TC Electronics - Stereo Chorus Flanger [pcb+layout]  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
User avatar
disconnector
Information
Posts: 1
Joined: 26 Nov 2009, 03:57

Post by disconnector »

A quick question - I've got a 90's SCF and I think a cool mod would be to make the delay adjustable like on the 1210. Can someone (Bajaman!) please point out which trim I need to bring out to accomplish this? If I do make this adjustable do you think it will work? I would love to have a piece of that TC1210 goodness in a pedal.

Thanks!

User avatar
Fender3D
Cap Cooler
Information
Posts: 573
Joined: 08 Aug 2009, 02:40
Location: Helltaly
Has thanked: 121 times
Been thanked: 153 times

Post by Fender3D »

SCF has no delay trimmer inside...
You may add a trimmer between T102's emitter and ground.


Another quick question...
Can you please confirm zener Z101's name?
It is inside the (usually) yellow tube going from Width's lug3 to resistors near status LED

User avatar
sadrew
Breadboard Brother
Information
Posts: 148
Joined: 08 Apr 2008, 08:45
Location: London UK
Has thanked: 9 times
Been thanked: 14 times

Post by sadrew »

i have bought an original SCF to repair

i was wondering how did you find out IC values

in my unit they are sanded down

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

In the one I have opened, they weren't, it's as simple as that :thumbsup

User avatar
aion
Solder Soldier
Information
Posts: 230
Joined: 22 Mar 2012, 00:12
Location: Des Moines, IA
Has thanked: 9 times
Been thanked: 472 times
Contact:

Post by aion »

Did Bajaman ever post the finalized project for this, either here or someplace else? I saw the most recent component layout but never the full project file. (Gerbers, artwork, enclosure drilling, etc.) I'd be interested in a PCB group buy for sure.

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

If think there's everythi,g needed to build one, but a calibrating procedure.
I fear the stuff you need to calibrate this+the parts to build it would be expansiver than getting a 2nd hand unit : it's not really the ez to do habitual cheap chorus you find in most of pedalboards. :wink: In fact, this is more a "for your culture" topic than one where you will build something, just like if s.o would "crack" the MoogerFoogers : I guess nobody built a clone! All you could do would be an approximative calibrating based on where I've put a little bar on the trimpot of my handtraced layout...
Well, if you can put up a calibration process, but considering the fact you can get an original 2nd hand unit for 150€ as now TC has re-edited the SCF (well, wiith surface mounted stuff, I know), which wasn't the case when I did the tracing, SCF used to becoming more and more expansive at this time...

User avatar
lohstah
Solder Soldier
Information
Posts: 237
Joined: 08 Jul 2007, 20:08
Has thanked: 214 times
Been thanked: 96 times

Post by lohstah »

maybe it would be interesting to do a "just the chorus part" true bypass 9V in voltage doubler version of the circuit.
i have an original at home that i got broken and repaired ages ago (this is how the whole stompbox stuff started for me years ago),
but i would not mind having the chorus part on one of my pedalboards. it is excellent for bass guitar, especially fretless.

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

the bypass is not a problem and it"s a better way to do it than a shitty true bypass which would make pops or the Boss/Maxon/Ibz fet shit, a chorus ans a flanger are technicaly spaking the same effect, the problem ain't the complexity of the circuit but really the way to calibrate the cho/flg as this is not those shitty cheapo chorus unit...
If u want something easy to build, you know, there are Small Clone, Electric Mistress and Boss CE-* wich have a full calibrating process documented...
Better consider the SCF, and the same thing for the marvellous MoogerFoogers, that these are normally rackmounted effects, the trick is that the Boss of TC (which conceived the SCF all alone, these were the young days of TC) as well as Bob Moog, are real geniuses which issued so well made layouts that they could put a full rack in a pedal enclosure and there was no surface mount shit when these were created.
Maybe you do not know, but Moog let you access to the schematics of Foogers! Don't you have no idean why there ain't "boutique" clones of TC SCF or Foogers, and even lotsa EHX stuff?
Because they are sold at a right price and well, it ain't interesting at all to clone it : you'd have to buy a big bunch of parts to make their price becoming interesting and it is hard to build as a single person as I had a real hard time "cracking" it. No joke, if you want a cheap SCF, better buy a 2nd hand one! It was interesting to consider the DIY path as long as TC had it totally discontinuated and 2nd hand ones had there price skyrocketting at higher prices than new units... BTW, the SCF RI has metal film resistors vs. carbon film for the old ones, as a thing made for being put in an amp loop, the RI is even nicer than the vintage, no surprise the vintage price felt to 150€. I bet buying new parts to make a single unit ain't a good bargain at all, it's not like with all tho "boutique" overdrives and fuzz where you pay 400€ or maybe more for a simple hot rodded fuzz face or screamer or any Cornish Big Muff clone!

User avatar
lohstah
Solder Soldier
Information
Posts: 237
Joined: 08 Jul 2007, 20:08
Has thanked: 214 times
Been thanked: 96 times

Post by lohstah »

if you are talking to me, how come you assume that
i want a cheapo chorus to build
that i haven´t already built all the chorus boxes you mention
that i don´t know that the SCF is worth it´s price

???

i knew this sort of rant would be coming when i posted before...

true bypass or not is a matter of taste. i prefer to have it in the boxes that i build and my boxes do not pop loud enough to be a problem on stages, where i play quite regularly.
and if you would have read my post thoroughly, you would have noticed that i am not interested in cloning the whole thing, because i usually use just the chorus part, but not on my stage pedalboards because i do not want to mix up 220V and 9V effects because it is complicated enought to get one 220V outlet for your pedalboard near enough where you want to set it up. yes, i could bring my own power distribution, and no, i don´t want to.

also, i just use self-built circuits on my pedalboard, that was another reason i was interested in doing just the chorus part as a 9 or 12V bipolar or whatever version. good god.

and i did not write "hey, somebody do this for me", i thought about the very idea before this thread resurfaced, and maybe somebody else would be interested, so i posted.

if you care to search for other things i posted, you may notice that i contribute to the community on a more or less regular basis (playing bass is still more important for me than building boxes and will always be), i reversed the MP blueberry, the 3BOD, the diamond bass comp, the ocd long long ago (although i did not take credit for it at the time).

so please, don´t school me with things i already know.

rant over.

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

Do as you please, dude, but one of the very good point to the SCF is that you can pilot the bypass from a distance, so you can avoid looooong audio cables between the effect loop and the chorus. Maybe you have never used C-MOS bypasses : it's probably the best method you can use.

User avatar
Fender3D
Cap Cooler
Information
Posts: 573
Joined: 08 Aug 2009, 02:40
Location: Helltaly
Has thanked: 121 times
Been thanked: 153 times

Post by Fender3D »

iznogoud wrote:the bypass is not a problem...
Expecially when you have a "gain" control.
You won't have a "mathematically" correct unitary gain @ output, since you should set gain for an optimal BBD's operating point.

BTW
there's no CMOS switching here (mode select aside), since bypass is achieved shorting to GND IC2's pin 16...

Come on iznogoud, why involving in DIY if you're afraid of challenges?
Build such a complex circuit, would make everyone proud, be it expensive or not...

..and please, open your SCF an tell US what's the f*cking zener...

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

You have big balls trying to lecture me about challenges, is that you that has ripped the SCF? This baby lasted 30 years w.o anybody trying to reverse it and you dare talking about challenges? What have you done in serious reversing? If you hope that by talking to me like that I will open my SCF to look at this zener value, you are dreaming! Have fun going on with this project w.o my help!

User avatar
Fender3D
Cap Cooler
Information
Posts: 573
Joined: 08 Aug 2009, 02:40
Location: Helltaly
Has thanked: 121 times
Been thanked: 153 times

Post by Fender3D »

Dude,
I'm not trying to lecture anyone.
I was referring to your previous replies to aionios and lohstah, where you basically say cloning SCF is not worth...
I think a DIY shouldn't worry about costs, rather, he builds for his personal pleasure.

Calm down,
my request for the f*cking zener is just for a topic completness sake, since you said
this is more a "for your culture" topic
In the '80s there were not so many zener values up to 15V, and breadboard is a nice buddy...
iznogoud wrote:What have you done in serious reversing? If you hope that by talking to me like that I will open my SCF to look at this zener value, you are dreaming! Have fun going on with this project w.o my help!
I admit I've posted here, very few schematics out of the hundreds I R.E. since '78...
but the real difference is I know the calibrating procedure... :secret:

User avatar
uncleboko
Cap Cooler
Information
Posts: 509
Joined: 25 Mar 2008, 20:19
Has thanked: 58 times
Been thanked: 41 times

Post by uncleboko »

Anyone reversed the EH Flanger Hoax yet??

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

So post your full calibrating procedure and maybe I'd open my SCF for you...

User avatar
iznogoud
Breadboard Brother
Information
Posts: 61
Joined: 10 Mar 2012, 20:14
my favorite amplifier: Triaxis+Marshall 20/20+ Electrovoice
Location: Lothringen
Has thanked: 13 times
Been thanked: 34 times

Post by iznogoud »

And according to the fact TC has reissued it so now, the 2nd hand price has felt around 150€ (twas 'round 300/350€ at the time I did the reversing), yup, it doesn't worth the effort especially as some parts can be expensive nowadays...
BTW, from my point of view, DIY is not a challenge : it's all about cost-effictivity...

About Flanger Hoax : I have sever doubts about the cost-effectivity of cloning EH stuff too, at best, mod original stuff to your specs, i.e actually built Muff becomes a triangle Muff or a Cornish clone after you operate in...
Anyway, as the FlangerHoax has surface mounted parts, even with full doc, 't'would be a pain in the ass to build...
You could get some infos on a small stone mod making it near a FlangerHoax here :
http://www.ehx.com/forums/viewthread/574/#7450
And you can get an idea on how to structure a work-alike shit with it :
http://www.musicoff.com/articoli/hoax/schemahoax.jpg
Looks like an heavy modded smallstone with a delay...
IMHO : if you want smth cheap, look for old Aria dual-mode series phaser and flanger and update the AOPs. If u want some mad DIY phaser, go for the ModMachines KrautRock Phaser KRP1 (Thomann used to sell these around 550€! It is discontinued since Jurgen Haible passed away) which is the reissue of the Schulte Kompakt Phazor A used by Blackmore, Tangerine Dream (their famous wooooooshhh), Kraftwerk, etc: full doc is online on Jurgen's site and it's one of the best phasers ever made with the MoogerFooger MF103, de Moog 2U rack and the Roland 2U rack. (BTW, if u build the KrautRockPhaser, you can always make 2 PCB board, as the 2nd would be for me (except if u want a stupid price or if I've decided to make it on my own, and I'm enough crazy to hand trace a PCB with a pen to not spend mony on it :twisted: ).
Frankly, I wouldn't care upon building some FlangerHoax or cheapo EHX shit (don't miss my point, I like EHX stuff, as I like Danelectro guitars too, all these are very sympathetic and usefull stuff and I got lotsa stuff like that, but these are cheappo mass produced shits too), better build real powerfull stuff which is nearly impossible to find and/or very expensive...

User avatar
Fender3D
Cap Cooler
Information
Posts: 573
Joined: 08 Aug 2009, 02:40
Location: Helltaly
Has thanked: 121 times
Been thanked: 153 times

Post by Fender3D »

I almost forgot about this thread...
until arjepsen kindly asked me about the calibrating procedure.

BTW
the missing zener diode is a BZX79C 4,3V.
courtesy of Mark Hammer.

This is not official TC procedure, instead it is my deduction about the schematic posted.

Ok then, for all non-cheap-ass-iznogoud daring to clone SCF:

VR4 trim for lowest THD @ IC2's pin 7

VR1 trim for lowest clock noise @ BBD's output (best checked @ ic3's pin 8)

VR2 sets the wet level; wet signal must be the same amplitude as dry signal in flanger mode. The easiest way I found is to lift R33 for wet-only, measuring signals @ IC2's pin 10.

VR3 trim for lowest THD @ IC2's pin 10

There are other parts whose value affects functioning:
R8 sets bias voltage
R18 sets ic3b's gain to compensate for BBD level loss @ highest clock
R11 sets IC2a's DC offset

Please note that for a proper cloning we are missing clock frequency
good souls may post values here: https://www.freestompboxes.org/viewtopic ... 28&t=22623

User avatar
arjepsen
Information
Posts: 24
Joined: 18 Apr 2010, 14:12
Has thanked: 5 times

Post by arjepsen »

Awesome man - Thanks a bunch.
I've been looking over the schematics for a few days, and I'm in the process of making a clean version in eaglecad.
There are a few missing values in the schematic, but for the most part I've been able to find them on the sketch posted earlier in this thread.
Now I finaly got the zener value down thanks to Fender3D!!
One curiosity though, are the listed values of a few components in the schematic - for example R8. I assume that what is written means that the value can be between 30K and 56K...?
But does this mean that any value in that range will work properly, or?? Could someone with better circuitry knowledge educate me on this??

If anyone who has one would be willing to open it up and take photos, it would be really helpfull.

Anyway, a thanks to everyone who's help me get this far!

Regards
Anders

User avatar
Fender3D
Cap Cooler
Information
Posts: 573
Joined: 08 Aug 2009, 02:40
Location: Helltaly
Has thanked: 121 times
Been thanked: 153 times

Post by Fender3D »

Those are the values used by TC.
as i said they must compensate for chips differences, then pictures are of minimal help...
Only a good use of an o-scope will tell you what values are the best for your build.

User avatar
arjepsen
Information
Posts: 24
Joined: 18 Apr 2010, 14:12
Has thanked: 5 times

Post by arjepsen »

Ah ok, I see.
So this is the case for three resistors, as far as I can tell: R4, R8 and R18.
I do have an oscilloscope, but so far I only used it to work on my tube amp builds - and in honesty I don't know how to use it for the application you mention.
(Tube amps are quite simple circuits - this pedal is quite a bit more complex to me).
Any chance you'd be willing to give me a guideline? :D

Post Reply