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Re: MCI JH 618, Rise from the dead!

PostPosted: Mon Feb 26, 2018 11:53 am
by Ryebot
As requested, some pictures:


Before... (old bolster upholstery.)


The lower motherboard in the master section looks like it had some bad dental work done by the previous owner(s) but it beeped out fine!


in progress...


Some of the mic pres have this type of mod. Jim Williams, is this similar to what you've described?


Family portrait :-) JH 110 C from 1984 in decent shape! It will be the next project...

I re-capped re-socketed and re-chipped the Master and Monitor Module- with the exception of the tantalums. The distortion is still in the 2Mix output, but not when patched from Stereo Out to Aux in. Could it be the tantalum caps? The master fader? Or perhaps one of the J111s?

Jim, I'm moments away from sending my other Master module to you to work your magic, and then I might have both flavors available...

Thanks to all for your interest, advice and encouragement!



Re: MCI JH 618, Rise from the dead!

PostPosted: Mon Feb 26, 2018 12:25 pm
by Jim Williams
That mic pre card only has the output el cap replaced with an Elma? and a Wima poly film bypass cap.
The 5532/4 opamps are still there with the same messy biasing scheme. I change all of that. Only the LM394 transistor front end is retained. It ends up being a total redesign with different resistors, re-wired bias from the opamp outputs and the psu caps are changed and moved.

Re: MCI JH 618, Rise from the dead!

PostPosted: Sun Mar 04, 2018 5:32 am
by Sirbastian
Thanks for the pictures, looks great!!