TC Electronic Chorus/Flanger

[Mark Hammer]

I have an old SCF chorus/flanger/vibrato pedal.  The flanging is...okay...I guess, but seems to aim for the range where chorus and flanger overlap.  I'd love to be able to mod it with a little toggle to select between flanging delay ranges, and get something that doesn't sound quite so hollow.  Only trouble is, I can't figure out, based on the schematic, which cap (or caps) set the range of the clock.  If it used an MN3101 along with the MN3007, it'd be a breeze, but they didn't use that clock chip.  Any ideas?

http://www.angelfire.com/ego/sitruuna/images/tcA.jpg
http://www.angelfire.com/ego/sitruuna/images/tcB.jpg

[Rob Strand]

Summary:
- IC4 clock pins 2 and 6 go to circled wires 5 and 6.
- Then those circled wires go to IC105 pins 3 and 4, which is flip-flop a producing the square clock output.
- The VCO is generated at IC102.
- Clock frequency is determined by R144 (and R138, R137), C117 and the current down the collector of T102.

So you could tinker with R144 and C117.

However you could also play with the drive level to T102 via R141 perhaps adding an offset by switching a resistor from the base of T102 to Vcc or ground.   Depending on the amount of shift the added resistor could affect the sweep range so you might need to drop R141.  I guess it depends if you want to change the base-line delay and the amount of sweep as part of your mods.

A caveat would be whether the existing R144 and C117 allows you to get the range of frequencies you want.

[Mark Hammer]

Disassembled the unit, only to find that the BBD used is a TDA2107.  I gather it is a direct sub for an MN3007?  Wonder about its availability.

Sadly, the board is not legended, so it may take a bit of prodding with a good light and magnifying glass to locate C117.  Unfortunately, the schematic does not give its value.

[Fender3D]

It should be a 470pF cap connected with LM339's pin 5 almost in the middle of the potentiometers board.
BTW
TDA2107 is european made MN3007

[Mark Hammer]

Do the TDA2107s have any greater current supply/availability than the MN3007?

[StephenGiles]

Crickey Mark, I remember seeing during a visit to Cricklewood Electronics (in North London UK), a "bargain box" containing many TDA 2107s, and when asked the guy told me that they were "just discontinued opamps" - selling for 10p each, if only I'd known at the time!!

[Ben N]

There's an old thread at "the other forum" in which the SCF was traced, and the two chips are deemed pin-for-pin interchangeable, BUT as far as I can see, it was only actually built once, recently, with very little post-build evaluation, except that the chorus seemed to the builder to be weak.

[Rob Strand]

TDA2107

I've never come across those before.

I'd guess it's Philips part.   If you can find which old  philips databook had the TDA1022 the TDA2107 might be in there.  Some of the old philips databooks are online.

[kermito]

Late to the party, but I was researching the tc chorus/flanger just now, and came across this thread.

I gather it is a direct sub for an MN3007? 

TDA2107 is european made MN3007

According to a post by analogguru (I believe also a member here) elsewhere (https://groupdiy.com/index.php?topic=21694.0), the TDA2107 is a rebranded matsushita-made MN3007.

There's an old thread at "the other forum" in which the SCF was traced, and the two chips are deemed pin-for-pin interchangeable, BUT as far as I can see, it was only actually built once, recently, with very little post-build evaluation, except that the chorus seemed to the builder to be weak.

If the above is true, the "weak" chorus probably wasn't due to the MN3007.

[anotherjim]

Funnily enough, I heard that the MN series originated at Philips. The Panasonic products were a licensed second source. Philips got out of the BBD market and left them to it.

[Rob Strand]

I heard that the MN series originated at Philips.

Didn't know that.

I've got a some Philips papers from late 60's and early 70's going through the evolution of the device and the ideas inside but it's all early days stuff.  Well before any handovers or licensing.

FWIW, I've got a few papers from the early days of Reticon.    One paper is the guy from Reticon going though his ideas.    Not sure if it was written pre or post the making of Reticon devices.

BTW, I found this stuff on-line;   I don't have the links on this computer.