Emu XL-7 & MP-7 User's Group

First of all I just joined and just got a hold of a MP7. It had the following problems: burnt 'L7' part on mainboard, and the SPDIF jitter-ed like no tomorrow.

After some research and trial and error I was able to solve and fix the unit.

Here is what I did so that other might repair their units.

1. 'L7' labeled part seems to be an inductor. i have no idea what micro henry it requires and what Amp rating. I instead just used a 300k 1/4 watt resistor in it's place. Well the burnt area messed up the smt solder pads so I had to solder jumpers following the trace. It turns out the pads go to +5v and Leg #3 on the Master pot. The higher you go in resistor value the lower the overall main boost. So 300k - 370k is good. Anything below 220k and you get saturated distortion.

**This how ever made the Master Volume no longer useful, the unit only works with the master knob all the way up (clockwise). If anyone ever finds the spec of the part location 'L7' please inform. 

2. On my unit it turns out E-mu PCB engineers goofed up, they forgot to ground the SPDIF outer ring on the RCA jack. I simply soldered a jumper from the bottom spdif jack (tested with a voltmeter) and jumpered/solder to the bottom midi jacks, the metal bracket). That fixed it real quick, no more dam jittering.

Overall I am really impressed on the OS 2.0 and the sound of the unit. It has meat as far as sound. I am however not impressed by the poor e-mu team that designed the main board layout. The pcb traces could of been thicker and not so 'auto routed'

To get around the headphone problem since my unit only works at full blast, I bought a cheapo China DAC Headphone metal box. Behringer Mini Headphone Amp would be good too.

It is definitely an inductor, I tried a 220R resistor in it's place and yup it was clipping. 300k works best. On my particular command station the Volume knob no longer works. It does not do a smooth volume gain, only full or you turn it down a bit and you lose sound like off.

I just got a 10uH inductor to try it out and it did not fix the volume problem or it did not clip but it did introduce a whine sound so I put back the 300k resistor instead, that gives no whine.

Oh well I give up.
Better then nothing, I am using an external headphone amp as a solution when I want to work in private with no booming sound.

I did pimp out my MP7, I changed LED's to Blue, Orange, Yellow, and white. I also replaced all the tactile switches. 

I might sell this one on ebay maybe because now that I know how to fix these I scored on (2) more command stations really cheap: an xl7 and one more Mp7. The volume works on both of those. I have no idea how to measure the inductor on those. There is no marking either.

--- In xl7@yahoogroups.com, Alwyn <zardac@...> wrote:
>
> >
> > 1. 'L7' labeled part seems to be an inductor. i have no idea what micro
> > henry it requires and what Amp rating. I instead just used a 300k 1/4 watt
> > resistor in it's place. Well the burnt area messed up the smt solder pads
> > so I had to solder jumpers following the trace. It turns out the pads go to
> > +5v and Leg #3 on the Master pot. The higher you go in resistor value the
> > lower the overall main boost. So 300k - 370k is good. Anything below 220k
> > and you get saturated distortion.
> >
> 
> Is L7 the same sort of PCB footprint as a SMT resistor or capacitor?  If
> its one of them it might be a ferrite bead.  they have some similarities to
> an inductor for it's filtering, but they don't have the coils to build up
> the magnetic force. If it is a ferrite bead, then a 100R resistor will
> behave in a similar way for audio frequency signals.
> 
> If L7 is indeed meant to be a ferrite, then the clipping might suggest
> something else isn;t working?
>