Author: Ronny Morris

10593Re: [01v96] Re: 01V96 dust free fader replacement problem
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•	dcharette
Sep 17 5:58 PM
Hi Ronny,

Thanks for the great tips regarding your experience with the faders.

I did finally have success, so, for others that may attempt this fader swap out,here's some tips to make it work.

Before swapping out any faders, a quick check of the motor drive circuitry will help save some time in case there happens to be some bad ones.

The fader motor uses differential drive to move it. There's a BJT H-bridge(2 NPNs and 2 PNPs) which need to all be functional in order for the fader to move. I have now seen multiple instances of the original 2SB1181 PNP transistors going bad in a rather unusual way that isn't so common with BJTs. Typically, when a BJT fails, the collector to emitter usually burns and and causes a direct short, and subsequently act as if it's fully ON or a little worse than full saturation. In the case of the 01V96 PNPs, the base to collector junction opens up and the transistor stops operating and in this sense, it's helpful because it prevents excessive current from burning the fader motor.

So, if you notice during fader calibration, any of the faders going all the way up, but not coming back down, this is a symptom of a bad PNP in the motor driver circuit.

These transistors are all surface mounted on the reverse side of the PCB from where the faders are mounted. They're easy to see once you open the console and flip up the surface of the console.  The groups of transistors are all along the very bottom edge of the fader PCB. To gain access to them, it's necessary to disconnect all the ribbon cables connecting to the main PCB, and power supply from the upper part of the console. Once you do that, the upper section can be removed and laid face down so it's easier to work on the fader board. There is a clear plastic acetate plastic over the bottom side of the fader PCB that needs to be removed to access the transistors. They're in groups of four, in the same general vicinity as the corresponding faders they drive, so locating the particular faulty transistor is a matter of just finding the group transistors near the fader in question, and then measuring the junctions with a multimeter in diode test mode. With the faulty PNPs, you'll find the base-emitter junction normal, and the base collector junction opened up. When measuring it still in circuit, the diode drop will be something like 1.5V instead of the normal 0.6 or so. While the PCB is on the bench, it's a good idea just to go through them all and make sure all the junctions measure like a good BJT should. I haven't yet seen an NPN fail here, it's always the PNPs that go. When I replace them, I don't use the factory originals, I use a Fairchild MJD45H11. These seem to be a bit more robust and less susceptible to damage.

Once all the motor drivers are seemingly good, I then proceed to the following: 

1)  I lubricated the drive belt slot with a very thin viscosity silicon oil. Just a small drop of the oil placed on the curved guide track right next to the belt drive gear on the motor. I manually moved the fader slider back and forth to ensure a smooth travel.

2)  I insert a small screwdriver just enough into the fader handle slot to lift up the dust proofing plastic and then I run the screwdriver back and forth a little just to bend the plastic up a little so that it presents a little less friction on the fader handle. It's important to not insert anything sharp and be careful not to go in to far and scratch the fader substrate. I perform the same on all the faders.

3)  Leave the fader knobs off, until the movement calibration is completed. The knobs just add additional load to the fader motors and make the movement calibration procedure less likely to complete. It's necessary though to put them back on for the position section of the calibration for precise alignment.

4)  Make sure the console surface is as flat as possible, and the surface isn't lifted up or on the side. Flat, in the normal way the console would be operated seems to present the least load on the fader motors.

5)  As an additional help, I left the console outside in direct sunlight for an hour or so just to heat up the faders a little to provide extra freedom on the movement.

Now, during the calibration procedure, there is a selection for calibrating the fader movement  or position. It's the movement section that is the problematic part. So, to save time, just select fader movement instead of both.

Once the procedure starts, the fader sliders will attempt to all zero out at the bottom of their travel. The next part is that all the fader handles will start to very slowly rise up in a small pulses. If you see any faders lagging behind, then the procedure won't complete correctly, so shut the console off and try it again.

I managed to get to a point where almost all the faders were moving freely, but I had a couple still kind of sticky. So, I use a long ruler wide enough to span the distance between fader one and the master, and then I sorta followed the faders along in the procedure, using a slight pressure on the ruler to make sure all the fader handles moved together but not too much pressure to actually push the faders. It's only necessary to apply pressure to the ones that lag behind. It's a little tricky learning the timing and knowing what direction is coming in the procedure, but after a few times, I picked up on it and managed to get the procedure to complete. 

Once the movement section is complete, then the position section can be done. And as you said, you need to get right up on the fader positions to insure you're getting the numbers to jive with the software, so that when using the studio manager, the numbers will match closer.

After that, the calibration data is stored and the console boots to normal operation mode. And the faders all seem to move quickly and firmly without any sticky ones.

Thanks again for the tips, and I hope this might be of help to others that might be trying to install the same dust free Alps faders in their 01V96.  It's definitely NOT the same as swapping them out of an LS9 or M7CL... those consoles are way less finicky with the fader replacements.

Good luck!
Dan