com/smfforu...?topic=76364.0 I still haven't been able to find a substitute for the dual n-channel jfet (8 pin) J406 or J412.

Any ideas?

Enzo · 16th May 2009, 01:52 PM

I didn't feel like joining the other board to post, but here...

That GK00008 or whatever on your ICs looks to me like a GK house number. SO while chips from that era, like the TL604 I see, including dual FETs might have fallen to obsolescence, it is possible GK still has them. You might contact Gallien Kruger and ask if they could supply them.

Probably best not to talk a lot about wanting to build a copy of their circuit though.

You might suggest you needed one for repair and ask if there was a sub for it or perhaps a workaround - like glueing two JFETs together. The pinout would be helpful. And then offhand, "or could you sell me a few?"

And you mentioned a M8841 or something printed on it. Note the photo someone posted of some other IC also had an 88 number. That just looks like a date code to me - late 1988.

sm3000 · 19th May 2009, 02:11 PM

I'll definitely get in touch with them and see if I'm able to find some of those JFETs or at least an equivalent. Thanks for the idea!
Here's the pinout of that double n-channel jfet:
N/C-------N/C
S----------G
D----------D
G----------S

Is there anyone able to help me out with the layout? I've never drawn one before..

16th May 2009, 07:08 AM	#1
sm3000 diyAudio Member Join Date: May 2009	Gallien Krueger 250ML overdrive.. (J406/J412???) Hello everyone, I'm starting a project about building a pedal that would capture the overdrive of a Gallien Krueger 250ML. As you can see in this thread http://www.diystompboxes.com/smfforu...?topic=76364.0 I still haven't been able to find a substitute for the dual n-channel jfet (8 pin) J406 or J412. Any ideas?

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16th May 2009, 01:52 PM	#2
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	I didn't feel like joining the other board to post, but here... That GK00008 or whatever on your ICs looks to me like a GK house number. SO while chips from that era, like the TL604 I see, including dual FETs might have fallen to obsolescence, it is possible GK still has them. You might contact Gallien Kruger and ask if they could supply them. Probably best not to talk a lot about wanting to build a copy of their circuit though. You might suggest you needed one for repair and ask if there was a sub for it or perhaps a workaround - like glueing two JFETs together. The pinout would be helpful. And then offhand, "or could you sell me a few?" And you mentioned a M8841 or something printed on it. Note the photo someone posted of some other IC also had an 88 number. That just looks like a date code to me - late 1988.

19th May 2009, 02:11 PM	#3
sm3000 diyAudio Member Join Date: May 2009	I'll definitely get in touch with them and see if I'm able to find some of those JFETs or at least an equivalent. Thanks for the idea! Here's the pinout of that double n-channel jfet: N/C-------N/C S----------G D----------D G----------S Is there anyone able to help me out with the layout? I've never drawn one before..

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