Metronic Dualis 441350 R108 value

[deltatango]

Trying to fix a Dualis box which has a burnt out R108 resistor on its power supply which feeds a zener diode.

Seems to be known about, have tried to email (France) Metronic but they remain silent on this issue, so can anyone help me please.

Have fixed the rest of the supply though, suprised to find 85deg caps used in a switch mode supply which explains why a couple had puffed up, so a lot a better now with 105deg types and low esr.

Many thanks from David

[deltatango]

Well for now I have settled on 470ohm as a suitable value (one day I will find out its true value).

This was chosen by using a variable resistor of under 1K and checking the current through the zener, up to 7mA caused its power supply no problem in holding the feed voltage to it.
While 13mA started to make it fall fast, given this zener is 1Watt rated I thought it must pass a reasonable current so in true technical style chose 10mA as a round figure which is also a good level which ensures it is at a stable voltage point of operating. Checking that its feed supply voltage had only dropped a few hundred millivolts at this point seemed reasonable (you don't get owt for nowt).

Checking the resistor value with a meter which came to near 470ohm @ 50mW, so I hope this helps anyone else fix their unit, please note this is not the official value so any repairs are at your own risk (Just covering the bases).

David

[PaulR]

Thanks for posting your results.

As you might have guessed no-one was able to help you but your post may be able to help someone else.

[deltatango]

Sadly Metronic are sticking to their guns and will not say what its value is, I will give one last try but I doubt they will answer.

That said I think my chosen value will not harm it in any way, manufacturers I have seen though can be more cruel to their products, leaving components to overheat with no heatsinks etc, (thats my gripe over) to save money.

I will continue to seek an answer (when its no longer needed anymore) to this question just because it irritates me not to know.

Best regards to all for now from David