Sequencer stopped working, suggestions?

[ebbflo]

In late August 2012 I finished my xox concept kit. I had the sequencer and control sections working fine last I turned the machine on.
The sequencer worked and I recorded sequences but no sound.
I could get a continuous tone that changed pitch with the sequencer if I shorted two pins of Q32.
I had to return to school so trouble shooting took a break.
Last night I looked at the board very carefully and noticed I had not placed d34 in...
I thought sure that this was the issue.
I soldered it in and now the control section(sequencer, leds, keyboard, etc...) now does not work.
Before I left the project a couple of week back all leds were shining and the encoders changed banks/functions as they should.

Now nothing. the voltages from the power supply seem fine.

Any suggestions on where to start looking for the problem?

thanks in advance

[aminoacid]

Are you sure that your 5v supply isnt dead?

[ebbflo]

I am getting the correct readings from j4.

It seems that the analog section is getting powered but none of the control section is.

Its odd because it was all working fine before, leds, encoders, sequencer, etc...

any suggestions where/what to check next?

thanks

[MMM]

I am getting the correct readings from j4.

It seems that the analog section is getting powered but none of the control section is.

J4 is the power supply for the analog part; the power for the digital part comes via J3 (and the power for the headphone amp via J5).

So at this point it would be a good idea to check the digital supply: Please measure on IC3 (the processor) from pin 20 (ground) to pin 40.

I personally find the digital side comparatively easy to debug because there are so few parts. Do you have an oscilloscope?

[ebbflo]

on IC3 pin 20 to pin 40
I get 0.033v

[MMM]

on IC3 pin 20 to pin 40
I get 0.033v

That's not nearly enough.

Please measure on the IO Board from the metal tab of the +5V regulator to pin 3 or 4 of J3.

[ebbflo]

Thanks, I get the same reading , 0.033v

thanks for helping!

[ebbflo]

I discovered the problem. The right most pin of the 5v regulator had snapped from stress(I had an alligator clip on the heat sink while I was building and used it for a ground when testing) I managed to complete the connection with some solder.

Now the digital functions as it did.

I am still having the same problem with triggering the sound. If I connect the center pin of q32 with either the right or left pin I get a continuous(non-gated) tone(I get the same results on q31). The notes are triggered by the sequencer, keyboard, etc while I have them connected but nothing is triggered when I remove the connection.

Any ideas?

Should I start a new thread?

[MMM]

On to the next problem.

I am still having the same problem with triggering the sound. If I connect the center pin of q32 with either the right or left pin I get a continuous(non-gated) tone(I get the same results on q31). The notes are triggered by the sequencer, keyboard, etc while I have them connected but nothing is triggered when I remove the connection.

Do you get a Filter envelope reaction when playing notes?
If yes, please measure the voltage on D34, D35 and D36 when playing a note.

If not we'll start tracing from the beginning of the whole envelope section.

[ebbflo]

Yes when I short the pins of q32 I can hear the filter alter the sound as would be expected.

when I measure across d34 I get about .23v regardless if I have q32 shorted or press the trigger buttons.

when I measure across d35 I get 0.034v when q32 is not shorted and 0.465v when it is, there is no change from those readings while pressing the triggers in either case

When I measure across d36 I get about 0.035v regardless of triggers or the q32 short

thanks

[MMM]

Yes when I short the pins of q32 I can hear the filter alter the sound as would be expected.

Which means that the Gate signal from the processor is reaching the envelope section and the filter part of the envelope is generated. Good.

when I measure across d34 I get about .23v regardless if I have q32 shorted or press the trigger buttons.

Not across: Please measure against ground. Both sides of the diodes.

[ebbflo]

thanks,
d34 11.92 -|>-11.63
d35 11.93-|>-11.63
d36 0.00-|>--0.02

no change on any when triggers are depressed

best,
neil

[MMM]

OK, please measure D37 as well. Please watch the multimeter very carefully as there might be a short "spike" that levels off.

[ebbflo]

D37 0.00 -|>- -0.05

no spike

[MMM]

D37 0.00 -|>- -0.05

no spike

That's odd and doesn't make sense. On the cathode side of D37 you should see the filter envelope. Since you say this would actually be audible when playing a note I would expect a swing up to about 12V here (with a gradual decay depending on the setting of the decay knob).

Please measure again.