Help Identifying the Limits of This Switch Model

[dylanhunt]

I'm hours (not consecutive) away from getting started with wiring up a crazy series/parallel Brian May mod, but now I am wondering if the 4PDT switches I got on Ebay are really 4PDT switches.  This is the John Hewitt-inspired, Andrew Roberts design that uses three switches for on/oop/off and one switch for series/Easter-egg/parallel, but-- because it's 3+1 instead of 6+1 switches--all of them need to be 4PDT switches and each must have an on-on-on configuration. 

The NKK switches were sold as M2044 models, but have "M2040" on them instead.  The only information about M-2040 switches comes from an NKK catalog in Japanese, which I cannot read.  Luckily, it is fairly easy to figure out what is going on in the catalog based on the English-language examples, and it looks like there are clear matches across the different model numbers (e.g., M2040=M2044, M20408=M2046, M20409-M2047).  Unfortunately, because my experience with switches is too limited, I can't tell from either catalog whether:
1) I have 2P3T switches that cannot be used as 4PDT on-on-on switches because of conductive magic internal to the switch,
2) I can use the M-2040 as a 4PDT because external wiring is required to turn the 4-pole base into a 2P3T, but I cannot use them with an on-on-on configuration, or
3) I can use the M-2040 as a 4PDT with an on-on-on configuration.

Maybe there is a test I can do with a multimeter if no one has an answer deciding between options (1), (2), and (3)?  Thanks!

[JohnH]

Definately test them no matter what!

The lugs will be on a 3x4 layout. The poles will be the middle four.

Set meter to resistance. With lever flicked down, the poles should all connect to the upper lugs, and to the lower lugs if flicked up.

Check there is a Middle lever position. If so, the poles should then connect to lugs left to right, down, up, down, up.

It may instead be down, down, up, up or vice versa. If so, can still use them but need to swap some lug wires.

If there's no middle position, or there's no connection in the middle setting, then no good

[dylanhunt]

I did some testing and I think I am in the clear.  I'm still confused why neither the Japanese catalog nor the US catalog refers to the switch model as a 4P, but only as a DP3P. 

My method was to test the connections listed under each of the three toggle positions on each NKK switch (the rocker for serial/parallel is a C&K switch and I'll get to that next, but no apparent problem arises in the specs for it).  I assume that each of the 4 parts of the test for each position (one part for each of the 4 poles on each switch for a given position) involves a single connection between two terminals.  [Each part of the test involves testing a pair of terminals.]

The On position involves the bottom and center rows of terminal: {3,6,9,12} and {2,5,8,11}.  The Off position involves the top and center rows of terminals: {1,4,7,10) and {2,5,8,11}.  The center position involves (left to right with keyway on bottom): the bottom terminal (#3) and center terminal (#2) on Pole A (left-most pole), the top terminal (#4)and center terminal (#5) on Pole B (middle left), the bottom terminal (#9) and center terminal (#8) on Pole C (middle right), and the top terminal (#10) and center terminal (11) on Pole D (right most).

When I connect each of the pairs of terminals, I get continuity:
On Position: {2,3}, {5,6}, {8,9}, {11,12}
OOP Position: {2,3}, {4,5}, {8,9}, {10,11)
Off Position: {1,2}, {4,5}, {7-8}, {10,11}

I don't get continuity when testing other pairs in any position. 

Hopefully, that is a definitive test.

[JohnH]

That looks fine to me, the usual 4-pole on-on-on, as assumed in ARoberts diagrams.

Also, if you think it through, it makes no difference if you spin the switch 180 degrees and renumber the lugs to suif. So the position of the keyway etc is not critical.

[newey]

So, you can visualize this as if it were 2 DPDT On-On-On switches mated to a single actuator. The internal logic is the same as 2 DPDTs side-by-side.

[dylanhunt]

Thanks JohnH and newey!!!

By the way, I did realize the arbitrariness involved in orientation, but three of the switches are installed on the back and the rocker is installed on the front.  Once the reference numbers for the terminals are applied to ARoberts/YogiB's wiring diagram, that establishes the switch behavior (i.e., up means on, center means oop, and down means off).  The keyway was crucial for helping me establish a cardinal direction particular to the switch in its proper place on the guitar and helps me from getting confused.

Thanks so much for all of the help!

[dylanhunt]

Sept 17, 2021 0:32:21 GMT -5 JohnH said:

Check there is a Middle lever position. If so, the poles should then connect to lugs left to right, down, up, down, up.

It may instead be down, down, up, up or vice versa. If so, can still use them but need to swap some lug wires.

If there's no middle position, or there's no connection in the middle setting, then no good

This is off topic, JohnH, but in trying to get a working schematic for my Jag project (3 x DpDT, 1 x 4DPT: NxM/parallel/MxB), I found the hurdle was in how the center position is wired internally.  When I originally had the switching problem on this thread ("Help Identifying the Limits of This Switch Model"), the lugs on the switch I was using connected (L to R) down, up, down, up--which created no surprises.  Unfortunately, that internal wiring will not get me what I want on my current project.  However, an up, up, down, down internal wiring for the center position is exactly what I need.  You said that there are some switches out there like that.  Do you know if there is any keyword or term I can use to help me search for 4PDT switches with that internal wiring specifically?  Thanks! 

[dylanhunt]

I'm gobsmacked.  A Google search led me back to CN2: guitarnuts2.proboards.com/thread/1111/4pdt-3-position-switch-varieties

I'm not sure this old thread will help me track down the switch I need, but it's a start.

[JohnH]

Could you not just swap the wiring on a couple of poles, if they are in a different order?

[newey]

Let's let ChrisK simplify things. There are 3 types of 4PDT switch, as shown in the left-hand column here:



The On-Off-On variety isn't what you want, obviously, so that leaves only 2 choices. One of the 2 is the Kent Armstrong BM switch, which is available only a few places and is so designated. Since the long-ago days of unklmickey's post, no one has ever found/posted any other types, so any 4PDT switch you buy that isn't called a Kent Armstrong switch will be as per the second diagram below. And, (again, as far as we know here), the center position links are (with switch terminals vertical and facing you) just like 2 DPDT On-On-On switches together (i.e., lower left and upper right connected to commons). There is no mirror-image version as far as we know.

Obviously, as JohnH said, check your switches with a meter- as you should do with all your switches, as manufacturing defects do occur.

[Yogi B]

Oct 22, 2021 6:57:21 GMT -5 newey said:

There is no mirror-image version as far as we know.

I too don't think I recall seeing a mirrored version, but I can't be sure. I do however remember that solderburn had some that were a different variation, the centre position connecting the terminals in an up‑down‑down‑up pattern (See my post in the original thread), even UnklMickey didn't foresee that as an option back in the day!

(The original pdf to which I was referring in that post seems to be gone from OTAX's site. I have found what appears to the replacement documentation, however it's less clear what's going on with the switching because they've listed the connected terminals as though the external jumpers that convert it to DP3T operation are present. So it looks like I have some hunting to do... Never mind, I was looking at the incorrect page )

[dylanhunt]

Thanks all!  John H: Q) Can I make wiring accommodate standard 4PDT internal wiring? A) Well, that remains to be seen, me being a bear of very little brain, but I'm going to have to do more fundamental analysis since a surface reconfigure with the right outcome doesn't seem possible.

Using the diagram below (from UnklMickey), what I am looking for is labeled "3a", though I should think I could rewire easily to make 3b work. 

It sounds like, Newey, that you're saying nobody has seen this endangered species in a while.  The diagram doesn't show solderburn's switch, nor did UnklMickey's original post (https://guitarnuts2.proboards.com/post/10740/thread).

[dylanhunt]

Oct 22, 2021 5:13:41 GMT -5 JohnH said:

Could you not just swap the wiring on a couple of poles, if they are in a different order?

I'm not used to wiring 4PDT switches, but your question makes me wonder if it's a trivial matter to go from 3c to 3d [corrected] needing 3a to making it work with 3c; i.e., whether there are surface equivalences from one combination of pole states to another (e.g., down-up-down-up <--> up-up-down-down).  Because of jumpers, things are a little complicated but I'll do my homework and post on the other thread I started if I run into trouble.  Using a switch I have is easier than buying a new one, but buying a switch is easier than moving the rusty cogwheels in my head.

Updated: Got it in the end... very rusty cogwheels.  Thanks for the push, JohnH.