To: time-nuts@febo.com
Reply-To: swith...@alum.mit.edu,
Discussion of precise time and frequency measurement
time-nuts@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
-nuts-boun...@febo.com
Date: Fri, 23 Mar 2012 21:07:45
To: time-nuts@febo.com
Reply-To: swith...@alum.mit.edu,
Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Anyone familiar with SR-620 repair?
You don't need expensive test equipment
...@febo.com
Date: Fri, 23 Mar 2012 21:07:45
To: time-nuts@febo.com
Reply-To: swith...@alum.mit.edu,
Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Anyone familiar with SR-620 repair?
You don't need expensive test equipment to find this kind
My SRS SR-620 counter died last weekend. After superficial
troubleshooting, it looks like there's probably a short on one of the
power supply rails. Symptom is that nothing lights up when power is
turned on, but one or more of the three terminal regulators gets very,
very hot (can't tell
Not w/ that instrument, but try the following. I assume you have the book
w/ schematics.
Power the unit and with a DMM or VOM check the PS rails to see which is sick.
From the book, locate all bypass caps on that rail.
Put your DMM across each in turn. The one with the lowest drop is likely
the
Great advice. I have the manual, but it doesn't include schematics. I
think someone on the list has a PDF of the schematics, so I'll be
digging around for that before I start digging into the box.
John
On 3/23/2012 2:36 PM, J. Forster wrote:
Not w/ that instrument, but try the following. I
Very nice to see schematics.
I do not have a sr620. Looks good.
You have been given some great guidance on seeing what supply is loaded.
Thats the first step.
Then I look for those nasty tear drop tants. Sometimes there is a clue they
are baking or as I think John said feel them when they have
On 03/23/2012 07:32 PM, John Ackermann N8UR wrote:
My SRS SR-620 counter died last weekend. After superficial
troubleshooting, it looks like there's probably a short on one of the
power supply rails. Symptom is that nothing lights up when power is
turned on, but one or more of the three terminal
I should have added that you can get a pretty good idea of whick branch on
a PCB is drawing current by probing along the trace. This is especially
useful if the rail has a bunch of branch distribution lines.
Also, if the three-terminal regulator is overheating, disconnect it and
power just that
On 03/23/2012 09:30 PM, J. Forster wrote:
I should have added that you can get a pretty good idea of whick branch on
a PCB is drawing current by probing along the trace. This is especially
useful if the rail has a bunch of branch distribution lines.
Also, if the three-terminal regulator is
Shame you do not have a Hall effect probe to drag down the trace.
John WA4WDL
--
From: Magnus Danielson mag...@rubidium.dyndns.org
Sent: Friday, March 23, 2012 4:58 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Anyone familiar with SR-620
Hi Magnus,
I very much doubt you could get anything useful out of a TDR. There is no
reason I can think of that a power rail should look anything like a
transmission line and the rail should be an AC short every inch or so.
FWIW,
-John
On 03/23/2012 09:30 PM, J. Forster wrote:
To: time-nuts@febo.com
Subject: Re: [time-nuts] Anyone familiar with SR-620 repair?
On 03/23/2012 09:30 PM, J. Forster wrote:
I should have added that you can get a pretty good idea of whick branch
on
a PCB is drawing current by probing along the trace. This is especially
useful if the rail has
HP once made a kit with DIP logic clip, logic probe, logic pulser, and current
tracer. Pulser and tracer made finding shorts pretty easy. For the SR-620 you
could disconnect the regulator and inject current pulses there, follow them
around with current tracer. The same basic trick works given a
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.
Another
One technique that works for me is to remove the bolts holding the regulator
tabs against the heat sink, and ensure that the tabs are not touching same.
Then, starting with the unit at ambient temperature, apply power for ten
seconds or so, and then use an IR temperature sensor to determine which
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
The HP 547A Current Tracer is an AC only instrument, as I thought. It uses
a coil as a pickup, not a Hall device.
See: http://cp.literature.agilent.com/litweb/pdf/00547-90006.pdf Page 11
Too bad. :((
-John
==
In a message dated 3/23/2012 14:13:57 Pacific Daylight Time,
Shouldn't be too bad, a 10uF cap would have 15 Ohms impedance at 1KHz, 150
Ohms at 100Hz, and one could inject at different places on the trace...
away from the big bypass caps.
Doing the same with DC and a simple multimeter should work too.
bye,
Said
In a message dated 3/23/2012
Most instrument PCBs have scores of bypass caps... all in parallel.
-John
=
Shouldn't be too bad, a 10uF cap would have 15 Ohms impedance at 1KHz,
150
Ohms at 100Hz, and one could inject at different places on the trace...
away from the big bypass caps.
Doing the same with DC
On our side of the pond there is/was a device called the Polar
Toneohm. It used a hall effect device to translate the current
flowing in a track to a tone - rising pitch, higher current. These
could be very effective in finding shorts in power rails etc, also in
multi-layer boards. Google Toneohm
In my opinion, if you are hunting for a short, there is a little to do with
the current: it is always the same, better use a voltmeter/millivoltmeter
and hunt for the least voltage across capacitors or the greatest voltage
drop on traces...
On Fri, Mar 23, 2012 at 11:36 PM, Geoff Blake
time and frequency
measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] Anyone familiar with SR-620 repair?
Great advice. I have the manual, but it doesn't include schematics. I
think someone on the list
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)
measurement
time-nuts@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
time and frequency measurement
time-nuts@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
,
Discussion of precise time and frequency measurement
time-nuts@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
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