HP Logic Comparator finds VCC and common by itself - what sourcery is this? - Page 1
Forum section: electronics / beginners

author: py-bb
author_rank: Regular Contributor
timestamp: July 30, 2023, 01:04:33 pm
content: I have a HP 10529A and it's great.The manual claims it'll find VCC and common by itself - I've looked at a service manual for the circuit diagrams but I seem to only get the input board with the ZIF socket.It seems to work really well.How does it do this?It seems to work fine with open collector stuff (page 13) it's certainly great with TTL/push-pull/totem-pole (I prefer the middle name - I don't judge whichever you know it as)https://xdevs.com/doc/HP_Agilent_Keysight/HP%2010529A%20Operation%20Only.pdfCan anyone share this with me?Does it assume that all non-vcc-or-common-pins will be within a diode-drop of the other pins?ThanksPS I also have the logic clip but some LEDs appear to be a bit iffy. Any ideas on getting inside and getting it back together?

author: radiogeek381
author_rank: Regular Contributor
timestamp: July 30, 2023, 01:16:38 pm
content: Sections 2-12 and 2-13 in the manual describe soldering the reference IC GND and VCC pins to specific positions on the reference module.Not that it isn't possible to find GND and VCC if you put some restrictions on the conditions. (Like none of the pins are moving.)

author: py-bb
author_rank: Regular Contributor
timestamp: July 30, 2023, 01:19:30 pm
content: Quote from: radiogeek381 on July 30, 2023, 01:16:38 pmRespectfully you note makes no sense.The first bit - you don't have to use those cards.There's a test card that has a ZIF socket, you drop your chip in and go. The DIP switches are ONLY for marking outputsThe clip will go on the DUT and draw power and find VCC and common by itself.You're confusing the "cards" you can make, it comes with 10 cards and a drillbit, you mangle the metal traces of outputs (or inputs, RTFM) - like setting the DIP switches on the ZIF module and solder VCC and gnd to your test chip which you then solder inNote that the VCC and common traces are already there, it finds them for you and provides them to your "reference chip" for you to connect to it.

author: alm
author_rank: Super Contributor
timestamp: July 30, 2023, 02:39:04 pm
content: Maybe it assumes any digital input will have ESD protection diodes to ground and Vcc. So the pin that is the cathode of the diodes of many other pins is vcc, and the pin that is the anode is gnd. Apply voltage to a set of pins and look for pins one diode drop above or below this voltage. If one of each, then they are your Vcc and ground. If not, then supply voltage to another set of pins.Also Vcc and ground pins were standard on most logic gates.

author: edavid
author_rank: Super Contributor
timestamp: July 30, 2023, 02:43:43 pm
content: It just has diodes from each pin of the test clip to Vccand ground. The highest voltage on the clip is Vccand the lowest is ground.

author: py-bb
author_rank: Regular Contributor
timestamp: July 31, 2023, 11:03:13 pm
content: Quote from: edavid on July 30, 2023, 02:43:43 pmQuote from: alm on July 30, 2023, 02:39:04 pmYou were both right.Aim/Alm - you were off in that it DEFINITELY doesn't assume positions.What diodes and how many thought?http://bitsavers.org/test_equipment/hp/probes/10529-90005_10529A_Logic_Comparator_Operating_and_Service_Manual_197308.pdf#page=58&zoom=160,11,465That transistor and the "CR" strike me as some sort of active system, it seems to like any system - I've tried it with some 3.3v stuff and some 6v stuff - it says 7v max so no 12v stuff.