# Lubrication or Not AF 720A Turnouts



## BrokeCurmudgeon (Feb 8, 2016)

Should the sliding metal parts in a remote 720a be lubricated? If so, what and where? I se no evidence of past lubrication . The problem is that the solenoid mechanism doesn't move the frog. Any suggestions?


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## cramden (Oct 13, 2015)

I don't think the switches were ever lubed and I don't lube them. How tight is the frog movement by using your hand to move it back and forth? Make sure you are using the fixed voltage post to power the switch. It should snap quickly. You possibly could have a weak solenoid from having the controller held too long or just old age. Flyernut probably has some more things to check since he rebuilds these frequently. Hopefully he'll chime in.


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## flyernut (Oct 31, 2010)

Here I am!!.. Broke, the only places where I put anything called oil is on the bottom of the frog where the switch pilot stud lives, and on the "regular or 2 train operation" slide switch. I put a small drop under the frog and smear it with my finger. Do not put any oil on the solenoid plunger, it shouldn't be there.I also oil the switch mechanism where the lamp socket sits. You'll see where it slides back and forth as they'll be slide marks.. When you trouble shoot your switches, first dis-connect the screw that attaches to the under-side of the frog. The frog should move freely. If not, drive out the pivot stud, clean the under-side, and put a tiny drop of oil there.. Once you remove that screw, and the frog slides easily, the bind could be in the switch tower mechanism, or the spring and/or plunger. You must have tension on that plunger, but not so much as to prevent the movement of the linkage. Too much pressure, and the frog will bind; too little, when the loco goes over the frog, the frog will move and you'll lose current flow, stalling the engine, or possibly causing a de-railment. The next area to check is where the link assembly slides into the tower assembly. You'll notice that the piece that slides up into the slider can be put in 2 different ways. One way will bind, the other way will be correct. Check out those areas and get back to us....check the wiring to the solenoid, there could be a break, or the solenoid could be shot.


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## angelfj1 (Dec 15, 2017)

*720A Don't assume your problem is mechanical*

Hello, there has been an ongoing discussion about these switches on the Yahoo S-Scale Train Group. You should check the voltage at your transformer and your switch at the moment you activate the lever (switch). I did some testing recently and found that a properly adjusted and lubricated 720A requires approximately 14 volts at the solenoid to operate reliably. When I measured the voltage at the solenoid, I found, in my case, the voltage at the transformer (measured from the base post to the outside 15V terminal) was approx. 15 volts. At no load, this same voltage was 15.9 volts. This means that there was a voltage drop of 0.90 across the transformer winding and 1.0 volts across the wire. The measured current was approx. 4.5 amps. The transformer used is a No.2, one of the smaller capacity units, but certainly enough for these switches. The only electrical variables are the size (gauge) and length of your connecting wires, the capacity of your transformer, and the voltage at your outlet.
Try to consider the following:
1 if your switches seem sluggish, don’t assume the problem is mechanical.
2 measure the voltage at the transformer before and after you activate the 720A
3 if the voltage at the transformer terminals seems low measure the voltage at the outlet.
4 If the voltage at your outlet is less than 120V, you might want to plug into another outlet. However, our AF trains were produced during a time when most households were served with 220/110VAC. Since the turns ratio of your transformer can't change, your transformer secondary voltage is probably within proper range. Assuming you have 120V, your secondary is probably 120/110 x 15 = 16.4V at no load. My outlets run at approx. 119 - 121 V depending on the season and time of day.
5 If your voltage at the transformer is about right but the voltage at the 720A is still less than 14, the next thing to do is consider the interconnections. There are only two variables. The length of the interconnections and the gauge of the wire. The wire used by ACG for the 720A activating switches came in at least two gauges. The black and yellow wire between the transformer and the activating lever switches is short, but the gauge could be larger. I have rewired all of mine with No. 18 awg stranded cu. I use the same wire to replace what was originally ACG rainbow type, the wire between the lever switches and the 720A . Also, if like me, you have a permanent layout, allow only enough extra for a neat and unstressed connection at the 720A. If you have a very large layout, many track switches, accessories, lights, etc., you may have to consider a heavier gauge wire, 16 or even 14awg. Also, you might want to dedicate a transformer to your 720A track switches. 

P.S. Someone in another forum suggested a solution of replacing all of the incandescent light bulbs with L.E.D.'s. While I have nothing against doing this, don't expect it to be a likely solution. The bulbs in the lever switch and inside the 720A, draw approximately 0.1A, not really enough to make a difference.

Best regards,

Frank


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## BrokeCurmudgeon (Feb 8, 2016)

flyernut said:


> Here I am!!.. Broke, the only places where I put anything called oil is on the bottom of the frog where the switch pilot stud lives, and on the "regular or 2 train operation" slide switch. I put a small drop under the frog and smear it with my finger. Do not put any oil on the solenoid plunger, it shouldn't be there.I also oil the switch mechanism where the lamp socket sits. You'll see where it slides back and forth as they'll be slide marks.. When you trouble shoot your switches, first dis-connect the screw that attaches to the under-side of the frog. The frog should move freely. If not, drive out the pivot stud, clean the under-side, and put a tiny drop of oil there.. Once you remove that screw, and the frog slides easily, the bind could be in the switch tower mechanism, or the spring and/or plunger. You must have tension on that plunger, but not so much as to prevent the movement of the linkage. Too much pressure, and the frog will bind; too little, when the loco goes over the frog, the frog will move and you'll lose current flow, stalling the engine, or possibly causing a de-railment. The next area to check is where the link assembly slides into the tower assembly. You'll notice that the piece that slides up into the slider can be put in 2 different ways. One way will bind, the other way will be correct. Check out those areas and get back to us....check the wiring to the solenoid, there could be a break, or the solenoid could be shot.


I have cleaned and done all of the above plus checked the voltage and current (15.1VAC , 3.6Amps) applied to the turnout. Voltage OK. Frog and pawl free from binding. It seems as if the solenoid doesn't have enough push or to move the frog arm. Maybe I need to rewind or replace the coil in the solenoid? :dunno:


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## flyernut (Oct 31, 2010)

BrokeCurmudgeon said:


> I have cleaned and done all of the above plus checked the voltage and current (15.1VAC , 3.6Amps) applied to the turnout. Voltage OK. Frog and pawl free from binding. It seems as if the solenoid doesn't have enough push or to move the frog arm. Maybe I need to rewind or replace the coil in the solenoid? :dunno:


Sounds like you found the problem...good job.


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## angelfj1 (Dec 15, 2017)

BrokeCurmudgeon said:


> I have cleaned and done all of the above plus checked the voltage and current (15.1VAC , 3.6Amps) applied to the turnout. Voltage OK. Frog and pawl free from binding. It seems as if the solenoid doesn't have enough push or to move the frog arm. Maybe I need to rewind or replace the coil in the solenoid? :dunno:


So, I take it that the solenoid is trying to move, but not developing enough force to move the linkage. The current you measured is a little low. Here's a suggestion. If possible, either disconnect the 720A and connect it directly to your transformer with two lengths of #18awg wire. The wire should be just long enough to make the connections. If you don't have #18, use double or even triple parallel wires. Nothing else in the circuit. This is only for the test and just trying to minimize voltage drop. Alternatively move the transformer close to the 720A. Unless your transformer has an on-off switch, unplug the cord. Then, connect the two wires to the 720A and transformer. Make sure that the knurled nuts are clean and tightly secured. Now, momentarily plug in the transformer. Did the 720A operate correctly? If it did, you need to use a heavier gauge wire or parallel runs in your layout. If this operation did not work and you have ruled out mechanical binding, friction, etc., you probably have a partially shorted solenoid as you suggested above. The force produced by a solenoid is proportional to (turns x current) squared. So, it's easy to see where the loss of just a few turns will reduce the force.

By the way, I use parallel conductors all the time. A neat and efficient way to make them is to measure the amount you need, add 2 feet and twist them using a power drill. Just attach the end of the wires to a door knob and chuck up the other end, pull the wires to take up slack and spin them up. You'll find that the total length is shorter now due to the twisting. That's why you added the additional 2 feet. Now, you need to repeat this for all of the wires between the transformer, control switch and turnout. I have never seen rainbow wire in heavier gauges, but it may be available. 

Before you reach a conclusion and if you have other 720A turnouts, repeat the test on those. This could uncover something that is otherwise not obvious.

Incidentally, I lubricate all of my turnouts and accessories with very sparce amounts of white lithium grease. Even fine watches and scientific instruments are lubricated where two moving metal surfaces come in contact. The secret is learning how much lubricant is enough!

Good luck, Frank


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## mopac (Feb 24, 2011)

Broke, I checked ebay. I could not find just a solenoid. One of the parts houses may have it.


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## AmFlyer (Mar 16, 2012)

For what it is worth here is my experience using 720A turnouts. Prior to assembling the layout I checked all the turnouts, made sure the contacts underneath were clean and used a very small amount of white lithium grease on the plunger. The lanterns had 24V bulbs installed. I used a 4B set to about 12.5 volts for power. All the turnouts snapped firmly when thrown. Turnout wiring is all original Gilbert with about 2’ of black/yellow power supply to the controller boxes and typically 8’ of rainbow wire to the turnout. 
I have included a picture that shows the transformer knob setting on the 4B. It is the grey transformer on the right of the control panel just to the left of the 19B. In addition to the 6 pairs of track switches connected to the 7-15V post all the Gilbert accessories on the layout are powered from the 15V fixed post. 
Based on many, many years of building these layouts if the turnouts are not snapping instantly when connected to the 15V post there is something not right about that turnout. It could be made to work with larger conductors but to me it sounds like the solenoid is drawing too much current and therefor failing.


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## BrokeCurmudgeon (Feb 8, 2016)

mopac said:


> Broke, I checked ebay. I could not find just a solenoid. One of the parts houses may have it.


Thanks Mopac! Portline has an assembly listed as XA10930, I think? I will call Doug tomorrow. 
Meanwhile, back on the ranch...
I am suspicious of my 22004 transformer that I use on the bench. It is now reading 14.8 vac. I think that the difference between 15 vac and 14.8 vac should not be a great factor but who knows? I will get my 15B transformer after I garner enough courage to venture outside to the garage. As far as wire lengh and gaugeI am going to try something different. Stand by.


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## BrokeCurmudgeon (Feb 8, 2016)

angelfj1 said:


> So, I take it that the solenoid is trying to move, but not developing enough force to move the linkage. The current you measured is a little low. Here's a suggestion. If possible, either disconnect the 720A and connect it directly to your transformer with two lengths of #18awg wire. The wire should be just long enough to make the connections. If you don't have #18, use double or even triple parallel wires. Nothing else in the circuit. This is only for the test and just trying to minimize voltage drop. Alternatively move the transformer close to the 720A. Unless your transformer has an on-off switch, unplug the cord. Then, connect the two wires to the 720A and transformer. Make sure that the knurled nuts are clean and tightly secured. Now, momentarily plug in the transformer. Did the 720A operate correctly? If it did, you need to use a heavier gauge wire or parallel runs in your layout. If this operation did not work and you have ruled out mechanical binding, friction, etc., you probably have a partially shorted solenoid as you suggested above. The force produced by a solenoid is proportional to (turns x current) squared. So, it's easy to see where the loss of just a few turns will reduce the force.
> 
> By the way, I use parallel conductors all the time. A neat and efficient way to make them is to measure the amount you need, add 2 feet and twist them using a power drill. Just attach the end of the wires to a door knob and chuck up the other end, pull the wires to take up slack and spin them up. You'll find that the total length is shorter now due to the twisting. That's why you added the additional 2 feet. Now, you need to repeat this for all of the wires between the transformer, control switch and turnout. I have never seen rainbow wire in heavier gauges, but it may be available.
> 
> ...


Thanks Frank! I appreciate the technological explanation.:thumbsup: It helps clear up this old mind of mine.:hah::hah::hah:


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## BrokeCurmudgeon (Feb 8, 2016)

Ah hah!!!  The voltage drop in the test leads that was connected to the 22004 Transform was dropping 1.2 vac or there about. They were small but not sure about the gauge. Originally the test leads were on a multimeter. I used the transformer and test leads to troubleshoot my locomotives. I wonder if may that was also the source of my confusion about making the E Units work better? Duh???:smilie_auslachen: Back to basics and Ohm's Law.:laugh::laugh::laugh:


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## angelfj1 (Dec 15, 2017)

AmFlyer said:


> For what it is worth here is my experience using 720A turnouts. Prior to assembling the layout I checked all the turnouts, made sure the contacts underneath were clean and used a very small amount of white lithium grease on the plunger. The lanterns had 24V bulbs installed. I used a 4B set to about 12.5 volts for power. All the turnouts snapped firmly when thrown. Turnout wiring is all original Gilbert with about 2’ of black/yellow power supply to the controller boxes and typically 8’ of rainbow wire to the turnout.
> I have included a picture that shows the transformer knob setting on the 4B. It is the grey transformer on the right of the control panel just to the left of the 19B. In addition to the 6 pairs of track switches connected to the 7-15V post all the Gilbert accessories on the layout are powered from the 15V fixed post.
> Based on many, many years of building these layouts if the turnouts are not snapping instantly when connected to the 15V post there is something not right about that turnout. It could be made to work with larger conductors but to me it sounds like the solenoid is drawing too much current and therefor failing.
> 
> View attachment 392970


These kinds of electrical failures are common in industry, but easy to service. Unfortunately, the 720A was not designed for easy service, e.g. solenoid replacement. The magnet wire ACG used at that time was probably equivalent to today's class O, 90˚C max. and that is reasonable for a toy, especially for intermittent duty in a turnout. I think there is a tendency to hold the control lever too long, which over time would cause overheating. In time the insulation between windings fails and each turn lost reduces the force that the solenoid can produce. If a replacement solenoid is not available, a rewind is an option. It’s not too difficult. Just unwind the coil and measure the length, then use a wire gauge or calipers and measure the wire size. Get some magnet wire of the proper gauge and temperature class, at least F or even H if you can find it. Then carefully re-wind it onto the solenoid armature, resolder the connections and you should be good to go.

Good luck, Frank


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