RMweb Premium melmerby Posted September 3, 2016 RMweb Premium Share Posted September 3, 2016 Hi all I have a NCE Switch-8 decoder which has become faulty. It wasn't an instantaneous failure but gradual over about 12 months. What happened was that about 12 months ago one decoder appeared to be sometimes "asleep" i.e. when first powered up (DCC track powered) it did not work. There was no DC at all going to the Tortoise motors it contolled although there was track DCC on the input, all the other Switch-8s would power up and take up the slack in the Tortoise mechanisms. It didn't happen very often at first and powering down and up again usually cured the problem. However recently the problem had became more regular and it sometimes needed switching on/off more than once to wake it up. Finally about two weeks ago it became permanent asleep. It is not a wiring problem as a straight swap out with a replacement cured the problem and the faulty unit is still faulty on the bench. N.B. for the electronics people out there the PIC onboard oscillator is working and the PIC has the correct 5v supply and the LM324s have the correct rectified track voltage supply. All the PIC output pins are fixed at either 0v or 5v and don't change when a turnout command is received The LM324s have the correct output for their input voltages coming from the PIC. e.g. all are 0v Some questions: Anybody else had a similar problem? Is it possible to do a full reset? (E.g. like CV8 in a loco decoder) Can it be replaced for a nominal cost in the UK just like it can in the USA ($10 + pp)? Any other suggestions? Cheers Keith Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted September 3, 2016 Author RMweb Premium Share Posted September 3, 2016 Further to the above I have established it's not the PIC as substution between the good and bad units does not cure the problem! Keith Link to post Share on other sites More sharing options...
jpendle Posted September 3, 2016 Share Posted September 3, 2016 What DCC controller are you using? I have Z21. I had to turn Railcom off AND I have to send a DCC command to a loco before the Switch 8's will turn on properly. Regards, John P Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted September 3, 2016 Author RMweb Premium Share Posted September 3, 2016 What DCC controller are you using? I have Z21. I had to turn Railcom off AND I have to send a DCC command to a loco before the Switch 8's will turn on properly. Regards, John P My Switch-8s turn on the instant they get DCC track power and move the Tortoises to their last set position as they should according to the NCE info. Lenz 100 or Digikeijs DR5000 it makes no difference. I think I've found the fault. One of the LM324s has a "pop" hole and I think it's failure is dragging down the reference voltages to the others. Just have to remove it and double check. Keith Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted September 3, 2016 Author RMweb Premium Share Posted September 3, 2016 If it is the LM324, your repair bill is pennies. It looks as it's been replaced before as the soldering is not as neat as the flow on the other 3. However the unit was bought brand new in the original packaging! Have to be careful removing the IC as the SM pads are very small. Not unusual as "brand new" electrical stuff has sometimes been repaired, presumably in the factory. I had a JVC VHS recorder which when I came to scrap it and get the recoverable parts out of it showed signs of a PCB board repair. That was brand new in a sealed carton. Keith Link to post Share on other sites More sharing options...
RMweb Gold RFS Posted September 3, 2016 RMweb Gold Share Posted September 3, 2016 There is a known weakness with the MK1 Switch-8 in that port 1 can lose its address and have to be reprogrammed. This happened to two of mine - probably caused by the same glitch as the fault showed up on each unit within an hour. Decided to reconfigure them both so that port 1 was not in use, but then a 3rd unit suffered a port 8 failure which then could not be recovered. I contacted NCE who said to send them all back for repair which would be free of charge, including return postage. I only had to pay outgoing postage which cost me about £12. When they received them they offered either to complete the repairs (with no guarantee that the fault would recur) or for $90 they would replace them with brand-new MK2s which have all these faults corrected. I chose the latter option and there have been no problems since. Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted September 4, 2016 Author RMweb Premium Share Posted September 4, 2016 There is a known weakness with the MK1 Switch-8 in that port 1 can lose its address and have to be reprogrammed. . Haven't had a problem with mine apart from this one. I think I have 6 or 7 around the layout. I have removed the suspect 324 and the other 6 ports now work fine so I need to get another SMD 324. Saves having to send anything back to NCE! Cheers Keith EDIT: Here is the removed 324. the blown up mark can be clearly seen: When I passed a fine wire behind the pins as suggested by Dutch_Master a small spider of solder appeared so I think that may have been the culprit which cused the failure! Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted September 7, 2016 Author RMweb Premium Share Posted September 7, 2016 I've now replaced the faulty 324 and it works - almost! The fault meant one port of the PIC has been damaged and is permanently 5v so I only have 7 outputs working correctly (2-8) Output 1 just switches betwen 0 and 12v rather than going +/- 12v. Substituting the PIC proves the rest of the circuit OK. Switch-7 anyone? Keith Link to post Share on other sites More sharing options...
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