# Original Ibanez SD-9 Sonic Distortion (not the re-issue) owners



## prodigal_son

Can anyone who owns one of these tell me what they are supposed to sound like in the "off" position? I just picked up one of these and they sound bloody great but when I switch it off it just sounds plain awful with a massive volume drop. Any ideas? Thanks in advance.


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## Guest

I've owned two originals. One went to a guy in Toronto a few years ago actually...

Anyways; they're buffered off, but it should be transparent. There might be a volume difference between off and on depending on where your gain and level knobs are on the pedal. There's a ton of boost available in that box.

That's a great pedal BTW. One of my favourite ODs. I carried one as a backup in case my Mesa Single Rec bit it. The SD-9 and the red channel were spot on clones of each other.


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## prodigal_son

Cool man. Yeah, for sure!! This is a wicked sounding pedals dudes. I am absolutely in love with it but.. The volume kill off switch thing. What the frig is going one here? I need to fix this!!


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## mhammer

The SD-9 is essentially an MXR Distortion+ on steroids, with a Big Muff tone control tacked on the end. That's a bit of an oversimplification, but not THAT far off. Where it differs significantly from the Dist+ is that it adjusts gain via that 250k feedback resistance, rather than via adding resistance in series with R5 (470R). This means it won't lose bottom end as you increase gain, but _will_ lose top end as you increase gain (rolloff starts around 2.5khz at max gain, a good thing in an overdrive). Note as well that its' max gain is just over 600x where the Dist+ maxes out around 213x.









How loud is it in the off position, relative to when you simply plug your guitar straight into the amp? In other words, is there something so wrong with the "off" position that it is taking away substantial amounts of signal level?


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## prodigal_son

Yes!! There is no other way to put it other than very significant volume loss. I literally have to put the Level knob down to 1 to get both channels to be similar in volume. I can crank the Master on my amp and even past half way it still exhibits extremely low volume output when the pedal level is dimed. The "off" position absolutely sounds horrble. It still distorts, drops volume, and does not sound right at all. The overdrive on the pedal works fine but the clean (buffered bypass or whatever) is totally messed. I noticed that the pots are scratchy. Perhaps I will give them a spray and see if this does anything.


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## mhammer

Okay, given that the SD-9, like many other Ibanez pedals, uses an electronic switching arrangement, the chances are very good that one side of the flip-flop circuit is not working.

Found a more accurate schematic (the one I posted earlier omits the original electronic switching) here: http://www.experimentalistsanonymou...Distortion Boost and Overdrive/Ibanez SD9.pdf

That schematic shows that the FET used for switching is a 2SK30A-Y, which will be legended on the actual part as simply K30A. The gate pin on these is pin 2, the pin found in the middle if the part is standing up with the flat side facing you. The drain and source are the two outside pins. For purposes of switching, it doesn't matter which is where, since it is being used only as a resistor and not as an amplifier.

If you bridge those two outside pins, that transistor is bypassed and the circuit is permanently "on". What you need to do is find out if bypassing that transistor will restore the feedthrough of the clean sound, since it seems as if something is electronically obstructing the bypassed signal.

So, find out which of the two K30As on the board the clean side is. It will be traceable back through a 100nf (0.1uf) cap to the output pin of a 4558 chip (either pin 1 or pin 7). Once you have found it, solder a small piece of wire stripped at both ends to one of those outside pins on the K30A. You can simply use the solder pads on the copper side of the board. With the guitar plugged in and the pedal plugged into an amp, touch the free end of your little wire bridge to the pin on the other side of the FET. It's a good idea to make sure there is no masking lacquer or flux buildup on that other pad that might insulate it and make it seem like our temporary bridge doesn't fix the situation. You can pick the coating away with a small X-acto blade.

In theory, if it is simply the JFET that is shot, or some aspect of the circuit that turns it on, then simply bridging the tranny should get you back your normal bypass volume.

Do that test, and report back. We'll take it from there.


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## prodigal_son

Thanks again mhammer. I unfortunately am not an electronics pro. I followed what you said totally but I would rather not attempt this in fear of destroying the pedal. Could you recommend anyone who could fix this for me?


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## mhammer

Unless you solder with a welding torch, it is a very trivial sort of repair. Really. If you have an appropriate soldering iron, you can do it. In fact, if you can manage to stop the pedal from jiggling, you don't even HAVE to solder; you can just touch the two ends of the wire to the appropriate pads to see what happens. It will NOT fry anything, you have my word. At the very least, if you wish to have it repaired by someone else, it will be worth your while to say "I checked out such and such and the problem seems to be (or doesn't seem to be) X". That'll save you bench time.

I can't recommend anyone in your area, as such (Sydenham is near Owen Sound, right?), but a quick search says that Fromager Music in Owen Sound might be able to assist you, is you do a bit of the detective work up front.


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## prodigal_son

OK. Here is a progress report:

I opened it up and just did a visual inspection to make sure nothing looked broken inside. Closed 'er back up and plugged 'er back in. Problem seems to have fixed itself somewhat. Not entirely though. Now when I switch back to clean it goes wonky (see post 1) like before but only for 1 or 2 seconds before it goes clean and problem free. Problem almost fixed!! Any more ideas?

<edit> Sydenham is just north of Kingston. Think: English Lord of Sydenham </edit>


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## prodigal_son

Update:

Sprayed the pots and the problem is gone comepletely now. Yay!!

It unfortunately now seems to have a new problem. When I switch to bypass you can hear the clean channel as expected but there is also a small bit of what I can only describe as "distortion bleed" quietly layered beneath the clean sound. I have tried changing cables, comparing sounds with and without the pedal, changing settings on the pedal, etc.. The only thing that gets rid of the distortion bleed is setting the Distortion knob on the pedal to the lowest setting. Not how I would like things if you know what I am saying. The distortion bleed on the bypass channel also increases as the Distortion is increased. 

Does anyone know how to fix this? Thanks in advace.


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## mhammer

I should have used Mapquest instead of Google maps, one gave me a Sydenham between Owen Sound and Collingwood, the other gave me your Sydenham right away.

Okay, we're getting somewhere. Does the switch back to effect mode happen normally and instantaneously?

Whenever time gets factored into the misbehaviour of a circuit, the problem is either thermal (i.e., heat build-up) or a capacitor (since their storage and discharge of current takes time). The switching circuit is that part of the PDF schematic shown in the lower right, with the "criss-cross". You can see that there are 5 capacitors associated with it: two at 47nf (.047uf), and three at 1nf (.001uf). The 47nf are not likely involved since all they do is smooth out the transition between on and off as each JFET is switched (i.e., it inserts a couple of milliseconds of lag so that you don't get an audible pop). Which leaves us the .001uf caps.

On a completely different track, it is also possible that there is not a cap problem, but rather that there is a hairline fracture somewhere in the PCB. I say this because opening and closing the box should not have any impact on the capacitors. And if the problem appears to clear up in a way that was different from its previous behaviour, that suggests a mechanical/continuity issue; i.e., something is only making contact intermittently and not continuously as it should.

This is one of those times when I recommend to people to take some Q-tips and methyl hydrate and clean up all the flux residue on the copper side of the board so they can see the solder traces clearly.

But good on ya for being willing to take a stab. We'll "git 'er done" eventually. Just be patient and systematic.


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## prodigal_son

New progress report:

Ok, I gave it a chance to sit over night and things have changed again. I was playing last night on my son's practice amp and it was switching fine with no volume drops but there was the distortion bleed. Worked like this for about an hour last night.

I hooked it up today and it still has the distortion bleed in bypass mode. Now, it is also doing what it did before where it has a massive volume drop and distorts for about 3 or four seconds (kind of sounds like it's warming up as you play it or something) only when you switch back into bypass mode. Switching to effect mode exhibits no delay or time issues what so ever, it is only when it is switched to bypass mode where it does this.


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## mhammer

The pedal uses one single chip, one half of which is used for the distortion and the other half of which is used for the bypass signal. If it sounds okay in effect mode, then the bypass mode's crappiness is very unlikely to be the result of somehow "frying" only one half of the chip (i.e., such matters rarely happen). Both the input and the output go through the same two transistors (2SC1815), so it can't be them, for the same reasons.

All of which leads us inexorably to the K30A which connects the clean signal to the output. This is where the "bridging" trick (connecting the input and output pins of the JFET) is pretty much the only way to go. My guess is that you'll find out that bypassing/shunting/bridging this transistor will magically get you the clean signal.

Now, that does not necessarily mean that this JFET is the only source of the overall problem. There may well be a crack in the PCB, but the first thing to confirm is that bridging the K30A gets you a consistent reliable clean signal that never disappears.

Incidentally, if you were to solder the little wire bridge I suggested in place and close the box up, you'd find that when you step on the switch and engage the effect, you'll have the clean signal mixed in with the distortion. Turn down the distortion signal to nothing and you should still hear clean.

Again, you've come this far, so it's time to strip a little piece of wire, find out where the two K30A pins are, and solder that little devil into place, or get a friend to do it. As long as you aren't applying too much heat, you won't damage anything. To help, make sure the little wire to be added is tinned on both end (i.e., solder properly coats the stripped wire). Heat the wire with your soldering iron and it will help to melt the solder on the board. (Remember that the board absorbs the extra heat and directs it away from the area to be soldered, so heating the wire end assures that all the heat will be concentrated in on small spot).

Tag, you're it.:smile:


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## prodigal_son

http://www.experimentalistsanonymou...Distortion Boost and Overdrive/Ibanez SD9.pdf

Dead link. Not sure why. Definately gonna do this though.


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## prodigal_son

@mhammer 

Welp. Tried what you had mentioned. Used clips so I did not have to solder. Now the pedal has low volume on both effect and bypass mode. I hope I did not wreck this pedal. That would suck large. I had to try something. Thanks again for the advice. Keep it coming if you have any other ideas as I am totally lost at this point.

I am in communication with Analog Mike and so far the guy tells me that I should contact CAE in San Fransisco as they could most likely fix it. 

Uuuugh!!!


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## mhammer

I hope I gave you the right two pins. It never ceases to amaze me how, with only 3 pins, there can seem to be an infinity of pinouts for even the same transistor number on the part of different manufacturers!

What you did should be reversible, and I sincerely hope it was.

Is it possible for you to post some pics of the board, both component and copper side, and maybe that would assist in getting to the root of the problem.

Failing that, if you're ever up Ottawa way, bring the pedal and give me a shout. I should point out that generalguitargadgets sells PCBs for the SD-9 ( http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=87&Itemid=26 ), and the parts are all easy to get. Maybe it would be easier to just make your own? (nudge, nudge)


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## prodigal_son

I had my processor in the effects loop and it was shut off when I wrote that last post. The pedal is still the same as before. Dirt channel works and the bypass has issues. I took it to a shop in Kingston. Just waiting to hear back on it. I miss it already. Was playing it the other night on my son's Traynor international series practice amp with headphones. This pedal even made that amp sound good.


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## prodigal_son

Problem solved. Was merely a loose pot that needed to be tightened according to tech who actually said he "couldn't find anything wrong with it at all". This pedal rocks!!


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## mhammer

Well, now there's a happy ending! I like those sorts of stories.

Congratulations. :smilie_flagge17: ....and as always....:rockon2:


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## ZenJenga

hey. I'm a NooB round here. I'm a regular at offsetguitars.com and shortscale.org. Name's Judson. I currently live in Newfoundland.
I just found this place whilst looking for info about my SD9
I have the same pedal with the same exact problem.
It bleeds distortion into the bypass signal.

You say tightening the pot helped???
What exactly do you mean?
I'd like to get it in good working order, as it's a deadly pedal.

:smilie_flagge17:


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## mhammer

Welcome, b'ye! :wave:

Prodigal Son's problem was different than yours. Bypass-bleedthrough happens to a lot of pedals. The issue is the FETs used for switching. They are being employed as resistors that can be changed from having a very high resistance (no signal passes through) to having a very low resistance (signal becomes audible). The problem occurs when, for whatever reason, the FET is being set to some value in between being "off" and "on". The LED may be turned off, and the clean signal may be heard, but off in the background there is still some effect signal coming through because the FET that is supposed to block it is juuuuuuuusssst a little bit "on".

Can it be fixed? Sure. Is it a simple thing to do. Well, that would depend where you live and how much you know. In principle, it should be a simple matter of swapping the FET for another that doesn't turn on at all under the same circumstances. Or it may be a question of tweaking the component values in the "flip-flop" circuit that turns it on and off. Indeed, I responded to a post on another forum today from someone trying to build an Ibanez effect from scratch, and the schematic showed a sort of "black box" mystery code in two places in the circuit that does the FET switching on and off. Those mystery codes may well be because the precise values depend on the batch of switching FETs they happen to use for a batch of some pedal. At least that's what I'm thinking. It's not like the circuit is any great secret since it is widely shown in many Boss and Ibanez pedals. So, the only reason to withhold such info is most likely because it would "depend" on the peculiarities of the FETs used, so they simply aren't in a position to specify. Once you've worked with FETs, you realize pretty quickly that just because they have the same part number and manufacturer doesn't necessarily mean they have the exact same properties.

What some folks do in such circumstances is to leave the thing on and use some other means to switch it, like a loop selector. I'm sure you want to hear about a simpler, less costly and less involved solution, but we know that one works, at least.


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## ZenJenga

right on. I've got a loop switcher, I'll have to use it that way for the time being. I'm a NooB with pedal technicalities, but I've been reading as much as I can lately, as I hope to start building them myself and coming up with my own inventions. So much to learn. I'll probably end up getting some sort of elec. engineering under my belt in the meantime.

thanks for the response.


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## prodigal_son

All I know is that he said he "tightened a loose pot" and she worked fine again when I got her home. Not sure how you tighten a pot but it fixed my problem (problem being that it would cut out for about three seconds before it finally cleaned up after being switched). Still has a trace bit of distortion bleed, though not as severe. I use mine in a loop on my GCX so no bg deal. From what I can gather, they all have the bleed. Mine is a 1981 SD9. Not sure about yours. I'd like to compare it to the Maxon SD9's some day.

It could also just be reacting harshly to high output pickups?


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## mhammer

First, read this article: http://www.geofex.com/article_folders/potsecrets/potscret.htm

The resistive strip inside the pot is essentially bonded to the piece of phenolic or whatever. The solder lugs are essentially rivets with bits that stick out so that you can solder to them. Most of the time, they fit nice and snug against the resistive strip and make good contact. Sometimes, not so much.

What I generally do when I get new pots is pop the backs off and pinch the rivets just a bit to make sure they make good contact with the ends of the resistive strip. It is possible that when the repair guy said "tighten", that's what he meant.

Alternatively, sometimes the pot is not secured very well to the chassis, and it rotates a little bit to the side and one of the solder lugs makes contact with something it shouldn't. Perhaps, by "tightening", he meant that it was moved away from any accidentally contact and the retaining nut was tightened solidly to prevent such accidental contact. Being well familiar with such incidental unintended contact, these days I slip a little piece of heatshrink tubing over the solder lugs on pots so that they can't touch anything even if they do move.


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## ZenJenga

Thanks Mhammer.
Very useful. I think I've got it sorted. I used some contact cleaner on everything while I was at it. It seems to be fine for now.


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## mhammer

Proper t'ing!:smilie_flagge17:

Often, mechanical contacts like switches and pots present some of the major sources of malfunction or misbehaviour in pedals. Best to be familiar with the "natural science" of such movable/mechanical contacts.


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## Arhythmic

Hello all 
Sorry to resurrect a zombie thread, but I specifically joined this great forum (that I've been reading for a while prior to this) to thank MHamner for his detailed responses to this thread! I've bought a 1983 SD-9 a couple of months ago and the bypass signal was almost inaudble... Thanks to this thread I fixed it! The circuit had some damage from a battery leak (I resoldered some small pieces of wire on top of the traces) and the big problem was a invisible crack in the trace on the circuit board that found by slightly manipulating the board while is was plugged with some signal going through.
This pedal is really great and it is permanently back on my pedalboard!


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## pandelis.r

Hope someone reads this before I open a new thread.
Finally fixed my SD-9 that was collecting dust for 20+ years. One of the 2SK30A needed replacing. 
Holy jumping does this sound good; however I'm not sure it's 100%.
Have a little bit of electronic knowledge so talk slow.
#1- The red wire from the battery is disconnected, I can't figure where it goes via the schematic. I use a power supply so this is really not an issue.
When I plug in a pwr supply it turns on without any jack input. Is that normal? This seems consistent with some but not all of my pedals. It turns on and off fine.
#2- In the off position the sound is not as if plugged straight into the amp, and maybe I'm hearing a touch of distortion. Ever so slight. Again maybe this is normal.
#3- If both the Tone goes beyond 50% and the Distortion above 60% it starts to feed back when not playing. Even worse with single coils, I did not own any 20 years ago. Once again could be the norm. 
I think #2 is the biggest issue that would prevent me from using it regularly.
Any feedback or help would be appreciated. Thanks.


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## pandelis.r

Sorry just saw mhammers’ response above. I don’t know how l missed it. I’m thinking the jfet l replaced could be my slight bleed through issue. Is making this a true bypass a possibility.


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## mhammer

It's a possibility. The question is really one of whether one can either machine the pedal appropriately to install a mechanical bypass switch, or rehouse the circuit in an enclosure more amenable to such a switch.

Note that, if one does so, you need to jumper the switching FET that connects the distortion to the output, and cut the connection from the input buffer to the output buffer that would normally provide the bypass signal.

As well, note that, like pretty much every electronically-bypassed pedal, the SD-9 does NOT include a terminating resistor on the input. This can result in switch-popping, when you go back and forth from effect to bypass. The solution is to attach a 1-2.2M resistor from the input of the circuit board to ground. This also prevents any true bypass pedals ahead of the SD-9 from producing pops in the SD-9.


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## pandelis.r

Thx mhammer, tough call, keep it original or make the mod. And l misspoke FET not JFET. I’m glad l have it working and will play with it for a while as is. If l was going to a new enclosure l might just build a clone. But how many pedals does one need…..always one more. X+1.
I’ve looked for other mods without much luck any suggestion?


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## mhammer

My bad. "FET" = "JFET". There are different subcategoris of "FETs", like MOSFETs. When it comes to e-switching, they're generally plain old JFETs.


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