Electronics Forum / Basics / October 2006

No

No

No

I would not assume that.

I would trace back to the nearest point of power input and look at the main
filter capacitor voltage. If it is 10 VDC, say, I would assume the input
should supply that or less.

MOST (but not all) items will be unharmed by any lower voltage, so I would
power the thing from a power transformer fed by a Variac, or from a variable
DC supply, and slowly increase the voltage. But you really need to trace out
the power supply first.

But tracing a board is never just about following traces.

You need an ohmmeter, and then you can actually see where there
is continuity between point A and point B.  It's amazing how often
one can lose track of the traces even when they are visible.

You follow visually when you can, make guess, and keep using the ohmmeter
to see if the guesses are right.

You need to look at the traces from the connector, and see if any of
the pins have no traces.  Even if all the pins on the connector are
being used, you only have five or so traces.  One or more should
go directly to ground.  

Power traces are often thicker than data traces, to handle the power, and
that makes them easier to follow.

Look up the identifiable ICs, even if that means only the eproms,
and find out which pin is ground and which pin is for the supply
voltage.  THere is no variation on that, so whatever pin is for
ground, then you can be absolutely certain that is a ground point.
Connect your ohmmeter to that ground pin, and then use the other
lead to go through the pins on the connector.  At least one will
have close to zero ohms, and it's not uncommon to have more than
one ground lead on a power supply connector.  Then put one lead
on the supply line pin of the IC, and use the other lead of the
ohmmeter to go through the pins on the connector.  One of them
may show close to zero ohms (and again, maybe more than one; if
the connector has more than enough pins, they might parallel some
for better current handling), then you know what voltage should
be on that pin, since the IC will have a voltage it's supposed
to run on.

But, there is always a possibility that you'll get no continuity
to the supply line pin of the IC.  It is always possible that there
is a regulator between the connector and the ICs.  There'll be
no continuity in that case, but on the other hand a regulator
on the board likely clears out the danger of applying too much
voltage.

Now since you say the device actually uses AC for testing,
that may simplify it all.  It's far more likely that the AC
adaptor just puts out AC voltage, since it's easier to turn
that to DC than turn DC to AC.  They can rectify and regulate
on the board, and still use the AC for testing purposes.  If
that's not happening, then likely two of the pins on the
connector are for AC voltage for the actual testing purposes.

The more pins you can separate out easily, the easier it
is to figure out the rest.

 Michael

Hi, Russ.  I see there was no info at sci.electronics.equipment.  Well,
it was worth a try.

I hope you've checked the resources I mentioned for used manuals.  Of
course you have to pay for the privilege, but I personally wouldn't
touch it without more info.

Another possible route you might check is a bit unusual, but it might
be worth a try.  If you google the company, you'll find various
financial statements with officer names.  Some of those people may
still be in the San Antonio area, possibly working with another
company.  It wouldn't hurt to spend a little time with Google and see
if you might be able to contact one of those people by email.  All
you'd need would be a contact person's name or email address.  Thirty
seconds of their time.  Couldn't hurt.

There is no rule about just using an ohmmeter to determine power supply
requirements.  That might work if there were purely resistive loads,
but not if there are ICs and other components.

Assuming you can stimulate the DUT with up to 18V, the board has to
supply it.  However, you may have a switching power supply on board,
that supplies the required voltages from the power supply.  You simply
don't have enough information, especially considering it's an eBay
special and isn't even guaranteed to work anyway.

Your circuit board is probably 4-layer.  Your odds of tracing things
through (especially if the power traces are in one of the middle
layers, as is usually the case) is poor.

Again, I'd spend a little more time trying to find a manual, or someone
who has worked with the instrument.

Good luck
Chris

[snip]

HTH

maybe you already found this but a quick
SEC filings  http://www.secinfo.com/$/SEC/Registrant.asp?CIK=1070799
for  ITS  revealed  filings  as recent as april 2006

ITEM  2.  DESCRIPTION  OF  PROPERTY

In  April 2006, we moved our offices to 20022 Creek Farm, San Antonio, TX
78259,
in  office space provided to us free of charge by our sole officer and
Director,
Carey  G.  Birmingham.  The office space at 20022 Creek Farm, San Antonio,
Texas
78259,  encompasses  approximately  150  square  feet  of  office  space.

PRODUCTS  ASSOCIATED  WITH  OUR  PRIOR  OPERATIONS
The products we owned and marketed up until approximately December 31, 2003,
the
date we effectively ceased all meaningful operations, were known
collectively at
the  CircuiTest  In-Circuit  Component  Test  System  and  included  the
2000S
In-Circuit  Component Test System, the CircuiTest 2100 Scanner Expansion and
the
2100  S/OAI  (Shorts/Opens  Adapter  Interface)  Shorts  and  Opens  Tester.

The  CircuiTest  2000S In-Circuit Component System was a personal
computer-based
product  which  was  used  to  troubleshoot,  test  and  allow for the
repair of
components  on  assembled  printed  circuit  boards.

EMPLOYEES

As of July 31, 2006, we had one employee, Carey Birmingham, our president,
Chief
Executive  Officer,  Chief  Accounting  Officer  and  sole  Director.

What are the part numbers of the EPROMS?  I didn't see the original post, so
I apologize if it was already covered.

...jerry

Not really, as others have said.

But if you look up the part numbers of the chips, that should give you
a pretty good idea of what kind of voltage it expects.

Good Luck!
Rich