AMI E-120 Jukebox Rebuild - Part 4 - Record Changer Mechanism

[@blakef413]

Hi Bob. I've now successfully figured out how to make the turntable 'gaskets' (for lack of a better term). On this year, 2 different sources have told me they used a 'flocked' material on the turntable. This is the material that was commonly used as a liner in girls jewelry boxes I saw as a kid. I found some bright red flocked fabric on eBay and went through some pains before getting a fabric circle cutter that would do the job. They look absolutely beautiful. The flocking looks like velvet, so they look great on my repainted bright red turntable. *I am happy to send you one* or you can do a DIY video on this too if it suits your fancy. For posterity, the outer radius to use on the cutter is 3-3/16" and the inner is 2-13/16". The cutter that works is an Olfa CMP-3. I use 3M Magic 77 spray adhesive to stick a piece of the fabric to a common teflon white cutting board. When you lock in the radius on the Olfa make sure to really screw the thumb-screw down hard- my only negative comment on that circle cutter is it moved when I thought it was locked with sufficient force. Tip: cut the circle and keep going, going back over it once to make absolutely sure you've cut all the way through the fabric. Cut the outer circle first, then remove the cutter and adjust to the inner radius. Tip: hold the teflon board with light behind it and you can easily locate the hole for the pin to place the cutter pin right back where it was. Now cut the inner circle. Last, don't try to pull the gasket out with your hand. Rather, use a box cutter blade not to cut, but to get under an edge and lift the gasket off the teflon. Once you have an edge up, you can lift the rest of the gasket off by hand- oddly enough, the Magic 77 adhesive doesn't stick that well to the teflon so it will lift off pretty easy. It will also be tacky from the adhesive. Easiest way to install it on the turntable perfectly is to lay it on and rotate the table while lightly holding the edge with a finger to align the gasket with the edge of the turntable. It won't really stick much of anywhere but it's repositionable if it does. Once you've gone around the edge with your finger to roughly align the gasket edge, keep going slowly, but pressing the gasket lightly to get it starting to stick. If it gets out of alignment you can stop, back up, pull it off slightly and redo the section that's mis-aligned. Keep going round and round getting it perfect, and once it's perfect, start pressing it fully down onto the turntable's raised portion to get it fully adhered. Don't press hard- just enough to get it to stick but without crushing the flocking. I can also tell you, the record on bare painted metal picks up some vibration noise probably coming from the motor through the turntable. Everything sounds quite a bit better now that there is a gasket on the table.

[@MRNBricks]

Thanks for sharing all this. It’s pretty interesting.

[@blakef413]

Never mind I figured it out. What threw me off was that my spring was mis-shapen. I got it working after I restored it to the proper shape according to pics from the manual. In case you or anyone ever encounters this, the way it works is that the spring is installed on the pivot post as shown in this video at 8:28 and the small 90 degree 'lip' of the spring is adjusted to 'slightly more than touch' the edge of the armature of the tone arm when it moves into the position where it drops down on the record. It then very slightly pushes outwardly on the tone arm. As the record plays, the armature slips past the spring's 90 degree lip and the small outward force stops. This serves to keep the tone arm from jerking into some records, as I noticed mine did sometimes. To adjust, unplug the turntable motor from the amp, then get the mechanism into playing position without a record by selecting an empty record slot, and once the arm is down turn the mechanism power off via the switch behind the carriage motor. The trick is to have the spring's bolt tightened enough that it won't rotate on the pivot post from the tone arm's movement, but loose enough you can move it to adjust it. It's not too difficult, it actually stays put real well even though it's not real tight. With the arm in the start position, rotate the spring on the pivot post so that the spring's lip goes a little too far over the armature, then you can get a small screwdriver to wedge and rotate the spring back until it's 90 degree lip edge is just slightly past where it would first touch. Now you can move the tone arm and watch how it exerts pressure at first, then slips off the armature and 'lets go' for the rest of the tone arm's travel. The manual says you want it 1/16" to 3/16" of tone arm travel at the far end (end of the tone arm with the needle). So it's very slight.

[@XORBob]

Blake, this is great. I'm going to do this adjustment on mine. I still have some alignment issues right in this area. Thanks for the detailed writeup!

[@blakef413]

@@XORBob Fun news for me too- last week I found an E-120 too and it is being shipped to me as I write this! Your restoration videos are much appreciated.

[@blakef413]

At approx 21:00 you mention that you believe the turntable was always spinning. This jukebox should have the turntable power plugged into the amplifier receptacle labeled "TT". The amplifier controls the power receptacle for the turntable. Inside the amp there's a clever circuit that has a relay that turns the turntable on and off and the relay is driven by current through the power tubes. What happens is the turntable won't turn on until the power tubes are warmed up (and current starts to flow in them) and the turntable turns off when the amp is turned off. Interestingly too, this amp is the fastest warming tube amp I've ever seen. It usually beats the selector mechanism to the finish line and the platter begins to turn before the arm sets down. But in case it doesn't they've made it so it doesn't start to play the record until the amp is ready.

[@XORBob]

Yes, thanks for pointing that out too

[@seeburgm100a]

I've rebuilt more of these AMi mechs than I care to remember. If I may say so, that ribbon cable is supposed to be flat. It should have had aluminum pieces that laid each piece of "lamp cord" side by side and flay. It has to lay under the mechanism when it passes over it.. and yes an 18 guage black lamp cord would be better suited to this. Remember that this ribbon cable has to bend up and under over and over and over again.. this is why a tightly knit ribbon which lays flat is ideal. The lamp cord won't rub against it self.. otherwise a very good instructional video on how to do one of these mechanisms.

[@XORBob]

Do you know where we can buy the ribbon cable you recommend? I'd like to replace what I put in.

[@seeburgm100a]

@@XORBob you have to make it up yourself. You lay out lamp cord (that you can buy in a roll) flat and side by side. As I recall there are four wires total laid side by side. There should have been flat aluminum pieces with your jukebox that fold over the cables to hold them flat. (look at video's of AMi jukeboxes from this era..) if you don't have yours you can make them I'm sure our of malleable metal.

[@seeburgm100a]

kzbin.info/www/bejne/iobLap2ha9WdqK8 this video shows some of the clips that hold the ribbon flat. Even this isn't the best job.. when making it up do your best to keep the whole thing flat. Good luck!

[@blakef413]

Hi. I am restoring a D-80. I am trying to figure out how the 'tone arm bias spring' works. The D and E models use the same arm and spring. I have the spring but it was removed from the mechanism when I bought the jukebox. After a lot of searching I can finally see one installed and in-position in this video at 8:28. But for the life of me I can't grasp how it is supposed to put 3-4 grams of pressure on the tone arm as the tone arm sets down on the record. Both the manual and your video seem to show the tone arm pickup wire running down there. Is the pickup wire somehow connected to the spring or something? Any help is appreciated. Thanks!

[@blakef413]

Learned something else interesting. You've probably noticed how fast the carriage stops when it comes across the selection. The manual has an obscure reference that they use 'dynamic braking'. I used my 2 years of EE courses and thought it through. What they've done is very clever: when the carriage comes across a selection, the left or right bank switch gets closed by the selection pawl sticking up, and this actuates the carriage 'selection' relay. One of the things the relay does is remove the DC voltage to the carriage motor and simultaneously SHORTS the motor terminals together. When voltage is removed from a spinning DC motor, the motor will actually act like a generator. In 'generator mode' anything that uses the generated voltage will impart a force in opposition to the rotation. So by shorting the terminals, a force in opposition to the rotation of the motor (which is spinning down naturally) is imparted on it, and with a dead-short the force is maximum. This causes the motor to come to a dead-stop amazingly fast. Once the motor stops rotating the opposition stops automatically. Once the transfer cam rotates the record onto the platter and sets the arm down, it hits a switch that causes a plunger to reset the selection pawl, which turns off the selection relay and everything is reset and ready for the record to end and engage the record re-rack sequence. I was sort-of forced onto this subject because my E-120 wouldn't reset the pawl and the transfer motor would hit a hard stop with the DC on and I'd have to unplug it and manually rotate it out. The issue ended up being that the cam leaf switch wasn't resetting the selection pawl because the black wire on the connector hadn't been soldered into the pin properly. Wonder how it ever worked. I resoldered the wire into the pin and everything works.