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

J. Forster jfor at quikus.com
Sat Mar 24 13:33:31 UTC 2012


MW or LW IR cameras are not exactly home shop stuff Peter.

-John

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


> I had a HP 3326 which had a power supply in foldback. All the modules are
> inaccessible unless you have a rather rare set of extenders anyway. The
> voltmeter method quickly led me to the board and a bench supply and meter
> again to the shorted cap. Very easy. Other times I've borrowed the FLIR
> camera from work, also taught the new EEs that trick as well.  It is a
> true lifesaver on dense surface mount boards. I haven't tried the liquid
> crystal sheet but it seems like an interesting idea so long as everything
> is about the same height.
>
>
> Peter
>
> On Mar 23, 2012, at 11:53 PM, lists at lazygranch.com wrote:
>
>> Prior to emission or IR microscope technology, liquid crystals was how
>> you found hotspots on ICs. I've done this with a goop that you dispense
>> with a syringe.
>>
>> One trick to make this more sensitive is you bring a soldering iron
>> close to the  liquid crystals. Not so close as to cause a change, but
>> you get them closer to the phase change point.
>>
>>
>> -----Original Message-----
>> From: Skip Withrow <skip.withrow at gmail.com>
>> Sender: time-nuts-bounces at febo.com
>> Date: Fri, 23 Mar 2012 21:07:45
>> To: <time-nuts at febo.com>
>> Reply-To: swithrow at alum.mit.edu,
>>    Discussion of precise time and frequency measurement
>>    <time-nuts at febo.com>
>> Subject: [time-nuts] Anyone familiar with SR-620 repair?
>>
>> You don't need expensive test equipment to find this kind of problem.
>> What
>> I use is a sheet of liquid crystal film with a transition temperature
>> just
>> slightly above your room temperature.  Just lay it on the circuit board
>> and
>> you can find where the power is being dissipated (even if pretty small)
>> by
>> watching the colors change.
>>
>> I think Omega Engineering sells a 8.5" x 11" sheet for about $18 if
>> memory
>> serves me.  I have used this trick many times and it works great to find
>> shorted (bypass) caps.  No disconnecting anything, no milliohm meters,
>> no 4
>> or 5 digit voltmeters.
>>
>> Regards,
>> Skip Withrow
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