TTSH Ver.3 (rev.8) General build thread

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amir
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Thu Mar 05, 2020 11:08 am

I posted pics a long time ago but I will get some new ones later today. Everything is in the right place. Out of insanity I started probing every diode on the main board last night and found two that were flowing in both directions. They are in the vca section. I am assuming these wont fix the current problem but I wonder if they were bad to begin with before i even put them on the board. it takes a lot to damage a diode to make it open up like this.

A board this big really needs some reference points. The original arp schematics are also a lot more helpful than the ttsh schematics which are purposefully made confusing. I don't understand why the builders think they've created something new and unique here and need to be so protective of the design. it is literally copying an old design. There is no intellectual property here, just post the trace.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Thu Mar 05, 2020 2:53 pm

The replaced diodes in the vca section display same behavior which points to the open circuit in them as being part of the larger circuit in that section (not a fault).

Pictures of 4012 card attached.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Fri Mar 06, 2020 12:52 am

So after a lot more probing... A few of the fine tune slider pins were shorting out. I followed it on the front of the board and my red wire for the -15v missing trace was sitting on top of one of its traces. Just sitting not making any contact that would allow a connection to be made. I lifted the wire up in the air and that short resolved itself.

The only other weird part in this section is the 3.3M resistor that sits right under the filter card. Every other resistor in this section came up as the correct value on the DMM but the 3.3M comes up as 187k with the filter card removed. I checked the colors and it is an actual 3.3M resistor. Is this normal based on where it is in the circuit and other components around it or is it bad? It is connected directly to the slider (pic attached).
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Re: TTSH Ver.3 (rev.8) General build thread

Post by fuzzbass » Fri Mar 06, 2020 8:14 am

amir wrote:
Fri Mar 06, 2020 12:52 am
So after a lot more probing... A few of the fine tune slider pins were shorting out. I followed it on the front of the board and my red wire for the -15v missing trace was sitting on top of one of its traces. Just sitting not making any contact that would allow a connection to be made. I lifted the wire up in the air and that short resolved itself.

The only other weird part in this section is the 3.3M resistor that sits right under the filter card. Every other resistor in this section came up as the correct value on the DMM but the 3.3M comes up as 187k with the filter card removed. I checked the colors and it is an actual 3.3M resistor. Is this normal based on where it is in the circuit and other components around it or is it bad? It is connected directly to the slider (pic attached).
There is no point in measuring component values in-circuit; you are measuring the combined value of every adjacent component. Is your filter problem resolved?
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Fri Mar 06, 2020 11:02 am

Not yet, it has improved a bit but something in the circuit is still not functioning correctly.

I am not getting any kind of signal on the inverted input line (vcf2?) either. The gain trimmer crackles as it’s being adjusted and the offset has to be maxed clockwise before any sound comes out. the resonance at zero produces a very faint sound but increased about halfway, the volume exponentially grows. I am focusing on this part of the circuit right now unless you guys have any other ideas.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Mar 11, 2020 9:00 pm

Delete.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Thu Mar 12, 2020 5:22 pm

Does anyone on here have the trace file for the filter cards?

The 2n3904 shown in the attached schematic are supposed to be thermally coupled and were on version 1 & 2 of the TTSH. For some reason they were not oriented in this format on the cards.

I want to make sure one is not supposed to be flipped around like many other things on this board. My signal gets very faint at this point in the circuit, which makes sense since this is what feeds the feedback part of the circuit. Looking at the board alone would makes me think that they are not making the correct connections.


That aside, has anyone tried these caps yet? I got some of the slow fade leds and they look really cool but want to dim down a bit with caps not resistors to keep the cool pwm looking color change. link: https://www.ebay.com/itm/NEW-10-FADER-k ... Sw7NVeS6ij

Led video:


thanks
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Sat Mar 21, 2020 2:18 pm

Few updates:

1) filter is still not working.

2) I’ve measured the incoming signal with and without the filter card in. The signal is getting reduced to ~2vpp on the pin where it enters the filter card. At the osc it is 10vpp and patched directly into vca yields same 10vpp. Something is happening in the filter section.

3) there aren’t many components in the main board part of the filter section. So I thought maybe something weird was happening in the led rails and bleeding into the sliders causing them to short the signal?

4) So next I checked the led rails with all power disconnected. I am getting some resistance between the -15v and ground rails but when I connect between 15v and ground or across -15v and 15v... I get no movement on the meter. It sticks at the default 1 value on the screen at all resistance ranges. Does this seem normal?

5) not sure what else to check. Any ideas would be greatly appreciated. Thanks

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Re: TTSH Ver.3 (rev.8) General build thread

Post by jandavidhoo » Wed Apr 22, 2020 5:31 am

Hey everybody!
I just finished my TTSH Ver3 and I'm so relieved everything works without too much troubles straight away. So much thanks to LED-man and Fuzzbass for the great guides.

I have two question somebody might be able to help me with, and I can't find an answer to when searching. So I'm sorry if this has come up before.

1. The 4012 filter is very noisy, way noisier than the 4072. I used matched transistors, and base frequency and V/Oct tracking is perfect. It's just very noisy and I don't know if this is designed. Calibrating does not help, and setting the trimpot gives me a scratchy potsound, but I think that might be normal since it's also messing with the DC offset. Anybody else had this problem?

2. The 4072 does not open above 2khz (when I open the resonance completely the peak is never above 2khz). I read that this filterdesign is flawed in that it does not open as far as the 4012, but 2khz really sounds like something might still be wrong.

Also I'd like to know what the Piher trimpot is for on the filtercard itself, because I can't find the answer anywhere. Is it for V/Oct tracking? Because the trimpot on the main board does (as designed) not work for this filter, and I the Piher trimpot does absoluty nothing audible to the frequency of the filter (And I can't get it to track v/oct properly, I reflowed the trimpot and the trimpot is functioning)

Hope anybody can help me out :) I'm still really not an electronics-buff.

Thanks!
David

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Re: TTSH Ver.3 (rev.8) General build thread

Post by FactoryDefault » Wed May 13, 2020 9:27 pm

Here's a potential improvement for the speaker-wire-to-board connectivity.
Maybe someone already suggested this but I haven't seen it.
I wanted to figure this out after a speaker wire pulled a pad from the board during the shapers mod install.
These terminal blocks works great:
https://www.digikey.com/product-detail/ ... ND/1150135
speaker terminal.JPG
I also tried an equivalent component by Wurth but it was too small to accept my speaker wire.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jun 24, 2020 9:27 pm

After a lot of reflowing and recalibrating my scope, I've gotten most of my VCOs saw/square to output anywhere between 10.2vpp to 11vpp on the squares. I am not sure if this is good enough? I get slightly better numbers when I switch the lm3046 for real ca3046 chips.

I am still running into two issues though and I need v3 specific help. My noise section has been entirely checked. Everything is soldered correctly and I even put brand new opamps and transistor in. The transistor is oriented correctly and currently has a 337-16 in it. I get 19vpp out no matter what I do. If I set my scope to 1 volt division, the signal goes out of range on my screen but my scope shows 11vpp in this setting. Am I just having a scope issue here as well or is there an unknown issue with the v3 board? Others have said they get a perfect 10vpp out of their noise section. If you get 10vpp, can you tell me what you are setting your scope settings to?

My second issue, and this may have been around previously but I never noticed it, is that when I have all output and filter faders down.. if I increase the pitch of any of my VCOs to max ear bursting level, it starts to bleed out of my left speaker. You can barely notice it. it is somehow going directly into that speaker and only starting at about 8+khz. Anyone experience this one before? I have visually inspected every joint and looked for parts heating up or smoking and it all looks good.

Otherwise it seems to be working 100% again / sounds like it should. Just not sure about the VCO bleed and noise section. Since I haven't received my vco pcbs yet, looks like I am going to have 3 extra 4027-1 boards sitting around.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jun 24, 2020 9:30 pm

These are some pictures from VCO2 outputs and the noise with my scope set to auto fit.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jul 01, 2020 4:25 pm

These should be easier to diagnose! Wish the entire board looked like this! Missing a few resistors but should hopefully be able to test these next week! :)

Still tracing the noise section but haven’t found any issues and it’s still outputting 19vpp on my scope. The osc sub board power supplies are on the noise section schematic. Are they related somehow? Could explain my osc vpp issues as well.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Tue Jul 07, 2020 12:24 pm

Built the new boards and I am getting slightly lower vpp numbers but I also hand picked every part using a lab multimeter. I was very surprised at how far off some of the resistors were, much larger than the advertised 1% range. Everything seems fine except vco2 square out. The freq is fluctuating a few hz up and down constantly. The other shapes are solid. The triangle every few seconds will move 1hz up or down. Is this normal behavior? If not, I am thinking it might be the 2n3906/2n5072 pair maybe?

Also why is the compensation cap missing on vco2 square opamp? Vco3 has it. I noticed the same thing on the arp schematics, was this a mistake? Is this why it’s unstable?

Thanks for any help!
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Re: TTSH Ver.3 (rev.8) General build thread

Post by fuzzbass » Tue Jul 07, 2020 1:07 pm

amir wrote:
Tue Jul 07, 2020 12:24 pm
Built the new boards and I am getting slightly lower vpp numbers but I also hand picked every part using a lab multimeter. I was very surprised at how far off some of the resistors were, much larger than the advertised 1% range. Everything seems fine except vco2 square out. The freq is fluctuating a few hz up and down constantly. The other shapes are solid. The triangle every few seconds will move 1hz up or down. Is this normal behavior? If not, I am thinking it might be the 2n3906/2n5072 pair maybe?

Also why is the compensation cap missing on vco2 square opamp? Vco3 has it. I noticed the same thing on the arp schematics, was this a mistake? Is this why it’s unstable?

Thanks for any help!
If you see your VCO2 pitch fluctuating, isolate the cause to either the 4027-1 (by moving it) or the CV summing section. If its in the summing section, you should be able to measure the voltage fluctuation with the core removed, in vicinity of the 84k5 resistor.

If you are going to be this thoroughgoing, the next thing to do is eliminate the sockets. You don't need them. I have on several occasions traced problems to bad contacts in what appeared to be high quality sockets. Also found that sockets in combination with cheap little pin straightening tool (squeeze for perfect 90 degree pins) was the road to heartache. I stopped using sockets about two years ago, no regrets.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Tue Jul 07, 2020 2:05 pm

Thanks fuzzbass! I have tried swapping cards but have same issue. I hate sockets as well. I’ll try retouching the main board sockets but it’s strange that only the pwm/square is fluctuating on vco2. The saw is solid without any movement. I’ve checked the cv summing section before and didn’t see any issues there but will double check. Is the dc offset very different on vco2 compared to the other oscillators? Maybe my counter is freaking out because of that?

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Tue Jul 07, 2020 3:41 pm

I measured at the 84k5 resistor with the core removed and I am getting some fluctuations. It appears to be after the resistor not on the slider side. I measured vco1 and vco3 they fluctuate as well but it’s not much, more like .00002v. Vco2 is around .00030v up and down constantly. I tested my ac decoupling theory at the filter with my meter and the freq seems to be staying constant there. Jumps up and down 1hz every once in a while. Still feels weird that it’s able to measure the other 2 at the osc output but can’t with vco2.

If that sounds ok, I am going to move on back to the noise section. I am still getting about 20vpp out there. I changed the 1k resistor just to be sure it wasn’t bad but that didn’t change anything. I have reflowed all of it and nothing changed either. I am getting a good noise signal but it’s going from -10v to 10v. I might just remove everything in that section and replace it all but worried it won’t change anything. :(

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Re: TTSH Ver.3 (rev.8) General build thread

Post by KSS » Wed Jul 08, 2020 3:15 am

Each time you do a whole swap of parts you're starting from ZERO. All over again. Don't keep doing that. It's why I bowed out. You can't fix a moving target. Change ONE thing at a time. Check ONE thing at a time. Only move to TWO things if you can't fix one thing.

I hear Dr Suess calling. Thing1 and Thing2!

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jul 08, 2020 3:21 pm

KSS wrote:
Wed Jul 08, 2020 3:15 am
Each time you do a whole swap of parts you're starting from ZERO. All over again. Don't keep doing that. It's why I bowed out. You can't fix a moving target. Change ONE thing at a time. Check ONE thing at a time. Only move to TWO things if you can't fix one thing.

I hear Dr Suess calling. Thing1 and Thing2!

I rebuilt all the VCO sub boards because I was sure that's not where the problem was coming from and at this stage I am assuming a near 11vpp square is just normal for the square signals coming out of this thing. Its impossible that across 6 sub boards I have managed to either install a bad part or damaged the same exact part on every single board. The original rare parts for the first 3 came from thonk and the new boards were sourced from trustable US sellers.

For the noise section, I am not replacing all parts. I have already replaced the opamps and main tranny. I have traced the signal all the way to the last opamp. It is a perfect 20vpp up to this point. after it leaves the last opamp, it is coming out as 20.8vpp. I plan on reheating the socket for this opamp just to make sure there are no cold joint but not sure what else to look at around this opamp because the signal is the same across the few passives here and I have already replaced the 1K resistor which is the point at which it should drop down to 10vpp. What would you do at this point? I appreciate any help that you guys can give.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jul 08, 2020 4:24 pm

Just for future reference, VCO2's square lm301 is missing its 3p3 cap. This is also present on the original 2600 schematics. I am not sure if this was a mistake but it creates a major dc offset that causes my freq counter to go crazy when measuring the output. It almost looks like it is self oscillating on my scope. I had some extra lf411 op amps and tried it out since it has internal compensation and the pins are already not connected. Now I have a perfectly stable pwm/square out of VCO2 and can measure the freq directly out of the vco2 output. The output went down to 10.7vpp also at the square. No more pulling my hair out. :D

edit: Tired so I am quitting for today but will need to run more test. I played around with it a bit and it finally sounds so good! Even VCO1 and 3 are sounding better!
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Re: TTSH Ver.3 (rev.8) General build thread

Post by fuzzbass » Wed Jul 08, 2020 6:15 pm

amir wrote:
Tue Jul 07, 2020 2:05 pm
Thanks fuzzbass! I have tried swapping cards but have same issue. I hate sockets as well. I’ll try retouching the main board sockets but it’s strange that only the pwm/square is fluctuating on vco2. The saw is solid without any movement. I’ve checked the cv summing section before and didn’t see any issues there but will double check. Is the dc offset very different on vco2 compared to the other oscillators? Maybe my counter is freaking out because of that?
Something here not adding up. The pulse wave is derived from the saw using a comparator. If the saw frequency is solid, then so is the pulse frequency. There is no frequency modulation possible in the pulse waveshaper. Are you sure you are not observing PWM, not pitch?
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jul 08, 2020 6:29 pm

Yes it was definitely pitch, going up and down non-stop about 10hz. It wouldn’t happen if I measured at the filter since I have the coupling caps there. With the lf411 it’s rock solid like the saw and vpp dropped as well.

The whole synth sounded a bit hollow to me before but the sound is much fuller now. Sounds massive.
Last edited by amir on Wed Jul 08, 2020 8:39 pm, edited 1 time in total.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Wed Jul 08, 2020 8:38 pm

.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by KSS » Wed Jul 08, 2020 10:58 pm

PWM often leads to perceived pitch changes. That's one of the reasons WF source for PWM matters. Kind of like what happens with FM modulation and why we like linear and TZ for that.

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Re: TTSH Ver.3 (rev.8) General build thread

Post by KSS » Wed Jul 08, 2020 11:16 pm

Somewhere in this synth there's a part wrong, ior a hi-Z current path, or.. The continuing noise issue points that direction, but as posted b4 the moving target approach makes finding the solution more difficult than it might be.

When referrring to the service notes keep in mind that the earlier one 100+ pages is using older boards and 1337 OPas. The newer one, 58 pages, is using 301's and mostly conforms to the orange black 2600's.

I've said it before and I'll say it again. Scope the rails. Not at one point only. Everywhere! Into *each* board, into *each* OPA. If you used polystyrene caps anywhere, be suspect of them. With all the re-flowing that's been happening, they might be compromised. I'm NOT saying to replace them -if they're even a part of the build. I *am* saying you've got to do some down and dirty TESTING to find out where the problem lies. Because problems like this DO 'lie'. Especially the way the later TTSH's have become a conflagration of several mods and 'fixes'.

Get back to basics. Start with power. EVERY WHERE. And not only with a silent synth. You need to look at the rails with things happening in the synth. Even parts you're NOT using for the direct test.

Don't fall into the traps that catches us *all* at times. You know the drill. You're looking for something, have a thought of where it 'might' be, and think, No, it wouldn't be there. So you-we go on looking everywhere -ELSE- and eventually find it in that place it "couldn't" be or "never" would be.

Fact is, you -and we- *don't know* what's wrong here. By definition, that means *everything* is still 'on the table'. Start low and close to mains input, METHODICALLY -with *written* notes- checking, crossing T's and dotting I's.

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