I have found mixed results using the BugTrap. It is very good at picking
up shorted output gates, and failed dividers, and fairly good at clock
errors, but it is not so good on marginal circuits (close to the
recommended load limits of the TTL ICs in question).
We do use ours on a fairly regular basis - I have the last model that
would even do Tri-state 20 pin devices (buffers! 74LS244s etc.) - and as
long as I double check the results it is handy to have.
I particularly like using it on old TTL logic boards - like PONG and
Computer Space and some others that are a PITA to trace through. I
sometimes just go through these boards with a collection of NTBG ICs and
start with the 7474's and work out. (In older TTL boards the 7474's and
similar flip-flops seem to fail the most along with 74161
(9316s)).
Can service some boards even without a schematic that way.
The first model (TTL only) works as well as the HP version, but you don't
need a bunch of cards - you just flip the switches to match
inputs/outputs. Like I say it is good on early TTL level boards. - I was
thinking of updating it with HCTL replacements but never got around to
it...
John :-#)#
At 08:51 AM 28/07/2003 -0400, James S. Bright wrote:
Actually, I just picked up an HP comparator
too. I had deferred getting one, mostly because of kev's
comments:
http://users.erols.com/mowerman/bugtrap.htm
(This is a "Bug Trap" but I believe
it's pretty much the same concept).
I'll be very interested to hear how you make
out. I tend to use a logic probe for checking most of the 74xxx chips,
but there are a couple chips, like shift registers, that I can't test
that way. I'm hoping that the logic comparator can help.
--James Bright
www.QuarterArcade.com
Restored Arcade Games for your Home
- ----- Original Message -----
- From: Chris
Toseland
- To: TechToolsList
(E-mail)
- Sent: Monday, July 28, 2003 8:24 AM
- Subject: HP Logic Comparators
- Hi All,
-
- This Weekend I've been trying to use my HP
Logic Comparator to help fault find some boards and am getting some very
hit and miss results.
-
- What I'd like to know is are there certain
chips that this equipment won't test correctly?
- I know that if an output is onto a bus
it'll read bad but what about simple stuff like 74ls04 it fails that then
works fine with a 74ls08. It definately doesn't like
74ls283's.
- I have tried 3 or 4 different comparison
IC's so it's not down to a bad one of them.
-
- It even fails chips on known working boards
that I'm using for signal comparison with the scope.
-
- I'd like to use it so I can some of my
backlog out of the way but it seems just to unreliable for serious fault
finding.
-
- Do I just put it down to tarnished IC legs
or something? Any of you have any input?
-
- thanks
-
- Chris
-
- http://www.muppzlab.co.uk