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Gallien Krueger 100 MPL

Started by onebaldbloke, March 07, 2021, 11:09:21 PM

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onebaldbloke

Hi,
I've recently acquired a GK 100 MPL, which is not working as it should (I have had two in the past, so I have a good idea of what "working properly" means :-) ).

Any schematics out there?

Cheers,
Bob.
Guitarist, songwriter etc - Skyhooks, The Angels, Rose Tattoo.

willpirkle

#1
This is the complete service manual, scanned from my paper version that I got from Bob Gallien back in the 90's -- it has all of the gory details including the digital programming. It is almost 80MB in length and won't fit as an upload, so I added a link from my website below. I have no plan to remove the link, but an admin may want to store it in a more permanent manner on an SSGA server for future use.

This is a digitally controlled analog product; e.g. it uses vactrols for channel switching and other routing. It is also a treasure-trove of interesting circuits (log amp for the compressor, use of the LMC835 to implement the GK active EQ filters (in addition to the graphic EQ), noise reduction ckt, even an R/2R DAC).

The schematic pages were repeated within the documents, so there are two sets of them (didn't have time to go back and remove them).

http://willpirkle.com/special/GK_MPL100_COMPLETE.pdf

Enjoy!

Will


onebaldbloke

Quote from: willpirkle on March 08, 2021, 08:06:55 AM
This is the complete service manual, scanned from my paper version that I got from Bob Gallien back in the 90's -- it has all of the gory details including the digital programming. It is almost 80MB in length and won't fit as an upload, so I added a link from my website below. I have no plan to remove the link, but an admin may want to store it in a more permanent manner on an SSGA server for future use.

This is a digitally controlled analog product; e.g. it uses vactrols for channel switching and other routing. It is also a treasure-trove of interesting circuits (log amp for the compressor, use of the LMC835 to implement the GK active EQ filters (in addition to the graphic EQ), noise reduction ckt, even an R/2R DAC).

The schematic pages were repeated within the documents, so there are two sets of them (didn't have time to go back and remove them).

Enjoy!

Will

Kind Sir!!

Now I need to find someone in Australia crazy enough to look at it!  :dbtu:

Cheers,
Bob.
Guitarist, songwriter etc - Skyhooks, The Angels, Rose Tattoo.

Jazz P Bass

That is one heck of of a circuit description write up!!!
You have not noted what is wrong with the unit but a good tech should be able to narrow it down with that excellent info.

onebaldbloke

Quote from: Jazz P Bass on March 10, 2021, 12:32:28 AM
That is one heck of of a circuit description write up!!!
You have not noted what is wrong with the unit but a good tech should be able to narrow it down with that excellent info.

I don't know what's technically wrong, only that the sound is miles from where it should be. I have messed around with the internal bias trim pots, and that has helped marginally, but has not corrected the main problems, hence the need for a proper tech. :-)
Guitarist, songwriter etc - Skyhooks, The Angels, Rose Tattoo.