MFOS 10-Step Sequencer Issues

Chartreuse-J · Joined: Jan 21, 2014 Posts: 8 Location: Dixie

Greetings,

First post, I have to be abrupt with my first post (of many more) but here goes.....

First the Wall Wart Issue....

Got everything together, hooked up the (Jameco 120v AC 9w, Output 12Vac 500Ma to the populated PCB, No dice, found out I misoriented the small yellow caps (C10, C9, C5, C4 Respectively) No big deal just unsolder and reorient. Great, still no dice, check volt meter on wall wart leads, dead supply.

Ok so now time to try a different wall wart, this time it is one from an old Boston speaker system. Here are the specs (12vac 1500mA output) Ok great worked great for like 10 seconds and the led lit up on the 10-Step. But oh no, I see smoke coming from component CR1 (1N4004 General Purpose Rectifier) No good, disconnected and gave up on that for now. Is the Rectifier fried? Suggestions?

OK, now on to the MFOS 10- Sequencer Issues....

Scroll down for unabridged version

So now I've decided to test the Sequencer. I now have 2 banks of 8 double AA batteries for a total hooked together to produce a +12v and -12v and ground to the 10 step PCB. Hooked everything up, all the leds light and only one problem nothing cycles, I can step through the leds with the step button and I get CV voltage and Gate voltage and the thing resets, but it will not cycle through the gates or adjust said Gates when I move each pot for each channel. The switch for the Gates work, but it just does not cycle. Not sure what to do.

Here is a synopsys of the problems...

THIS IS PROPERLY FUNCTIONING

Gate- Yes - Gets Voltage
L0-L9 - Yes - Leds Light up through Step button press
CV1,CV2,CV3 - Yes I am getting voltage here
PB1,PB2 - Yes both Reset and Step buttons work
LCOM - I assume this works
GCOM - I assume the Gate works due to the switches working gates off/on

THIS IS NOT FUNCTIONING PROPERLY

PB2 - No Start or Stop function
RNG - CV/HI/LOW switch does not work
GL2 -GL1 - The Portamento pot does not work
X0-X9 - 12 Pot Switch does nothing ( Pretty sure this is wired correctly)
CR2,CR3,CR1 - The Clock Rate pot does nothing
V0-V9 - These wires to the the Gate pots are not functioning

So you can see I have quite a mess here and no clue as to what is wrong, my first thought was it might be the CD4016BE (CMOS Hex Schmitt Trigger) chip in U4, but I regress.

I have an Arduino, if anyone knows of programs that would possibly test these CMOS chips or whatever someone might recommend. Question

elmegil

Chartreuse-J · Joined: Jan 21, 2014 Posts: 8 Location: Dixie

Thanks for the reply....

Ok checked U3 Pin outs.

I do not have an Oscilloscope, just a volt meter, so bear with me. Embarassed

Anyway Pin 7 on U3 reads 9 volts and Pin 1 reads 9 volts for both TL072 Dual Op Amps. So these are getting power.

The 2N5457 JFET is getting power as follows...

D-Leg 7.85 Volts
S-Leg 9.83 Volts
G-Leg .24 Volts

These voltages are steady on the JFET.

elmegil · Posted: Wed Jan 22, 2014 7:05 pm Post subject:

Have you checked AC readings? 1) you should have some kind of AC voltage if you're getting clock pulses and 2) you should be able to measure duty cycle or Hz as well.

Chartreuse-J · Joined: Jan 21, 2014 Posts: 8 Location: Dixie

Alright pictures speak a thousand words I hope this will help....

Will post AC results ASAP..

But here are some pictures I hope will help trouble shoot this.

I also have a parts requisition list from Jameco and Mouser.

IMG_0241.JPG

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This is what I am working with as far as tools go.....

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Wall Wart Dead at the moment..

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IMG_0244.JPG

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What I'm using to power it currently

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IMG_0245.JPG

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The board in question

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IMG_0246.JPG

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Another of the board

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Chartreuse-J · Joined: Jan 21, 2014 Posts: 8 Location: Dixie

The start stop feature to cycle through the gates is now intermittently working. Sometimes the unit just stays on the 1st gate and will not move to another gate, I think there might be a loose wire as I used solid core wire instead of stranded. Oh well..

Will post those AC results soon, as I might put this off until tomorrow.

elmegil · Posted: Wed Jan 22, 2014 8:45 pm Post subject:

Yeah, that sounds like grounding issues....

Chartreuse-J · Joined: Jan 21, 2014 Posts: 8 Location: Dixie

As for the Sequencer

Was not grounding issues and still DOA.

As for the power supply.

I replaced the Diodes and the Caps and bought a new 3000mA 12v AC and junked the 500mA.

All caps/diodes were originally oriented correctly.... (so no fault there)

The problem was the high current from the BA Transformer fried the diodes.

So that was solved