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208p build thread (papz's PCBs)
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3 ... 14, 15, 16 ... 20, 21, 22  Next [all]
Author 208p build thread (papz's PCBs)
There are dual outputs stages for the panel settings and for the program card slot settings. Your problem is probably related to the card one and affects the global performance when in both mode because both stages are active.
If swapping the 4013s (there are 2) doesn't help, there's maybe a short or bad contact somewhere.

I hear a little "the pulser" in the co, is there a solution to this little problem ?

a trim to turn ?

but may be is it normal, this is the first time that i use this machine.
100% noob

thank you again
Let me quote the build notes. wink

LEDs and bleed
The LEDs, mostly the pulser's and envelope's ones, affect the oscillators pitch. This can be
attenuated by the addition of series resistors. To add a resistor to the pulser's and envelope's LED, cut the
PCB trace between the 2N1711 and Molex connector (there's only one, on the solder side) of
boards 3 and 4 and bridge the cut with a resistor.
Add a resistor in series with the other LEDs can be done on the motherboard the same way.
Depending on the LEDs you use, select a resistor in order to achieve the best possible
compromise between LED brightness and oscillators drift.
With the LEDs suggested above, 10k resistors are fine.

If the sequencer sometimes erraticaly skips a step, the 4013s are probably in cause. Some new
ones work fine, others don't. All the NOS ones I tested are ok.
i reed build notes a long time ago but i forget, that's perfect !!! thanx

i command V4013D and after it will be ok i hope/think

10K is perfect !!!

for the information

v4013D won't fix my sequencer problem in "both mode" in the first time

very frustrating

i switched ic 2 to 4 and 4 to 2 and ok with 4 and 5 steps but problem with 3 steps

sad banana

thumbs up thanks for the info
4001s may have weird behavior, I had problems with some too, despite my IC tester says they are ok.
i change the ic3 on card 1 and everyting seems ok now
It's peanut butter jelly time!
thanx again
My issue with this was solved with decoupling caps on half of the chips on card one nanners
Yes decoupling caps can help too but I prefer to have good working ICs.
I can't help thinking that adding caps heals the symptom but doesn't cure the disease, despite it works.

Having an issue with my MO. This is also effecting the square, however the triangle is completely fine.

On a separate note: CO sine had a small dimple in it that was solved after replacing card 8’s 4066 to a 4016.
Did you try and replace the ICs on board 6 ?
MO has many troubles.
You need luck and detailed troubleshooting is to succeed.
Solved after replacing ic’s. Thanks.

On to calibration. Does the HF trimpot have a very narrow range? I’m not getting much of anything out of it during calibration. I’ve got the frequency pretty well matched up to the panel, I’ve replaced R14 with 44k and tried everything from 90k to 200k on R44, but can’t really get good tracking.
The trimpot range is limited, it's for fine tuning in the high frequency only.
With the resistor values mentioned in the BOM and proper adjustment of the panel trim and MO range trimpots you'd be able to get good tracking over about 5 octaves for 1V/oct or 1.2V/oct.

It's good to let the synth warm up for 10 minutes at least before tracking calibration.
None of the pitch inputs to the CO change the pitch (including the fine tuning knob).

I've looked carefully over boards 7-9, and can't see any obvious construction errors. Any ideas what I should look at?
The pA726 board (or other expo converter you may have used) or its connections to board 7 could be in cause.
Just to narrow it down a bit, could you let me know what voltage range I should expect to see at the input to the pA726? (ie. on pin 1).

(I knocked up some cables to allow me to work on Board7 on the desk whilst it is plugged in, and can now do proper testing/measurement/scope stuff. Everything looks good for the pitch control voltage until it goes out to pin 7 for the front panel range trimmer. The bit I see between pin 8 - the trimmer return - and the input to pA726 looks pretty small, so I'd like to confirm that's expected before moving forward through the circuit).

On pin 1 I measure 0.06V with the pitch slider to bottom, -0.08V to top.
Fine pot fully CCW.

You can replace temporaly the pA726 with 2 NPN transistors such as 2N3904 for test purpose :

B1 : pin2
E1 : pin 3
C1 : pin 4

B2 : pin1
E2 : pin10 (square pad)
C2 : pin 9

If it works with the transistors, the pA726 is faulty.
Yep, it was the pA726 - not sure why yet, but it's a great start. Many thanks!
You're welcome.
It shouldn't be hard to fix.
Hello all, what is the approx. total cost of this build? I can see the pricing for the PCBs but does anyone have a prepopulated mouser cart? thanks
These questions and many others are answered in the FAQ
It's all working well now apart from the sine shaper stuff...

I've ordered a bunch more 2n4339 equivalents (actually J201s) so I can try to find one in spec. The 2n4339 I have in there now doesn't seem to do anything, even if I change R41: the output is always a triangle wave. (adjusting R41 marginally changes the amplitude, but not the shape).

If this is likely to be just an out-of-spec 4339, then no worries - I'll see what happens when replacements arrive. If not, do you have any ideas?

Lastly, the pa726 don't say 'remove the jumper' at the end of the calibration process. I presume that means they should stay on for normal operation?

A 4066 in IC2 on card 8 may upset the sine shaper. It's the only spot where a 4016 is recommended over a 4066.

The pA726 jumper should stay on for normal operation.
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