Fader problems and V-Pots

[anyhorizon]

I recently acquired a 166 Mhz D8B running v3.0 & the Service Pack.

I've read some of the threads re: replacing faulty motor drive IC's that seems to work sometimes but not always. I reloaded the OS and the SP just in case. The data cable is not stock, but it works on my other D8B. As far as cleaning the faders, great photos of the process are available in this database, but I'm wondering why no one seems to like a product like Caig FaderLube 5%, which is supposedly made for cleaning and lubing faders. The V-Pots are also really filthy, so I'm looking for a cleaning procedure for them as well. Are they composite wipers or optical encoders?

Any suggestions are welcomed. I didn't want to invest in a fader bank (or two) to find out there is another reason for the -7.5dB deficit.

I would like to know the answer to the question you asked about the fader lube as well, I was told by mackie tech support that the faders are motorized so they dont recommend using it on the d8b, they said fader lube was made for faders with no motors like analog faders but then again I was told by the store manager of a music store (no names mentioned) who ownes a d8b for years to use deoxit fader f5!!!???

I answered the question in my post immediately above yours.

Peter

[anyhorizon]

BTW, do not use Deoxit. It is fabulous for connectors that are static. It is far from this on moving wipers.

Peter

[anyhorizon]

BTW, "Modify Levels" is found under the "Edit" menu or by selecting Alt-M. It is a function that allows level changes to automation or overall to selected channels. When saved, that's how it stays, either in a startup session or other session, hence my request that you delete all startup sessions and deactivate "Load last session at power up".

Peter

[Dreamsequence]

Thanks Peter.

[synthjoe]

I'd advise against using any liquid for either. V-pots are the regular wiper type, not optical. The best way I've found to recondition them was to take a good length of string, loop around the knob on the pot and pull back and forth a few times. This works the pot a few 10 turns in a very short time, plus the rotating forces might help dirt flying away from the wiper inside the pot, which - while preserves the 'silkiness' - usually cleans wipers fairly well. If you take the PCB's out, you'll also find two small holes on each side of these pots, which is a possibility to try some compressed air through.

Hole on the V-pot

IMG_2126a.JPG (Array KiB) Viewed 2099 times

As far as the motor faders are concerned, I've been in contact with both Mackie and Alps. Neither of them gave the exact details of the resistant layer and other materials used, or adivsed to use any product for cleaning. Therefore I'd be reluctant to use anything but compressed air on them. For that you'll need to desolder and disassemble the faders, which is quite a tedious work and you'll have to be extremely careful with the microscopic 'fingers' of the wiper - but well worth the effort. I think I've sent some pictures to Peter earlier (or maybe in another post), let me know if you want me to send them again.

[Dreamsequence]

Thanks. I've viewed the fader disassembly pics; excellent resource. As far as the rotary faders (trims, V-Pots), in the regular D8B Database someone volunteered using a clean IPA (Isopropyl Alcohol) solution, like 97% pure, and gently wicking some down the control shaft (after removing the knob). It should not be damaging nor leave any residue, although he reported the 'silky' feel diminished for a time. I considered your solution previously, as the way we used to clean analog pots on 'old' consoles was to simply rotate the knobs until they self-cleaned (mostly high quality composition pots). I wonder if a little IPA coupled with some rapid 'spinning' of the control would better flush the debris to the outside, away from the wiper and film surface, where the IPA would evaporate.

In any event, I will try your suggestion. Nothing ventured...

[synthjoe]

I would not try IPA, which - even if not doing any damage as a liquid - will definitively alter the feel of the pot, which I personally would avoid at any price. The rotation was greatly sufficient in the case of my pots - they were jumping all over the place on my board when I got it, but after this treatment nobody working with the board ever compained to me. The good thing with the V-pot is that the travel is not limited, i.e. endless, so it is very easy to perform many turns in one pull of the string. Worked really well for my board, as I've said...

[Dreamsequence]

Thanks Joe. I found an old drive belt from a turntable that should be super-slick for this.

Care to hazard a guess about the two fader boards that won't calibrate correctly (-7.5dB down)? They are correct on the monitor display, but physically they come up short, whether calibrating or sending a command (All Faders to Unity). This still has me baffled, and I'm waiting for a used/rebuilt fader PCB to try (one is definitely failed, so I have one that's dead and one that reads low on both of the first group ribbon cables 1-8 and 9-16).

[Crash]

This fader issue is a stumper. Hopefully Joe will think of something we have not. Have you tried an OS re-install? I am curious if you might have something corrupt in the OS causing these oddities. Trashing the startup file is another one to try, in fact maybe that one first and if no improvement then try the OS. Since things appear to be correct on the GUI, then likely my suggestions will be the equivalent of pissing into the wind but just for the sake of conversation, thought worth mentioning.

[synthjoe]

Sorry guys, have been thinking about it already, but I don't really have a firm idea. I'd check the output of the +5V regulator on the fader board (U3 under the 3rd fader near the ribbon connector) and pin7 of U904 (which should show +2.5V as a result of the voltage reference set by R933 and R934). If none of these show an anomaly (what I expect to be the case), then U908 must be outputting the wrong voltage, and the only thing to check there would be pin1 and pin9, which should be +5V and 0V (GND), respectively - and I dont see how there could be a problem with those, unless a dry or failed solder joint. Make sure you measure the lead of the chip, as there might be a microscopic fault in the solder joint - which even though not visible, will prevent current flowing to the chip. Also, simply touching such a faulty joint might cure temporarily the problem, so make sure to do a through check. If unsure, a quick (and precise!) blow with a heat gun to melt the solder might solve the problem permanently.

Not much more than that - I don't know if it helps... No idea how the U908 (AD8803) chip could be checked in circuit.

I found an old drive belt from a turntable that should be super-slick for this.

That's a nice find, even though a plain old fasioned hemp string, or even a plastic one, or a flexible wire (with plastic isolation, so as not to damage the knob) should do. I reckon that the belt will be too elastic and maybe weak for the task - but you'll let us know, I'm sure!