Chorus Pedal ACH-I ?

[Arn C.]

Howdy Folks!

I have this old chorus pedal, that works, but I don't use a chorus.  Don't really like them.  I was wondering what I could use the IC's for?  Flanger?
Not sure what they do either, but has to be better than a chorus.

The IC's are MN3209 and MN3102 for BBD and Driver
also has UPC339C, 2-CXA4558

Transistors 5-C1815GR, 1-K30AGR

Can't seem to find a schematic for this one.

Peace!
Arn C.

[dosmun]

Is it an Arion SCH-1?  If so you would be better off selling it on Ebay.  The older ones are a pretty hot item.

[Mike Burgundy]

If it's an Arion, that's a hot item - sell it. Does it look like this inside:
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=21880&highlight=arion+chorus

If it's some really obscure "valueless" thingy, you can probably mod it towards flanging. The MN3102 should have a small cap setting the time base between two legs - lowering that will shorten the timebase and move the whole thing more towards flanging.
the 339 is a quad-comparator, the 4558 is a regular dual opamp.
I believe the SCH-1 did have the NEC comparator and two 4558's, but wasn't there one more IC?

[Mark Hammer]

Boy, is that ever suspiciously like the Washburn chorus I have, in terms of components.

One of the more tempting things is the presence of a 3209, which ought to be able to get, in theory, some very nice flanging sounds.  With only 256 stages, ultra short delays are possible without having to push the clock circuit too hard.  Whatever the current value of the timing cap is on the MN3102, chop it by 3-4 (e.g., drop 220pf down to 56-68pf) and tell us what happens.

[Arn C.]

Thanks gents!
   Between what pins on MN3102 is the timing cap?  I looked at a bunch of diferent schematics and it seems between 5 and 7, but on mine.... okay, I see,  5 is not hooked up, but pin 7 goes to 220 pf.  I will assume this is the cap?
If so, I will change it and let you know tomorrow or tonight what I hear.

Thanks again!
Arn C.

ps.  Mike, mine does not look like the pic, simmilar, but not the same!

[EdJ]

Mark,is that a washburn mcx:14 you have?
I bought one of those a few weeks ago for 25 euro and like it a lot.
It has that (Jeff Beck`s)People get Ready sound qiet nice hasn`t it?
Greetings,Ed

[Mark Hammer]

Ed,

It is an SC-7 Stereo Chorus.

I pulled the 3209 and stuck in a 3207 with a clock timing cap change for a slightly thicker sound.  I had the 3207's sitting around and wanted a 3209 for a flanging experiment in the future.

Arn,
It will be whatever <.001uf cap is butted up against the MN3102.  Seriously.  I have never ever seen another cap it could be confused with.  For a variety of design reasons, the timing cap needs to be jammed up against the 3102, and the 3102 needs to be jammed up against the BBD, making the timing cap HIGHLY distinctive in terms of its location.

[Arn C.]

According to the data sheet(MN3102), pins 5 & 6 I believe are supposed to have a timing cap.  In my chorus, pins 5 and 6 are not used!  But pin 7 is used

In the data notes it says:  Pins 5,6,7   (C & R are connected)
IN case of self oscillation
In case of separate excitaion oscillation  Pins 5 & 6 should be opened,
Pin 7 is set to OSC Input


Pin 7 goes to pin 1 of upc339C, diode, and a resistor(diode and resistor beside and connected to upc339C

So, where is that timing cap?

Peace!
Arn C.

[Mark Hammer]

Yeah, a little confusing.  Most of the data sheets will display a schem/app involving a *fixed* delay time, rather than a swept one.  In these instances, the cap goes between pins 5 and 7, whereas its a little different when the clock is being swept by an externally applied voltage from an LFO.  I will affirm, however, that no matter WHERE the cap is tied to, I dare you to find another one as low in value as close to the MN3102.  Trust me, you can take this to the bank.  If it's anywhere within a cm of the MN3102 and its 500pf or smaller, THAT'S THE ONE.  If you are in any way doubtful, simply identify the relevant solder pads, and temporarily tack on a parallel 220pf cap on the solder side with a smidgen of solder.  You will most assuredly notice the change in delay time and especially the more pronounced pitch wobble.

[Arn C.]

Mark,
    I have looked at this thing many times and I see no small cap near the mn3102.   According to the data sheets, pin 7 comes out goes through a resistor to pin 6 and goes through a cap into pin 5.   Pin 7 already goes to a resistor, diode and to pin 1 of upc339C.   pin 5 and 6 are just soldered to the board and are separate and go nowhere.  So, would I solder on the 220pf cap to pins 5 and 6?  If so, I will try that with different values on a switch(rotary) and see what happens.

Thanks Mark!
Arn C.

[DiyFreaque]

Out on a limb here - I'm not sure what the upc339C is - it it like an LM339 comparator, anyone?  Anyhoo, wonder if it's not the oscillator that's actually driving MN3101 pin 7, rather than using an RC time constant on the MN3101.  This is a scheme I've thought about - the MN3101 would have guaranteed waveshaping for efficient operation of the BBD, and the honus of modulation would be on the external clock itself, which in some cases may give a bit more freedom in what one might want to do (say for example, using a 4046 as a VC Clock).

Anyway, in that case, the cap would be somewhere close to the 339.  Guessing here.

Cheers,
Scott

[vanhansen]

Does anyone have a schematic of the ACH-1?  It would sure help.  I can't find one.

[Arn C.]

It appears that it is an  "ARIA ACH-1 Stereo Chorus"  I was searching around a bit and this is what I came up with and it is made in Japan.

upc339C is a comparator=NTE834  Quad comparator  

Pin 7 from the MN3102 goes to pin 1 of the comparator which is an output from the comparator.  There is a 220pf cap that goes from ground to pins 2 and 6 of the comparator(upc339C)pin  2=output 1 pin 6 input 2 (-)

If any of this helps.  the 220pf is smack up against the upc339c

Peace!
Arn C.

I can't find a schematic either!

[Mark Hammer]

Well, if that's where it is, I say stick another cap in parallel.  If you follow general rules of good practice, tacking a 100pf cap in parallel with that 220pf will not harm the pedal.  Set your rate to something medium, and crank the width/depth.  If it is the timing cap, you will notice much more pitch wobble. Once the critical cap is established, THEN you can fritter around with values that yield the tone you like.

Note, however, that varying the timing cap value/s so that the pedal ends up overlapping with delay ranges more typical of flanging STILL won't get you regeneration, which is an important part of flanging.  However, I've found that smaller cap values can achieve some really nice slow Leslie tones from some chorus pedals.

[j0shua]

Is it an Arion SCH-1?  If so you would be better off selling it on Ebay.  The older ones are a pretty hot item.

Arion Chorus is one of the best chorus i ever play, better than Boss, Ibanez, DOD, etc..  is better if you sell on Ebay or trade in other place for a flanger ......

[Arn C.]

Joshua,

   Mine is an "ARIA"  not   "ARION"

Mark, I will give it a try tonight! Thanks!


Peace!
Arn C.