Troubleshooting and Fixing a Quantum Board

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audio school
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Joined: Sun Oct 29, 2006 11:31 am

Quantum interest

Post by jacobehrmann » Tue Jul 27, 2010 6:30 am

Hello everybody. Its been some years since I chimed in about Quantums, but Im getting back into it. Ive got three now. A series 22 broadcast, a black face Qm-168 (with the monitor expansion and direct outs), and a Quad 8 colored QM-8A. (also with direct outs, patch points and an another unknown molex- S3) I have no original docs on the either the black-face QM-168 or the QM-8A.

I did get a manual and schematics for the Series 22, and I am happy to scan and post if there is any interest.

I very much appreciate the docs posted here, but my QM-168 has some significant differences (options I guess) than the model in the scanned docs- like always on phantom power (28v, not 48) and balanced line in's. (Pin 3 hot by the way)

Does anyone out there have any more documents on these or any other Quantums? Any and all info would be much appreciated. I find that I am mixing and matching information from different sources/Quantums and starting to get a better understanding of my specific quantums.

Thanks again for all of the previous posts. After many, many years of not learning the required basics of electronics, I am finally getting around to learning what I should have learned 15 years ago. Certain mysteries about why some things work well and others dont are beginning to disappear and Im excited. I want to fully understand my boards, get them all up to snuff and then cascade them into one another so I can have their individual sounds at my finger tips. Best of the three worlds/decades, if you will.

Thanks again for any help, Jacob

audio school graduate
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Joined: Wed Jul 12, 2006 4:01 pm
Location: los angeles

selling a quantum qm 8..check it out.

Post by vcode » Thu Feb 12, 2015 11:33 pm

Jim Williams
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Joined: Sat Jun 03, 2006 8:19 am
Location: beautiful Carlsbad, CA

Post by Jim Williams » Sat Feb 14, 2015 9:27 am

I rebuilt a QM-8 for Hyde Street Studios in SF a few years back. It got a new external power supply and cable. All the opamps are National LME series. All the el caps in the signal path are gone, permanently. It's now direct coupled, no caps from line in to mix out. I used quality film caps in the EQ and moved a couple of frequencies. I installed soft-white LED's into the meters. The four output groups were redone lowering the gain and using MJE output transistors. All the caps are gone there too.

The mic pre's got a gain pot added for a variable 20~60 db gain range. The gain switch was reconfigured for 48 volt phantom power. The grounding buss was thickened up with 14 awg wire soaked in silver solder.

The console is dead quiet, punchy and clear. Original input transformers were kept. They use it on a roll-around cart to move it between rooms.
Jim Williams
Audio Upgrades

gimme a little kick & snare
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Joined: Wed Oct 21, 2009 8:56 pm

Re: Troubleshooting and Fixing a Quantum Board

Post by creaturesleeper » Sun Oct 01, 2017 7:09 pm

I am currently diving into the QM128 I've had for years (not really working) I couldnt get it to reliably pass a signal so am pulling the boards one at a time and wiring up to go through seperately. Its working out so far. I love this console and its a big project for me. I usually build and work on tube gear so its a challenge.

gimme a little kick & snare
Posts: 83
Joined: Wed Oct 21, 2009 8:56 pm

Re: Troubleshooting and Fixing a Quantum Board

Post by creaturesleeper » Sun Oct 01, 2017 7:10 pm

I know this thread is ancient but I have the technical manual for the 128

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