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91
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by krawitjr on November 03, 2020, 03:08:50 PM »
Hi,

No problem. 

Statement comes from an early tracker manual with signature examples - Huntron Tracker Operator Manual for models: 1005B-1S, 1005B-1ES, 1005B-1JS -  (Section 11.1) - Specifically 11.4 "Memories".  The last sentence of 4th paragraph was what I quoted.

I tried to attach the PDF it to this post (it's only 2.3MiB) but the forum software claims it's too big or broken or whatever, so I'm placing it on my Google drive for the time being (not forever).  Grab it while you can, it's a good read!

https://drive.google.com/file/d/1qf2eSfvAdV-V4ecmDxte5A5YWCfbC4jx/view?usp=sharing

Now before anyone starts claiming this is an obsolete tracker and not my model.  Yeah, I'm aware of that...it's also the BEST Huntron document for examples of real device signatures I've ever come across!  Much better than the scant amount in the Huntron 3200S manual or the training documents.  I highly recommend this document for anyone wanting to know what different components (like rectifiers, SCRs, etc...) actually look like on Trackers normally.

So this document off-handedly states a "stuck bus" (while powered) can be tracked for DC shift.  Please elaborate.
92
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by admin on November 03, 2020, 08:21:05 AM »
I think we are running into semantics here. I would not necessarily consider a memory battery to be external power. What we are trying to prevent is someone using a Tracker on a PCB that is powered up i.e. by wall power, power supply, etc. In such as situation damage to the Tracker can occur very quickly. DC offset is usually caused by very low power sources like on-board batteries and sometimes caps or super caps. Regarding a stuck bus shift, you will need to tell me where you see this reference so I can get some context.
Thanks.
93
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by krawitjr on November 03, 2020, 03:05:10 AM »
I thought my first question gave evidence otherwise. 

You said a DC shift is caused by external DC voltage present on the circuit. The memory (stuck bus) section of the training manual tells you to look out for a such a shift. 

What am I missing? How can I have a shift without external power, so that means the circuit has power?

What am I not putting together?  This is what started my confusion in the first place. 
94
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by admin on November 02, 2020, 11:16:32 AM »
I don't recall anything from Huntron suggesting that you can test circuitry with external power applied. Maybe the references you had in mind are referring to using the Tracker pulse generator?
95
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by krawitjr on November 02, 2020, 11:10:00 AM »
Ok, I understand the concept the the Huntron might tolerate some amount of line voltage but given the risk, it seems, well, too risky. I realize IC TTL-style signals are current limited, but you have to be very very sure.  Unless your power source is a small coin cell battery, I don’t think I’ll ever be that sure.

I think this explains the big shift in advice from the very old tracker (1000HB & 2000) manuals to the most recent 3200 manual.

Probing with active device under test power has been removed from recent advice/learning. 

I was trying to read everything to become more familiar with what could be done.  I’m still having trouble with the nuance. But I guess the older and more dangerous techniques were basically playing without a safety net and risking Huntron damage. So were phased out?
96
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by admin on November 02, 2020, 08:35:01 AM »
Good question. Looking at worst case with the Tracker set to the 10ohm range, the range resistor is rated at .75W so maximum theoretical current (square root of power divided by resistance if I remember correctly) it can handle is about 275mA. Maybe a bit more before risking damage. The Tracker protection circuitry is voltage based so if an external voltage above 20Vpk is applied through the signal line then the relays open up and you see an Overvoltage indication on the display.

The 200mAPk referenced on the front panel and in the manual refers to maximum current output from the Tracker.
97
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by krawitjr on October 30, 2020, 09:41:34 AM »
Oh, OK.  For the manual reference that kind of makes sense (looking a for an internal IC short where external voltage was added, or leaked, from another path).

But that brings up a huge can of worms question.  With the 3200S, compared to the much older equipment, the manual doesn’t state any tolerance for power present on the device under test.

How much power can the latest Huntron model withstand being input into its probes/channel before damage is done? As some of the older documentation claims you may troubleshoot with device power on?  I assume perhaps just for stuck/shorted IC signals.

The 3200s manual has a single reference to input protection which says 200mAPK.  Does this mean 200mA of current?  I wasn’t really sure why this meant or if it was related/relevant. 

Thanks
98
General Discussion / Re: Can anyone describe what a Waveform DC shift is?
« Last post by admin on October 30, 2020, 08:28:47 AM »
Welcome to the Huntron Users Forum.

DC offset is basically a shift in the signature position to the left or right caused by a DC voltage being present on the board. This is most commonly seen when testing a board with a battery on it such as those used for memory circuits (i.e. PC motherboard).
Thanks.

Admin
99
General Discussion / Can anyone describe what a Waveform DC shift is?
« Last post by krawitjr on October 30, 2020, 01:15:04 AM »
Hi, I recently acquired a gently used secondhand Huntron 3200S.  I am re-reading all my old documents to try to get up to speed on more advanced signature recognition.

Reading some of the older Huntron manuals, as well as drawing from personal experience, I’ve seen a waveform DC shift exactly twice in my experience.   

One was on a transistor and the other was on a capacitor (both in circuit).

In both instances the waveform was not only subtly distorted but it was shifted to the left and didn’t go through the origin. 

Older Huntron documentation mentions that this is very meaningful. But I’ve found no other description of what this means. 

Can someone please describe what it means when a signature doesn’t appear in the center origin as you would expect and instead is shifted to the right or left in the display. 

And to be crystal clear, I’m not talking about an improperly adjusted display. Im describing when you are using the tracker under correct conditions and suddenly touch a component to find its signature shifts to the left or right of the origin. 

I’ve read just about every other military, NASA, Huntron, and other paper I can get my hands on describing signature analysis. I’ve never seen this phenomenon documented or explained. With the exception of the old Huntron 1000 manual. The manual has a single sentence under the memory device section that claims that you should look for this phenomenon.

Can anyone shed light on this? As it appears to be very meaningful.
100
Current Software - Huntron Workstation 4.X / Setting Common Pin for Scanner Users
« Last post by admin on October 12, 2020, 03:18:45 PM »
There is a quicker method to set the Common Pin 1 setting (Ranges tab) than right-clicking the column header and selecting "Set Current All - Pins" (which only works for the selected range).
First, set your Common Pin 1 for the first Range (image 1). Right-click the row header for the selected Range and choose "Group Edit" (image 2). In the Group Edit window, select all the pins the bottom left list, check the Common Pin 1 checkbox and click the Update Pins/Ranges button (image 3). You will see that all of your Ranges and Pins are set to the Common Pin you selected earlier.

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