Many problems..

[eisenhower]

Hi all,
I recently discovered I had switched la4140 and ba6110 chip. I've fixed that, but still have numerous problems.
The tempo light/knob works. In keyboard mode, the LEDs light when pressed except for LED31 and 36. LED17 stays lit in keyboard mode.
There is basically no output. Occasionally I do hear a random sound. It is faint though.
The sequencer does not work at all (as far as I can tell): the top LEDs do not light.
When in Pattern Edit mode, the top LEDs will light while going through the patterns, except LED13.

I've been debugging using the analog section reference voltages. The problems I've found so far are:
- Middle pin of Q27 is 0V (should be 5.8V), and the subsequent circuitry connected to it.
- Pin 10 on IC9 is at 5.34V (should be 0V)
- Pin 1 on J5 is at 2.92V (should be 5.96V) and pin 3 is at 5.91V (should be 341mV) -- the pins match between boards, FYI.

The voltages on IC14 and IC15B are correct.
The voltage reading on J4 is correct. While building, the VCO test passed. I didn't do any other tests while building besides those. IC20 gets warm, but not hot.

My only ideas are that Q27 is dead, IC9 is dead, and/or the microcontroller is dead.

[guest]

double check that you get signal from the vco
then listen on the resonance pot for signal
and if thats good
listen on the volume pot for signal

check cv and gate out in keyboard mode
and make sure cv changes and follows the keybord
and that the gate out goes to 12v and back down

[eisenhower]

double check that you get signal from the vco
then listen on the resonance pot for signal
and if thats good
listen on the volume pot for signal

check cv and gate out in keyboard mode
and make sure cv changes and follows the keybord
and that the gate out goes to 12v and back down

Do I need to supply 2VDC to R89 again to check for the signal?

[guest]

if your x0x is fully built
you do not need to apply any control voltage

[eisenhower]

double check that you get signal from the vco
then listen on the resonance pot for signal
and if thats good
listen on the volume pot for signal

check cv and gate out in keyboard mode
and make sure cv changes and follows the keybord
and that the gate out goes to 12v and back down

I get a signal on the waveform switch. I'm not sure it is working as its supposed to though.. The signal is on two adjacent pins
when the switch is on sqr setting, and switching it to the saw setting only has the signal work on one of those pins, and the signal stays the same, as far as I can hear.
I get nothing on the resonance pot, except noise one of the pins
I get nothing at all on the volume pot.

The cv and gate work as you say.

[guest]

one of the waveforms is really quiet
but i forget which one
but if you can hear a tone
and that tone changes as you play differenet notes
then your vco is working

since you are not hearing anything on the resonance pot
the problem is most likely in the vco
check all the voltages in the vco
in comparison to the ones given on the voltage map
that is in the making x0x forum

[eisenhower]

So I prodded around with my meter, and checked against the voltage references, finding a few numbers that are different..
but after plugging in headphones my x0x appears to be working (somewhat). I'm not really sure what I did. I re-measured and many values are still off.

On J5 I am still getting pin1 = 2.92V and pin3=5.91V
On J6 I am getting pin1=2V and pin3=11.85 while C is pressed, and 0 after it is unpressed (the reference says it should be 0.99V??)
Middle pin of Q27 is still 0V

IC12:
1 - 35mV
2 - 0
3 - 50mV (decreases though)
4 - 27mV
5 -18mV
6 - 39mV
7 - 0
8 - 11.85
9 - 19mV
10 - 10.75
11 - 2.0
12 - 2.0
13 - 2.0
14 - 1.98

Q35
1 - 0.0
2 - 0.0
3 - 0.6

The readings that are very off from the reference are bolded. I am not really sure which voltages should match with the reference. My IC9 measures much differently than the reference too.

The LED's I listed still aren't working. I will test the LED's themselves then.

There is "filter warble" (if that is the right term); when I set resonance high, env high and decay high, when playing notes quickly the filter will oscillate quickly. I measured the voltage drop across C8 to be 24.3VDC, so it's probably not the power supply. I also tried swapping the an6562 in IC11 for an opa2134 I had, and it didn't fix it.
I have another 4066, so I could replace the one in IC12, but it isn't socketed right now, I'll replace it if its a good idea. I also found a couple of 2sa733p's, so I could replace Q27 if it is worth it.

[guest]

if there is a lot of intermittent behaviour
then it is likely that there is a bad solder joint
it might be best to just quickly rehit all the joints in the vcf
and see if it makes a difference
if you have flux it will help with this

the ic12 voltages arent bad
but the q35 is wrong
turn off the power
and measure the resistance to ground from all its pins
although this shouldnt effect the sound being present or not

the j5 and j6 voltages seem fine

what do the voltages on q12 q22 and q21 look like

the warble is a bit of a mystery
i originally thought it was a powersupply thing
but im not so certain anymore
someone reported making it go away by replacing q22 if i recall correctly
its something that happens in the vcf
as the power draw of the vcf increases at higher frequencies
this makes me think its related to r115 r95 c30 or c28

[eisenhower]

Q22, Q21, and Q12 voltages match the reference:

Q12:
5.33
9.8
4.85
9.8
5.33

Q21:
3.43
6.00
2.84
5.90
3.43

Q22:
11.26
11.70
11.69
11.70
11.26

I measured resistance to ground of the Q35, and it seemed correct (middle pin wasn't shorted to ground).

[guest]

those all look fine

if all of the voltages in the vcf section
match those in the voltage map
then it is more difficult to troubleshoot

do you have access to an oscilloscope
or a high input impedance headphone amplifier

[eisenhower]

those all look fine

if all of the voltages in the vcf section
match those in the voltage map
then it is more difficult to troubleshoot

do you have access to an oscilloscope
or a high input impedance headphone amplifier

I do have access to a nice oscope.
I ordered new 74HC595's (IC4-IC8), 74HC174 (IC9), and 4066 (IC12).

I'll swap those parts with new ones, reflow the solder, and clean the board. If that doesn't do it, I'll check the vcf.

Did the voltages on Q27 seem fine? They don't match the reference, but my VCO is working. I have some spare 2sa733p's, but I'll only use them if needed..

I tested the LED's that aren't lighting up, and they work on their own. Replacing IC4-IC8 might do the trick though, since I was using ST micro 74HC595, which as know have had issues: viewtopic.php?f=12&t=27199

[guest]

q27 always reads funny
if the vco works its fine

[eisenhower]

It is working now
All I did was reflow all the joints in the VCF section.
The LEDs are also working.

EDIT: the filter warble came back...?

[guest]

glad to hear its working

if you want to hunt down the warble
see if you can isolate when it happens

[eisenhower]

glad to hear its working

if you want to hunt down the warble
see if you can isolate when it happens

It happens when the resonance is up high, if that's what your asking.

I tried reflowing the solder again, but it didn't fix it??
I'm perplexed as to why it fixed it temporarily before.