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Looks like the three chorus sections are identical so if you trace one you get them all. The vactrols are might be for the three intensity knobs if I'm guessing. Taking the output of the LFO to split it to the three clocks maybe?

That is correct. The chorus section looks like are the same with different calibration

There are a few short threads on the original TSC over at fsb.org, search there for "Tri Stereo Chorus."  One has some interesting details cut & pasted from other threads on harmonycentral and Reddit.

That would be this link https://www.freestompboxes.org/viewtopic.php?t=30909

There is another resource that explaining how chorus BBD works but I can't recall it. I'll keep research on that. The best way to trace is to use photoshop (I guess) and start to match the top and bottom layers. After that, then I can work on the schematic. Once the schematic is complete then I can study more the concept behind it. It'll take some time for sure.

Any idea what the vacrols are for?  That and the number of trim knobs are intriguing.

The trimmers are intended for calibration. There are certain frequencies to get that schmo which it can definitely get calibrated by reading the voltages or look over the signals on the scope.

For the vactrols, that I have no idea. Again, still mystery to me.

Would the Jurgen Haible Triple Chorus be a starting point? Pretty sure the schematics are still out there. Not sure of the Fulltone unit would share the same blocks but it's pretty well documented last time I was marveling at it.

This is good info though not really TSC. The concept theory is there. Here are some couple references that I got so far

https://gearspace.com/board/so-much-gear-so-little-time/980440-any-one-know-how-make-tri-stereo-chorus-effect.html
https://www.freestompboxes.org/viewtopic.php?t=30909

In 2012, LaceSensor also interested with the same topic. I'm not sure if he got it or he dropped the effort due to he found something else

https://www.madbeanpedals.com/forum/index.php?topic=4942.0

There was one more Tri Stereo Chorus clone, The Wave, by an Italian company (Shiva/Red Seven.)  They built 35 and then moved on to other things: https://www.redseven-amplification.com/the-wave-t-a-m-c/  .  No schematics or internal pics, unfortunately.  They say their Lil'Wave chorus pedal (still made) is a derivative and uses one of the three delay lines in a mono format.  For a DSP version, Eventide's TriCeraChorus is supposed to be pretty good.

Mike, I contacted Red Seven and they have no Shiva left. If they have, then I'd love to get that. I think that is also built based on Dytronics/Chuck Monte design. I talked with Chuck last year and he said that it's really hard to find one and he sold his last unit last year. He is retired and doesn't recall any info related the TSC. The best luck to recreate it or study the design will be through TERC or something similar. I have Eventide TCC which is great and that is currently used in my Dann Huff's rack. However, it is still big mystery to me to unveil TERC or TSC.

I have been itched to get hands on That 80 Rack Chorus. I'm currently working on learning the design behind it with a hope to recreate it or even design a better one. I need some help on figuring out the block diagram of the Fulltone TERC to start. Here are some pictures of TERC that I have pulled out. It sounds instant Landau/Huff/Lukather for sure. Also, it is based on TSC-618 or CS-5 Songbird Dytronics which is a legendary unit.

















It looks like there are some Op amps and BBD ICs. Three BBD for sure with share intensity/speed. The chorus part I think something can be tweaked with proper calibration like flanger. Also, there's VU meter to show the output levels L/R. The input can be instrument or line. It looks like if it's line instrument then it goes to buffer.

If anyone can chime in the idea of building great TSC then I would appreciate the help

I was thinking the same. I see there are several parts that can be a replacement

https://www.amprepairparts.com/switches.htm

FOOT SWITCH, SPDT, MOMENTARY, FOR SWITCHING AND EFFECTS.
Important:  This is one of two types of momentary 3-pin SPDT footswitches using the same footprint.   Click on the diagram to the left, compare the switching with your requirements.   The other switch is the FS-602-PC, with the opposite switching logic.  Customer is responsible for testing and selecting the switch with the correct switching logic - Studio Sound Electronics is not responsible if the wrong switch is selected.
Made for switching and effects units which require a momentary connection rather than a latching connection.    PC terminals.  Has 3 terminals. 
Part #FS-502-PC


FOOT SWITCH, SPDT, MOMENTARY, FOR SWITCHING AND EFFECTS.
Has 3 electrical terminals (single pole, double throw). Solder lugs for wire. This is a "soft click" momentary switch - not latching.   See drawing for switch open/closed arrangement.
Part #FS-398-M

FOOT SWITCH, SPDT, MOMENTARY, FOR SWITCHING AND EFFECTS.
Important:  This is one of two types of momentary 3-pin SPDT footswitches using the same footprint.   Click on the diagram to the left, compare the switching with your requirements.   The other switch is the FS-502-PC, with the opposite switching logic.  Customer is responsible for testing and selecting the switch with the correct switching logic - Studio Sound Electronics is not responsible if the wrong switch is selected.  Made for switching and effects units which require a momentary connection rather than a latching connection.  PC terminals.  Has 3 terminals.   Used in the 5-way foot controller on the Marshall™ TSL-100 amps for the clean, crunch and lead switches. 
Part #FS-602-PC

Not exactly the same but pretty close. I don't know about the clearance though. It might be hard to find out. I guess I need to ask Bob Bradshaw (CAE) if he has a switch replacement/part substitute for it.

MBP folks,

I'm in the process repairing old MIDI switching. I came across one switch that needs to be replaced. I know the logic is SPDT but I can't find the part number or even where to source it.

Here are some pictures for the switch.







One of the connection is normally closed and when the switch is pressed, it'll be normally open. I believe it's the logic/trigger for MIDI microcontroller.
It's heavy duty switch and similar to the VFE Carling switch 110 type I've gone to Carling and sent them email as well with the pictures but I'm thinking someone here might have better answer.

If you have some ideas/clues about the switch, then thank you for sharing.

  rack gear is back and it's awesome. I always want to have sound like Landau/Lukather. Dan Huff is amazing back then. He did tons of session and definitely under rated guitar player. I didn't have a chance to meet him in person when I was in Nashville. However, I think if I have everything repaired/assembled back and all works, then Brandon might share with him. Hopefully, he will notice and appreciate it when everything comes back together.

The hardest part now is getting great condition of H3000 D/SE and TC2290. Dan also uses Kasha Rockmod I.I can't find that unit and even trying to make one, the unit is protected. Rockmod II has some info about the schematic and PCB. Basically, it's two channels preamp (clean and dirt). Other route is going with unpowered Kemper which can be easily obtained these days.

I think the best deal is the strategy 400. That unit itself can cost a lot these days.

UPDATED:

I finished the whole rack restoration. It was a fun project. Made new friends and reconnected with lot of friends. It was a great journey

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As the title said, recently I acquired a historic musical piece. Yes, it's one of Dan Huff's Giant rack system. It's all started by this video below;

https://youtu.be/pj3lOeH0Ijg

Luckily, I was the highest bidder and Brandon was kind enough to coordinate being the items back to San Diego. Then I ended up in Nashville last week and packed, shipped, brought the items back.

https://youtu.be/Yss8Yz8NNTQ

For reference, it's the same rack that he has been using over the years since 80s/90s. That instructional video has been inspiration for me since I was teenager.


Packed the items and ready to sent it out. I also flew back with some rack items. I didn't drive all the way from San Diego to Nashville. I flew and shipped the item to home.


Rented the truck just to haul the racks away from the studio. I picked it up at Castle Rock Studio. It is the studio that Faith Hill, Keith Urban, Brad Paisley, Madonna, and many artists to make records. Pretty cool studio and I did quick tour to see the equipments.

I thought it might be a good ideas to write something down while I plan to create a YouTube journal. It's all in work. Let's start with some pictures of repair that I've been going through.

First one is Mesa Boogie Strategy 400



Retubes due to keep blowing fuses. Checked the grid screen resistors and all are in good condition.


One of the cap 22uF is burned so I replaced that as well with higher voltage rating




Checked voltages for the filter caps and all are in good condition; surprisingly. I also changed the power cable due the old one was bad.



Next one is peavey valve verb. It doesn't give output. Trying to replace the filter caps and I'm suspecting the output tubes have gone bad. I don't have 12AT7 handy but it's in order. Same with filter caps. Hopefully, it will work after that. Need to do more diagnosis on this unit.



Mesa studio preamp. Surprisingly, this unit is still good running condition. Only I had to change the tubes. Though it does have some serious hum and I assume it might come from the ground lift. Still investigating but pretty positive that this unit will work just fine.




Korg wave station. The only problem was the battery and that's all I had to change. Everything else works perfect. The rack connects to MIDI controller/keys and it does have amazing preset like in 80s synth. Great addition collection for my synth 80s rack.



Rocktron RSB set. All works and got all the callings the main processor/rack system requires XLR 6 pins replacement. I ordered it and everything else looks good. It has some Dan old patches like rhythm, lush chorus, etc. pretty cool unit. The case was rusted and might need new hinges. Pulled the hinges over the weekend and looking to replace it soon.




Here are the units all stacked. Missing the Boogie Strategy 400 but overall these are the units that left out. I'm getting SPX 90 II and still hunting for H3000/ TC2290. I can't get Kasha Rockmod and plan to just DIY it at some point. If I have time and bandwidth, then I'll do single channel preamp for crystal clean like Fenderish/ Peavey classic add to this project.



SDE 330 Space Echo. Concentric pot is broken and ordered replacement from smallbear. 3D printed the knobs. Apparently this unit can be converted to SRV330. The unit has Dan favorite delay patch before he goes all in with flashback delay.



The power button SDE 330 also needs repair. Ordered replacement from syntaur and possibly recap the power supply.

Got the invite. Thanks, Bean

Has the zoom link already sent out?

I'm in. This is what we have been waiting for. Really looking forward to see inspirational build from others and excited to learn more

If we would grow it to podcast then let's do it before 2022 ends!

Also, if we can record it, maybe we can post it on MBP YouTube or something. People who won't be able to join can play it back

This weekend Zoom, bean?

Yasss!!! It's still on. Can't wait to see amazing projects