"Coils" & "Solenoids"--ADJUSTMENTS

[Ron Rich]

Hi All,

As I am most familiar with Seeburg products, this pertains mostly to them, however, I think this is true for many other items, as well as other jukebox brands.

For this discussion, a "coil" is a round cylinder that activates a round plunger, usually in the inward direction and is spring returned to it's "normal" resting place. A "solenoid" is a "squarish" item with an electrical  winding, that also pulls in a (squarish) plunger.

There are several different types of coils, serving slightly different purposes. Seeburg used three types. 1. Self contained within a metal frame ( coin coils, most models "pop" meter coils), 2. Non contained --having a separate front and separate rear, retainer (used as the "detent" coil-- and subtract coil, in the pricing unit, in most post war models).  There are 2 "sub species" of the above coils--1 has a removable back-stop core with a brass tail piece inserted in it (which can be broken-- check / replace if needed), and some have a rubber "deaden-er" which can deteriorate . The other (#3) has a welded back stop core, with or with-out, a brass insert.

"Solenoids" are self contained, body and plunger as one unit. The brand used by Seeburg was always "Guardian". There are other substitute brands, that can be used. Regardless of brand these ALL were, equipped with anti magnetic springs, of some type, which tend to get broken after a million or so uses-and sometimes lodge in the plunger area--causing BIG problems, such as "buzzing" when energized ! --Quick check on this-- detach plunger from anything --hold solenoid with plunger facing up- lift plunger-allow it to fall down-- if it falls all the way and does not self lift back up a "hair", springs have failed ! If/when this happens, the plungers on these solenoids tend to "stick" internally into their housings.

As for adjustments-- see the appropriate Seeburg ( or other) Service Manual. In most instances you will note the coil/solenoid is mounted in an elongated groove. It may have 2 or 4 mounting places. If a coil, in Seeburg's case, screws used for mounting, and washers MAY be different types/sizes, and if removed should be replaced exactly as found ! In MOST cases, you do NOT want to  mount this at the very end of the mounting slide space !  What you want to do is examine how it should operate. Apply only enough rearward bias ( using your hand--power off !), to assure that whatever the plunger pulls, it "bottoms" on the stop, it does whatever action required, but that it causes NO strain, on the linkage. The "slide space", is there to compensate for any "differences / ware" in the linkage.  Ron Rich

[jukeboxgeek]

Hi Ron
Very good write up on “solenoids “ and “relays”.....it’s been my understanding that solenoids are generally used in design applications that involve/require more mechanical power than a traditional relay.?..........solenoids such as the ones used for pulling in the “Latching Solenoid” on a Rockola when a coin(s) has been credited or a free-play has been initiated ,....require more power than a traditional relay could provide.......power needed to engage mechanical linkages and levers. Wurlitzers have something similar for the same function......ie They keep the selection sequence “active” until the selection sequence is completed(selection push buttons are depressed)......at which time the solenoid is released and the sequence will repeat when either inserting more coins; pushing the Free Play button again.......or a “Free Play” modification has been made to the jukebox (such as those you have suggested ......and which I’ve seen in many Wurlitzer forums.) However there is an inherent problem with the “permanent free play” which I have seen on most all the early model Wurlitzers I’ve worked on......,and just recently on a Rockol 1493.....The selection solenoid in my Wurlitzers tend to get “cooked” from being engaged for long periods of time and the Rockola “Latching Solenoid” runs hotter-than-hell.....both eventually failing over time. This is such a prevalent problem .......read about on many different forums ......that I looked into the design. To summarize ......these solenoids in this application were NEVER designed to stay active for long periods of time......say more than 3 minutes........time enough for someone to depress the push buttons to select their song. For sure it was never designed to stay engaged forever.......which is what happens when a “permanent free play” modification is made to the jukebox. Wurlitzer ,and it appears in the Rockola schematics.....that they have attempted to improve the solenoid design by adding a circuit feature .....sorry have to run now .....more later.
Mike

[Ron Rich]

Hi Mike,
I distinguish coils/solenoids and relays differently then you appearently do. I consider a coil, that has a plunger to be a coil, like that used by WurliTzer to pull in the plunger. A solenoid assembly also pulls in a plunger, but it's usually a self contained assembly, such as used by Seeburg/RO to hold the keyboard locks.  A "relay" also has a coil, but, it also has an armature, rather than a plunger, and usually "relays" info via contact points after it has been energized. 
As far as I know-- WurliTzer designed their latch coil, used on the 1700, up, models, to with stand constant duty, by adding the resistor, and the switch, that inserts it in series with the coil, after the coil is fed full initial power. WurliTzer used two different brand coils, along with two different value resistors. I have never seen a "cooked" coil on one of these due to free play ? Seeburg and RO, used the same Guardian built solenoid assembly, which WAS NOT constant duty, and WILL catch fire ! Ron Rich

[jukeboxgeek]

Ok ...I have returned.
Wurlitzer and Rockola both have an electrical circuit that drives their solenoids, called a “Pick and Hold “ circuit ....its quite clever ...what it does is initially drive the solenoid to its “On” latched position by iapplying a lot of current (max current) .....it has to do that initially to be able to pull or draw-in the metal plunger in the solenoid.....if you’ve ever seen that grade school demonstration using wax paper and iron fillings? You have seen that most of the magnetic flux (field) in an electro magnet is along the length of the magnet (solenoid coil) and not at the ends of the coil......so the initial max current is needed to creat a field at the end of the electro magnet to be able to have enough power to pull the solenoid shaft into the solenoid itself......that’s what’s called the “pick” part of the circuit .Once the solenoid has been “picked” the solenoid needs only about 40% of the max power (current) to “hold” the solenoid in place. Both Wurlitzer and Rockola reduce the power to around 40% by switching in a high wattage resistor .......39 to 390 ohms......after the solenoid is picked.....,the high wattage is switched into “series” with the solenoid coil . The current thru the coil now drops to 40% .....which is enough to “hold” the solenoid....,but prevents the solenoid from getting hot.......You probably know already that the other 60% of the initial (max current).......gets absorbed by the current limiting resistor (39 to 390 ohms)....by absorbed I mean the current thru the current limiting resistor gets turned into heat. Think of it as a jukebox’s own little space heater . And that is the design limitation of these “hold” circuits using a current limiting resistor........they were never intended to hold but for a couple of minutes......and for sure never intended to be On (holding) all the time. In conclusion it should come as no surprise that these current limiting resistors ALL get “cooked” after being On (holding ) for an extended period of time .....ie hours. In some jukeboxes I’ve seen where the current limiting resistor got cooked and was burnt in half.....so there was no “holding” current.....but it doesn’t/didn’t take much to also figure out that there is a set of contacts that get “opened “ up when the solenoid gets “picked” which is what puts the high wattage current limiting resistor in series with the solenoid coil . If you bend this set of contacts to stay closed all the time.... things start working again. Unfortunately now there is no “holding” current........just the maximum “pick” current being run thru the coil....so yes things still work but now the solenoid coil gets cooked in a real short time! Hopefully it makes a bit more sense now why it’s NOT a great idea to keep the Latching Selonoid (Free Play) engaged all the time. Described another way........faking out the Accumulator (mechanically) into thinking it has unlimited “credits” is the same as modifying it for unlimited “Free Plays”....not a great idea.
Sorry for the lengthy dissertation ......but hopefully you found it helpful. Please let me know what you think......and I’ll be glad to send you several ways you can modify the pick/hold circuit so that it’s not turned into a space heater or coil killer! It’s not all that complicated; and works quite well,
Mike

[Ron Rich]

Hi Mike,
Yep-- Most jukeboxes were not designed to be on "Free Play" ! I have seen a couple of WurliTzers with fried latch coils, and a few with open resistors-- the fried coils always had a "jumper across the resistor " ! When ever I set one on free play, I increase the wattage of the resistor to 10 watts. Never had any problems with that. Why don't you start a new thread, and post that circuit--seems like a good idea to me -- Ron Rich

[jukeboxgeek]

Ok thanks.....
I’ll start a new thread and submit a write up on how I modified the Rockola 1493 to “free play “ in a way that wont cause the Latching solenoid to overheat.
Btw what’s the best way to post a sketch of a circuit diagram on this fourm?
And many thanks ......this forum is great!
👍
Stay healthy!
Mike

[Ron Rich]

Hi Mike,

I dono-- you somehow need to copy/paste it here now, as we are supposedly out of space" ?

EDIT-- See how to post photo's, above in FAQ's

Ron Rich

[Ron Rich]

Hi all
Been axked this several times, so I thought I'd write it up here--
In my humble understanding of English-- A "coil" is a round object, with a non connected plunger. Some coils are constructed with core stops, of various designs, and others allow the plunger to pass totally through the coil body. A "solenoid" is a wire wrapped around a core, which is usually rectangular in nature, and has a plunger that usually does not detach from the body of the solenoid.
The above being said, will be the definitions used for this discussion.
Once correctly adjusted, if designed correctly, they should almost never need re adjusting ! If you think one does, examine other avenues before re-adjusting ! Coils with adjustable mounting slots, and a core stop, need to be adjusted so the plunger hits (bottoms) firmly on the stop, with ZERO "strain" on any linkage, but enough distance to allow whatever it is pulling to properly detent. Core stops must be un-damaged-- this includes a brass de-magnetizer, if used. If there is any type of "back-stop" for the coil's actuator, it also must not strain the linkage ! A "solenoid" in most cases is the same as the core stop, coil, and needs the same care in adjusting, except that the solenoid usually has spring steel "de-magnatizers". These often are broken and once in awhile slide into the hollow, the plunger should ride in. When this happens, the plunger is likely to "stick" on the broken steel section, or if that section falls out, the plunger becomes "magnetized", and does not release (in time?). Once in awhile-- the broken section works it's way deep in the hollow, and causes a loud buzz when the solenoid is powered. A quick check on this, for a solenoid, is to hold it with nothing connected to the plunger, and the plunger facing up- push the plunger all the way into the hole--it MUST pop back out--you will see the springs force it out-- note-- there are supposed to be two springs ! In "the old daze" I had a source for the replaceable springs Guardian used in their solenoids-- if anyone has a source today, please inform us ! Ron Rich

[edison]

Quick question. Well, maybe two. Both pertain to the latch solenoid constantly being engaged for too long. I've got a 1015 Wurlitzer that has been on free play for years. The coin mech has been "incomplete" missing parts missing since my Dad bought it in the late 80s.

If I remember correctly, the Wurliter lights will stay off with only the Wurlitzer light until a coin is inserted. The second model is an M100-C Seeburg. There are free play adapters, but I don't know how good they are. Can you rebuild a latch bar solenoid by wrapping it with new copper or are they one and done items? I don't know of high heat situations with Wurlitzer, then again I've never experienced the model when not on free play.

[Ron Rich]

Hi Edison,
The 1015 uses no "latch bar", thus, no coil/solenoid --
The C solenoid is re-wrap-able-- used to be a gent who did it "for everyone"--suitable for "continuous duty", however-- time takes it toll--
The problem with just re-wrapping them is the anti residual springs are usually shot too---and as far as I know NLA.
As for the free play adapter for the C-- I sell one that I have been using commercially, for about 40 years--ZERO failures, no solenoid failures that I know of--- Ron Rich

[edison]

Okay thanks. So I take it I can just leave the Wurliter on Freeplay. Coin mech is in shambles though all together. I think volume control is going because songs are getting louder than back to normal setting. Will need to do the amp over regardless.