Project PRO2021 - A Pro-One keyboard synth

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Troubleshooter
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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Troubleshooter » Sat May 02, 2020 7:28 am

Hi everybody.

I have enjoyed my 2021 for a long time but today I tried to use the MIDI input and all it does is give me a clicking sound on note on/off meggages.
The midi in LED is working and I checked the polarity of the 2pole connection between turbo cpu and board A.
Any ideas what could be my problem?

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Sat May 02, 2020 1:42 pm

Hey buddy! Long time no see!

Stupid question to get out of the way first: the MIDI in worked before ie. this isn't the first time you are testing it?

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Troubleshooter » Mon May 04, 2020 5:59 am

Hi Devin, long time indeed, I have been using cv-gate all the time so yes it is the first time.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Mon May 04, 2020 10:56 am

Ah OK, I see.

The MIDI in circuit is very simple, so if you have the LED responding then it seems the optocoupler and 7414 is working.

What MIDI channel are you transmitting on? By default the TurboCPU SHOULD be set to CH1, though you can change it see page 7 here:

http://www.musictechnologiesgroup.com/f ... r_v141.pdf

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Troubleshooter » Fri May 08, 2020 5:57 am

Hi, I checked all midi channels and also factory reset the whole cpu to defaults. No success. The scope shows data arriving on the cpu.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Fri May 08, 2020 10:00 am

So, data arrives on the CPU, but when you trigger MIDI notes, the gate LED does not come on right?

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Troubleshooter » Sat May 09, 2020 12:56 pm

That is correct midi in LED reacts on note on/off but no gate LED

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Mon May 11, 2020 11:17 am

I feel like this might be something with the Turbo CPU. Let's see if we can get Grant to comment on this.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Wed May 13, 2020 11:31 pm

Just looking again at the schematics, it seems like if you have signal GATE (which you do because the synth works on its own), then it must be either:

A) the wiring from the MIDI section to the TurboCPU
B) the turboCPU
C) The MIDI section

For A you say you checked it, but I guess double check the wiring of your MIDI connector pins and the 2 pin from the MIDI section to the TCPU. For B, I'm not sure but I just emailed Grant since he tends to not knock around on here as much anymore to see if he has any immediate ideas. For C, there is not a lot going on. For kicks, you could try changing the 6N137, but since you are getting the LED flicker, I'd reckon the optocoupler is OK.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Thu May 14, 2020 10:21 am

Here is a exerpt from Grant at MTG:

"Assuming the keyboard works then the CPU is probably fine, especially if
the LED is working. The LED is driven off of a different gate than the
MIDI so lots of possibilities there. Soldering on the TTL chip, bad
chip, fake chip, wrong resistors, but most likely it's the wiring to the
jack or that 2-pin header. The MIDI THRU is a copy of what the CPU sees,
so that should tell you something about the MIDI IN if the MIDI THRU
does what it should. No scope I assume? Does the MIDI OUT work?"

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Troubleshooter » Tue May 19, 2020 3:17 am

Hi Devin,

As I told you I checked midi arriving on the CPU board itself so yes I do have a scope.
The CPU translates them to very short gate-pops instead of full note lenght gates. Only audible with certain ENV/filter settings. The CPU however translates the keybed scanning into perfect gates.
One of the next days I will check the THRU port.

Thanks for contacting Grant.

Give me a couple of days, in contrast to other people I am very busy @ work for the moment.

Kind Regards,

Gerd

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Cablebasher » Sun Jun 28, 2020 6:28 am

Hey guys

For all the power related wiring. Are people using solid or stranded core wire?

Or does it not really matter?

Thanks.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Sun Jun 28, 2020 12:02 pm

I use stranded, more flexible

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by KSS » Sun Jun 28, 2020 11:45 pm

The logic is simple and accurate. Wires which move should be stranded. Wires fixed between two unmoving points can be solid.

It gets more complicated in the real world, where pretinned stranded is essentially solid and minimoogs used solid for the wires going from the module to the KBD. Which were then stressed everytime the module was set at a working-playing angle.

But the physics still holds true, so if you have a choice, use stranded for wires expected to move. And don't solder connectors designed for crimping; it reduces their ability to handle wire movement and will reduce life expectancy and increase likelihood of service requirement.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Cablebasher » Mon Jun 29, 2020 2:33 am

Thanks for the info guys.

Very informative.

Up to now I have always used solid for everything as it found it easier to work with.

Always learning!

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Mon Jun 29, 2020 10:50 am

Yes! KSS is right. Good crimp connectors are extremely reliable and when you solder them, you lose flexability which can lead to failure and they also can fail in high vibration environments.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Kevin Mitchell » Wed Jul 01, 2020 11:23 am

Yeah I wouldn't recommend soldering connectors. But the wires within the shielded cables SC provided were so small I had to or else they'd slip out. Perhaps my tool wasn't good enough, but it was within the AWG rating.

The cables I had used for everything else worked just fine. I think I used AWG-24 stranded.

-KM

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by gslug » Thu Aug 06, 2020 11:49 am

Finally completed my Pro2021, but I've got a few problems. VCO1 is effectively an LFO: During calibration (adjusting TP120) the highest I can get for low C is around 4Hz. I'm assuming this is likely to be an incorrect resistor somewhere.

More strangely, both VCOs drone all the time - the VCA seemingly does nothing! Any pointers?
One day I'll get an avatar!

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Thu Aug 06, 2020 3:54 pm

Can you voltage probe the outputs (pin 1 and 14) of U104? Check the octave switches to make sure you get 0, 1, 2, and 3 volts added with each position.

For the VCA issue; does the main volume knob function correctly? Also, obviously check that the synth is not on "Drone" mode! :D

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by gslug » Thu Aug 06, 2020 4:02 pm

Thanks for the quick reply Devin! I've put it away for now, but will probe at the weekend and let you know what voltages I get.
One day I'll get an avatar!

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Cablebasher » Sun Sep 06, 2020 2:48 am

Hey Guys,

I have read through the whole thread but was wondering how people measured the 0.01% resistors?

Wheatstone bridge, fancy multimeter (fluke 85 maybe?) or expensive pre matched from mouser?

I have never had to measure this exact a resistance before.

Thanks as always.

Cheers.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by nigel » Sun Sep 06, 2020 4:50 am

Cablebasher wrote:
Sun Sep 06, 2020 2:48 am
Hey Guys,

I have read through the whole thread but was wondering how people measured the 0.01% resistors?

Wheatstone bridge, fancy multimeter (fluke 85 maybe?) or expensive pre matched from mouser?
I've built a Wheatstone bridge to match resistors for other projects. Mine has a 9V battery, three 100k resistors, a connector for the resistor being tested, a connector for the probes on my (cheap!) multimeter, and a switch. Get 100 1% resistors, and it doesn't take long to find some matching sets. To get consistent readings, I connect the resistor under test, toggle the power switch, wait ten seconds, then jot down the meter reading (and power off again before disconnecting the resistor).

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Cablebasher » Sun Sep 06, 2020 9:41 am

Thanks Nigel.

Time to investigate Wheatstone bridges and get the Old
breadboard out

I didn’t fancy spending big on a new multimeter i would rarely find use for.

My other big job is dremeling off the end of the pots for the knobs

Other than that I think im set.

The PCBs are like a work or art!

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by Kevin Mitchell » Wed Sep 09, 2020 7:42 am

Cablebasher wrote:
Sun Sep 06, 2020 2:48 am
Hey Guys,

I have read through the whole thread but was wondering how people measured the 0.01% resistors?

Wheatstone bridge, fancy multimeter (fluke 85 maybe?) or expensive pre matched from mouser?

I have never had to measure this exact a resistance before.

Thanks as always.

Cheers.
I wrote this up as a result of matching to .01% for the Pro2021
viewtopic.php?t=221045

-Kevin

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Wed Sep 09, 2020 10:57 am

Cablebasher, you also have the option of using SMT resistors for the .01%s. I put the dual-purpose pads there for that. Newark has them for about 30 cents a pop:

https://www.newark.com/multicomp-pro/mc ... p/74AC1394

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