[jsteiger]

@trumanaudio, are the opamps you are using tested in something else so you are 100% sure they are solid? That is always the very first thing to rule out.

[trumanaudio]

I haven't tested them in something else. I am getting pre-built opamps tomorrow that I will try.

Just seems strange because both units Im working on are functioning in the same way, same issues, and with 4 different op-amp kits.

[jsteiger]

I haven't tested them in something else. I am getting pre-built opamps tomorrow that I will try.

Just seems strange because both units Im working on are functioning in the same way, same issues, and with 4 different op-amp kits.

There is likely some other issue then. Maybe something is wrong with your testing setup. Do these modules pass audio close to unity gain? I would reset the RV2 trimmers to half way. Do this by turning them repeatedly one way until you here a slight click coming from the trimmer acoustically. Then count 12.5 revolutions back the opposite way. This should be close to mid value. IIRC throughput signal will be .5dB or so low. If yours its drastically off from that then there are bigger issues at play here.

[trumanaudio]

Maybe I'm sending a -10dBV signal into the ML2 but monitoring the output of the ML2 at +4dBu? I dont know how I would correct this using my DAW (Logic 9)
I will be using legit testing equipment tomorrow.

they both come back in at -19dB when bypassed and -20dB when active, after I reset the trimmers. Ill do what I can to eliminate the opamps, sine wave, and monitoring setup tomorrow as possible problems.

If the monitoring is the problem, that still wouldnt account for the RV2 not adjusting the signal, correct?

The Fader works as it should and the last 2 clicks bring up the crazy harmonics that are happening. I think it is something with my monitoring setup

[jsteiger]

Or the opamps are problematic and/or maybe the DF's.

You should be send a balanced +4 signal in and expecting the same thing out.

[Blackdawg]

I emailed Jeff to ask this but its been a week with no reply.

Does anyone who has some of these know what the current draw is? Trying to build a mixer with TAC racks and hoping to power 3 with one PSU.

Thanks!

Monte

[jsteiger]

I emailed Jeff to ask this but its been a week with no reply.

Does anyone who has some of these know what the current draw is? Trying to build a mixer with TAC racks and hoping to power 3 with one PSU.

Thanks!

Monte

Sorry I must have missed the email. Things get hectic around here. I have not had a built unit here in ages but don't think they were much over 75mA per rail per unit.

[Blackdawg]

Sorry I must have missed the email. Things get hectic around here. I have not had a built unit here in ages but don't think they were much over 75mA per rail per unit.

Thanks Jeff!

No worries. I know you are super busy. So so SOOO stoked for the summing mixer. Photos on IG look amazing.

Thats good news for me! Cemal said as long as its around 100ma we can make it work. Thanks!

[Blackdawg]

Jeff,

Do these have pin 7 and 9 active? I just figured out that to do send and returns on my new 500 chassis that it uses pin 7 and 9 for the send and return. Hoping to use these as the faders for a mini 500 series console with this chassis, but if the ML2 doesn't us pin 7 and 9 then not sure what ill do.

[Blackdawg]

Dang I found Chugger's full build write up and was able to count the card..no 7 or 9 on the card.


Well....crap. So much for that idea.

[ninopelo29]

Hello,

I own two ML2 Rev B.3 units and one of them has an issue with the LED's for Bypass and Actuate: neither will light in either position of the respective switch.

I pulled the unit and PR4 is completely burned. It still reads 9 ohms in-circuit (PR3 is reading as 10.1 ohms), but it is clearly damaged.

I can replace the resistor, but I imagine there is another issue that is causing the current to be too high through that resistor.

Would you be able to provide a bit of direction of what could be wrong? I am able to read schematics and repair the unit if you see fit to send me one.

Thanks for your help.

[jsteiger]

Hello,

I own two ML2 Rev B.3 units and one of them has an issue with the LED's for Bypass and Actuate: neither will light in either position of the respective switch.

I pulled the unit and PR4 is completely burned. It still reads 9 ohms in-circuit (PR3 is reading as 10.1 ohms), but it is clearly damaged.

I can replace the resistor, but I imagine there is another issue that is causing the current to be too high through that resistor.

Would you be able to provide a bit of direction of what could be wrong? I am able to read schematics and repair the unit if you see fit to send me one.

Thanks for your help.

The LED circuit for this build is very simple. I would first think that you have them in backwards.

PR4 is the power damping R for A3, the receiver opamp. You have a build error on that opamp or it is not seated fully.
https://capi-gear.com/catalog/DOA_Install.php

[ninopelo29]

The LED circuit for this build is very simple. I would first think that you have them in backwards.

PR4 is the power damping R for A3, the receiver opamp. You have a build error on that opamp or it is not seated fully.

SOLVED: The LEDs were installed correctly, but one was making contact with one of the pads from the Bypass switch, so it was shorting out. I added shrink tubing to keep things copasetic. Something to check for anyone experiencing dead Bypass LED's.

The burned resistor (PR4) is a bit more mysterious. I replaced it with a similar 10 ohm resistor and measured the current with both a known-good Receiver amp and the "bad" one and read 0.02A on both.  I let it run for about 30 minutes with no issues.

Initially I thought the shorted LED might have drawn excessive current through PR4, but after taking the whole thing apart, I discovered that the LED's are connected before the damping resistor.  Current thru PR4 is only for Receiver +V.

I've had power issues recently that have caused some power supplies to get damaged. It's since been fixed by the power company, but maybe this was another casualty. Maybe the Receiver re-seat did the trick?

Not sure, but everything is good now.  Thanks, Jeff!

[Blackdawg]

Hell Jeff,

I have one unit calibrated, went smoothly.

2nd unit thought quite odd. The level is is almost 45dB different. It is lower, signal going out is -14.8dBFS(+10dBu) and return is -42.4dBFS.

Obviously the trimmer does not have enough in it to get it back up to where it needs to be. I've looked at all the resistors and they appear to be correct with the calibrated unit. No Caps are backwards. Is there somewhere I should look specifically?

These units are stock by the way, not modded.

Thanks!

Monte

[jsteiger]

Hi Monte

I would first rule out opamps, if they were built from kits.

[Blackdawg]

Hi Monte

I would first rule out opamps, if they were built from kits.

Hi Jeff,

Definitely not the op amps. I'm using two Rogue5s from LTLO. In fact to make sure I used the same two in the first unit that calibrated just fine.

Monte

[jsteiger]

Hi Jeff,

Definitely not the op amps. I'm using two Rogue5s from LTLO. In fact to make sure I used the same two in the first unit that calibrated just fine.

Monte

OK since you have a good module, inject a sine wave and measure AC voltage at the Test Points. Notate all of you readings on the good one. Then do the same on the bad one and report back where things go bad.

[Blackdawg]

OK since you have a good module, inject a sine wave and measure AC voltage at the Test Points. Notate all of you readings on the good one. Then do the same on the bad one and report back where things go bad.

               
Hi Jeff,

Here are my measurements.



                 Unit 1   Unit 2
TP +1   1.718   1.716
TP -1   1.728   1.729
TP 2   1.708   1.706
TP 3   3.043   3.042
TP 4   0.75   0.04
TP 5   0.748   0.04
TP 6   0.744   0.04
TP 7   0.742   0.04
TP 8   0.742   0.04
TP 9   1.775   0.078


Something g definitely off from TP4 onwards

[jsteiger]

               
Hi Jeff,

Here are my measurements.



                 Unit 1   Unit 2
TP +1   1.718   1.716
TP -1   1.728   1.729
TP 2   1.708   1.706
TP 3   3.043   3.042
TP 4   0.75   0.04
TP 5   0.748   0.04
TP 6   0.744   0.04
TP 7   0.742   0.04
TP 8   0.742   0.04
TP 9   1.775   0.078


Something g definitely off from TP4 onwards

The only things between  TP3 and TP4 are the output transformer T1, the stepped fader and the trim switch. I would make sure that the fader is set to 0 and then first probe at the T (top) of the fader connection.

[Blackdawg]

The only things between  TP3 and TP4 are the output transformer T1, the stepped fader and the trim switch. I would make sure that the fader is set to 0 and then first probe at the T (top) of the fader connection.

Think I figured it out.

the Elma switch wafer is backwards. The cable connections on the working unit face towards the bottom of the module. On the one that doesn't the wires are on the top.

I confirmed this by twisting the knob. While running -12dBFS to the unit, where 0db is marked my output measures -38.7dB. The -12dB mark on the faceplate shows -1.7dB.

To get it where I think I could trim it with the timmer I have to go to -24dB on the Faceplate. Then its at -13.1dB.

So will take the wafer off and swap it!

The Key on the switch is facing all of the green SMDs and should be facing the Black correct?



Edit:

That fixed it. My Elma wafer was backwards. easy fix!