I am pretty convinced it's NOT the decoder. If the decoder was bad, it wouldn't run at all The only possible way it could be the decoder in this case is if one of those end to end traces is somehow cut, somewhere between where the front truck wires connect and where the rest of the circuit taps off this power to operate the decoder. Not too likely, at least by accident. And if this were the case, there would be no continuity betwwen the left rear wheel and left front wheel, or right rear wheel and right front wheel, as those decoder traces sit right in the middle of all that. I believe you have a pickup problem between the wheel and the pickup itself, where you have just soldered the wires.
Do you have a headlight hooked up? Does it go out when you lift the rear truck off and the motor stops? Witht he rear truck insulated from the track, try wiggling the front truck around and see if the light flickers on or the motor gives a little jump - that would pretty m,uch prove intermittant pickup.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
OK, here is the latest.
I desoldered all four pick up wires from the decoder teminals and reverse them, connecting the front pick up wires to the rear decoder terminals and the rear pick up wires to the front decoder terminals.
Once I did that, the front trucks were working and the rear trucks were not working.
So, that tells me that the problem is one or both of the front terminals on the decoder.
There is power being picked up by all four trucks and delivered to the decoder, but the front terminals of the decoder are not sending power to the motor.
Am I testing and reasoning correctly, or am I missing something?
Rich
Alton Junction
richhotrain OK, here is the latest. I desoldered all four pick up wires from the decoder teminals and reverse them, connecting the front pick up wires to the rear decoder terminals and the rear pick up wires to the front decoder terminals. Once I did that, the front trucks were working and the rear trucks were not working. So, that tells me that the problem is one or both of the front terminals on the decoder. There is power being picked up by all four trucks and delivered to the decoder, but the front terminals of the decoder are not sending power to the motor. Am I testing and reasoning correctly, or am I missing something? Rich
If that's the case, I would forget about trying to diagnose what the problem is. Re-install the truck wires where they should go, then solder a jumper wire on both sides from the front tab to the rear tab.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
You are correct. The problem moved so that eliminates the pickup. Do what Mark said and you will be done with it.
Jim
richhotrain I have an NCE DA-SR decoder on an Athearn Genesis F7B loco. If I lift the rear truck off the rails, the loco loses power and the motor linkage stops spinning. With the rear truck off the rails, I put a pair of wires connected to a 12 volt incandescent bulb onto the terminals of the decoder where the pick up wires from the front truck connect. The bulb lights. So this would seem to indicate that the pick up wires are carrying power from the rails to the decoder. So I am confused. Is it a decoder problem where power is not transmitted from the terminals to the motor? Rich
I have an NCE DA-SR decoder on an Athearn Genesis F7B loco.
If I lift the rear truck off the rails, the loco loses power and the motor linkage stops spinning.
With the rear truck off the rails, I put a pair of wires connected to a 12 volt incandescent bulb onto the terminals of the decoder where the pick up wires from the front truck connect. The bulb lights. So this would seem to indicate that the pick up wires are carrying power from the rails to the decoder.
So I am confused.
Is it a decoder problem where power is not transmitted from the terminals to the motor?
Now I would like to understand this, third paragraph,or third sentence, if you like.
Cheers,
Frank
Rich;
Do you have a meter? I have a DA-SR in front of me with no wires attached. The back of the decoder defines the right rail conections as the side of the decoder with the two motor connections. Obviously the other side of the decoder is where the left rail connects.
Disconnect the wires to the decoder.
With the meter set at an ohms value, connect one meter lead to the front right rail connection point and the other lead to the rear left rail connection point. Your meter should read zero ohms. This is as it should be because the front and rear connection points are connected on the back side of the decoder with a large connecting trace as Randy mentioned previously.
Now re-connect the meter leads to the left side connection points. You should again get zero ohms.
I also connected the meter to the left and right rail connection points on one end of the decoder. With the meter set at 20K ohms or less, I read an open circuit, meaning that there was sufficient resistance from the decoder components to show an open circuit. I did check across these same points with a higher resistance meter setting. With the meter reset to 200K ohms, I read 63 ohms from the left to right rail connections. I reconnected the meter to the terminals on the other end, and got basically the same values.
I believe that the only thing you can check on the decoder is the front to back continuity. If you have that, then in my opinion there is a decoder fault. What I can't tell from looking at the decoder is how the board components connect to the two large traces. I would think that the two traces are the main connection points and everything is in series with them. But I suppose it is also possible that there is some sort of parallel circuit where there are duplicate connections from each of the traces so the there is redundancy in case one end or the other of the decoder goes bad.
Do you have another DA-SR? Connect that and see if there is any difference.
I just had another thought. Why don't you connect your light bulb to the decoder motor terminals. Connect one set of track leads, power up the decoder, and see if the bulb lights. If it does, then swap the power leads to the other end of the decoder and try again.
Any holes in the board have plating through them to connect front traces to back traces - even the ones where you connect the truck wires. You should never drill through these holes to enlarge them to fit a wire through.
Mark R. Any holes in the board have plating through them to connect front traces to back traces - even the ones where you connect the truck wires. You should never drill through these holes to enlarge them to fit a wire through. Mark.
maxman Mark R. Any holes in the board have plating through them to connect front traces to back traces - even the ones where you connect the truck wires. You should never drill through these holes to enlarge them to fit a wire through. Mark. I didn't see where anyone recommended this. Did I miss something?
Just a thought as to maybe why one end is getting power and the other isn't. If the through hole plating is damaged, you will lose your connection as well. Might not hurt to test each pad top to bottom with the meter.
zstripe richhotrain I have an NCE DA-SR decoder on an Athearn Genesis F7B loco. If I lift the rear truck off the rails, the loco loses power and the motor linkage stops spinning. With the rear truck off the rails, I put a pair of wires connected to a 12 volt incandescent bulb onto the terminals of the decoder where the pick up wires from the front truck connect. The bulb lights. So this would seem to indicate that the pick up wires are carrying power from the rails to the decoder. So I am confused. Is it a decoder problem where power is not transmitted from the terminals to the motor? Rich Now I would like to understand this, third paragraph,or third sentence, if you like. Cheers, Frank
Frank, the reason that the 12 volt incandescent bulb lit on the front decoder terminals with the rear trucks lifted off the rails was because there was power on those front decoder terminals. That was the indication that I was getting all along. This is clearly a decoder problem where the power from the front terminals is not reaching the motor.
Incidentally, I did a Google search and it is interesting, though not surprising, to me that others have experienced similar problems with the DA-SR decoder. There is more than one complaint out there about the front trucks appearing not to pick up power to the decoder only to discover that there is power at the front decoder terminals.
Mark R. richhotrain OK, here is the latest. I desoldered all four pick up wires from the decoder teminals and reverse them, connecting the front pick up wires to the rear decoder terminals and the rear pick up wires to the front decoder terminals. Once I did that, the front trucks were working and the rear trucks were not working. So, that tells me that the problem is one or both of the front terminals on the decoder. There is power being picked up by all four trucks and delivered to the decoder, but the front terminals of the decoder are not sending power to the motor. Am I testing and reasoning correctly, or am I missing something? Rich If that's the case, I would forget about trying to diagnose what the problem is. Re-install the truck wires where they should go, then solder a jumper wire on both sides from the front tab to the rear tab. Mark.
Mark, I could do that, but it only masks the problem. With a slow moving loco crossing over a dead frog, the loco could stall when the rear truck crosses the frog. I have a spare DA-SR decoder and I will swap it today for the bad decoder. I expect that will solve the problem for once and for all, but you never know.
maxman Rich; Do you have a meter? I have a DA-SR in front of me with no wires attached. The back of the decoder defines the right rail conections as the side of the decoder with the two motor connections. Obviously the other side of the decoder is where the left rail connects. Disconnect the wires to the decoder. With the meter set at an ohms value, connect one meter lead to the front right rail connection point and the other lead to the rear left rail connection point. Your meter should read zero ohms. This is as it should be because the front and rear connection points are connected on the back side of the decoder with a large connecting trace as Randy mentioned previously. Now re-connect the meter leads to the left side connection points. You should again get zero ohms. I also connected the meter to the left and right rail connection points on one end of the decoder. With the meter set at 20K ohms or less, I read an open circuit, meaning that there was sufficient resistance from the decoder components to show an open circuit. I did check across these same points with a higher resistance meter setting. With the meter reset to 200K ohms, I read 63 ohms from the left to right rail connections. I reconnected the meter to the terminals on the other end, and got basically the same values. I believe that the only thing you can check on the decoder is the front to back continuity. If you have that, then in my opinion there is a decoder fault. What I can't tell from looking at the decoder is how the board components connect to the two large traces. I would think that the two traces are the main connection points and everything is in series with them. But I suppose it is also possible that there is some sort of parallel circuit where there are duplicate connections from each of the traces so the there is redundancy in case one end or the other of the decoder goes bad. Do you have another DA-SR? Connect that and see if there is any difference. I just had another thought. Why don't you connect your light bulb to the decoder motor terminals. Connect one set of track leads, power up the decoder, and see if the bulb lights. If it does, then swap the power leads to the other end of the decoder and try again.
maxman, I like your suggestions, but Randy made me nervous when he warned against using an ohmmeter on a decoder. Unless, that is, if he was referring to the use of an ohmmeter when power is on to the layout.
Earlier, when I was using an ohmmeter on the decoder with power off to the layout, there was continuity between the rear terminals and the front terminals on the decoder.
Rich,
I've followed this thread from afar, thinking all the time that the problem MUST be the continuity between the wheels/pick up and the motor. I strongly felt that the decoder could not possibly be the problem as one truck was pulling power and it was transmitted to the motor.
HA, you proved (to me) that the decoder was in fault, something that just doesn't make sense (I'm a DCC guy but not big on electronics) to me.
Throw that sucker out, and put in a new one!
ENJOY
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
Later today, I will swap the bad decoder for a spare good one.
Presumably, that will solve the problem.
If it does, I will send the faulty one to NCE and tell them what the problem is so they can repair or replace it and confirm that, indeed, the front terminals are not transferring power to the motor.
You just have to be careful to not apply power to an output of the decoder, like the motor terminals or the light terminals. Checking continuity from one front truck connection to the correpsonding one at the rear will not harm the decoder.
If you have continuity between each of the front power terminals and the corresponding one at the back, then I am puzzeled as to how the one side's power gets tot he decoder and the other does not. One or both of those paths must be open to cause this issue.
It's not a valid test with the wires all hooked up - the continuity is then through the rails. If all this time you were testing with the truck pickup wires still attached, no wonder the results were so confusing.
Randy, be gentle, LOL, I told you that I was an electronics illiterate.
The real test, though, was when I wired the front pick up wires to the rear decoder terminals and the rear pick up wires to the front decoder terminals.
When I did that, the front trucks worked with the rear trucks off the rails as opposed to the original situation where the front trucks did not work with the rear trucks off the rails.
With the wires reversed as described, the rear trucks no longer worked. Unless I am badly mistaken, that tells me the front decoder terminals are not transferring power to the motor.
I, too, am puzzled by this occurrence. But, am I wrong in my test and in my conclusion?
I am going to call Larry at NCE today and discuss this issue with him.
Since you've already found that one end of the decoder is not supplying power and the other end is, why not install jumper wires like I suggested on page 2? If you would do that, the shell would be back on and all would be working.
Chuck - Modeling in HO scale and anything narrow gauge
trwroute Since you've already found that one end of the decoder is not supplying power and the other end is, why not install jumper wires like I suggested on page 2? If you would do that, the shell would be back on and all would be working.
Chuck, I could do that but aren't I just masking the problem?
Besides, what good would a jumper do if power is not reaching the motor from the front terminal on the decoder?
Rich, it might be masking the problem, but it is a solution that works. What you need to do is, solder both right side truck wires together, and then the left together. Then branch off of that with a couple of wires and solder them to the truck inputs on the decoder that work. You will then have all wheel pickup and the decoder will get its power.
I hope that is clear! I have installed over 2000 decoders for myself and a couple of shops and have done this in the past. It does work.
trwroute Rich, it might be masking the problem, but it is a solution that works. What you need to do is, solder both right side truck wires together, and then the left together. Then branch off of that with a couple of wires and solder them to the truck inputs on the decoder that work. You will then have all wheel pickup and the decoder will get its power. I hope that is clear! I have installed over 2000 decoders for myself and a couple of shops and have done this in the past. It does work.
Chuck, I agree with you. It does work, and I have done it on a couple of decoders myself.
I am reluctant to do it here because I am fed up with the decoder problems that I continue to have with the DA-SR decoders on this ABBA consist. I bought a set of four DA-SR decoders for these four locos back in 2004, and I have had periodic problems ever since, mostly with this exact issue. I have already replaced one of the DA-SR decoders, and this will be the second one. I have also had issues with the function outputs on these decoders.
Needless to say, I am not fond of the DA-SR decoder.
I called Larry at NCE to discuss the problem, and he agrees, based upon what I described to him, that there is a fault with the decoder.
He did confirm that the front and rear power taps are interconnected through traces on the circuit board.
However, he also indicated that a hairline crack in the trace could prevent power from reaching the motor.
I am going to send it in and have the boys at NCE take a look at it and see what the problem is and whether the decoder can be repaired or else replaced.
richhotrain Needless to say, I am not fond of the DA-SR decoder. Rich
Wow, Rich! Sorry to hear about all of the problems. I think I might be ready to try another brand. At least you have a spare that you can install to get them back up and running while the other is being repaired.
trwroute richhotrain Needless to say, I am not fond of the DA-SR decoder. Rich Wow, Rich! Sorry to hear about all of the problems. I think I might be ready to try another brand. At least you have a spare that you can install to get them back up and running while the other is being repaired.
Thanks, Chuck, and believe me when I say that I appreciate all of your advice.
I feel so much better now that I have a fully operative decoder in this loco. It has been a long and winding road, so to speak.
richhotrainI feel so much better now that I have a fully operative decoder in this loco.
So, you replaced the decoder with a spare and it is now okay?
Earlier you indicated you were having this issue with three units. 2 B's and an A. Initially I thought it was something common to the units. Now it is clear it is the decoder. I recently got two four packs of these decoders. Right out of the package I found 2 of the first 4 had this same problem.
So the other two decoders could also have this issue.
Because, my sense is that decoders are fragile I felt a means to test the decoder was needed for my install work. For this reason, I got a decoder tester to make sure I'm starting with a good decoder. It is an added expense, but if your going to do a number of installs it will save you from this kind of frustration. With this tool, I know it it doesn't work after install, the problem lies with me.
Larry
So many trains, so little time,
www.llxlocomotives.com
zstripe Rich, Did you ever,remove the front truck wires from the decoder and then test for continuity? You may find that is your problem, if you do not remove,the wires,you will get continuity,because of the connection to the decoder. You have to isolate,the truck. You don't mention if you ever did that. Cheers, Frank
Did you ever,remove the front truck wires from the decoder and then test for continuity? You may find that is your problem, if you do not remove,the wires,you will get continuity,because of the connection to the decoder. You have to isolate,the truck. You don't mention if you ever did that.
Like I have said,times before,,''I don't know nuttin''.
Old Man,Frank
richhotrain Thanks, Chuck, and believe me when I say that I appreciate all of your advice. I feel so much better now that I have a fully operative decoder in this loco. It has been a long and winding road, so to speak. Rich
You're welcome, Rich. I only chime in when I feel I have something to contribute. Not much for rambling!
maxman richhotrainI feel so much better now that I have a fully operative decoder in this loco. So, you replaced the decoder with a spare and it is now okay?
Oh geez, I forgot to post the final result. Sorry, I was up all night with a faulty sump pump in the midst of a 2.5 inch rainstorm. I am not thinking straight.
Yes, I had a spare DA-SR decoder, and I installed it in place of the faulty decoder. My Athearn Genesis F7B now runs like a charm, power from all four trucks being transferred to the motor. Turns out, the trucks were fine all along. The problem was the decoder.
I will send the faulty decoder back to NCE for repair, and Larry has promised to have either Matt or Mike report back to me on what was exactly wrong with the decoder, although Larry suspects a hairline crack in the trace on the decoder.
I am glad you got it fixed. And I have to say you did a good job of diagnosing the problem.