Very simple question about a DPDT slide switch

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Roodillon, Aug 7, 2008.

  1. Roodillon

    Roodillon Member

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    I have to add an on/off switch to an old Deluxe Big Muff. right now the leads are just wired together to be always on.

    I purchased a DPDT slide switch as it was the only one that fit correctly in the chassis of the pedal. Now here is my very simple question. Which leads on the DPDT should I use for the simple on/off? Here is a picture of the type of switch that it is. It has six terminals on it. I need to know what the terminals correspond to when the switch is not hooked up; ie. which ones can I use for which purposes? Which two should I use across for the simple on/off?
    Thank you!
    [​IMG]
     
  2. brad347

    brad347 Member

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    are you talking about the battery connection or the signal connection?

    If you're talking about the battery, you don't need the whole DPDT. You can just use half of it as a SPST.

    Cut either lead from your battery. Solder one half to the middle lug on one side, and the other half to either the one directly above or below it (depending on which direction you want to be "on."

    You're done.
     
  3. Roodillon

    Roodillon Member

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    Hello, I am talking about the AC power lead because this one runs on AC power. I know that I did not need a DPDT switch, and the extra terminals here are only confusing me. But it's the only one that Rat Shack had in the size that I needed for the pedal's chassis. I wanted a buy a SPST. Anyway I gotcha now, but I am not sure which terminals on the switch you mean by "above" or "below." Perhaps this will help. Here is a link to a picture of my switch http://www.zshare.net/image/1669001427f420f7/ I put numbers to the terminals. Please refer to this diagram. The leads that are circled are the two that I will be attaching, one goes to the power transformer and the other to the effect stomp switch. Thank you again!
     
  4. brad347

    brad347 Member

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    Attach the two wires to either 1 and 2 or to 2 and 3. It doesn't matter which goes where.

    You could also do 4 and 5 or 5 and 6. It doesn't matter. The DPDT is like two SPST's side-by-side.
     
  5. Roodillon

    Roodillon Member

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    Thank you! It makes perfect sense now.
     
  6. Roodillon

    Roodillon Member

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    OK well it did seem to make sense to me anyway... But I described it wrong. And I think that I may need the DPDT anyway. Here is the correct version of what I need to hook up: There are two black wires coming from the AC power supply transformer inside the box. Then there are two black wires coming from the AC power cord that goes to the wall. Nothing goes to the stomp switch as I said previously. That was an error. So - before, the switch was bypassed. One wire from the power cord went to one on the transformer, and the other went to the other one on the transformer, so it was always on and you plugged/unplugged it to power it on/off. So I need to install the switch in between the power cord and transformer.

    I did it once and blew a fuse! I connected the power cord to 1 and 2; and connected the transformer to 4 and 5. I can hear you laughing already! I blew a fuse on my surge suppressor. Oh well that's what they are for. So now I have to hook it up properly. Should I perhaps re-connect the wires that were spliced together and connect one pair each to terminals 1 and 2? That would be my next guess.
     
  7. mark norwine

    mark norwine Member

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    Guess?

    You're messing around with 120Vac, and you have no clue what you're doing.

    Not trying to be mean or sound harsh, just working with the data you've provided.

    You need to see a tech. 120V can hurt you.
     
  8. Roodillon

    Roodillon Member

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    I hear you man. I'm not THAT clueless though. It sounds worse. I've (mostly) repaired everything 120Vac that I've tried to over the past 25 years. I just don't have a schematic or picture of the wiring for this pedal, and although it sounds simple I could not find basic schematics of standard switches. Don't worry, I am not taking it as harsh. Reading back my letter now I do sound like an idiot, but it's really not that bad. I respect electricity and take the proper precautions. I purchase the correct tools to use. I'm not one of those people who would put a .22 caliber bullet in place of a fuse! I have fixed an large variety of things in 25+ years but right now I am trying to learn it properly and have been studying books and learning to read schematics.

    If you could direct me to a book that would be good for learning to repair effects pedals that would be nice. I have not found a single book that takes it from that perspective. It does not have to be about effects pedals per se. But something that focuses mainly on those types of circuits and on the types of components used such as SPST and DPDT switches and so on. I don't need to learn advanced microwave theory (at the moment anyway). But there are so many books that take way too long before they get down to diagnosing and repairing simple circuits. They are more like textbooks. I've written textbooks in other subjects. They are majorly padded out for reasons of taking up a semester's worth of time, justifying a large and expensive book, justifying updates and expensive new editions, and occasionally teaching you something. But they don't work well for home study. I already know who Frederick Ohm is etc. I agree that that stuff is important to learn, but I have. I don't need to keep reading it over and over again. But every book I find is either too focused that way, or way too specialized and advanced. I need a book about basic circuits that was written for the learner, not the author. I don't mind buying a project kit either, the ones made especially for learning circuits. If I think that they are useful I will buy one. Something more complicated than a light bulb circuit, or the AM radio. I'm not that green. Are the useful?

    Believe me I am not going to hurt myself or anyone else. I just need to know where to connect the wires. I've taken 120Vac and even 220Vac (straight to my bare chest, it was not my fault. It was bare wires hanging in the dark in a supposedly dead building that I was replacing the plumbing in). I have even been struck by lightning. Now, I tried doing the right thing and asking the people at Rat Shack but that was no help. As if... They could not tell me the difference between the SPST and the DPDT. But back in the day it seemed that you had to know the basics before you got a job at RS.

    As for technicians, I am not anti-technician but I am not sending my pedals to them. This I can do myself. I already sacrificed a couple of pedals when learning to solder. I have lots of pedals so it's ok. The last time I took anything to a technician was a home CD player around 1990. It suddenly stopped reading discs. They had it for a week or so and then called to tell me that it was the lasers and it would cost more to fix than it was worth. They asked me if I wanted it back anyway. When I said yes, they told me that they had to take it all apart to test and that there was a charge. I think that it was $40 but maybe more, and it was 1990. I paid it and took it home. I plugged it in and noticed that the LCD no longer worked. I removed the cover of the player and found that the reason that it stopped playing discs was because one of the children had placed a cardboard "disc" of the type that they put in a new disc player so that you have to read it before you place a disc in. And it was so thin that it stayed on there and did not eject with a disc. It only kept it from being read. It was the old type of player that you fed the disc into, not where the tray ejected. So the cardboard "disc" could not be seen from the outside of the player. ANYWAY, so of course I removed it and put the cover back on and voila! It played beautifully. But the LCD no longer worked and it never did again. So what did I get for taking my player to the technician? Well, I lost a week of the cd player. I paid at least $40. The LCD never worked again. I did call the shop but got nowhere. I asked them how, if they had taken the unit apart as they said, that they did not find the cardboard? It would be the first thing that anyone would see! They flat out refused to acknowledge anything. That's what these people do. They defended the work and the charge. But they just wanted to keep the unit and resell it. A lot of shops do that. When I called them on it they suddenly had to charge me, and they probably broke the LCD in spite. I could have pursued it but my mental health is worth more than a cd player and $40.

    I'm not saying that all techs are bad. I know they are not. But many are. My friend's father was a TV repairman in the 1970's and 80's. Remember those guys? They always offered to "dispose of" the old unit that would cost more to repair than to replace, to save you the hassle of picking it up. But they always had a ton of used televisions for sale too, right? Just in case you're not sure, my friend told me flat out that his father would tell people that they were too expensive to fix, then fix them with a ten cent part and sell them. So please don't leave me at the mercy of techs. I've broken things and I've taken juice and I can handle both of them.
     
  9. strymon

    strymon Member

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    The best book for an introduction to music electronics is "Electronic Projects for Musicians" by Craig Anderton. That's only my opinion of course but I think the book is great.
     
  10. strymon

    strymon Member

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    one more thing, some general switch information:

    SPST: "single pole single throw"
    SPDT: "single pole double throw"
    DPDT: "double pole double throw"

    An SPST switch is most commonly used for an AC power switch as that is all that is required, however an SPDT or a DPDT can be used by leaving some terminals unconnected. SPDT and DPDT switches are commonly used for effects bypass switches. DPDT is required for "true bypass."
     
  11. donnyjaguar

    donnyjaguar Member

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    A friend of mine, now in his 50's, became a tech largely because he was so enthralled with the TV repairman that came to his house to repair the family TV when he was 10 years old. Clearly, this repairman had magical powers. He bumped into him years afterwards and realized this guy knew next to nothing. If he couldn't find the fault with his tube caddy, cross reference guide, cool-it spray, box of condensors and some alignment tools see posting above about "beyond repair".
     
  12. Roodillon

    Roodillon Member

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    Quote:
    Originally Posted by strymon [​IMG]
    one more thing, some general switch information:

    SPST: "single pole single throw"
    SPDT: "single pole double throw"
    DPDT: "double pole double throw"

    Actually I understand that part.

    An SPST switch is most commonly used for an AC power switch as that is all that is required, however an SPDT or a DPDT can be used by leaving some terminals unconnected. SPDT and DPDT switches are commonly used for effects bypass switches. DPDT is required for "true bypass."

    There's where it stops making sense for me. An SPST is simple to the point of not needing explanation. But when I get to the point of needing to leave some terminals unconnected on a switch, I think "why would I want to do that?" I know there is a reason, but I don't know what it is. Or, as in my example, I have a total of four wires. Where to place the four wires on one switch? I know it's ancient news to you guys but until I have done something and understood why it was done that way then it's all gibberish to me.


    I'm not completely green. I am currently making the break from someone who has installed thousands of AC powered devices like water heaters, dishwashers, pumps etc. as well as diagnosed and replaced their more easily serviced parts like thermostats, elements, switches, impellers, etc; -- to someone who can diagnose and repair the more intricate issues as well as understand them. To equate that to music gear, to go from being able to replace pots, switches, jacks, leads etc. to finding and repairing the more intricate electronic components that make up the gear. I've repaired lots of pedals for myself, and many for resale with not one ever coming back. But it was all jacks, pots, switches, battery leads, or cold joints. I never diagnosed and replaced a faulty chip, for example. Or a bad cap. That's where I am trying to get. You guys must have recognized a similar point in your education, whether self study for your own use or scholarly for a profession. The point where it goes from nuts and bolts (or switches and jacks) to a place where more knowledge is needed. Separate the men from the boys, as it were. I never felt like I needed that much knowledge to repair and replace the smaller stuff, although even that put me above those that could not and must take everything to a repair shop. I knew where to attach which end to which end, and how to do it safely. But I want to better understand the stuff that comes next, the stuff after you become proficient at soldering and wiring components and of light diagnosis. That is where I am at right now. So once I study and understand these switches and their applications then I will know it and that's that. I don't plan to learn about every switch or component in the world, but I do want to have a good working knowledge of the ones that I will be mainly working with.

    I just want to be mostly self-sufficient when it comes to my music gear. I am not enthralled by television and have a 19" mono TV which suits me fine. The only things that I have to repair these days are pedals, amps, electric guitars and other gear. As for the Craig Anderton book I will start reading it. I have it somewhere as a .pdf or ebook, among others. I did not know which ones were good.
     
  13. strymon

    strymon Member

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    No offense meant with the simplistic explanation. Somtimes I find it's just best to get down to the very basics. The reason you speak of why you'd use a switch with more terminals that really need is actually simple as well. It may be that the style of switch you'd like to use simply isn't available in the configuration you want. In your case, the style of slide switch you want to use is extremely common in DPDT and extremely uncommon in SPST.

    My advice to you in continuing your electronics education is to read the Craig Anderton book, build a couple of his projects (kits are available from paia), and get VERY comfortable reading schematics and understanding why everything works starting with the simplest schematics.
     
  14. Roodillon

    Roodillon Member

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    That is good advice. Thank you. I am doing it right now. I have a couple of hundred effects pedals so I don't mind sacrificing a few in my pursuit of higher knowledge! I already melted a few components when I was working on my soldering. I eventually repaired those with parts salvaged from other broken pedals (I bought some broken pedals for parts) and sold them; not one has ever come back. I try to do things right, for example when replacing something I go all the way back to the board and desolder the old wire and solder the new one directly to the board instead of splicing it. I've bought old pedals and found five or six splices in the battery leads alone, unsoldered with electrical tape hanging off. It takes a little bit more time and effort but I think that it's worth it. With all of the broken pedals that I bought and repaired/resold I always did it like that. I never spliced them even though it works and would have been faster. And if I find lousy old splices on another component besides the one that I am actually working on then I remove them and replace with a new solid wire from component to board. I like things to be reliable. It's just a little thing and I don't mean to make a big deal out of not splicing wires, just to say that I prefer to do use best practice procedures instead of cutting corners whenever possible.
     

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