[time-nuts] Symmetricom S200 PSU

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Thanks for the reply Clint. I spent some time on it today with no luck, I do have some more info though…

The primary seems ok, there is a steady 329volts DC across the big cap after the rectifier diodes.

When you power it up under its normal load you can hear the transformer whistle, which you could not hear when it was working, also measuring the DC outputs gives almost exactly half the expected output, i.e.

+2.54v
+6.02v
-5.88v

Unfortunately I only have a multimeter and no ‘scope so any further fault finding is difficult. I guess the next step is to replace the mos fet that drives the transformer, or I guess it could be the feedback loop, which looks like an opto-isolator, doubt that the isolator itself would die, but there’s a PNP transistor driving it…

If anyone has any other ideas I’m listening !

Thanks,
Chris


> On 18 Sep 2017, at 20:21, Clint Jay <cjaysharp at gmail.com> wrote:
> 
> Hi Chris, if it's not blowing fuses and you're sure you've got all the capacitors ( low value ones in the primary specifically) then check all the high value resistors on the primary and continuity from reservoir capacitor to switching transistor. 
> 
> The average SMPSU usually doesn't deviate wildly from the application notes of the switching controller so if there's no specific schematic that might be a lifeline.
> 
> 
> 
> On 18 Sep 2017 20:08, "Lists via time-nuts" <time-nuts at febo.com <mailto:time-nuts at febo.com>> wrote:
> Hello Fellow Time Nuts,
> 
> Does anyone know where I can get either a circuit diagram or a replacement PSU for a symmetricon S200 NTP server?
> 
> I’ve fixed the original one twice before by replacing all the electrolytic caps, this time it’s popped something more critical and refuses to come back to life.
> 
> So I either need a new PSU or a circuit diagram so I can fault find on the original.
> 
> I’m in the UK.
> 
> Thanks,
> Chris
> 
> 
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