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
DCCconcepts
