Upgrading/cleaning up old effects: ? for Brad Sarno

[ajm]

You seem to be into this stuff, so I thought I'd start a new thread.

I've got a lot of old 70s effects. The one that I'm fixated on at the moment is an Electro Harmonix Electric Mistress Flanger, the 2x9v battery version.

Have you ever tried replacing caps, etc. to clean one of these up? Ever have any luck?

I've looked on the web for info at several sites but no one has addressed this topic.

Thanks.

[James Ingram]

There use to be person on ebay that sold old stomp boxes. he had large collection with link to his web site. He has his own list of effects he,s looking for him self. Sell,s others as he goes. He might be able to help you. just do search on ebay for guitar effects .you,ll probably get hundreds of hit,s. just check each one out. I,m electronic buff in my own right. if i can get it apart i usually can fix it. if i can get part,s. probably your biggest problem is with dirty scratchy control pot,s. that just need shot of contact cleaner. unless your getting some real bad noise from effect.that could something else entirely too. hope this helps. i had a electro harmonix big muff from 70,s myself.

[Donny Hinson]

I'll also throw in a couple of points until Brad checks in. A lot of times, schematics aren't available for the old units, and that makes them hard to work on. You must determine the signal path, and then go from there. (That can take a lot of time.) Many of these older solid-state devices were designed at a time when noise factors and frequency response weren't a big part of the equation. (It was considered "successful" if it worked at all!)

Most of these ('60s-'70s) devices contain a lot of components (a high population of "discrete devices", as they say) and would lend themselves to "tweaking" a lot more that today's stuff, which contains fewer components...called L.S.I., or "large scale integration" (where a single I.C., or modular circuit can perform several, or most all, functions).

There are drawbacks, however, to working on these older boxes. The aforementioned lack of data and schematics, the difficulty of repeated service (i.e., removing and replacing components several times without damaging the printed wiring boards), and the lack of available parts. (Some of the old transistors, I'C.s, and optical coupling devices are quite hard to find, as they haven't been made in 20 years.)

Still, if you can "do it yourself", or find another "gearhead" who like to tinker with older stuff, you might be able to attain your established goal. Most times, though, it's better (read "faster and cheaper", as well) to find something newer that'll suit your purpose.

(But if you want to give it a go, the easiest things to try would be to clean the controls...as someone else mentioned already, and then replace the old electrolytic caps, the ones with a + and - on them, with new ones. That's where I would start. )

<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Donny Hinson on 16 April 2002 at 05:07 PM.]</p></FONT>

[ajm]

Thanks much guys, still waiting for more from Brad or anyone else.

The electrolytics seem to be a common point of skepticism whether it's an effect or an amp or whatever, and I'll try them for sure. I was actually thinking of replacing ALL of the caps just for kicks (or at least the ones in the analog signal path).

I got a schematic from a website a couple of years ago that doesn't exist any more. But, the Analog Man web site seems to have just about any pedal schematic that you want. He only asks a couple of bucks for copies and IMHO it's worth it if you're into this stuff.

I've studied the schematic and pedal and they seem like they match so far. This thing is actually half processing circuitry and half clock generation/modulation circuitry. I was surprised that the clock portion took up so much real estate.

I know a little about electronics and having looked at the schematic I have a couple of ideas to try to get the noise down. But this thing sounds pretty good anyway. I used to play in a few rock bands back in the 70's, and it really nails that thick Trower/Marino sound, especially if you feed it with a distortion of some kind. I've also tried it with a steel, and IMHO it sounds better than the Ibanez chorus that I've got. The flanger isn't stereo, though.

[Brad Sarno]

It's funny. I've always considered old effects pedals to be sort of sacred. Old fuzz boxes and phasers and flangers all seem to have a grungy vibe to them and it's often my inclination to leave it that way. Guitar isn't really a hi-fi kind of thing although I would say steel guitar is. I remember messing with some old fuzz boxes that used the classic dual shorting diodes for clipping, like the old MXR Distortion + or the Ross Distortion or many others. With those and others I was trying different germanium and silicon diodes and transistors and that was cool. Germanium has a neat sound for fuzz. I also mess around with the heavenly Ross Compressor. I like the stock sound but you can definitely clean up the signal path. I seem to prefer the old stock crappy sound. It kind of introduces a color or distortion that makes it more rock and roll.

So really I'm more of an amp tweaker than an effects pedal tweaker. When it comes to rack gear like the Profex or other opamp based devices, I love to throw in the Burr Brown opamps in place of the stock crappies. The Burr Brown audio opamps have a very sweet, smooth sound to them. I see them in all kinds of hi-end audiophile and pro audio gear. The Profex mod is cake. The opamps are all socketed so just unplug the old and plug in the new.

The one thing I stress is that whenever possible, try to have the ability to A/B gear modifications. For instance I've really gone to town on my pair of '60s Fender Deluxe Reverb amps. I'll keep one constant while I mod the other. That way I can really control the comparison and get my ears around what the mod did and if I liked it or not. I'm rambling...

Brad Sarno