Boss TW-1 parts query

[Yazoo]

I am building the Boss TW-1 autowah. I have the schematic and parts layout. Unfortunately the image is very grainy and I have been unable to find a better copy. I'd be grateful for help in confirming some of the parts values. The schematic is available on this forum and here: http://files.effectsdatabase.com/docs/schematics/boss_tw-1.jpg

R14 in the feedback loop of IC 1 pins 1 to 2 looks like 220k or 230K (?). R49 which is connected to R7, then to the collector of Q2 looks like 1.5K (?).

I also tried to find photos of the pcb. There were a couple, but these didn't help.

Thanks in advance.

[11-90-an]

R14 looks like a 330k...

For R49... Maybe try placing a trimpot or pot and tweaking until you get the sound right...?

[Yazoo]

Thanks, a new pair of eyes is helpful. It does look like 330K.

[Mark Hammer]

Perhaps this will help you out.

[Yazoo]

Thanks!

[Mark Hammer]

Like yourself, I couldn't find any gutshots by doing a Google image search.  However, I saw an ad for one for sale, that showed that back of the PCB.  Since that is sometimes accompanied by other internal shots, I went to the site, and sure enough, this photo was also provided.

Sadly , the parts placement in the photo does not appear to correspond perfectly to the diagram/drawing in the service notes.  You will note that it uses a 3403 quad op-amp instead of a pair of 4558 dual op-amps.  I gather the photo shows an earlier issue.  You may recall that the first issue OD-1 also used a 3403 quad op-amp, and later switched to a pair of 4558s and eventually one 4558 and bipolar buffers.

All of this makes it a bit of guesswork as to which resistors and caps in the photo correspond to which in the drawing.  It's certainly close, but perhaps no cigar (do people even use that expression anymore?).

[11-90-an]

But I believe, Mark, a top shot is needed, but a bottom shot is also required to see which component is connected to which! 

Problem is, most likely the component in question, R49, seems like it would be the one of those STANDING resistors to the right and left of the Q2! 

[dfx_pedalpcbs]

Have you found a modern equivalent for that inductor choke?

[Yazoo]

Thanks for the information. The members on this board have always been very helpful when I have posted queries.

I found information about the Boss AW-2 which is supposed to be very similar to the TW-1 and there is a good clear schematic for this here: http://www.eserviceinfo.com/downloadsm/41767/Boss_AW2.html

A lot of the circuit is indeed the same and where this is the case, the values mostly agree, so I feel more confident going ahead with the build.

The inductor is 700mH and I was able to get a custom wound one off eBay from a real gent in Greece who did the job for me at his standard price and I received it within a week of my purchase.

[Yazoo]

This is my build. It went pretty well. I had two goes at the diy photocoupler. The first attempt with a yellow led wasn't very good. The wah intensity was too low. I used a high brightness red led instead and it is wahing well now.

I left out the 11 volt zener because I am just using a 9 volt DC supply, and I added a Schottkty diode in series for reverse polarity protection. 

[antonis]

It seems that ICs hate each other..

[Yazoo]

They are back to back, ready to walk ten paces, turn and fire.

[Mark Hammer]

Nice work.  The original doesn't have any control over the feel.  Consider monkeying around with the value of R28 (68K) to get different decay times.