RMweb Premium Ray H Posted June 9, 2012 RMweb Premium Share Posted June 9, 2012 I have been tasked with investigating a Gaugemaster (Model W) handheld controller that has (apparently) ceased to function in one direction. It seems to perform quite happily when the DPDT (centre off) slide switch is in one direction but seems as dead as the proverbial Dodo when the switch is in the opposite direction. I've removed the switch and that seems to be functioning normally when off the board. I've remade all the soldered joints and removed and tested (with the test meter probes) in isolation the electrolytic capcitor and the smaller of the two transistors (I've also checked the larger transistor in situ with the smaller one disconnected) and didn't find anything unusual. What puzzles me, shows my ignorance of electronics and may (or may not) be related to the fact that I'm using a cheap battery powered analogue test meter is that when I connect the meter probes to the switch's supply points on the pcb I get a significantly different resistance reading with the probes one way round compared to when the probes are the other way round (with or without the switch soldered in position). I presume that this is because of the various diodes in the circuit. Unfortunately I don't have ready access to an AC supply so all I can do is to take the controller back and try it again unless anyone has any ideas what else I could check before doing so. Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted June 10, 2012 RMweb Premium Share Posted June 10, 2012 I have been tasked with investigating a Gaugemaster (Model W) handheld controller that has (apparently) ceased to function in one direction. It seems to perform quite happily when the DPDT (centre off) slide switch is in one direction but seems as dead as the proverbial Dodo when the switch is in the opposite direction. I've removed the switch and that seems to be functioning normally when off the board. I've remade all the soldered joints and removed and tested (with the test meter probes) in isolation the electrolytic capcitor and the smaller of the two transistors (I've also checked the larger transistor in situ with the smaller one disconnected) and didn't find anything unusual. What puzzles me, shows my ignorance of electronics and may (or may not) be related to the fact that I'm using a cheap battery powered analogue test meter is that when I connect the meter probes to the switch's supply points on the pcb I get a significantly different resistance reading with the probes one way round compared to when the probes are the other way round (with or without the switch soldered in position). I presume that this is because of the various diodes in the circuit. Unfortunately I don't have ready access to an AC supply so all I can do is to take the controller back and try it again unless anyone has any ideas what else I could check before doing so. I'm not familiar with this exact item, but here is some general ideas. How about temporarily soldering a couple of wires to the 'switches supply points on the PCB' and connecting up a temporary DPDT switch and seeing if that works. Could be that the switch is high resistance and so open circuit. Also is the switch the last item before it goes out to the track? Kevin Martin Link to post Share on other sites More sharing options...
RMweb Gold gwrrob Posted June 10, 2012 RMweb Gold Share Posted June 10, 2012 These come with a lifetime guarantee from Gaugemaster if you have no luck yourself.I'd send it to them. Link to post Share on other sites More sharing options...
RMweb Premium Ray H Posted June 10, 2012 Author RMweb Premium Share Posted June 10, 2012 Thanks chaps. I did have the idea of feeding dc into the circuit after the rectifier bridge and seeing what happens then - that would rule out a number diodes if things hadn't improved. I extended the lead on the unit some while ago - it has been working fine in between - so I suspect that I have invalidated the warranty but I will bear it in mind if I don't have any luck. That said, the cost of replacing all the components probably isn't much more than the postage for sending it back so I could just do that. I'll get a chance to experiment at the end of the week but in the meantime would welcome any further suggestions. I've currently re-assembled the unit but if it comes apart again I'll rough out the circuit diagram and see whether I can deduce what the problem is although to my mind a defective switch still has to be favourite. Link to post Share on other sites More sharing options...
cpman46 Posted June 11, 2012 Share Posted June 11, 2012 Ray I was given a Type W controller a few months back. There was nothing wrong with it but I wanted to replace the lead so took it apart and whilst it was open sketched out the circuit which I have attached for your information in pdf format. Gaugemaster W Controller Circuit.pdf The switch is the last item before the output to the track so the fact that yours works ok in one direction but not the other effectively rules out the electronics. Your analogue test meter will give significantly different readings across the output when you reverse the leads because of the 1N4002 diode across the output. (The test meter output voltage will effectively forward bias the diode in one direction giving a lower reading, and reverse bias it in the opposite direction giving a higher one). Incidentally, if you wished to feed dc into the unit you do not need to bypass the bridge rectifier or worry about polarity as the diodes within the bridge will automatically feed the correct polarity to the circuit which follows. As Kevin Martin suggested, to prove you have a defective switch, temporarily wire a DPDT switch in place of the slide switch and check that the output changes polarity. Kind regards Mike Link to post Share on other sites More sharing options...
Brian Posted June 11, 2012 Share Posted June 11, 2012 Hi As all Gaugemaster dc controllers are covered by their 'Lifetime warrenty', do not open it, alter or resolder anything inside or try to repair it. Simply Jiffy bag it up and post it to Gaugemaster House, Ford Road, Arundel, West Sussex, BN18 0BN and it will be repaired for you or replaced if beyond repair! No cost to you other than any postal charges! Link to Gaugemaster http://www.gaugemaster.com/index.html Link to post Share on other sites More sharing options...
Kenton Posted June 11, 2012 Share Posted June 11, 2012 Brian, it sounds like it is far too late for that course of action. I've removed the switch and that seems to be functioning normally when off the board. I've remade all the soldered joints and removed and tested (with the test meter probes) in isolation the electrolytic capacitor and the smaller of the two transistors (I've also checked the larger transistor in situ with the smaller one disconnected) and didn't find anything unusual. Though worth remembering for anyone else with a Gaugemaster problem. Cast iron and solid guarantees are worth their weight but there are limits! Link to post Share on other sites More sharing options...
RMweb Premium Ray H Posted June 11, 2012 Author RMweb Premium Share Posted June 11, 2012 Thanks once again to you all. As I said previously I changed the lead some while ago thus invalidating the warranty. The unit was then working fine for several weeks until the latest problem arose. I can't try it again on Thursday - I doubt that I shall get time to do anything with it in the mean time, but if I do (I have already reassembled it) I'll try connecting a DC supply as suggested and see what happens. Fortunately, earlier fears that the DPDT switch had unusual terminals were needless and I should be able to pick up a replacement from Maplins quite easily. I suppose that there's always a chance that there was a dry joint between the switch and the pcb and removing and refitting has resolved the issue. I've replaced the lead on several Gaugemaster handhelds and without exception have thought the quality of the soldering on the pcbs to be quite poor. I'm far from an expert but I think even I could produce a better quality job. Has anyone else thought this? Link to post Share on other sites More sharing options...
RMweb Premium Ray H Posted June 15, 2012 Author RMweb Premium Share Posted June 15, 2012 Just to close this off, I returned the controller to the layout from whence it came yesterday, connected it up, turned it on and it behaved fautlessly all the time we used it. I can but assume that there was a dry joint between switch and pcb. Many thanks for all suggestions. Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted June 16, 2012 RMweb Premium Share Posted June 16, 2012 Just to close this off, I returned the controller to the layout from whence it came yesterday, connected it up, turned it on and it behaved fautlessly all the time we used it. I can but assume that there was a dry joint between switch and pcb. Many thanks for all suggestions. Good to hear you had some success, Ray. Kevin Martin Link to post Share on other sites More sharing options...
cpman46 Posted June 17, 2012 Share Posted June 17, 2012 Just to close this off, I returned the controller to the layout from whence it came yesterday, connected it up, turned it on and it behaved fautlessly all the time we used it. I can but assume that there was a dry joint between switch and pcb. Many thanks for all suggestions. Excellent news Ray! I can only concur with you on the subject of the poor quality of the soldering on the controllers I have come across. Mike Link to post Share on other sites More sharing options...
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