[time-nuts] Anyone familiar with SR-620 repair?

[J. Forster]

> Here is a trick or two that may work:
>
> feed a very small AC voltage with say 1KHz and 10mV into the bad power
> rail. It won't hurt anything.
>
> Then use an old cassette players' magnetic pickup and amplifier to  follow
> the signal to the short. No need for expensive hall effect meters.

Good bypass caps are near AC shorts. I've not tried it, but am not
optomistic. It would work on stuck signals lines, but not well on power,
IMO.

> Another trick that I often use is force-feed power into the bad power
> rail.  If it's a 5V rail, then say 5V at 2A.
>
> That can work by having the bad part get hot really quickly, by allowing
> you to DC probe with a millivolt setting, or it can backfire if it's a
> tant
> cap  by blowing it up. I would use that only as a last resort if the first
> trick  didn't work, as the second trick can be dangerous!

Be aware, you can overheat and burn out PCB traces or vias. Small
capacitors don't make a real mess when they poip, but I would most
certainly wear glasses.

-John

==============

> So please be
> careful, any  repair should be done only with proper equipment (using a
> 110V isolation  transformer for example)...
>
> bye,
> Said
>
>
> In a message dated 3/23/2012 14:13:57 Pacific Daylight Time,
> jfor at quikus.com writes:
>
> Are  there Hall Effect probes for chasing DC faults?
>
> I'm very familiar with  the HP Logic Current Tracer, but AFAIK that is
> only
> sensitive to fast  pulses, from the Logic Pulser for example.
>
> The threashold is  adjustable, so maybe it will sense DC currents.
>
> If it is DC sensitive  it'd be even more wonderful. I'll try it after
> dinner.
>
> Thanks,
>
> -John
>
>