MST Dual AD/ ASR Envelope Issues

piano39 · Post by **piano39** » Wed Mar 16, 2016 5:46 am

I appreciate the tips that came up in the recent posts. Life has got in the way, though, and I will not be able to spend any time on my workbench until the upcoming weekend.

Will keep you posted.

calaveras · Post by **calaveras** » Sat Mar 19, 2016 12:59 am

Well I found a few pins that were not soldered all the way on the multipin interconnects.
I've fixed these, fired it up and still no good. I also made sure to use some flux wash this time as well. I am now getting a little effect from the switches and such but nothing is triggering.
It is getting kind of tedious for me because my bench is located someplace else, where I don't have anything to trigger it with!
I will need to dig out my old X0Xbox and use that just to throw triggers at it.

I think I may also have to investigate the possibility that I have some dud chips. Have another project that is also exhibiting some bricky behavior, which uses chips from the same batch.

Maxx mayhem · Post by **Maxx mayhem** » Sun Mar 27, 2016 10:35 am

calaveras wrote:Well I found a few pins that were not soldered all the way on the multipin interconnects.
I've fixed these, fired it up and still no good. I also made sure to use some flux wash this time as well. I am now getting a little effect from the switches and such but nothing is triggering.
It is getting kind of tedious for me because my bench is located someplace else, where I don't have anything to trigger it with!
I will need to dig out my old X0Xbox and use that just to throw triggers at it.

I think I may also have to investigate the possibility that I have some dud chips. Have another project that is also exhibiting some bricky behavior, which uses chips from the same batch.

May I ask where you sourced your chips? (As I am wondering if that is my problem)

calaveras · Post by **calaveras** » Sun Mar 27, 2016 1:56 pm

Well I forgot to take my MST enveloper with me to my bench last time I went so I haven't had a chance to take advantage of the advice Mr.Mattson gave us.
The TL074s I bought are from Tayda. I have heard people report bad things about some chips from them in the past, but I have never had an issue.
I'm going to actually get around to cracking it open again Thursday or Friday.
I've also got a X0Xbox to fix and a few other things, so I expect to hit the bench for a couple days.

Maxx mayhem · Post by **Maxx mayhem** » Sun Mar 27, 2016 6:13 pm

Mine were from Tayda as well. I too have had better luck earlier... I think I'll pick up some chips from Mouser and just see what happens...

Maxx mayhem · Post by **Maxx mayhem** » Mon Apr 04, 2016 6:28 pm

Well, got one of my envelopes working today - for 5 minutes, which is about how long it worked initially. I'm going to try and track down bad traces, but all I can say right now is

calaveras · Post by **calaveras** » Tue Apr 05, 2016 12:26 am

Finished an MST VCO last night. Also not working.

I really need to bench it out and figure if I have dud TL074's or some other issue. All I know is that for every MST diy that I have bricked I've completed 2 or 3 other projects with no issues.
I'm going through some family health issues right now so I've been using the soldering as a way to relax my mind. But when it comes to troubleshooting I get very frustrated and pissed off very fast.
Let's just say I am your typical male that can not deal with emotions very well.

So I haven't had time to avail myself of Geo's advice.
I have visually inspected the crap out of both, checking the polarity of every single thing. Checking all the joints to be sure they are good.
I really hope it is not bad traces. That would suuuuuuuck.

Maxx mayhem · Post by **Maxx mayhem** » Tue Apr 05, 2016 9:20 am

I talked to ST yesterday before I even tested my envelope and related to the ongoing problem of my VCO. Now, In the envelope, these capacitors keep getting blown. On the VCO, these diodes keep getting blown. As to the diodes (and I would assume this may be the same thing with the caps as well) ST told me to look for a broken trace on the vco, and using a meter, as the break would likely not be visible under light magnification. Their advice was to start in the area of the affected parts and work outward. Now, I am having problems with 2 /3 of the envelopes I have built, the first one being fine right off the bat. I have run into snags with 4 of 28 kits attempted so far, 1 I replaced, the others I'm intent on defeating. :cat:

Maxx mayhem · Post by **Maxx mayhem** » Sun Apr 17, 2016 3:58 pm

OK so now I am thinking the problem is that the caps I'm using (blowing) are 25V. The BOM sends you to Mouser for 50v caps, so that is my next step.

mmm · Post by **mmm** » Sun Apr 17, 2016 4:57 pm

Maxx mayhem wrote:OK so now I am thinking the problem is that the caps I'm using (blowing) are 25V. The BOM sends you to Mouser for 50v caps, so that is my next step.

I doubt if the cap voltage is the issue. Polarity on the electrolytics I'd believe. If they're backward, they'll blow.

The highest voltage in the EG is 12V. 25V caps can handle double that.

Maxx mayhem · Post by **Maxx mayhem** » Sun Apr 17, 2016 5:08 pm

mmm wrote:
Maxx mayhem wrote:OK so now I am thinking the problem is that the caps I'm using (blowing) are 25V. The BOM sends you to Mouser for 50v caps, so that is my next step.
I doubt if the cap voltage is the issue. Polarity on the electrolytics I'd believe. If they're backward, they'll blow.

The highest voltage in the EG is 12V. 25V caps can handle double that.

I verified the polarity, the module worked for a few minutes before failing. Am I looking for a broken trace somewhere?

mmm · Post by **mmm** » Sun Apr 17, 2016 6:15 pm

[quote="Maxx mayhem"[/quote]

I verified the polarity, the module worked for a few minutes before failing. Am I looking for a broken trace somewhere?

I have no idea what you're looking for. The dozen or so I built all worked.

Start posting pix of both sides of both boards. Maybe a second set of eyes can catch something you're overlooking.

I'm assuming you sourced your own parts and didn't get the full kit.

Maxx mayhem · Post by **Maxx mayhem** » Sun Apr 17, 2016 7:52 pm

George, I photographed the logic board, and then put it into photoshop and blew it up. Hit a few joints that looked a bit funky , but then I noticed that if I hold my finger on the bottom 4 pins of U4 (tlo74) it cycles.4-7. One hour later, replaced a resistor in one spot, worked, but now seem to have another issue. I'll hammer this abit more before putting up pix. Thanks

Maxx mayhem · Post by **Maxx mayhem** » Sun Apr 17, 2016 9:02 pm

Alright, I threw around 9 cents worth of parts at it, it was still intermittent. THATs when I figured out I forgot to solder one of the headers.

So now I have 2 rather fine MST Dual envelopes working, one still to get working, but you know... Meatloaf. Anyway No. 3 will have to wait till next weekend.

mmm · Post by **mmm** » Sun Apr 17, 2016 9:22 pm

Maxx mayhem wrote:Alright, I threw around 9 cents worth of parts at it, it was still intermittent. THATs when I figured out I forgot to solder one of the headers. So now I have 2 rather fine MST Dual envelopes working, one still to get working, but you know... Meatloaf. Anyway No. 3 will have to wait till next weekend.

So technically, Synthrotek was correct. It WAS a broken trace.... sort of, the result was the same...

debolish · Post by **debolish** » Fri May 06, 2016 8:47 am

Failure here as well. We just finished both the dual VCA and the dual AD/ASR. VCA is working perfectly, AD/ASR not so much. Been checking, and re-checking and re-re-checking our work, had others check & re-check our work, No happy ending here. Just emailed Synthrotek.

Maxx mayhem · Post by **Maxx mayhem** » Fri May 06, 2016 1:02 pm

I just got some chips from Mouser to replace the tl074s from Tayda. Might get to it this weekend, Hoping that's the problem, because I have got the front panel fixed now AFAIK, but the logic board still isn't cycling.

debolish · Post by **debolish** » Fri May 06, 2016 1:16 pm

We replaced the chips as well. Was hoping that would be the fix, but no dice.

Maxx mayhem · Post by **Maxx mayhem** » Fri May 06, 2016 3:10 pm

Do you get an led blink on power up?

debolish · Post by **debolish** » Fri May 06, 2016 4:00 pm

Long story short-ish, 1 of 6 knobs and 2 of 6 switches were missing from the kit. The module doesn't seem to receive a trigger input to fire the envelopes. It just puts out a constant dc level based on the env depth knob. The invert switches (which were the 2 missing, which we replaced), do have an effect on the dc output level, but just change the scale. Both channels function the same. We also replaced all the tl074 and cd4011 ic chips with no difference. We also verified power supply continuity getting to all of the ic chips.

Maxx mayhem · Post by **Maxx mayhem** » Fri May 06, 2016 4:22 pm

Hard to say - I've got 2 of 3 working, the inv. switch adds 5v to the output level of the inv out. I am assuming that you now have all of the knobs...

debolish · Post by **debolish** » Fri May 06, 2016 4:47 pm

Yah. Good on the knobs. May have to throw in the towel on this one.

Maxx mayhem · Post by **Maxx mayhem** » Fri May 06, 2016 6:53 pm

Then evil wins. Sometimes best to put a module aside for a week or 2 and then look at it fresh. I'm still getting no love from a VCO, but I'm not giving up on it yet.

silenttxa · Post by **silenttxa** » Tue May 24, 2016 3:03 pm

I too have had issues. I've assembled most other MST/Synthrotek modules with no problems until i started working on this guy. I first bought the kit, which was missing some pots and switches from Sythrotek, and they sent out the missing parts.

Never got it to work, so i bought the PCB and put a BOM together of the parts needed for the rear PCB. 2nd try i can get it to work, only if i wiggle the power plug into place. Even then the lights on the front are extremely dim.I noticed that the guide on the site has not been updated to accommodate the latest PCB rev, as some components have been moved, etc.

debolish · Post by **debolish** » Tue May 24, 2016 5:09 pm

I gave up and ended up sending mine back. Waiting on the word as to what the issue is.

MUFF WIGGLER

MUFF WIGGLER

MST Dual AD/ ASR Envelope Issues