Celebration

Location:Pontoppidans gate,Oslo,Norge

Success at last!

Finally! The hihat started working five minutes ago :-)

I did a lot of debugging on the circuit itself:
- touching up on all solder joints in the HH circuit
- checking every single path in the HH circuit (measuring conductivity)
- checking every solder joint through a magnifying lense
- measuring every resistor value
- checking that no electrolytic capacitor legs had broken off

Through all this I found a few suspicious solder joints, as well as created (and later discovered) a short circut. I also found three errors in the 9090 Hihat schematics, two of which does not matter and one that certainly do - however, the PCB is the correct one...

Anyway - I am not sure of any of this actually had much to do with the error. After taking a very close look at the various connectors involved in the HH, I discovered that a crimp in the HH tune connector was bent out of shape. It makes sense if this was the error, as it would affect both the closed and open hat. After replacing the crimp, I put the PCB back in the box and hooked up all cables - and whaddaya know, it works! :) Now, this was the last known HARDWARE error (excluding the rotation encoders that are just anoying, not really an error).

I also tried moving the headphone amp away from the circuit board to remove the noise (after all the previous supply line tricks failed to do so), however, this did NOT work. The noise in the stereo mix main out is not that bad though.

Now all I have to do is put everything back together again, and pray for everything to work once that is done :)


The bent crimp is seen through the right hole.

Output working

No idea why, but when I switched back to the old output stage, it worked perfectly fine. Some loose connections somewhere, bad solder joints or something maybe.

However, this means that untill the problem comes back again, I will leave the circuit board in the box. This also means that I won't replace C6 and C7 (changing from 1uF to 10uF would have improved the bass responce as the 1uF filters away anything below 140Hz, greatly impacting the bass drum when tapping the signal from the stereo mix jacks).

Now, if I could only get that Hihat working again. Tried swapping U42 for a new, known good opamp, but no luck.

Also, I will try moving the headphone amp away from the box to see if I can get rid of some noise.

New output mixer tested

Instead of unmounting the entire circuit board from the machinebeats, I decided to make a new output mixer on a prototype board. The output mixer consists of 7 components - four capacitors, two resistors and an TL072 opamp (+ the necessary connectors), which means that I only need to check a very limited amount of circuitry on the original board if the new one works.

Well, after 1 1/2 hours of building, and 10 seconds of testing, I conclude that it is indeed one of these 7 components or attached solder points that don't work as intended. I still have to remove the circuit board, but at least now I know where to look :-)

Cymbals fixed

The cymbals and hihat have never been loud enough, rather, they've been much quieter than the rest of the voices.

Today I searched through the archives at yahoo groups, and discovered that this is a well known problem that has a known fix. After replacing three resistors, the cymbals are much louder :)

However - the stupid silent hihat is back. Earlier this year I had problems with the hihat not triggering (or not making any sound at least). When I put a probe from my oscilloscope to either the collector of Q73 or pin 2 of U42, it worked, but when removing the probe it stopped working again. Somehow I managed to make it stay working, but now it is broken again. No idea why, this really frustrates me!

Also, the main output is way too low and the main output pot is working the wrong way, turning DOWN the sound when moving to the right. Strange.

Rudolph the Red-tinted synth

Right.

Through some huge conspiracy, my girlfriend Belle and my friend Knut managed to keep the fact that she has been seeing him behind my back a secret... Luckily though, the reason for the rende vouz was that Knut had a desireable little VA for sale :-)

To my great surprise and pleasure, I got this VA as a christmas present from my girlfriend! :-)

Thus, I can cross off one more synth from my need-to-get list. The updated list looks like this:

Oberheim OBXa (Jump! Need I say more?)
Oberheim matrix-12
Oberheim OB-8
Roland JP-8000
Roland JD-800
Roland JX-3P
Linn drum
Korg mono/poly
Moog memorymoog
Korg polysix
Korg ms-20
Moog minimoog
Roland Juno-6
Roland Juno-60
Roland sh-2
Roland vp-330
Roland vpc-350

Synths I now HAVE:
--
Clavia Nord Lead 2 (february 2012)
Korg Micro-Preset MP500
Roland Jupiter 8
Roland Juno 106
Roland JX-8P
Roland D-50
Roland TR-808
Roland MC-303
Sequential Circuits Prophet 5
Sequential circuits drumtraks (february 2012)
Yamaha DX7-IIs
Yamaha DX7-IID
Yamaha MU-10
Korg M1
Korg DS-10 (softsynth for Nintendo DS)
Crumar BitOne
Moog Little Phatty Australian Redback Edition
Casio MT-400
Casio VL-1
Novation KS-Rack
Oakley Sound Systems TB-3031
Introspectiv 9090 (with custom sequencer/controller by me)
Yusynth modular system (work in progress)

Modding the power wiring

Just finished rewiring the internal power lines tonight. I have had some serious problems with digital noise in the headphone stage. The headphone amp drew power from the same board as the midi controller and other digital electronics reside on. I have changed this so that it now draws power from the card closest to the transformator. Also, I have re-added a 5v voltage regulator to the controller board and added a separate ground wire. I hope this fixes some of my problems.

While having the lid off I've also added the missing 500ohm (or actually dual 1k in parallell) pot to BD Accent, so now I thing everything except for the too-low samples/output levels are fixed. Fingers crossed, will test tomorrow!