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Discussion Starter · #1 ·
Has anyone experienced motors going short-circuit in this model or other similar models? I'm referring to the motor itself, not shorts between the chassis and the PCB or the motor contact strips. If so please can you let me know exactly which model it is and whether you were using DCC.

I've had two of the original production run (66135 and 66610) fail in this way, destroying two expensive decoders in the process. I'm interested to know how widespread the problem is, to assess whether the same might happen to my later series model (66200) or if I get a spare motor.
 

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QUOTE (Edwin @ 4 Dec 2007, 23:12) <{POST_SNAPBACK}>Has anyone experienced motors going short-circuit in this model or other similar models? I'm referring to the motor itself, not shorts between the chassis and the PCB or the motor contact strips. If so please can you let me know exactly which model it is and whether you were using DCC.

I've had two of the original production run (66135 and 66610) fail in this way, destroying two expensive decoders in the process. I'm interested to know how widespread the problem is, to assess whether the same might happen to my later series model (66200) or if I get a spare motor.

***Hello Edwin. Are you saying that the motor has/motors have actually failed/cooked? Please explain in more detail

Richard
DCCconcepts
 

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Discussion Starter · #4 ·
QUOTE (Richard Johnson @ 4 Dec 2007, 15:07) <{POST_SNAPBACK}>***Hello Edwin. Are you saying that the motor has/motors have actually failed/cooked? Please explain in more detail

Richard
DCCconcepts

On removing the motor from the locomotive, putting meter leads on the two copper tabs and rotating the motor by hand, the lowest reading is around 5ohm on one motor and 0.5ohm on the other. I would expect to see a value of about 12 volts divided by the stall current, and indeed I get at least 30ohm on each of the four working locos I have checked. No obvious signs of damage to the motor or decoder but it's a can motor and I don't think it can be opened without destroying any evidence.
 

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QUOTE (Edwin @ 5 Dec 2007, 00:15) <{POST_SNAPBACK}>On removing the motor from the locomotive, putting meter leads on the two copper tabs and rotating the motor by hand, the lowest reading is around 5ohm on one motor and 0.5ohm on the other. I would expect to see a value of about 12 volts divided by the stall current, and indeed I get at least 30ohm on each of the four working locos I have checked. No obvious signs of damage to the motor or decoder but it's a can motor and I don't think it can be opened without destroying any evidence.

***Cooked motors are actually rare but that certainly looks to be the case. The normal reasons are (1) badly assembled motor - the plastic end caps are not seated properly and the motor overheats. Bachmann has a whole production batch like this a year or two ago!! (2) stiff chassis, with the motor caused to try to overcome this over a long period it cooks. (3) Over voltage or DCC system at too high a voltage. Let me explain this one.

DCC controllers are made universal and ex factory settings are supposed to work from Z to G scale. That means that track voltage is always too high for Z and N scale

Lots of experience shows me tha tthe most reliable running and most stable DCC systems have voltages lower than those set by EU makers in particular.

The ideal voltages I've struck by test are:

Z/N 10.5 to 12v
H0/00 and similar (ie ON30) 11.5 to 14 volts

You cannot measure the voltage with a standard meter - even a high quality one with rms AC etc. The DCC singal frequency is too high for them to properly read it.

to read quite accurately set the meter to DC and put it on the positive blue and the negative white light function wires (make sure light functions are turned on :). Add 1 volt to the reading and that is track voltage (the 1 volt compensates for the bridge rectifier in the decoder)

Its hard with some brands to adust voltage, especially EU ones - some have NO adjustment including the ESU!

To drop rail voltage buy some 5 amp high speed diodes - standard ones aren't good enough.

each diode will drop voltage about 3/4 of a volt.

Make two strings of several diodes and reverse one, then parallel them. Connect into one of the track leads. The diagramme inset shows the way to do it.

I hope this helps your question and gives some possible answers - and I hope the "voltage" issue is noted by DCC'ers and adopted, as it will improve layout stability, decoder life and other things!

Regards

Richard
 

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Discussion Starter · #6 ·
Thanks Richard for this full and useful reply.

QUOTE (Richard Johnson @ 5 Dec 2007, 04:36) <{POST_SNAPBACK}>***Cooked motors are actually rare but that certainly looks to be the case. The normal reasons are (1) badly assembled motor - the plastic end caps are not seated properly and the motor overheats. Bachmann has a whole production batch like this a year or two ago!!

My two were produced in late 2005 so it could be this problem. A couple of people have replied on other forums about similar problems with the same batch of the same loco. Do you have any more details of which motors were affected?

QUOTE (Richard Johnson @ 5 Dec 2007, 04:36) <{POST_SNAPBACK}>The ideal voltages I've struck by test are:

Z/N 10.5 to 12v
H0/00 and similar (ie ON30) 11.5 to 14 volts
...
Its hard with some brands to adust voltage, especially EU ones - some have NO adjustment including the ESU!

To drop rail voltage buy some 5 amp high speed diodes - standard ones aren't good enough.

each diode will drop voltage about 3/4 of a volt.

I'm using a Lenz set 100. According to the manual this allows voltage adjustment but I have not adjusted it so it should be still at the default value of 16V. However all my track laid so far is fitted with Littfinski block detectors which put two diodes in series with the track feeds, so my track voltage should be about 14.5V. On non-detected sections I plan to fit two strings each of three diodes arranged as you suggest, to reduce the voltage even lower so a train bridging between detected and non-detected track will still be detected.

I use Zimo MX620 decoders and these have a CV for reference voltage, which I have set to 12V. I think this means the motor will never see more than that voltage, though the manual is not absolutely clear on this. The question of track voltage has also arisen in the MERG group recently, they have published a circuit that will allow a standard meter to measure DCC voltage. I will do some further measurements and probably reduce the output on the Lenz by a couple of volts to be on the safe side.

Evidence so far seems to suggest a faulty batch of motors or possibly a stiff chassis. As a precaution I've wired an 800mA polyfuse into the motor circuit of my one surviving Class 66 - this may save the decoder if that motor goes the same way, though if it happens suddenly I suspect the decoder motor drive will cook before the fuse can operate. This is a newer model with a different batch number on the motor so I'm hoping it will be all right.
 

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QUOTE (Edwin @ 5 Dec 2007, 18:37) <{POST_SNAPBACK}>My two were produced in late 2005 so it could be this problem. A couple of people have replied on other forums about similar problems with the same batch of the same loco. Do you have any more details of which motors were affected?

The worst incident was actually on their HO Scale Pennsylvania K4 pacific loco - totally epidemic - another one of their LNER OO loco's from memory. I must admit I haven't seen an "epidemic" of N scale problems, but it certainly sounds like a fair claim to me.

However I'd simply pack up the motors with a letter explaining that they just died within a year of purchase and ask for two new ones. Be nice (I love your stuff and I'm so disappointed etc etc.... and DON'T yell at them - and I think you will find that they will be responsive). Include a credit card number and offer to pay if necessary & a phone number. Most CS staff will look kindly on a polite and disappointed letter!

QUOTE (Edwin @ 5 Dec 2007, 18:37) <{POST_SNAPBACK}>I'm using a Lenz set 100. According to the manual this allows voltage adjustment but I have not adjusted it so it should be still at the default value of 16V. However all my track laid so far is fitted with Littfinski block detectors which put two diodes in series with the track feeds, so my track voltage should be about 14.5V. On non-detected sections I plan to fit two strings each of three diodes arranged as you suggest, to reduce the voltage even lower so a train bridging between detected and non-detected track will still be detected.

***DO reset the voltage - 16volts is far too high even for OO or HO. remember that a momentary short will generate a peak voltage thee times the rail voltage - beyond the tolerance of decoders long term, and the cause of much decoder death!

QUOTE (Edwin @ 5 Dec 2007, 18:37) <{POST_SNAPBACK}>I use Zimo MX620 decoders and these have a CV for reference voltage, which I have set to 12V. I think this means the motor will never see more than that voltage, though the manual is not absolutely clear on this. The question of track voltage has also arisen in the MERG group recently, they have published a circuit that will allow a standard meter to measure DCC voltage. I will do some further measurements and probably reduce the output on the Lenz by a couple of volts to be on the safe side.

***Yes thats what it means, but a decoder reset will clear it and then U are not protected - DO reset the controller :)

QUOTE (Edwin @ 5 Dec 2007, 18:37) <{POST_SNAPBACK}>Evidence so far seems to suggest a faulty batch of motors or possibly a stiff chassis. As a precaution I've wired an 800mA polyfuse into the motor circuit of my one surviving Class 66 - this may save the decoder if that motor goes the same way, though if it happens suddenly I suspect the decoder motor drive will cook before the fuse can operate. This is a newer model with a different batch number on the motor so I'm hoping it will be all right.

*** rig up a DC test track and put your meter in series with one of the power leads to the track.... check it by adding some pregressively greater resistance and see what the "Only just wheel slipping" current is - if the motor is OK then it'll be below 400mA.

Don't STALL it or if U do stall for only a moment... thats a good way to have burnout #3 :) :)

If you are going to use a polyfuse use one of 250~300mA or less - they are very slow to act and are very tolerant - about +25% of rating before they start to act after a very long second or two - if you use 300mA I really doubt it'll ever trip and it has half a chance of protecting things - HOWEVER - I thought Zimo had overcurrent protection - or am I wrong???

Kind Regards

Richard
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Discussion Starter · #8 ·
Thanks again. I'm still thinking about how to approach Bachmann especially as one of the locos was over a year old, did not run much until my layout was somewhere near workable. 800mA was the smallest polyfuse I had to hand, I'll have to get some smaller ones.

QUOTE (Richard Johnson @ 5 Dec 2007, 12:10) <{POST_SNAPBACK}>I thought Zimo had overcurrent protection - or am I wrong???

I thought so too. But I transferred one of them to another loco and the motor runs poorly and only in one direction, so I guess part of the H-bridge has gone and it is now an expensive lighting decoder...
 

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QUOTE I thought so too. But I transferred one of them to another loco and the motor runs poorly and only in one direction, so I guess part of the H-bridge has gone and it is now an expensive lighting decoder...

I've got an MX620 like that. I don't think they've got the same protection as the MX63 so unless I'm really pushed for space, I've decided to stay away from them.

David
 

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Discussion Starter · #10 ·
QUOTE (dwb @ 5 Dec 2007, 18:03) <{POST_SNAPBACK}>I've got an MX620 like that. I don't think they've got the same protection as the MX63 so unless I'm really pushed for space, I've decided to stay away from them.

Interesting. I thought about the MX63 but concluded it was slightly too big for Farish diesels.
 

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QUOTE (Edwin @ 6 Dec 2007, 18:44) <{POST_SNAPBACK}>Interesting. I thought about the MX63 but concluded it was slightly too big for Farish diesels.

**Edwin - try a TCS M1 with back EMF - you'll be pleasantly surprised - the slow running is every bit the equal of a Zimo and its half the price - plus it has a "goof Proof" warranty so if the loco does it again you are covered....

Richard
 

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Discussion Starter · #12 ·
QUOTE (Richard Johnson @ 6 Dec 2007, 12:38) <{POST_SNAPBACK}>**Edwin - try a TCS M1 with back EMF - you'll be pleasantly surprised - the slow running is every bit the equal of a Zimo and its half the price - plus it has a "goof Proof" warranty so if the loco does it again you are covered....

Thanks but I need four functions for independent tail lights, plus I may need ABC and Railcom in the future.
 

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QUOTE (Edwin @ 6 Dec 2007, 21:54) <{POST_SNAPBACK}>Thanks but I need four functions for independent tail lights, plus I may need ABC and Railcom in the future.

***M4 then :)

- and there are better ways to do things than ABC and railcom if you look carefully.... Both are largely vapourware still as far as practical layout benefits are concerned, and they'll be leapfrogged within 24 months. Especially railcom.

There are intersting times ahead

Richard
 

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Discussion Starter · #14 ·
QUOTE (Richard Johnson @ 6 Dec 2007, 14:10) <{POST_SNAPBACK}>***M4 then :)

- and there are better ways to do things than ABC and railcom if you look carefully.... Both are largely vapourware still as far as practical layout benefits are concerned, and they'll be leapfrogged within 24 months. Especially railcom.

There are intersting times ahead

Richard

According to the TCS site the M4 is not BEMF-fitted yet.
 

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QUOTE Interesting. I thought about the MX63 but concluded it was slightly too big for Farish diesels.
I'm OO, so even with small UK sized boilers I can generally manage.

QUOTE they'll be leapfrogged within 24 months. Especially railcom.
ooh! I hope that Zimo keep up and make new software available for their decoders. I wouldn't like to have to re-equip in 2 years time.

David
 

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QUOTE (dwb @ 8 Dec 2007, 03:36) <{POST_SNAPBACK}>I'm OO, so even with small UK sized boilers I can generally manage.

ooh! I hope that Zimo keep up and make new software available for their decoders. I wouldn't like to have to re-equip in 2 years time.

David

***No, you won't - the whole point of new developments currently mooted is that they won't be "One special feature dependent" "One bus dependent" and "one brand of decoder" dependent.

I hark back to a comment I made in an earlier thread - features that don't require track gaps and diode drops are the future - the direction the last so called "new wonders" such as assymetric braking and railcom are taking things is actually back to the bad old days of DC with lots of sections, lots of added cost and special wiring.

What's the point?

Richard
 

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QUOTE ***No, you won't - the whole point of new developments currently mooted is that they won't be "One special feature dependent" "One bus dependent" and "one brand of decoder" dependent.

I hark back to a comment I made in an earlier thread - features that don't require track gaps and diode drops are the future - the direction the last so called "new wonders" such as assymetric braking and railcom are taking things is actually back to the bad old days of DC with lots of sections, lots of added cost and special wiring.

So long as "old" kit can be upgraded, I'll be happy.

I don't like having extra track gaps and diode drops either but that's all that's "visible" to me as a punter, so if it can deliver something I can use now then I'll go for it. Since I have a separate power bus and build my own "diode drop" modules, the cost of changing will be small for me. I do not intend to go as far as the Lenz BM2, BM3 type of solution.

David
 
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