# AF Reverse Unit Testing



## Nuttin But Flyer (Dec 19, 2011)

I did a search but am unable to find a thread that describes a good method of testing AF Reverse Units. I cleaned the one for my #290 Pacific Steamer, removed the drum and cleaned the copper surfaces, replaced the fingers -- top and bottom -- cleaned and very lightly-lubed all moving parts. I then rewired everything according to the sketch I made before disassembly. I even double-checked the wiring diagram in both a service manual and Tom Barker's book. It all seems correct. Yet upon reassembly, the engine will not power-up. When I by-pass the reverse unit the engine works fine. When I apply power to the tender wheels, the reverse unit functions flawlessly -- drum ratcheting, etc. The fingers appear to have good contact with the drum. However, my observation shows that the replacement fingers (the copper strips) appear a bit longer than the originals. Could this slightly longer length prevent the fingers from contacting the drum on the necessary copper face to provide power when it should? I am no electrician, but tried to do continuity checks with a mulitmeter. I checked resistance between points and get zero resistance between the jackplate connections and certain points on the reverse unit to prove the connections are sound. I know that seems vague as I am not detailing each of the connections I have checked. But I was able to determine that each of the 4 tender wires to the jackplate have not been compromised or severed. I was hoping to find a method here that I could follow to determine where the electrical connection is failing me.


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## tjcruiser (Jan 10, 2010)

If you can, poke each of the fingers with a toothpick. Chances are, one of them isn't quite touching the drum the proper way, effective creating a short in the circuit.

TJ


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## Nuttin But Flyer (Dec 19, 2011)

I had tried doing that but didn't persist in the effort. Perhaps tonight I will give that a try again. I didn't like having power applied to the reverse unit for any length of time fearful that the continuous power would burn out the coil.


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## gunrunnerjohn (Nov 10, 2010)

The traditional E-Unit was designed to have power on it all the time you were running, that could be hours.


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## Reckers (Oct 11, 2009)

John's right---the coil is meant to stay energized whenever the train is running. The plunger is held up by the coil, then when power is cut, it drops and rotates the drum. The easiest way to test the fingers might be to start at the jackplate and see if you're getting any power to the two posts, using the low ac setting on your multimeter. Same thing for your wires to the field coil for the engine's electric motor. If you draw a blank, rotate the drum before you assume anything: you may have a 4-position E-unit in which two are not going to provide power to the motor. You know the motor runs, so you've pretty much narrowed the field to a bad drum, bad fingers, or wrong fingers. If you haven't checked both the drum and the parts of the fingers that contact the drum for wear and carbon, that would be something to look at. Both can get crud buildups and the drum can get a groove worn in it. Finally, you might also check both ends of the wire between engine and the front truck on the tender. If you have a bad connection at either end, you'd have everything on the tender working but nothing on the engine. Jumping the engine by wiring from transformer directly to the engine would result in the engine running just fine and blaming the E-unit.

Best of luck with it,


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## THE TYCO MAN (Aug 23, 2011)

Yes, I also suggest checking any connections finger wise. If one is real loose, thats a problem. I say re-check the fingers or buy some new ones to solve the problem.


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## Stillakid (Jan 12, 2010)

Last time I had a problem like that it was in the Jack Panel.


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## Nuttin But Flyer (Dec 19, 2011)

Thanks for all these suggestions. I'll get to them one-at-a-time soon. Just FYI, I already re-built the reverse unit with new fingers and thoroughly cleaned the drum as my first part of this project. The metal surfaces shine like the top of the Chrysler Building, to quote a favorite musical my kids used to enjoy. I'm inclined to believe a problem with the fingers contacting the drum surface or the 'new' wiring between the tender and jack panel. Certainly I'll post my results....or a more help needed request, if it comes to that. One item I noticed, is that the new finger metal tabs seem longer than the original ones. I was wondering if they are not contacting the drum at the exact point where they need to in order to conduct the power. This is one issue that Doug Peck listed in his online Reverse Unit Clinic -- poor quality. The only problem with that is I bought the new fingers from him.


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## tjcruiser (Jan 10, 2010)

If need be, you can remove (to later reinstall) the fingers, and put a slight bow in each one to essentially shorten the length just a biit. I'm not suggesting you do this right now, but consider it down the road, if needed.

I'm saying all of this from Lionel experience, not AF. Are the fingers on AF curved at the end, like Lionel? If so, are you sure you installed them with the curved side (rather than the cupped side) facing the drum?

TJ


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## Nuttin But Flyer (Dec 19, 2011)

I had already added a slight bow so they have complete contact on the drum, yet just enough not to cause drag when it needs to rotate. Yes, the figer contacts have the slight bowed or curved end pre-formed into the ends to improve drum contact and yes, I have them oriented to be bent toward the drum face. Something I had hoped to obtain with this post was a method to determine if the unit was providing current to the jackplate properly. In other words, a test method that describes exactly which contacts to test in pairs and the expected result on a multimeter when it is a successful contact. I am not an electrician and find it difficult to simply spell the word. But if I figure this out, I will post a procedure of steps that describe step-by-step what one should do to achieve successful test results. If any should step should fail through the process, certainly that step would need to be resolved before moving forward. Kind of a flow diagram.


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## Stillakid (Jan 12, 2010)

One other thing. In the past, I've picked up separate engines and tenders. I always assumed that they would be, "P-N-P!" Twice I had to re-wire the engine to match the tender. If your tender reverse unit works properly, and the engine also functions, it sounds like the jack panel isn't matched up to the 4-conducter cable.


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## Nuttin But Flyer (Dec 19, 2011)

The issue has been resolved :thumbsup:. Apparently the new finger copper/brass contacts were too long to reach the correct point on the drum to transfer power. I removed each set of fingers and effectively "shortened" them by bending the curved ends into a tighter radius than they originally were produced with. I also added a slight bend downward (toward the drum) to ensure good contact. Apparently it was just too much as the drum hesitated to rotate. Some re-adjustment on that pressure ensured the drum now rotates freely and the engine receives the power to go forward and reverse. As mentioned in my last posting, I saw in Doug Peck's (Portlines') Clinic that finger contacts may be too long due to quality issues. The ironic part of that is these were purchased from him . At least the ole girl is working now. Just gotta clean-up the motor section, check the brushes and springs, and lube/oil her and she should do well when finished. Thanks to all for your suggestions. I still would like to determine a good step-by-step, contact-by-contact method to determine if the voltage is reaching the engine jack panel and post it in the "sticky" section.


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## gunrunnerjohn (Nov 10, 2010)

Great, glad to hear it's cookin'!


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## tjcruiser (Jan 10, 2010)

< sniff ... sniff >

I just love a story with a happy ending!


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## Nuttin But Flyer (Dec 19, 2011)

Yea, me too. Especially when it's for me !!!!


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## Reckers (Oct 11, 2009)

Nice job of resurrecting the dead, Flyer!


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## Nuttin But Flyer (Dec 19, 2011)

Thanks Reckers -- means a lot coming from the "Master".


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## Reckers (Oct 11, 2009)

*BOL* From who???? I'm just the village idiot on this site! At one point, there was even a saying on MTF: "It's so easy, even Reckers could do it!"

But I do thank you for the compliment---there are others here far more deserving of that title!


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## Nuttin But Flyer (Dec 19, 2011)

Don't sell yourself short. I've reviewed enough of your postings and learned a lot by just reading them. You have provided more than your share of valuable assistance, perhaps without realizing it. I'm sure my turn will come when I can consider myself the Village Idiot on this site. With so many projects going on at once, I'm sure to fall into that category soon enough.


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## Reckers (Oct 11, 2009)

Well, thank you kindly. I can honestly say I knew nothing about model trains when I first stumbled across this site; in fact, I wasn't sure if the train I'd inherited was made by a company called American Flyer or if that was just the name of a certain run like "The Orange Blossom Special". The people on this site taught me everything I know about trains and were very patient in teaching me. I try to repay that debt as best I can by helping others, something they also taught me.

Sincerely,


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