828 MK II LEDs crap out..

[NoFi Audio]

Well this is a new one on me.

MOTU 828 MKII, firmware V1.0

When I run audio through it (a submix from DAW gets assigned to MAIN OUT) all is well.
The minute I un-mute the stereo drum tracks I can see the level and activity LEDs quickly "fluttering" ... think of looking at an old digital clock and turning your head quickly. Except I don't have to turn my head. If I add a couple more tracks, this causes all the LEDS blink on and off... not just the mentioned ones, but also the sample rate LED... any LED that are lit will blink on and off in unison. If mute enough tracks in the DAW, the LEDS respond normally, and correctly. If I re-enable the muted tracks, the LEDs go bonkers again.

More LEDs, more current draw... points to a weak PSU?

What say y'all?

[mikehalloran]

There is a backlight that lights up the display. It and the power supply are known troublemakers when the unit gets hot and/or old enough. Sometimes it’s a cable or solder joint IIRC. Mine is so far not displaying this (pardon the pun) — yet? I am aware of the possibility down the road.

There are many threads here and Gearspace that discuss this and where to find parts (none are proprietary). Google is your friend—don’t limit the search to the mkII. Many old units have had this issue. The newest 828mkII is nearly 18 years old (I bought mine on clearance after the mk3 was announced).

[NoFi Audio]

Thanks for the reply Mike.

I think when I posted that the problem was just occuring. And I wasn't sure why, although I mentioned maybe a PSU issue.

Well I eneded up taking it apart and noticed on the display subassembly PCB that there was a 470µf cap, and it didn't look healthy. I just happened to have a few of those kicking around, so I swapped one in. That seems to have made the situation much better. When I'm driving a lot fo tracks though it and the LED count is climbing the LEDs still have that quick flicker effect... but they don't entirely shut off... I'm guessing that it's time to recap the power supply section. I have a Digikey account so I don't see getting them being a big issue.

S~

[HCMarkus]

Well I eneded up taking it apart and noticed on the display subassembly PCB that there was a 470µf cap, and it didn't look healthy. I just happened to have a few of those kicking around, so I swapped one in.

I love responses like this... serious DIY wherewithal! Well done NoFi,

[NoFi Audio]

Well I eneded up taking it apart and noticed on the display subassembly PCB that there was a 470µf cap, and it didn't look healthy. I just happened to have a few of those kicking around, so I swapped one in.

I love responses like this... serious DIY wherewithal! Well done NoFi,

Thanks. I'll be the last guy to give up on my old gear just because its "old"...LOL. This particular 828 MKII (#3) has been rock solid since it went under the knife. I did re and re a bunch of the caps including the PS section. This one is the only one I have that doesn't have that mic pre crackle (I don't really use those for much anyways...)

I'll be tackling another 828 MKII (#2) that went black screen on me mid session. I think the 3.3V rail is dead... I got nothing on the Test Point. Regulators on order.

[henris42]

You can pull the old backlight out as described in many documents. The suitable replacement is a 3mm (not 5mm) "superbright" led, which will actually fit the light guide. There are unused pads there, connect led cathode to "K", and bend it so its shines directly to the backlight plastic lightguide.

The anode side must be run to the big pad via a resistor. I put a 39ohm 1/8w one in mine. (It depends on the led). The anode side of the pad is not connected to anywhere....

[NoFi Audio]

My issue isn't with that display, it's with the LED meters to the right of that. For each channel that is active, there is a green (single) LED that shows you there is audio traffic. The Input meters over top of those light up whenever I'm recording or playing back from the PC since the Input to the 828 is via the channel strip Direct Outs. So, whether its live or memorex there is always activity on the inputs. Thats where my blinking is coming from, not the GAIN/MIX display