Wiring resistors and wire onto multi-deck rotaries best practices?

[rollmottle]

Hey folks,

Hope this is the right place.

Bit of context:  I purchased a dude's abandoned DIY Racked MQ5. I have been re-habbing it in an attempt to get it to function as is and it's 95% there. I'm going to want to eventually re-do all the rotaries because a lot of the solder and resistor work is less than ideal. I am confident it will work after my go-through, but I'm going to want to go back and re-wire a new set of rotaries with matching wire gauge/color, uniform wire lengths, clean resistor install, etc.

I want to do it right. I've seen pictures of some of you more experienced folks' rotaries and hope to match the cleanliness. Can anybody point me to tutorials or write ups of best practices regarding how to wire rotary switches -- Specifically, I'm interested in techniques of wiring two-pole uraltones rotaries and how to properly solder in the resistors between the two decks and properly drop in the wire so when it comes to final assembly fitment isn't an issue. Or if anybody can post some pictures of what they consider quality-wired and soldered rotaries, so I can have a closer look at what you did, it would be super helpful!

Thanks in advance. Sorry if this is the wrong place or if there's a thread already. Couldn't find it in the search.

 

[Gold]

As it happens I’m in the middle of making a bunch of rotary switches for an EQ. They are Electroswitch C4’s . I can snap a photo tomorrow.

I’m not familiar with the Uraltones. One concept I’ve found common to wiring all rotary switches is let gravity be your friend.

Clamp the shaft of the switch in a vise with the shaft pointing up. That way you can load the resistors in the tabs and they hang down or are held in place by the tabs.  Now nothing is moving and you can solder everything.  I like load, solder, repeat.  Some like to load everything and then solder.

Inspect everything carefully with a magnifying glass when you are done.  Poke every resistor to check for bad solder joints.

 

[TwentyTrees]

Paul is absolutely spot on, a clamp or helping hands-type doodad is incredibly helpful for rotaries. It’s definitely a case of “measure twice, cut once”, especially with the Uraltones - there’s not a lot of space around with those and they’re not well marked up, so worth checking and rechecking which tab is which pole before loading the switch. I then go to town with a marker pen.  ;D

Final thing that’s helped me is using the smaller resistors - I forget which brand / series, but I used a bunch that were 600mW but were only about 3mm long, which meant they dropped into the switch tabs really nicely and didn’t need any creative lead bending to fit! Minimised the overall profile of the switch too. That was with Lorlins, but it might be worth measuring up the spacing between solder tabs on your switches and choosing resistors accordingly to make life easier for yourself. Alternatively, there’s a seller on eBay in China who sometimes has Uraltones loaded up with SMD resistors in common pot values (eg 10k lin, 50k log, etc) - search “Valab attenuator”.

Really great question though - good to have a chance to learn from other people’s techniques. Let us know how you get on!

Andy

 

[rollmottle]

As it happens I’m in the middle of making a bunch of rotary switches for an EQ. They are Electroswitch C4’s . I can snap a photo tomorrow.

I’m not familiar with the Uraltones. One concept I’ve found common to wiring all rotary switches is let gravity be your friend.

Clamp the shaft of the switch in a vise with the shaft pointing up. That way you can load the resistors in the tabs and they hang down or are held in place by the tabs.  Now nothing is moving and you can solder everything.  I like load, solder, repeat.  Some like to load everything and then solder.

Inspect everything carefully with a magnifying glass when you are done.  Poke every resistor to check for bad solder joints.

Thanks Paul! Would appreciate it. The effort to "do it right" will really pay dividends at final assembly as now I'm fighting against the original workmanship as I get the faceplate and knobs attached to the rotaries.

(Met you once years ago in 2009 when I was living out east and you mastered a record for my label. https://www.sentrall.com/releases/sen009-the-beat-broker-deep-sleep).

 

[rollmottle]

Paul is absolutely spot on, a clamp or helping hands-type doodad is incredibly helpful for rotaries. It’s definitely a case of “measure twice, cut once”, especially with the Uraltones - there’s not a lot of space around with those and they’re not well marked up, so worth checking and rechecking which tab is which pole before loading the switch. I then go to town with a marker pen.  ;D

Final thing that’s helped me is using the smaller resistors - I forget which brand / series, but I used a bunch that were 600mW but were only about 3mm long, which meant they dropped into the switch tabs really nicely and didn’t need any creative lead bending to fit! Minimised the overall profile of the switch too. That was with Lorlins, but it might be worth measuring up the spacing between solder tabs on your switches and choosing resistors accordingly to make life easier for yourself. Alternatively, there’s a seller on eBay in China who sometimes has Uraltones loaded up with SMD resistors in common pot values (eg 10k lin, 50k log, etc) - search “Valab attenuator”.

Really great question though - good to have a chance to learn from other people’s techniques. Let us know how you get on!

Andy

Interesting, didn't realize you could buy *smaller* resistors, though there are so many different valued resistors for these frequency rotaries, I don't know that I'd be able to get all the correct values in a smaller size.

Do you guys wire up your wires to molexes/crimps and THEN solder them to the rotaries or do you wire them to your rotaries first and then deal with attaching them to the molexes (or however you're attaching them to the PCB)? Just curious how folks approach this part of it as well.

Thanks guys!

 

[TwentyTrees]

Yeah, if you’re looking for specific size resistors then it’s an extra factor when sourcing parts that can be a pain in the proverbial...

Personally I attach wires to the switches once the resistors are in place, or even beforehand if it’s gonna be tricky getting the iron in there once populated. Crimping and lead dress is pretty much the last thing I do once everything’s installed in case and on panel, to make sure the wiring is short, neat and sensible.

 

[Gold]

Here is a switch that is done. I will remove the excess flux. More for looks than anything else.

 

[Gold]

Here is one getting started.

 

[Gold]

(Met you once years ago in 2009 when I was living out east and you mastered a record for my label. https://www.sentrall.com/releases/sen009-the-beat-broker-deep-sleep).

Ah, cool! I remember that!

 

[rollmottle]

That’s helpful. Thank you. What kind of switches are those? Those seem like they’d be way easier to work with than the cheapo Chinese ones I’m dealing with, though I know it comes at a significant cost.

 

[Gold]

They are Electroswitch C4. They are 12 position switches. The upside to them is that they are inexpensive compared to something like a Grayhill. They are indestructible unlike a Grayhill.  The downside is  they are physically large. They don’t easily go in a 1RU case.  They also require a lot of torque to turn  which some don’t like.

 

[Gold]

I’ve done my share of Elma 04’s. They are a PITA.  The concept is the same. Bend the resistors into the shape you need and hang them from the tabs . I was never able to make an Elma 04 to look as good as a Neve monitor switch but they looked okay and worked.

The C4’s look easier because there is a lot of room. The issue with these is that the tabs have a lot of open space. It’s hard to get good solder coverage without putting a ton of solder there.  That’s why it looks a little rough. Not like a thin shiny coating. It’s easy to think you have a good joint when you don’t . This is the first time I’ve wired a bunch of these at once. I’m still working out technique but they are getting better.

Personally I wouldn’t put in the work on a cheap switch. I subject stuff to heavy use. I only want to wire a switch once. With light use it might not be as much of an issue.

 

[rollmottle]

I’ve done my share of Elma 04’s. They are a PITA.  The concept is the same. Bend the resistors into the shape you need and hang them from the tabs . I was never able to make an Elma 04 to look as good as a Neve monitor switch but they looked okay and worked.

The C4’s look easier because there is a lot of room. The issue with these is that the tabs have a lot of open space. It’s hard to get good solder coverage without putting a ton of solder there.  That’s why it looks a little rough. Not like a thin shiny coating. It’s easy to think you have a good joint when you don’t .

Yeah, I don't think there'd be room in the case for those. The ones I would probably use are these (or similar) because I can't justify 10 or 20x the price on Elma's. Also, the thought of making a mistake on a $50+ switch vs. a $10 scares me away too.

https://www.ebay.com/itm/1pc-Rotary-2P-24Step-Round-Solid-Shaft-Control-Switch-Attenuator-Guitar-DIY/163376880316?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D9ac1f57afd8048578c961f2987ab00e3%26pid%3D100675%26rk%3D2%26rkt%3D15%26sd%3D273116033000%26itm%3D163376880316&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A3a14ac28-35fa-11e9-816a-74dbd180b05c%7Cparentrq%3A110093d21690a860ef41e9fefffc3677%7Ciid%3A1

The spacing on the tabs is super tight and spacing between decks similarly tight so it requires some wrangling. I can tell the guy who wired these had some trouble dealing with them and didn't really think about fitment later down the line. I've had to bend stuff the opposite way it was wired so adjacent switches aren't shorting each other. Less than ideal but functional is my goal at the moment.

 

[Gold]

Choices are limited if you want a 24 position switch with a small footprint. There are  a lot of choices with 12 position switches. If I need an Elma 04 I get them from Goldpoint with a PCB deck. It saves a ton of time but is more expensive.

You should use teflon tubing to avoid shorts on the exposed resistor leg and make sure there isn't an exposed lead on the other side of the resistor.

 

[rollmottle]

Those Goldpoints would be a treat to work on, but damn are they pricey. 

I feel like there's a gap in the market between $75 rotaries and $9 ones, but I guess if there really was a market, more affordable in-between options would already exist.

These 1P/12P Alpha ones are pretty nice and affordable vs. the all plastic Alpha ones. https://www.mouser.com/ProductDetail/105-SR2511F-12FN

 

[Gold]

A 1 pol/12pos C4 is $16.08 at Allied Electronics. A 4 pole/12pos is $42.94. The price along with the build quality is why I like them. You can shoehorn them into a 1RU case but it's tricky. A lot of creative bending and insulating.

 

[rollmottle]

Thanks for the tip. Half the battle is knowing where to look. 

 

[warpie]

How about using the smaller 0.25W resistors? Wouldn't that be easier to solder?

 

[rollmottle]

How about using the smaller 0.25W resistors? Wouldn't that be easier to solder?

I'm sure it would be though it would get expensive fast. It calls for these (as an example): https://www.mouser.com/ProductDetail/KOA-Speer/MF1-4DC3160F?qs=sGAEpiMZZMukHu%252BjC5l7YTGf9TaaIlKHkJCHGAqphM4%3D

In this instance, replace with this?
https://www.mouser.com/ProductDetail/Vishay-Dale/CMF50316R00FHEB?qs=sGAEpiMZZMukHu%252BjC5l7YRa3iqlr3Vuf%2FbjiouQJ3Xk%3D

There are 75 different resistor values for the resistor networks on the freq and gain rotaries so the cost would quickly add up seeing as the smaller ones are almost 5x the price per.  Think I just need to channel my inner zen and bite the bullet.

 

[rollmottle]

I know enough to order enough resistors to hit at least the first quantity discount.  On Mouser it's 10. For example, on this project I only need 4x on some of these values. So I ordered 12, using 3x as a multiplier. But maybe that's overkill when it calls for 20 and I'm ordering 60.

Do you all have a general rule of thumb for ordering above and beyond what you need when it comes to ordering resistors?