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Freq Central System X Envelope peculiar Decay issue
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Freq Central System X Envelope peculiar Decay issue
smcumber
I recently built a Frequency Central System X Envelope as my first completed DIY module, and it seems to be fully functioning except for one issue - the decay does not behave normally.

The outputs/input, LED, switch, and attack/sustain/release are all functioning normally as far as I can tell. The decay seems to act similar to the sustain, adding DC voltage when a gate signal is provided.

What's also odd is that say I hold a note, if you turn the decay knob COUNTERCLOCKWISE (i.e. reverse from normal) the decay adds more voltage; in essence the "bottom" of the range of the pot is what you would expect the "top" to be, and also when you turn it to the left it drastically increases the voltage in a very small turn range in what sounds like almost steps.

I have scoured the PCB for poor solder connections or unwanted solder bridges but can't seem to find any. I was also pretty fastidious about using the correct value resistors and I double-checked the values on the few capacitors that were in the build.

Does anyone have any suggestions as to finding the root of the problem? The only thing I could think of it might relate to is that I "adapted" vertical 9mm pots to be right angle - meaning, I bent the vertical leads from the pots to be 90 degrees relative to the shaft, then snipped the fat parts of the leads so that they would fit in the smaller holes.

Here is the link to the build doc from Freq Central:

http://www.frequencycentral.co.uk/wp-content/uploads/2013/06/System-X- Envelope-Ver2-Build-Doc.pdf

The Decay pot I used is definitely A1M, the correct value. Any help is greatly appreciated.
Starspawn
A friend had two with similarish problems.
One was cured by changing the single opamp to TL071, other is still to get a more thorough examination of the actual board as parts have been changed etc.
smcumber
Hmm. It wouldn't be expensive to order a TL071 with my next Tayda order, but would like to figure out if that's really it cause I was planning on building two more if this works out. I might email Rick Holt directly about it.
oootini
think i've noticed similar on my build.

report back here if you get an answer please.

i put it down to a quirk of the original circuit because everything else seemed to work just fine.
smcumber
I'm glad I'm not just going crazy. I emailed Rick from Freq Central about it, hopefully will hear back.
4floorsofwhores
Same issue with mine. Only finished building last week and assumed i'd done something wrong
smcumber
Bummer. It seems like it might be something inherent with the PCB, I'm not sure if this is a new iteration of the design or something. I'm still waiting on a reply from him.
n0rd
I've built a couple of these and they work fine / as expected. Don't have this behavior.

The PCB's I have are green with "Ver.2B May 2013".

Steve
degeneratedsines
Is this still an issue? I was about to order a couple of those adsr

EDIT: oh well... just ordered two smile
degeneratedsines
Mine are working fine. cool
I used TL071 and 2N3906 PNPs because I had spare ones.
matjinks
Does anyone have a Mouser cart they can share for the System X ADSR ? I built one and it does not work, and I wanted to check I have the correct parts, I'm a newbie DIY'er, it would be a great help before I abandon the build.

many thanks,


m.
Check Mate
Can you post a high res picture of your build please!
There isn' much you can do wrong on that one...
matjinks
Check Mate wrote:
Can you post a high res picture of your build please!
There isn' much you can do wrong on that one...


That's what I thought! I've successfully built Ornament and Crime and Temps Utile so i thought this would be a breeze, bu the build docs are minimal and the BOM is also not very detailed.
Here's an image,

any help much appreciated on this one.
Check Mate
First of all, I don't really see any obvious mistakes.
Except for the pots. They look really messy and you should clean these solder blobs up.
It looks like there is a connection between the left and the middle pin on the rightmost pot.

Did you try to swap the LF351 with a TL071?

Did you use BC547 and BC557 transistors or 3904/3906?

What I cannot see is if you wired the Jacks and the Switch correctly. Also a picture fron the ohter side would be helpful to look for bad soldering.
unvrsnyrgi
How does it not work? I mean do you get anything out of the module when you send gate in? Does the led blink?

My general troubleshooting things:

1. Double check the power. Make sure there are no bridges and that the cable is oriented correctly.

2. Are the ICs oriented the right way?

3. Measure voltages on the IC sockets. Do the IC's get the correct voltages?

4. Are there bridges on the IC sockets?

5. Are the transistors oriented the correct way?

6. Are the input and ouput jacks connected to correct pads and grounded?

7. Check for bridges everywhere.


I also think that frequency central's documentation is a bit too minimal. Especially in the beginning of DIY and synthesis when you don't know what the modules should do when working properly. I've spent some time googling pictures of their sandwich builds to find out wich way the pcb's should be connected.

But anyway the pcb's are very affordable and they work well and sound nice. I have made three of these envelopes and haven't had any problems. Good luck with troubleshooting!
matjinks
Check Mate wrote:
First of all, I don't really see any obvious mistakes.
Except for the pots. They look really messy and you should clean these solder blobs up.
It looks like there is a connection between the left and the middle pin on the rightmost pot.

Did you try to swap the LF351 with a TL071?

Did you use BC547 and BC557 transistors or 3904/3906?

What I cannot see is if you wired the Jacks and the Switch correctly. Also a picture fron the ohter side would be helpful to look for bad soldering.


Thanks for the reply, I used TL071 and BC547 and BC557 transistors, if I run my finger across the resistors the LED comes on briefly so I know power is getting in the vca opens briefly also and I hear sound, maybe the gate in is not working, the solder blobs were from attempts to earth the pots chassis to the empty pins, there are 5 pins on the PCB for each pot, which i've never seen before why? very confusing. I have everything oriented correctly, here are a couple more pics, maybe there are bad solders somewhere.
matjinks
Check Mate wrote:
First of all, I don't really see any obvious mistakes.
Except for the pots. They look really messy and you should clean these solder blobs up.
It looks like there is a connection between the left and the middle pin on the rightmost pot.

Did you try to swap the LF351 with a TL071?

Did you use BC547 and BC557 transistors or 3904/3906?

What I cannot see is if you wired the Jacks and the Switch correctly. Also a picture fron the ohter side would be helpful to look for bad soldering.


Okay I just got it to work, it was a really simple solder mistake at the gate input I had the wrong lug soldered because I had turned the socket around to solder all the earths together on the sockets....yay it sounds great!... one last question...what does the INV input do, is it a modulation input? thanks for your input on this, nice to know I'm not going crazy and doubting my builds, now I just have to work out how to get my Veils VCA to work, that's ones a mess!
fitzgreyve
matjinks wrote:

one last question...what does the INV input do


Its a negetive going output. ("norm" is the positive going output)
bobsynth
Hi,

Just so you know, the 5 pins for the pots, allow 9mm ones using the 3 inner holes and 16mm ones use the two outer and centre holes. The two outer holes are connected together.

Would have caused a problem if you connected the case of the pot to either of them unless it was a 0V connection.

The case of the pot is grounded through the metal front panel and 3.5mm jack grounds.

Glad to hear you have it working, built a couple here.

Bob
matjinks
bobsynth wrote:
Hi,

Just so you know, the 5 pins for the pots, allow 9mm ones using the 3 inner holes and 16mm ones use the two outer and centre holes. The two outer holes are connected together.

Would have caused a problem if you connected the case of the pot to either of them unless it was a 0V connection.

The case of the pot is grounded through the metal front panel and 3.5mm jack grounds.

Glad to hear you have it working, built a couple here.

Bob


Ahhh I see thanks Bob, when you say the two outer holes are connected together, should I connect those then if I am using 9mm pots with this 5 hole pcb?
bobsynth
Hi,

No need to connect the outer two holes, they are already connected on the PCB.

The PCB is designed to take either 9mm or 16mm pots, the two sizes have different pin spacing.

A few of the Frequency Central PCBs have this layout giving the builder the option to use the size pots they can get hold of.

Bob
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