jh 636

In the late 70's, over half of the records in Billboard's Top 200 were recorded and/or mixed using MCI equipment.

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jh 636

Postby redpulse » Mon Oct 05, 2009 5:11 am

Hello
I have a problem,
the left master fader is sounding ok but the right side is not the same volyme and when im put the volyme up i get a distortion (crackel)
what can it be
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Re: jh 636

Postby brianroth » Mon Oct 05, 2009 11:21 pm

Is the problem only in the monitoring, or does it "print to tape"? How many dB low is the right channel? Does the right channel seem OK in the low frequency (bass) range, or is it thin sounding as well as being low level?

The most likely culprits will be a capacitor or an opamp.

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Re: jh 636

Postby redpulse » Thu Mar 10, 2011 7:10 pm

Hello again,
the problem is not solved yet!
but the studio is up and running.
The problem is in Cont.Mon LR and and a bit less in Studiomonitor output.
its about 6db low in the right side and its in the low freq the high freq is ok


where should i begin to investigate?
In the monitor module?
i bought a used monitor module and the problem is still there

second problem the solo funktion dosent work.

what i can understand from the manual is that when u press solo it comes in the right speaker?


On the right side of monitor module u got two slots for aux modules but they does not work no power in the desk

and the last qestion in the back/floor of the console (left side standing behind) there is no semiconductor?

thx for waiting so long :P
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Re: jh 636

Postby brianroth » Sat Mar 12, 2011 2:59 am

Since you have the same monitoring problems with the substitute monitor module, I suspect the problem is in the monitor faders themselves due to many years of "wear and tear". Try reducing the gain of your monitor amplifiers (so you don't destroy your loudspeakers!) and push the monitor faders all the way to the top to see if the mis-balance of levels goes away. If the levels ARE "even" at with the faders at maximum, then the problem is definitely in the faders. They can be opened and cleaned, which MIGHT improve the situation.

If none of the solo switches function, there is likely a failure in the monitor module.

I am not quite understanding your questions about the aux modules, and the "no semiconductor" at the rear of the console.

Best,

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Re: jh 636

Postby redpulse » Thu Mar 17, 2011 4:34 pm

hello again the problem was not in the faders. :cry:
can the problem be under the console there are 4 motherboards can the problem be there?
is the signal directly out from inputmodule to monitor module or does it pass some other things first,
and from the monitor module where is the signal going.



aux modules (the 2 slots in right side)there is no power to the modules

and the semicunductor
http://www.google.se/imgres?imgurl=http ... 29,r:9,s:0

it looks like this and is located on the hatch to the 4 motherbords
'

thx for all advices
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Re: jh 636

Postby brianroth » Thu Mar 17, 2011 8:36 pm

Looking back at your earlier comments regarding the level mis-match in the monitor section, I noticed you mentioned the low frequencies were lacking in the faulty channel. That is almost certainly a defective electrolytic capacitor. However, it is a bit odd you have the same problem with a substitute monitor module. Are the levels and frequency response correct from the 2-Mix stereo output?

The circuit boards in the "belly pan" (which is on a long hinge attached to the bottom of the desk) are digital cards for the JH-50 automation system. In addition, there are multiple LM317 regulators (and several other types) attached to the rear of that belly pan which provide power for the automation. That should not have any effect on the level error you are experiencing.

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Re: jh 636

Postby brianroth » Thu Mar 17, 2011 9:36 pm

I forgot to ask you about the Aux module positions. What modules are you attempting to use in those slots? They were intended for "specialized" optional modules, and to be honest, I've never seen any JH-636 desk with any modules in those slots....just blank filler panels.

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Re: jh 636

Postby redpulse » Fri Mar 18, 2011 9:09 am

hello
when i patched monitors to 2 mix out the problem dissapered maby a littel less low freq in the right side

aux modules.

i have these special aux modules do you also use mci if so i could send you two of them as thx for helping me
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Re: jh 636

Postby brianroth » Fri Mar 18, 2011 11:09 am

A loss in low frequencies is almost always caused by old/defective electrolytic capacitors somewhere in the signal path. In really bad cases, even the mid and high frequencies are attenuated in level, but not as severely as low frequencies.

JH-636 desks are well-known to have failing capacitors after these many years after manufacturing. I STRONGLY suggest you re-cap the master and monitor modules before chasing other possible problems. Use low ESR electrolytics with a 105 degree C temperature rating. I have had good results with capacitors from Nichicon and Panasonic.

I am curious about the optional Aux modules you have. What functions do they provide? After I examined the schematics for the motherboards, I see there should be +/- 18 VDC audio power supplied to those two slots, but the various audio inputs/outputs terminate onto a number of Molex connectors which are marked as "Optional for special products use".

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Re: jh 636

Postby qdkj21 » Fri Dec 02, 2011 11:48 pm

That is weird. I bought a Toft ATB 32 on the stunning 636. I could have got the actual MCI for less really than I've in the Toft thinking about patch coves, stand, and so on. But when We considered its age cheap this uses Twenty Amplifiers for that power supply, not to mention you will likely need about One ton of air conditioning devoted only for it and that there is absolutely no way in order to ever get the automation operating, We went with the Toft. I'm glad Used to do.
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