#1
Hi guys, a month or so ago, my friend gave me a broken pedal he has. I've pretty much concluded that it has a broken IC. it has two of THESE there's the schematic right there on the first page... I could make a trip to radio shack and find all the right goodies that it'd take to make that and put the whole shibang in a (much) larger housing.

Is this practical? Am I begging for disaster? Biting off more than I can chew? The way I see it, I've got some free time and a broken pedal, so there's nothing to lose really.

Also, I've been trying to figure out how to just buy it, cause that'd be way easier and cheaper and better for everything. But it was manufactured in 1987 and I'm not getting any results.

Lemme know whatcha think. Thanks
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#2
firstly, how well can you solder? it'll be a tad difficult to do that style of IC with no socket and little experience, that's you're first concern. you can always find a replacement op amp
#3
Quote by blandguitar
firstly, how well can you solder? it'll be a tad difficult to do that style of IC with no socket and little experience, that's you're first concern. you can always find a replacement op amp

I can solder as well as I'd need to I think. but I can use a different op amp? I'd much rather do that, I want a working pedal, not a project to turn my workbench into a mess. If you can point me in the direction of how to go about this I'd be very grateful.
Quote by Strato-Massacre
yeah you shouldnt have told the pit to rape your mom.

Quote by Kensai
It's not sexist, girls are just too stupid and weak to hold up doors and stuff for themselves.
#4
What pedal are we talking about? That could help with IC suggestions.
How did you come to the conclusion that the IC was the problem? What does the pedal do when you turn it on? Any sound?
#5
Quote by Griffin Effects
What pedal are we talking about? That could help with IC suggestions.
How did you come to the conclusion that the IC was the problem? What does the pedal do when you turn it on? Any sound?

wonderful questions

It is a KMD Overdrive. Its an analog Overdrive made in the late 80's, early 90's I'm assuming. There's not much on the internet about it. But the Harmony Central review makes it sound like a great overdrive that I'd really like to have.

I don't have very in depth knowledge, but, The signal is getting through, very weak though. like if I had the volume pot on veeeery lightly, or had a bad cable, only worse. All the solder joints are good, so my googling has told me that this problem is most likely one of the IC's.

After further searching, I've found a few places online that sell them... but, since I overlooked getting a different one, I might as well take this as an opportunity to "upgrade" them. I love the fact that this pedal is supposed to have a very transparent gain, and very much overdriven. It is supposed to sound like it still doesn't completely saturate the signal, like it still sends some through unaltered and I'd love to preserve that with the new OP amps. If that relates at all..
Quote by Strato-Massacre
yeah you shouldnt have told the pit to rape your mom.

Quote by Kensai
It's not sexist, girls are just too stupid and weak to hold up doors and stuff for themselves.
#6
Aren't the KMD pedals the ones that look kind of like Boss pedals? I fixed a few of them over the years.
If you really think it's the IC, head out to radio shack and pick up an IC socket and pretty much any dual opamp and throw it in there. They should have at least one dual opamp I would think. I really recommend the socket just so you don't ever have to solder/desolder an IC in there again. Plus you will be able to test different ones out if you want without soldering. A 4558 or TL072 would do.

EDIT: OpAmps need to go in a certain way so if you don't know how, ask and I will show you.
Last edited by Griffin Effects at Dec 25, 2009,
#7
yeah, I'm going to need your guidance through this. It does look just like a boss pedal, you're thinking of the right ones. What do you mean by socket? will it just fit over the old one? are you saying I don't have to desolder it? or just, take the old one out and put the socket on instead and I can snap in and out the new OP amp? Are those models you suggested, good enough, or good. cause I'd like to do a good job on this one, but stay at one trip to radio shack.

Thanks a ton man, this is helping lots.
Quote by Strato-Massacre
yeah you shouldnt have told the pit to rape your mom.

Quote by Kensai
It's not sexist, girls are just too stupid and weak to hold up doors and stuff for themselves.
#8
This is a 8-pin IC socket: Socket. You take the old opamp out and solder this socket in it's place. The new opamp will just pop right in without having to solder it or any worries of burning it up.
The opamp you are taking out will have a circle or a notch at one end of it. This mark identifies the end pin 1 of the opamp is. Make a note to where the notch is. The notch also might be marked on the circuit board under the opamp. Not sure but it usually is. The socket has a notch on it also. Put the notch on the socket at the end where the notch was on the old opamp. Solder it in place. Take the new opamp and line the notch up with the notch on the socket and carefully pop it in the socket.

Here is an illustration. Opamp is on the left and the socket is on the right.
Attachments:
opamp-socket.jpg
#9
thanks so much, also, its a nine pin, so its all inline, not nice and 8 pin like your example. does that narrow my options much? and thanks again
Quote by Strato-Massacre
yeah you shouldnt have told the pit to rape your mom.

Quote by Kensai
It's not sexist, girls are just too stupid and weak to hold up doors and stuff for themselves.
Last edited by Lt.DanHasLegs at Dec 25, 2009,
#10
How do you know it's the op-amp anyway? Do you have an audio probe?
Gear:
Schecter Hellraiser Deluxe
Boss DS-1
Crate GTD65

GAS List:
Mesa Boogie Dual Rectifier Roadster
#11
Quote by Lt.DanHasLegs
thanks so much, also, its a nine pin, so its all inline, not nice and 8 pin like your example. does that narrow my options much? and thanks again

9 pin? SIL doesn't limit your options much but the 9 pin business does. Let me go take a look at the datasheet for your IC.
#12
Quote by asfastasdark
How do you know it's the op-amp anyway? Do you have an audio probe?

Thats what the chip says it is when I looked it up. everything else on the board is just capacitors and resistors and such.

I was looking around on the radio shack website, and I'm not finding anything ninepin... are they rare or something? cause I hotwire it somehow? Thanks.
Quote by Strato-Massacre
yeah you shouldnt have told the pit to rape your mom.

Quote by Kensai
It's not sexist, girls are just too stupid and weak to hold up doors and stuff for themselves.
#13
It looks like the chip you have has separate V+ for each internal opamp. If you take a look at the datasheet, and go down to where the drawing of the opamp is with the triangles in it. See how there is 2 triangles. That's the two opamps. Now see how there are two V+ pins. It has one for each internal opamp instead of one V+ for both opamps like an 8 pin opamp. Compare to the 4558's datasheet.

So take a look at your opamp you have in there. There should be voltage going to pin 1 and 9. If you have a multimeter, you can verify this.

Your going to have to pick up an SIL dual opamp which I doubt Radio Shack has or pick up a DIP opamp and use a DIP to SIL adapter. I personally would just get a SIL opamp.

The pins 2 - 9 on the opamp you have in there is the same as pins 1 - 8 on the 4558's. You just have to deal with the extra 9v pin that would be left empty. Technically you should be able to just leave it empty as the new chip won't need the dual V+. So if you put a 8-pin SIL 4558 in where pins 2-9 are of your current opamp, it should work. You can also get SIL sockets to solder in there just like the DIP one I illustrated. Radio Shack probably isn't going to have any of this though. I can help you find it if you need me to.

Is there any way you could upload some pictures on here so I can have a visual? It always helps.
Last edited by Griffin Effects at Dec 25, 2009,
#14
I would love help finding it. I don't really know where to find it or what to look for. I'm working on pictures btw.

thanks a bunch man, I really appreciate it.
Quote by Strato-Massacre
yeah you shouldnt have told the pit to rape your mom.

Quote by Kensai
It's not sexist, girls are just too stupid and weak to hold up doors and stuff for themselves.