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

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fuzzbass
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Post by fuzzbass » Wed Sep 11, 2019 9:55 pm

I have good results soldering jfets at 600f/315c and one let at a time, with 30 seconds between legs. Go fast on each leg.

If you have reverb hum that goes away when you create an alternate path to earth ground, I'm betting your AC-DC brick has a two prong AC plug. These bricks don't really shunt 0V to earth so things improve a lot as soon as a good earth ground path is established, such as patching something on the synth to a device with a clear earth ground path (or building a connection from the earth pin on your appliance receptacle to 0V on the TTSH). There are lots of ways to work around this, but if you find it to be an annoyance, get this Meanwell brick:
GST125A12-P1J. It does not have a floating ground.
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Post by ZatsuOn » Sun Sep 15, 2019 7:54 pm

Many thanks to all the TTSH experts who have posted their wisdom and experience here!

I have some questions about the PSU build that I don't see the answers to (unless I missed them the 78 pages!)

For the power regulators, what's the recommended way to deal with the heat sync pads? Do they get soldered? Gob of thermal compound? Just laid on top with no connection?

And for the 100uH coils, there's a long lead / short lead that presumably indicates which end of the coil each is attached to. Does orientation matter at all?

Finally, in the photo on the previous page I notice a fuse in the box next to the power inlet, but haven't found any discussion about that -- is that a recommended addition?

Thanks!

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Post by fuzzbass » Mon Sep 16, 2019 12:45 pm

ZatsuOn wrote:Many thanks to all the TTSH experts who have posted their wisdom and experience here!

I have some questions about the PSU build that I don't see the answers to (unless I missed them the 78 pages!)

For the power regulators, what's the recommended way to deal with the heat sync pads? Do they get soldered? Gob of thermal compound? Just laid on top with no connection?
The large square pad must be soldered to the big tab on the regulator. Don't put any thermal goop on there! What really helps doing this are 1. liquid flux or flux pen, 2. Constant pressure down on the regulator until solder hardened, 3. a fat tip on your soldering pencil, with a dab of solder on it to create more contact area.
ZatsuOn wrote:And for the 100uH coils, there's a long lead / short lead that presumably indicates which end of the coil each is attached to. Does orientation matter at all?
Either way around.
ZatsuOn wrote:Finally, in the photo on the previous page I notice a fuse in the box next to the power inlet, but haven't found any discussion about that -- is that a recommended addition?

Thanks!
That is a 1A PTC (resettable) fuse. Its optional, but prevents a situation where a short takes down one power rail, but not the other. This is imperfect however, because the regulators themselves have short circuit protection, and if that is faster than the PTC, it won't work. It does not hurt anything though.
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hofmann25
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Post by hofmann25 » Thu Sep 19, 2019 6:39 am

Has anyone converted the 4072 VCF into a Euro Rack Module?

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Post by sduck » Thu Sep 19, 2019 9:40 am

There have been several adaptions of the circuit - steffcorp's version comes up in a google search, but I'm pretty sure there are several other versions.
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Post by hofmann25 » Thu Sep 19, 2019 5:12 pm

sduck wrote:There have been several adaptions of the circuit - steffcorp's version comes up in a google search, but I'm pretty sure there are several other versions.
Ok cool.

Just confirming. I don't want to remake the circuit. I/we already have one built. I just want to make it into euro rack. I'd imagine you only need the pinouts? Then another PCB for Pots & I/O...

Found this>>>
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Post by fuzzbass » Fri Sep 20, 2019 9:03 pm

Is there a procedure for setting the bias trimmer on the 4072? It is not discussed in versions of the 2600 service manual that otherwise present the 4072.
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Post by hofmann25 » Sun Sep 22, 2019 5:28 pm

fuzzbass wrote:Is there a procedure for setting the bias trimmer on the 4072? It is not discussed in versions of the 2600 service manual that otherwise present the 4072.
Would that have a large effect on setting it up for Euro Rack?

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Post by nicdro » Thu Dec 12, 2019 2:25 am

Hi all’
Unfortunately I can’t get my sync working. I have VCO 1 and 2 connected to V1/2 and VCO 3 connected to S1. I used shielded cables. I’ve jumpered J3. I get weird constant syncing of VCO 3 by both other two oscs even if I have the Switches disconnected (which are shielded as well)
Is the jumper setting wrong? False components? It’s my second attempt with new pcb, cables and components. weird thing is that with or without the switches when I turn the synth on the vco3 is stable in the beginning and picks up the sync after 10sec or so.
Please help! Thanks!

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

Post by amir » Thu Feb 27, 2020 12:53 pm

Hey guys! I have a really weird issue and have chatted a bit about it with Patrick over email but haven't gotten anywhere. My 4012 worked for a few days after I finished my build around 3 years ago and then never came to life again. I replaced almost all components on it but eventually gave up and moved on to the 4072 which worked without any issues since then. A few days ago it suddenly cut out as soon as I patched in a sine from vco2 into the jack. This had never happened before. Over a few days I opened it up and even took the panel off and have been looking at the schematics and probing around like crazy.

As I was emailing Patrick a pic I suddenly noticed that one of my power caps (-15v side) was reversed in the filter section. I have no idea how I missed this nor how it had been working perfectly like this for all these years. I've used it on multiple recordings and everything was functioning as it should. So I got new 1uf cap and replaced it in correct orientation. Nothing around the board seemed to change from before.

Here is where I am stuck now. Neither filter outputs anything. I can measure the signals coming in at jack normals but after that they disappear to 0v. This is only with the filter cards plugged in. I have replaced the lm3900 with no results and even tried a tl071 on the 4012 (with cap removed) while I wait for new op amps to arrive. I can sort of get the 4012 to self oscillate like this by adjusting the trimmers to a very specific point but nothing else comes out.

Probing around with the filter cards plugged in, the 4012 is causing the power across the entire board to become reversed, all negative voltages become positive and positive become negative (edit: something may have been shorting the board on my desk when this happened as I plugged it in again and problem was not there). With the 4072 plugged in the negative rail only drops 2-3v. this didn't happen when I had the polarity of the cap reversed with either filter card. I know I am missing something very obvious but have been looking at it for such a long time that I just can't see it. Any idea where I should look or measure to try and figure out what's shorting out? I don't believe it is anything on either card as I have replaced almost all components on them and they are both giving similar results when plugged in. I'd appreciate any ideas, thanks!

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

Post by amir » Thu Feb 27, 2020 2:38 pm

Just an update, turns out the panasonic coupling caps are all bad. Not sure how that happened but running resistor legs across them gave me some sort of a signal coming into the filter. Not sure if the tl071 is the problem at this point on the 4012 but I can get the signal to come out of the filter only at a very specific point between all the trimmers. I can get it to also self oscillate at a very specific different point. Ill wait until the new op amps arrive unless someone has some ideas?

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

Post by fuzzbass » Fri Feb 28, 2020 7:41 am

Amir,
Does the synth behave well with neither filter board installed? Power rails where they should be?
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Fri Feb 28, 2020 1:03 pm

Everything else works as it should. I had one resistor in the reverb section go bad again but I think that is related to a loose cable separate from this. Power is measuring at 15v,0 and -15. I am running a linear supply going into the voltage regulators to separate the leds and on to power the rest of the board. I have some better op amps on the way but they won’t be here until next week likely.

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

Post by amir » Fri Feb 28, 2020 1:06 pm

It behaves well even with the filter boards plugged in, just no sound until I found one specific position between all the trimmer adjustments where a little sound came out. But slight turn on either trimmer would either distort the signal or cut it out completely. Same with self resonance which seemed to be tracking even but would cut out as soon as either trimmer was touched. Sorry for two message, typing on my phone.

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

Post by amir » Sat Feb 29, 2020 7:35 pm

Got some op amps in the mail to try out on the 4012. I am using a LF411 and the self oscillation sounds much cleaner. However still not getting anything out.

1) I tested all the transistors in the circuit using a multimeter in diode mode and they are all the correct type and seem to be working. the lead that goes to the dual jfet from the ladder drains on both pairs to zero after connecting the probes.

2) I used a scope and there is a signal coming in up to the first 2n3904, after that nothing or at best a very faint signal.

3) did same test on this 2n3904 transistor, as rest, with multimeter in diode mode and seems ok.

4) the side that is supposed to be going to the negative rail on this transistor is around only -1.06v <- this seems wrong as there are only few small resistors in between and seem like a large drop.

Should I replace that 2n3904 even though it seems to be working? don't want to remove anything unnecessary with desoldering risks. Makes sense damage would be somewhere in the negative rail as that is the cap that was originally backwards on the main board. Anywhere else I should look on the 4012 board that would also be connected to the negative rail and might be the actual issue and not this 2n3904 alone?

sorry if any of that doesn't make sense, please let me know if it does and I will clarify. thanks!

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

Post by LED-man » Sun Mar 01, 2020 9:18 am

I left some 4012 and 4072 pcbs, which are available for exchange.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Sun Mar 01, 2020 3:30 pm

I’ll let you know if I need them! I am about to pull my hair out at this point. I’ve swapped almost all the transistors at this point. Going one by one but I already know they are good. Are you guys certain the 2n3958 bug is present in the filter? Thats the only thing I havent tried yet. I want to pull it out and not flip the legs. Because everything else is new. The only things I haven’t replaced are the ceramic caps or the diodes. But I highly doubt they are bad because they pass diode test on multimeter and have very high ratings. Probably have to reverse them with 100v before they go bad and start leaking.

So again, are you guys sure the 2n3958 legs need to be swapped here? Without the board trace I have no way to know!

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

Post by amir » Sun Mar 01, 2020 7:33 pm

Removed and replaced all transistors. Luckily I had a bc558b left, not so lucky as soon as I plugged the 4012 card back and turned it on the bc558b started smoking and got super hot. Since I already replaced all transistors, not sure what it could be. :doh:

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

Post by KSS » Mon Mar 02, 2020 1:48 am

amir wrote:
Sun Mar 01, 2020 3:30 pm
I’ve swapped almost all the transistors at this point. Going one by one but I already know they are good.
Almost?? The dual FET is the most likely to be hurt during installation. Most sensitive and vulnerable of all transistors. It also lives at the 'end' of the filter chain, and should therefore be among the first suspects to check. Because it's expensive, it sometimes gets passed over. You can put a couple less expensive plain JFETs like J112's in its place to make a basic check that other issues are not the problem.
So again, are you guys sure the 2n3958 legs need to be swapped here? Without the board trace I have no way to know!
Don't have direct experience with V3. But even with that heinous dark solder mask you can still see enough to follow the traces. And if not, pull the suspected part and trace what you can using a meter. Old school fox hound, and crystal earphone with R/C are also useful for investigation and troubleshooting.

Whoever decided that dark soldermasks were a good idea needs to be forced to trace and troubleshoot these for a living. Opaque soldermasks are the spawn of the netherworld. AKA hipsters.

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

Post by amir » Mon Mar 02, 2020 2:54 am

At this point all transistors have been swapped. The final transistor that was replaced was the bc558b which smoked as soon as it was turned on. The jfet has been replaced a few times as well. I ran out of parts so I placed another order.

I am going to replace the 1n4148 diodes next before putting a new bc558b in. I have a feeling they might be damaged. It’s just not showing up on my scope or meter, causing the transistor circuit voltages to shift and creating an unintended open circuit resulting in the bc558b to burn up.

Changing the 2n3904/2n3906 pair had a significant impact with gain while the filter was only self oscillating. My meter had shown both those as being good also before I replaced them. I did those last right before doing the bc558b.

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

Post by fuzzbass » Mon Mar 02, 2020 7:49 am

Hopefully all of this has been addressed, but just in case...

There are multiple bugs in V3 affecting filter operation:

1. There is a trace missing on the main board resulting in one of the power rails not reaching the VCF sub board (not entirely sure but I believe V-).
2. 2N3958 on the 4012 has pins 5 and 6 reversed
3. Trace missing for V- to LM1458 on 4072
4. BC558 footprint image reversed on 4012
5. KBD CV and 1st FM input (normal ADSR) jacks may be shorted by VIAs and/or traces that encroach on component footprints.
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Re: TTSH Ver.3 (rev.8) General build thread

Post by amir » Mon Mar 02, 2020 1:43 pm

Thanks! All of those have been addressed. I feel there is another hidden bug in the filter section that nobody has discovered yet. Originally I had the negative rail power cap reversed, the 4072 filter functioned like this for 3 years almost without a problem. It even calibrated perfectly and was used on many recordings. Until finally some component gave out and I am guessing it’s the 3904/06 pair there too but haven’t got to that board yet. The 4012 filter is a bit more fragile it seems and burns out faster with whatever bug there is in this section that I haven’t discovered yet.

Essentially I think the components overall can withstand a lot of stress which is why nobody has caught this yet but there has to be another incorrect trace somewhere in the filter section. Or otherwise some of the board may have defective traces causing internal shorts. I’ve successfully built almost all of the MI boards and never had this many issues trying to get a simple thing as a filter to work.

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

Post by KSS » Tue Mar 03, 2020 4:38 am

amir wrote:
Mon Mar 02, 2020 1:43 pm
Originally I had the negative rail power cap reversed, the 4072 filter functioned like this for 3 years almost without a problem.
Essentially I think the components overall can withstand a lot of stress which is why nobody has caught this yet
Aluminum electrolytic caps can usually indefinitely withstand reverse current up to one half their rated working voltage. And some are known to have lived tens of years at close to full working voltage.

Don't try that with a tantalum cap! Although one tantalum was called out as the "Chuck Norris" capacitor for doing exactly that. Almost certain that particular case was a mismarked capacitor.

With Bipolar transistors it's the emitter-base potential you need to watch out for. While the others may be quite high, this E-B is often only 5 or 6 volts.

Also, one shouldn't put transistors reverse bias 'tested' as noise sources, into subsequent normal usage.

@fuzzbass Thank you for the list of V3 VCF specifics. :tu:

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

Post by amir » Wed Mar 04, 2020 10:13 pm

Replaced the 3 diodes that are back to back and the bc558b no longer burns out on power up. The funny part is that the diodes displayed as working on the multimeter also. Side note, buy up those bc558b transistors as they are obsolete now. Digi has a good amount still left in stock though.

I am finally able to get some noise out of the 4012 filter but it is very low in volume and still only at a very specific point between the 3 top trimmers. offset is turned max clockwise, gain is 3/4 full clockwise and freq trimmer is around center. If I boost resonance the volume increases overall but does not go into self oscillation. I have to move the trimmers to a different point to get it to self oscillate.

On the 4072 filter, I replaced the 2n3904/06 pair, the 2n3906 next to it, the electro caps, the lm3900, 1458p op amp but still no sound out of that one. Doesn't matter where the trimmers are. No self oscillation either. I need to match some transistors before I switch the rest.

Any ideas on the 4012 board? Everything (minus the resistors and caps) has been changed on that board at this point. :cry: :cry:

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

Post by KSS » Thu Mar 05, 2020 3:12 am

amir wrote:
Wed Mar 04, 2020 10:13 pm
Any ideas on the 4012 board? Everything (minus the resistors and caps) has been changed on that board at this point. :cry: :cry:
Did you already post clear photos of both sides of each filter PCB? At this point, those would be helpful.

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