CAD Maxcon

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CAD Maxcon

Postby vineyardgray » Mon Feb 24, 2014 7:41 pm

No section for "other" consoles, so I'm posting here. :)

Considering picking up one of these boards for a "parts" price. Mostly because it's in parts. A common comment is these boards are supposed to run hot. Not sure if I'm too concerned about that. Another common issue is the scratchy pots, which I'm hoping a can of deoxit would rectify. This could be a real showstopper if the pots are just cheap and are worn to the point of un-cleanable. Replacing 32 channels of pots would be a real PITA.

There's sweet little about these consoles on the net, no schematics, no operation manuals, no nothing. There's a Facebook users group, but not much information. Anybody ever use one?

Regards,

MR'
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Re: CAD Maxcon

Postby wado1942 » Sat Mar 01, 2014 12:12 pm

I haven't used one, but there's things you can do about the heat. I know a guy who had a 1/2 ton air conditioner just for his Neve, like its own self-contained room. Heat is the enemy of most electronics. Keeping them cool means longer life (especially for electrolytic capacitors) and less noise. I'm not saying you need an air conditioner for the board, but something to allow the heat to dissipate is good. You can cut a few small vents and maybe add a low-speed DC fan to provide some airflow. For every 10 degrees C you reduce the temperature, you cut noise by about 6dB and potentially double the life of the electronics. If it's a somewhat sealed cabinet (and looks like it is) then it's very easy to make a difference because right now it has virtually no way to dissipate heat.

As for the pots, problematic parts need to be changed. DeOxIt does worlds of wonder, but if they wear easily then you're only left with one choice. If you think that sucks, try changing over 120 capacitors.
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Re: CAD Maxcon

Postby vineyardgray » Tue Mar 25, 2014 7:41 pm

Hi Wado1942,

So I went ahead and picked up the board. You've made some good points there, and you're right, the modules are basically in a big steel tub, so airflow is lousy.

Here's what I've found out about the scratchy pots: the board is designed with each section servo coupled to the next. Which means, that as far as capacitors go, there are none in the signal path (except the obligatory phantom blocking caps). This is a good thing, because it means way way less caps to replace! But this benefit is offset because the constant DC across the potentiometers cause the pots to get scratchy (especially where the servos are out of adjustment).

Now, I don't profess to understand what exactly servo coupling is or how to properly adjust it for minimal garbage while pot twisting. This is just what I have gleaned from the 'net.

I spent some time going module to module (I haven't yet picked up the "tub", but I've got all the modules) making detailed notes and taking pictures of things that look weird and potential faults. So far I have noticed 6 missing PMI SSM2404, but otherwise, just a couple broken caps.

Regards,

MR
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Re: CAD Maxcon

Postby wado1942 » Thu Mar 27, 2014 9:46 am

Now, I don't profess to understand what exactly servo coupling is or how to properly adjust it for minimal garbage while pot twisting. This is just what I have gleaned from the 'net.


It just means that instead of using caps to decouple the op-amp in one part of the circuit from another, they just let the DC bias go right to the next op-amp. It means fewer components, but as you said, there's DC running through everything. If there's any dirt or wear at all in a pot, it momentarily/partially interrupts the DC, which causes audible fluctuations. Dirt & wear is a lot less noticeable with decoupled pots because there isn't a constant, steady current flowing through it to CREATE something to be noticed. Any way, good luck in your project. I hope that board serves you well. I need to upgrade pretty soon, but I have so many other expenses. :roll:
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Re: CAD Maxcon

Postby vineyardgray » Fri Apr 04, 2014 5:52 pm

Ah, I see. There is some mumbo-jumbo on the net about adjusting the servos, which I presume means there is a way to make sure the passing bias voltage is correct for the next stage. Since there are a bunch of trimmers on the pcb's I'm guessing that's what they're meant for. Although without a proper service manual (searching the net has only yielded a very rudimentary user guide - on Facebook of all places) I guess the only way to do it would be to check the data sheet for all IC's in sequence. ?

I know what you mean about too many expenses. I probably shouldn't have bought this thing - projects are piling up whilst I screw around with it - I'm hoping it's all worthwhile. :)
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