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**Paleo Pete** · 10-21-2007, 02:50 PM

Hmmm...2 days and no takers? Nobody has an idea what might be going on? Does anyone think the momentary contact switch might still be flaky even though it seems to be working? I've wondered about that...

I've looked over the solder joints with a magnifying glass, all seem to be solid. The input and output jacks seem to be good or it wouldn't get a distortion sound when turned on. No wires are corroded, loose or bare, but I did just realize I haven't tried pushing on the board and commponents with a pencil or wooden dowel to check for loose components, need to try that.

Any ideas? I know you can't test components without the board sitting in front of you, but from reading the posts here trying to find a similar problem I know some of you guys are amazing at educated guessing.

And so you'll understand my situation regarding schematics, I know what most of the symbols are, and how to find out the values, or look them up, but I can't for the life of me figure out WHICH resistor on the circuit board corresponds to the one on the schematic, unless both are numbered or it's the only 220k one in the whole thing. This board, unfortunately is not marked. This is really frustrating, I've always been able to learn anything I want to, from engine repair to optical repair, instrument repair, archaeology, astronomy, computer repair, working on camera repair now, play any instrument I want to, and loads of other stuff but schematics have always baffled me...the circuit board looks nothing like the schematic, and I can't figure out how you guys can look at one and know what resistor or whatever to look for and how to trace the signal path from that, it amazes me every time.

Any ideas? Need more info? And I do have the schematic...for what it's worth...

**Sock Puppet** · 10-21-2007, 07:28 PM

Originally posted by Paleo Pete View Post

Any ideas? Need more info? And I do have the schematic...for what it's worth...

Hi Pete,

Could you post the schematic here? I'm sure you'll get specific help.

Many of these posts can go unread, I hadn't looked at the forum for a week and saw 635 new posts... yours was on the first page.

BTW, FETs are housed in identical cases to the usual bipolar transistors with TO-92 cases popular amongst the small signal types that you would find in pedals http://www.fairchildsemi.com/product...f/to92_dim.pdf

S.

**Paleo Pete** · 10-22-2007, 06:38 AM

Thanks for the FET info, I'll check that out tomorrow, it's a bit late tonight.

Here's the only schematic I've found so far, and on closer look I see it says "modernized with pull down resistors, true bypass switch and readily available pot values", so it might not be exactly like the unit sitting in front of me. Hopefully close enough to work with though. I found a couple so far but all link back to that same one. I'm still looking.

Something else that I've been wondering about too, especially since this is not actually a true "bypass" style pedal, is bufilding a loop box to switch it with. Since it still works perfect, but only the distortion side, it would mean an extra box, but it might be worth a few bucks to build a loop box and just leave it on. [Off], the loop box goes straight through, [On] it switches to the SD 9, already on. Think that might be worth tinkering with? I can get everything to do it for $20 or less, possibly $10 or less, depending on switch price, and it wouldn't be too difficult. I'm about to rework my pedal board and the new one will have plenty room for the extra box. I'm undecided, anyone think it would be worth trying? In a perfect world I'd really rather fix it, however...all you have to do is take a look around and you'll know it ain't a perfect world...

**Sock Puppet** · 10-22-2007, 02:55 PM

The schematic isn't much use for fixing your problem unless you want to do the mod and given the collectablity of those pedals, I would, like you be more interested in fixing it properly.

I had no luck searching for a full schematic either (anyone?) but I'd assume that the switching is similar to the TS-9 one here:

http://www.freeinfosociety.com/elect...ew.php?id=1088

Can you read the transistor numbers in the pedal? In the TS-9 there are two FET switches (2SK30A), one fed from the clean input buffer transistor and one taking the signal from the output level control on the right. The common output, as onlyone FET should be on at any one time goes through the 0.1uf capacitor to the output buffer.

The two transistors below the FET form a switch with two stable states, and either the left or the right will be on at any one time - when the right one of the switch pair is off then the LED will light up so in your version this is working.

The FET on the left (assuming it's a similar circuit) is likely to be at fault though we'll see if anyone has the full circuit diagram of yours first (there's a threat of it coming soon on R.G.s Geofex site).

Meanwhile your bypass pedal is a good idea & will always be useful to have anyway.

There's a bit of food for thought for you here

http://www.geofex.com/Article_Folders/bypass/bypass.htm

and here

http://www.stinkfoot.se/andreas/diy/articles/fetsw.htm

S.

**52 Bill** · 10-22-2007, 04:44 PM

I agree with SP in all that he suggests. Fixing the pedal will be a much better solution than using a separate bypass pedal.

I've never seen a schematic for your pedal, but I have to believe that the switching is the same (or close enough at least) as the on the TS-9. If the led goes on and off with the switch, then the switch itself is fine. The two transisitor flip flop seems to be working as well, so the problem is probably with the fet for the bypass signal.

Use your meter's diode test to check the fets just like you would check a bipolar transistor. Because there are two of them in there, compare readings from one to the other and see if you find a fault.

Hope this helps.

**Paleo Pete** · 10-22-2007, 05:21 PM

OK, this looks like it might be progress...

I have two K30A transistors, (no 2S) but above and below, not side by side like the TS9. I have an old TS 9 (water damage, deep fried to a crackly crunch) and the board layout is completely different, but the K30A transistors are there, and oriented left/right. The SD 9 has them above/below, both boards oriented so the wires and power jack are at bottom, the Maxon label and board number upright as if reading them. The SD 9 board is printed with board number MP - SD 1301A. Maxon. TS 9 board D01201B Maxon. If that helps...and I still haven't found any other SD 9 schematic...

The K30A's on the SD 9 also have a symbol printed on the board, (none on the TS9) in the "D" shape of the transistor, with 7 vertical lines that are NOT there for the other transistors, they have just the D shape. (in this case the D would be laying on its back, the straight line at bottom, then the lines would be vertical.) I can't find this symbol anywhere so far, so it's apparently not a standard schematic symbol, just one to show the assembler the shape of the proper component and to denote that it's not the standard transistor. On the TS9 board they are also facing opposite directions, the SD 9 pair are both oriented with the flat facing the "bottom" of the board, oriented as described. Both boards do have hot/ground marks for the various components.

So I'm fairly sure these are the correct transistors, no other K30A's anywhere, the ones I can read are all C1815. There are 5 of those, I can read 4 of them, I'm pretty sure the 5th should be a C1815 also. But that's just a guess, the resistors in front of it create shadows so my flashlight and magnifying glass don't help much.

So...if I understand your info above correctly, one of these K30A's is dead, or at least one side of it, replacing it (or both, if I can't find out which one) should have a good chance of fixing it? I'm not looking forward to that, from what I understand about them, transistors are the most susceptible to heat damage from soldering, and this thing has no room for a heatsink, but I'll have to try my small alligator clips and see...I'm not touching anything until I have a good idea what will happen, I don't want to fry this thing altogether...and yes, I'd rather fix it, and I have NO interest in modifying it, I love the way it sounds exactly as it is. So the schematic I posted won't do much good I suppose, as I suspected...

Hopefully the heat issue won't cause problems, I know how to solder qiute well, I was taught by a friend who soldered calculators for Westinghouse every day for 8 years, I do a professional looking and very solid soldering job and I usually get in there and out pretty quick, by keeping a small dab of solder on the iron tip to transfer heat really fast. I've been replacing capacitors on motherboards for 5 years, you usually can't pick mine out except by the extra flux if I don't clean it off. I'm just really leary of transistors, since I've read all over the place they are skittish about heat. I'll see if I can test the transistors this evening, somewhere around here I have a book with the procedure and values for most components. I just hope they can be tested without disconnecting from the board, I can't remember if transistors are one of those or not, although it seems it would be more reliable to isolate any component for testing...but the last thing I want to do is screw it up worse...

I wish we had a decent shop here...the one I know about checked my Peavey out, through a local guitar shop. I left specific instructions I just wanted him to troubleshoot it, I could get parts and do the soldering, I just don't like anypone inside my amps with a soldering iron, I've seen way too many sloppy solder joints, even in factory equipment. The first thing the guy did was replace the filter caps, which I had replaced a week earlier. I hit the ceiling, I specifically told the shop owner I wanted NO parts replaced, just find out what and I'd replace it. So I don't think I want to take anything else to the same guy to work on, I don't know what he's going to replace just to grab a buck. And I know he's good...I just don't trust him. That's why I'm sitting in front of this computer asking questions...Oh, I didn't have to pay for the filter caps, I bought the caps I installed from the same shop owner, so he could verify that they were new and he settled that for me. I had also showed him the job, (I brought the amp in already pulled out of the road case, just the chassis) I was worried about the contact wires shorting so I put heat shrink tubing on them just in case. Overkill, but I knew they wouldn't short against anything if it got jostled around. Turned out to be a bad transformer - $120 plus shipping and a half hour to bolt/solder it in and it works and sounds great now.

Thanks for the other links, I'll take a look at them later, I have both open in other tabs for later reading. I already have a good idea what the bypass issue is, and what it does, but it looks like some interesting reading. Even if I get this thing fixed, I might still build a bypass box for it...just for the experience if nothing else, I've already built a footswitch from an old pedal case, rewired one for the Peavey, modded an older Peavey practice amp for both a footswitchable lead channel and external speaker jack that would cut off the internal one and therefore not cut the impedance in half...so it might be a project anyway just for fun...

**Paleo Pete** · 10-22-2007, 05:27 PM

52 Bill

Thanks for the suggestion on testing, I'll definitely compare the two. and as I mentioned above, I have no intention of modifying this pedal, and would much rather fix it than anything else. I'm still tempted to build a bypass pedal, just for the fun of it, but I'd really like this pedal to work right again, so I'm going to try for a fix if possible. The bypass pedal can be a project for later, just to see if I can get it to work.

Also, you confirmed what I already thought, the momentary contact switch seems to be functioning correctly, the LED does go on and off, and the distortion side of the pedal works fine. So I thought the switch was ok, thanks for confirming that.

I gotta go, I'll try to do some testing this evening and see what I can find out.

And thanks...

**Paleo Pete** · 10-23-2007, 04:22 AM

OK, here's what I get, in circuit.

Label side up, leads pointing toward you, K30A label on the left, the middle appears to be base, the (+) lead on base gives me 865-875 ohms, when tested on both sides, the (-) lead on base gets nothing both sides. Zero. This is the same for both transistors. Should be OK so far.

Outside leads (collector to emitter, if I'm right that base is middle) get 410-425 one way, 380-390 other way on one transistor, 480-490 one way and 550-560 the other way on 2nd transistor.

Now here's the wierd part...I get a random fluctuating reading over 1000 on any working combination from time to time, never the same pair twice in a row, but only in the working direction if I'm reading base to E or C. I've been over this thing a dozen times, and it can be B-E one time, B-C next time then C-E or vice versa, always over 1000 ohm, always fluctuating from 1000 to 1300. Yes it does the same for Collector/Emitter readings both directions, both transistors.

I'm not sure if this is related to being still in the circuit, and I'm seeing interactions from other components or possibly tarnished test leads or flaky contact...

**Sock Puppet** · 10-23-2007, 06:02 AM

Originally posted by Paleo Pete View Post

I'm not sure if this is related to being still in the circuit, and I'm seeing interactions from other components or possibly tarnished test leads or flaky contact...

See the attached pinout and take a look here for info on testing FETs:

http://www.opamp-electronics.com/tut...or_3_05_03.htm

Your initial tests look reasonable to me.

With the pedal in bypass mode and a guitar plugged in etc, you can identify the transistors by connecting a 470R resistor across source and drain.

Connecting the resistor between gate and source should turn the FET on also, if not then look at the diode on the gate and the resistor from the flip-flop.

S.

**Paleo Pete** · 10-25-2007, 04:17 AM

OK Ummm...

The weirder I sit here the longer this gets...

Tried the 470 resistor, once I finally found one. Couldn't see the yellow line on the tan background. Yes, I had my glasses on, no old fart jokes.

Pedal in bypass mode, plugged into my Fender Champ, no cleans, hit the switch and it gets distortion. Same as it's been since this started. Back to nothing, try the 470 resistor, it turns on distortion, then cleans. OK, transistors are working as far as I can tell. So I clicked the footswitch to doodle on guitar for a few minutes, distortion working fine, decide it's time to shut it down and find out where to go from here. Switch off distortion and I have clean guitar.

HUH??

This is what it did before, when I initially thought dirty switch and hit it with a squirt of contact cleaner. Worked that evening just fine at practice, next weekend plug in and no cleans, distortion works, and that's where it's been until this evening.

So I'm betting this is not fixed, I'll not believe it anyway, something is still acting like bad ground or flaky contact. And I can't find it, I've been over this thing with a flashlight and magnifying glass (in an already lighted room) a dozen times. It worked for an hour after I found out it was acting normal, I kept switching it back and forth, unplugged from it and went straight into the amp too and found no noticeable difference in the clean sound either way. Other than the usual doesn't seem like clean was that wimpy till I turned on the distortion pedal...That's every time. so it's not getting a really weak signal or sucking all of either end of the tone out. Sounds normal.

Is anything in there prone to resemble a flaky connection? Any components that will show an intermittent problem? According to what I hear everything is working for now...so nothing is definitely, undeniably burned out or it would get nothing still.

**Sock Puppet** · 10-25-2007, 06:55 AM

<scratches head>

I've looked at that switch for a half an hour now and everything I can think of keeping that fet turned off i.e. gate negative w.r.t. source is highly unlikely... and the fault is intermittent. Hmmm....

I hope you have a fresh battery in there

No cracked traces?
No correct diagram?
I'd run the soldering iron over the components associated with the clean signal path as well as you can including Q6 if you have one, same again for the gate control components.

If that does no good, change out the FET and the gate diode and 47n capacitor just for the hell of it. Oh, and that 510k and 0.1 on the source (or drain - scratching here).

Still doesn't work properly? Sell it as faulty on ebay for more than it's worth working and buy a bottle of Glenmorangie.

S.

Not much help I know

**Paleo Pete** · 10-25-2007, 01:34 PM

Good battery, nope and nope. Nobody has a schematic or diagram either one that I can find, except a modified one.

I thought about going over it with a soldering iron a while back, did that with my Champ and Super Reverb since both are pretty old, 73 and 74 models. Except for heating the transistors, it shouldn't make things worse...I've been over it with a magnifying glass several times, can't find any breaks in anything. My first thought was bad solder joint or a wire got weak and broke. Wires shouldn't be an issue though, until it didn't work one day it's never been opened up so the wires have never been moved around. But yeah, there's still that chance.

I'll see if touching up the solder does any good, if I can collect all the right colors I might swap out every wire in it. I can't see any corroded wires either, by the way, or leaky caps. (I've replaced lots of bad caps on motherboards, about 4 or 5 years ago someone made up a bad batch of electrolyte in Japan from a stolen formula, missing an ingredient that prevents formation of Hydrogen while in use, the caps pressure up like a basketball and explode. Replace them, the motherboard works fine. I'm typing on a machine with the first set of caps I replaced, I've been running it 24/7 for 5 years.)

Not sure what else to do, but will try to locate the parts you mentioned, replace those too.

Thanks a bunch for the help, if nothing else I now know a little more about electronics than I did a few days ago. I'll still never understand all of it, gave up on that long ago, as mentioned earlier I've tried to get a grip on electronics for years, it's one of the few things that eludes me.

**Paleo Pete** · 10-28-2007, 02:39 PM

Schematic?

I was looking through the links Sock Puppet posted in the "Pedal Schematics" thread a couple of days ago, and stumbled on one for the SD 9 that looks like it might be useful, at least it has different values in a few places and does not contain the notice about modifications.

This one was on one of the links I was browsing through, even if it doesn't help with the issues I'm having with my pedal, it might come in handy some other time...

I see several changes, but all I can do is compare values, the schematic itself might as well be the lyrics to "Comfortably Numb" in Greek, as I mentioned earlier I've never been able to get a grip on schematics...

I'm planning to try and go over the solder connections this weekend, if I could find a couple more colors of wire I'd replace all of them, but I don't have a couple of colors I need and no money right now to just run out and buy some...anyway, just thought I'd drop a link in here for this schematic, for future reference if nothing else.

**Sock Puppet** · 11-19-2007, 09:52 AM

Schematic

Success!

http://aronnelson.com/gallery/v/Sche.../sd_9.jpg.html

Or did you decide on this...

S.

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