MST Dual AD/ ASR Envelope Issues

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piano39
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MST Dual AD/ ASR Envelope Issues

Post by piano39 » Fri Mar 04, 2016 10:48 am

So I built this, was very impressed with the quality of the PCB, etc. However, the unit does not work. It is supposed to self oscillate with nothing plugged in, so I expected to see the LEDs happily dancing back and forth. Nothing.

Also, when I plug the gate out from my Microbrute, it does not trigger either envelope.

Here is what does happen. 1) When I power up, both LEDs light for a split second. 2) All outputs put out a constant voltage, which can be properly attenuated or affected with the output level controls and the INV +5 switch.

I am an experienced builder, built several MFOS, CGS and homebrew modules. I checked for all of the obvious suspects- solder joints, proper polarity on diodes, etc. Since there is no schematic, I can't troubleshoot anything further. Obviously, there is an issue which is affecting both EGs.

The only problem that I had in the build- the ICs U3 and U4 are too close together, I could not fully seat U4 without grinding some material off of the end. I tried pulling U4 out (with the thought that my grinding process destroyed the IC) and installed a fresh TL074 in its place, as best as I could without grinding. Same end result.


Anyone have any ideas?

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Post by Maxx mayhem » Sat Mar 05, 2016 11:06 am

If you push them in hard enough, you can bend the pins slightly, until they seat. I did however use these very expensive NOS Augat mil spec sockets I just happened to have in my parts box for the first one, so - who knows. But I don't think that's your problem.I have built 3 of these, the first worked without a hitch, the other 2 I'm still troubleshooting. :despair:

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Post by piano39 » Sat Mar 05, 2016 4:38 pm

It concerns me that you built three of these units, and only one works.
A couple questions for you,
- What problems are you having with the defective units? are you seeing the same problem that I described?
- have you tried swapping PCBs from the unit that doesn't work to the working unit? At least this way, you can isolate the problem to either the control board of the component board. Although, chances are, the problem is on the component board

Since my original post, I have went over every solder joint with magnification. I found four or five "iffy" connections that I re-soldered. No difference in performance. I also verified, with an ohmmeter, that the IC had continuity from the IC pins to each solder joint.

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Post by Maxx mayhem » Sat Mar 05, 2016 7:16 pm

I have not tried swapping boards - if I somehow manage to wreck my good envelope then I really fall below the threshold of working synth. (I've built around 2 dozen modules that work just fine). I believe it is a logic board issue, based on when I apply power, 1 led (lower)blinks once. This means that likely the top stage isn't firing. It is the same on both non working units. Currently, I need to place a mouser order to get a couple of sets of chips and some parts to make a radio music, In one unit I had a chip in backward and reversed it and it worked briefly then quit. In the second, (that I've spent the most time troubleshooting) I had a bad chip - not certain what killed it, but when it was in, both lights stayed on, when I replaced it, back to the one light blink. I'm not an electronics whiz, but I've been thru this board a lot. Did have more than one bad diode, but there is some part somewhere that is not right. I do have a scope that I did make a bit of progress with, but I'm all out of virgin chips so until I get new ones, I feel like I'm paddling in circles. Oh, and I reheated quite a lot of solder joints. This is a new board design, the working one was the old board design, and seemed to wet out better on a lot of components. I also need to get my vco working, but I found a diode that was defective in that one, Need some replacement chips on that too. But you know, once they work, they work.

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Post by piano39 » Sun Mar 06, 2016 3:09 pm

It sounds like our units have similar issues. Only difference, when I power mine on or off, both LEDs blink. You are having only one blink.

I tested the current draw. I am getting about 30 mA on the + rail and about 23 mA on the - rail, This is about three times the spec limits of 10mA and 8mA, respectively. This has to mean something.

I am beginning to wonder if there is a problem with the second run of PCBs.

I am running out of things to try. I may have to punt and contact them. I was planning on building about one or two modules a month. I will abandon that plan if I can't get this to work.

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Post by Maxx mayhem » Mon Mar 07, 2016 9:22 am

The startup draw, from what I understand, is higher than the running draw. Some process that is part of the initial power up may be occurring and holding(?) A resistor was relocated from a previous version of the board (as in the one of mine , 1st, that works).This may have been done to allow for spacers to be mounted, though they weren't included on the current BOM. However, I would imagine that they have sold quite a number of these, so unless a number of other recent buyers of these are experiencing a similar issue, it's probably something else. This and the VCO are the only ones that have given me any real difficulty(took 2 tries on the deluxe power but the second build went flawlessly). I built about 15 other modules in a week with no problems.

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Post by calaveras » Mon Mar 07, 2016 5:08 pm

I had that same problem with the sockets being too close together.
:(

Mine isn't quite finished yet. I forgot to do the 2 pin jumper on the back!
:doh:

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Post by piano39 » Mon Mar 07, 2016 10:15 pm

Hey Maxx Mayhem,
is it possible that the newer rev boards REQUIRE spacers? Curious that they redesigned the board to add room for three spacers. As you mentioned, the BOM does not mention spacers. However, it does list qty four 2.5mm and qty four 3mm screws. Assuming that one set of these is to mount the panel to the case, what would the other set be for?

And Calaveras, keep us posted on your progress. If you leave out the 2 pin jumpers, the unit should still work, but you just won't have the option of getting longer envelope times.

thanks,
piano39

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Post by piano39 » Mon Mar 07, 2016 10:23 pm

Just answered my own question. I ran an ohmmeter between the pads for the spacers on both boards. Perfect continuity. The pads are also ground points.

So, it doesn't look like the spacers would be required, circuit wise.

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Post by Maxx mayhem » Tue Mar 08, 2016 8:40 am

Piano, Synthrotek supplies for the common 2.5mm rails, as well as the 3mm rails from Tiptop with all kits. I had mentioned the spacer positions as they seem to relate to minor changes on the CB. But I had wondered about that as well...

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Post by wickedCircuits » Tue Mar 08, 2016 4:59 pm

Hey Guys! Patrick with Synthrotek here, sorry it's taken us this long to get to you, our normal customer service guy is out.

Piano39, it almost sounds like you may have a short somewhere in your circuit. I would start by checking power at all the ICs, and making sure they are getting the proper voltage. Then maybe check the polarity protection diodes that are near the 16 pin power connector.

The standoffs were added to the boards just to have some extra stability between the boards. We didn't change the circuit at all, just moved a couple resistors around for them to fit.

you guys can also shoot us an email at store@synthrotek.com for help, there are multiple people with an eye on that email account, so it may have a faster response time.

Best regards,
-Patrick at Synthrotek

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Post by piano39 » Wed Mar 09, 2016 10:43 pm

Hi Patrick,
I verified that all ICs are getting voltage. Since I am using a ±12V supply, it is delivering about ±11.1 volts to the ICs. I assume the voltage drop means that the diodes are working OK. Also, I checked all Diodes and Transistors on my multimeter prior to installation.

One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter. I installed the transistors per the diagram, but I know that occasionally transistors can be manufactured bass-ackwards. I do not believe the ones that I installed are incorrect, but this nags me.

Unless you can point me to something else to check out, I am going to have to send this back to you for repair.

Thanks,

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Post by calaveras » Fri Mar 11, 2016 1:57 am

piano39 wrote: One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter.
From what I understand the MST modules are designs licensed from Mattson Modular. So Synthrotek can not supply a schematic.
Yes this sucks for troubleshooting.
But it is what it is.

I do think the labeling on the PCBs could be better.

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Post by mmm » Fri Mar 11, 2016 12:34 pm

calaveras wrote:
piano39 wrote: One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter.
From what I understand the MST modules are designs licensed from Mattson Modular. So Synthrotek can not supply a schematic.
Yes this sucks for troubleshooting.
But it is what it is.
Yup, you can blame me for being protective of my IP.

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Post by Maxx mayhem » Fri Mar 11, 2016 8:52 pm

mmm wrote:
calaveras wrote:
piano39 wrote: One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter.
From what I understand the MST modules are designs licensed from Mattson Modular. So Synthrotek can not supply a schematic.
Yes this sucks for troubleshooting.
But it is what it is.
Yup, you can blame me for being protective of my IP.


Totally understandable,You've done a lot of work to create very nice kits that offer many of us who could not otherwise afford it to put together a synth with great features + sound. I personally have built 14 of your modules -11 of them worked right off the bat, the other 3 are throwing me for a loop. I want to be able to fix them myself, because in the end I want to have built this thing myself. So I'm wondering if perhaps it would be possible to put out a picture of the CB with the expected voltages marked at each end of each component. This couldn't harm your IP, because every single person with a working board would have this info already, and it would probably result in more sales, as successful builds it would seem would encourage people to buy more kits. IMHO

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Post by mmm » Sat Mar 12, 2016 12:30 pm

Maxx mayhem wrote:
mmm wrote:
calaveras wrote:
piano39 wrote: One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter.
From what I understand the MST modules are designs licensed from Mattson Modular. So Synthrotek can not supply a schematic.
Yes this sucks for troubleshooting.
But it is what it is.
Yup, you can blame me for being protective of my IP.


Totally understandable,You've done a lot of work to create very nice kits that offer many of us who could not otherwise afford it to put together a synth with great features + sound. I personally have built 14 of your modules -11 of them worked right off the bat, the other 3 are throwing me for a loop. I want to be able to fix them myself, because in the end I want to have built this thing myself. So I'm wondering if perhaps it would be possible to put out a picture of the CB with the expected voltages marked at each end of each component. This couldn't harm your IP, because every single person with a working board would have this info already, and it would probably result in more sales, as successful builds it would seem would encourage people to buy more kits. IMHO
Perhaps. Tnx for your support BTW :yay:

All manufacturing decisions are the responsibility of the respective manufacturers. I just submit the schematics. They design and lay out their own boards and provide their own documentation.

I can't generate the numbers since they change based on Vsupplies. So, They have to determine the specs of their designs.

But, yeah. Good info to have for troubleshooting...

G

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Post by calaveras » Sat Mar 12, 2016 2:07 pm

mmm wrote:
calaveras wrote:
piano39 wrote: One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter.
From what I understand the MST modules are designs licensed from Mattson Modular. So Synthrotek can not supply a schematic.
Yes this sucks for troubleshooting.
But it is what it is.
Yup, you can blame me for being protective of my IP.
as you have every right to be!
Especially given some of the past controversies in synths modular and not so modular.

Honestly I think most of us, most of the time are just fine without any kind of docs beyond a BOM. The simple stuff like the VCLFO or Noise S&H are pretty much paint by numbers. (great kits though! use them both Every day!)

The MST OSC and AD/ASR are a little more advanced though...

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Post by mmm » Sat Mar 12, 2016 2:33 pm

BTW,

I always use transistors that:
with the flat facing you, pins down;

Left to right, E B C.

I do that so I don't have to look it up on my own boards...
Age is a bitch....

G

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Post by Maxx mayhem » Sat Mar 12, 2016 7:37 pm

mmm wrote:
Maxx mayhem wrote:
mmm wrote:
calaveras wrote:
piano39 wrote: One minor aggravation (especially since you do not provide a schematic). It would be good if the transistor diagrams on the PCB showed the emitter.
From what I understand the MST modules are designs licensed from Mattson Modular. So Synthrotek can not supply a schematic.
Yes this sucks for troubleshooting.
But it is what it is.
Yup, you can blame me for being protective of my IP.


Totally understandable,You've done a lot of work to create very nice kits that offer many of us who could not otherwise afford it to put together a synth with great features + sound. I personally have built 14 of your modules -11 of them worked right off the bat, the other 3 are throwing me for a loop. I want to be able to fix them myself, because in the end I want to have built this thing myself. So I'm wondering if perhaps it would be possible to put out a picture of the CB with the expected voltages marked at each end of each component. This couldn't harm your IP, because every single person with a working board would have this info already, and it would probably result in more sales, as successful builds it would seem would encourage people to buy more kits. IMHO
Perhaps. Tnx for your support BTW :yay:

All manufacturing decisions are the responsibility of the respective manufacturers. I just submit the schematics. They design and lay out their own boards and provide their own documentation.

I can't generate the numbers since they change based on Vsupplies. So, They have to determine the specs of their designs.

But, yeah. Good info to have for troubleshooting...

G
I understand. Well, if perhaps you speak with the guys at Synthrotek, you might mention it. I'd sure like to have a few VCOs, but I've got to get the one working first. :hmm:

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Post by piano39 » Sun Mar 13, 2016 8:40 am

I agree. The next module that I was going to buy was the VCO. If I can't get this module to work, though.....

Voltage levels at key points would be a big help.

I certainly appreciate the IP issues, though, My day job is in manufacturing and my company has been hurt by IP issues.

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Post by calaveras » Sun Mar 13, 2016 9:36 pm

So I pulled mine apart and went over it checking the polarity of everything. All good. I added the jumpers I'd missed as well. Still not firing up. I just get a steady voltage out of the outputs, and I can mess with it with the level knobs or by flipping the inv/5v switch. Gate input and other controls have no affect. So I am thinking the comparator on the input is not happening for some reason. Since it seems everything downstream of that is, and I can't detect any telltale smoke coming off of this sucker.
I'll have to check and see if I can swap chips or something. I have a barrel of 74s in my parts collection but no extra 4011.

I am noticing that the assembly instructions dictated that the lectro caps go on the backside of the board. Mine were able to fit no problem on the front. Now I am wondering about this and whether in some way this has cause a polarity issue?
I double checked all of them being sure the + and neg stripe are on opposites from each other.

I'm kind of wondering about the way the TLO74 and CD4011 barely can fit next to each other. I had a very hard time getting mine to fit, as the other poster had mentioned as well. Even Synthrotek's site shows them mooshed up next to each other like teenagers.
Image

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Post by mmm » Sun Mar 13, 2016 11:06 pm

calaveras wrote:So I pulled mine apart and went over it checking the polarity of everything. All good. I added the jumpers I'd missed as well. Still not firing up. I just get a steady voltage out of the outputs, and I can mess with it with the level knobs or by flipping the inv/5v switch. Gate input and other controls have no affect. So I am thinking the comparator on the input is not happening for some reason. Since it seems everything downstream of that is, and I can't detect any telltale smoke coming off of this sucker.
I'll have to check and see if I can swap chips or something. I have a barrel of 74s in my parts collection but no extra 4011.

I am noticing that the assembly instructions dictated that the lectro caps go on the backside of the board. Mine were able to fit no problem on the front. Now I am wondering about this and whether in some way this has cause a polarity issue?
I double checked all of them being sure the + and neg stripe are on opposites from each other.

I'm kind of wondering about the way the TLO74 and CD4011 barely can fit next to each other. I had a very hard time getting mine to fit, as the other poster had mentioned as well. Even Synthrotek's site shows them mooshed up next to each other like teenagers.
Everything visually looks correct. The neg stripes on all of the caps should be all facing the bottom of the picture.

Usually, a reverse cap will take it or, blow up and let all of that hard-earned smoke out. But, they won't reverse polarify anything. Wow, polarify...new term :hmm:

Ch 1 gate`comes from J6 P1 and goes to 100K R22. The other side of R22 is connected to U4 (TL074) P3. Output from P1 to R20 thru cap C5 to U6 (4011) P2.

Ch 2, J8 P1, R23(100k), U4 P5, out P7 to R28 thru C4 to U2 P6.

Both U4 comparators Have a DC ref of 1.85-2.0V on P 2 and 6 derived from the junction of divider junction of R19 and R21.

The other two quadrants of each U4 and U6 are utilized in the EoC detection for each channel.

I'm going to guess U2 if you already changed out U4.
The proximity of the ICs is only a physical thing. You can file the ends if you wish. It won't hurt them. As long as you don't saw off a third of it....

But, ensure that the pins are making connection in the socket and a pin didn't bend up or something.

If you have a scope, you should be able to see the EG voltage pre buffer/amp directly off the emitters of the transistors.

:mmm:

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Post by calaveras » Mon Mar 14, 2016 10:54 am

Thanks for the troubleshooting info. When I have time to get to my bench I'll fire up the scope and DMM and check out the particulars.

Yeah that pic is not me, that is taken from the synthrotek site to show how jammed up the chips are on their example.
I was just kind of concerned that the chips are so jammed together that one or both may not be making contact on all pins. I've got the 'good' machined sockets for my chips so I'd hope they are all good.

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Post by mmm » Mon Mar 14, 2016 11:49 am

calaveras wrote:Thanks for the troubleshooting info. When I have time to get to my bench I'll fire up the scope and DMM and check out the particulars.

Yeah that pic is not me, that is taken from the synthrotek site to show how jammed up the chips are on their example.
I was just kind of concerned that the chips are so jammed together that one or both may not be making contact on all pins. I've got the 'good' machined sockets for my chips so I'd hope they are all good.
Nice to know that I spent an hour comparing the picture to mine just to find out that Synthrotek built is correctly....

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Post by Maxx mayhem » Mon Mar 14, 2016 6:35 pm

mmm wrote:
calaveras wrote:So I pulled mine apart and went over it checking the polarity of everything. All good. I added the jumpers I'd missed as well. Still not firing up. I just get a steady voltage out of the outputs, and I can mess with it with the level knobs or by flipping the inv/5v switch. Gate input and other controls have no affect. So I am thinking the comparator on the input is not happening for some reason. Since it seems everything downstream of that is, and I can't detect any telltale smoke coming off of this sucker.
I'll have to check and see if I can swap chips or something. I have a barrel of 74s in my parts collection but no extra 4011.

I am noticing that the assembly instructions dictated that the lectro caps go on the backside of the board. Mine were able to fit no problem on the front. Now I am wondering about this and whether in some way this has cause a polarity issue?
I double checked all of them being sure the + and neg stripe are on opposites from each other.

I'm kind of wondering about the way the TLO74 and CD4011 barely can fit next to each other. I had a very hard time getting mine to fit, as the other poster had mentioned as well. Even Synthrotek's site shows them mooshed up next to each other like teenagers.
Everything visually looks correct. The neg stripes on all of the caps should be all facing the bottom of the picture.

Usually, a reverse cap will take it or, blow up and let all of that hard-earned smoke out. But, they won't reverse polarify anything. Wow, polarify...new term :hmm:

Ch 1 gate`comes from J6 P1 and goes to 100K R22. The other side of R22 is connected to U4 (TL074) P3. Output from P1 to R20 thru cap C5 to U6 (4011) P2.

Ch 2, J8 P1, R23(100k), U4 P5, out P7 to R28 thru C4 to U2 P6.

Both U4 comparators Have a DC ref of 1.85-2.0V on P 2 and 6 derived from the junction of divider junction of R19 and R21.

The other two quadrants of each U4 and U6 are utilized in the EoC detection for each channel.

I'm going to guess U2 if you already changed out U4.
The proximity of the ICs is only a physical thing. You can file the ends if you wish. It won't hurt them. As long as you don't saw off a third of it....

But, ensure that the pins are making connection in the socket and a pin didn't bend up or something.

If you have a scope, you should be able to see the EG voltage pre buffer/amp directly off the emitters of the transistors.

:mmm:
Thank you George - this is the most helpful info I have seen on this yet. Hoping to have a couple of hours tomorrow after work to see what I can see... :tu:

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