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Metronic Dualis 441350 R108 value
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<blockquote data-quote="deltatango" data-source="post: 690307" data-attributes="member: 312296"><p>Ok in my case the zener diode had shorted out which then burned out R108.</p><p></p><p>The zener (glass bulb item near to R108) thats fitted has a 1Nxxxx type code and I think (memory fades) was a 30 or 33volt at 1.3W range, I mention this because that capacitor that popped must have got very hot.</p><p>This takes place if the voltage or ripple current through it becomes higher than it can tolerate so one thought is this zener diode may be open circuit (o/c) because it would consume some of this extra energy. If one end is unsoldered and an analogue meter (not digital) on high ohms scale you should only get a reading in one direction only, if you get none, or in both directions then it is faulty. (This is based on most meters not able to test with above 22.5V ( old AVO meters) on high ohms scale).</p><p></p><p>If you are still with me, then that capacitor is polarised and I tend to prefer fitting 105deg type capacitors instead of 85deg as they are more durable.</p><p></p><p>Now we get complicated.......</p><p></p><p>Many items we buy that work from mains used switch mode power supplies, fine no problem with that, but they used to be fitted with quality type capacitors that have "low ESR" (able to stand high action without getting hot inside). Now it seems to save money they fit them only in critical places and wonder why power supplies fail after a few years!</p><p>As these capacitors fail, they are unable to remove spikes and ripples which then inflict damage to other parts.</p><p></p><p>I would look at the other capacitors on that board and check for top swellings, they should be nice and flat, but bow upwards when failing, some also ooze their paste from below but this is harder to spot. </p><p></p><p>If you do have any that have swelled then change them for 105deg Low ESR types and also change the one (I think) at the transformer side or near the mains area which would be a 10,22,33 or 47uF mostly, as this controls critical settings on the power supply activity.</p><p></p><p>Its been a while to remember exactly what I did, if need be I will take the top off of mine to recall.</p><p></p><p>Please be careful with mains present, you can fire up the supply without it being connected to its main board and should get a 30+ volt a 12v and two or so at 5volt and maybe one at 5.6volt (I may be slightly in error as many other things have cropped up so things blur a bit over time) </p><p></p><p>Sing out if you need me again and please take care..</p><p></p><p>Regards from deltatango</p></blockquote><p></p>
[QUOTE="deltatango, post: 690307, member: 312296"] Ok in my case the zener diode had shorted out which then burned out R108. The zener (glass bulb item near to R108) thats fitted has a 1Nxxxx type code and I think (memory fades) was a 30 or 33volt at 1.3W range, I mention this because that capacitor that popped must have got very hot. This takes place if the voltage or ripple current through it becomes higher than it can tolerate so one thought is this zener diode may be open circuit (o/c) because it would consume some of this extra energy. If one end is unsoldered and an analogue meter (not digital) on high ohms scale you should only get a reading in one direction only, if you get none, or in both directions then it is faulty. (This is based on most meters not able to test with above 22.5V ( old AVO meters) on high ohms scale). If you are still with me, then that capacitor is polarised and I tend to prefer fitting 105deg type capacitors instead of 85deg as they are more durable. Now we get complicated....... Many items we buy that work from mains used switch mode power supplies, fine no problem with that, but they used to be fitted with quality type capacitors that have "low ESR" (able to stand high action without getting hot inside). Now it seems to save money they fit them only in critical places and wonder why power supplies fail after a few years! As these capacitors fail, they are unable to remove spikes and ripples which then inflict damage to other parts. I would look at the other capacitors on that board and check for top swellings, they should be nice and flat, but bow upwards when failing, some also ooze their paste from below but this is harder to spot. If you do have any that have swelled then change them for 105deg Low ESR types and also change the one (I think) at the transformer side or near the mains area which would be a 10,22,33 or 47uF mostly, as this controls critical settings on the power supply activity. Its been a while to remember exactly what I did, if need be I will take the top off of mine to recall. Please be careful with mains present, you can fire up the supply without it being connected to its main board and should get a 30+ volt a 12v and two or so at 5volt and maybe one at 5.6volt (I may be slightly in error as many other things have cropped up so things blur a bit over time) Sing out if you need me again and please take care.. Regards from deltatango [/QUOTE]
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Metronic Dualis 441350 R108 value
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