What model is this resistor-network? - Page 1
Forum section: electronics / projects

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 09:56:16 pm
content: I tried to draw a schematic,But I encountered an unrecognizable resistor-network.It is marked with" BI 8725 1698-99-0".If anyone could tell me the exact model or data sheet, it would be greatly appreciated, thanks

author: Andy Watson
author_rank: Super Contributor
timestamp: May 15, 2025, 10:11:03 pm
content: Looks like a resistor array - probably Bi TechnologiesUnplug the package and measure the resistance between the pins.

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 10:23:01 pm
content: Thank you, can you find the data manual?I want to know the pin definition

author: Andy Watson
author_rank: Super Contributor
timestamp: May 15, 2025, 10:37:15 pm
content: Quote from: daisizhou on May 15, 2025, 10:23:01 pmNo - there are datasheets for 18 and 20 pin packages, but I can't find data for the 16 pin DIP pacakages.QuoteUnplug it and measure the resistance. The resistors will either be isolated and connected between two pins (usually across the package), or they will share a common connection to one of the corner pins.

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 11:09:28 pm
content: Is that so?Looks special

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 11:30:24 pm
content: Could it be a capacitor? Because from the analysis of the PCB traces on the back,It looks like it is a pair of

author: thm_w
author_rank: Super Contributor
timestamp: May 16, 2025, 12:26:45 am
content: A capacitor wouldn't have resistance of 3k. You did measure with it unplugged right?Similar resistor array seen here:https://www.electronicsurplus.com/bi-beckman-1698-52-0-resistor-networkhttps://www.silicon-ark.co.uk/datasheets/898-1-resistor-networks-datasheet-beckman.pdf

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 12:31:45 am
content: Yes, I removed the chip and measured it offline.

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 12:57:14 am
content: I took the measurements again, see the picture below.I still don't know the internal structure.

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 08:38:29 am
content: I disassembled the chip and measured it again. The resistance below is as shown below

author: tooki
author_rank: Super Contributor
timestamp: May 16, 2025, 11:27:41 am
content: Quote from: daisizhou on May 15, 2025, 09:56:16 pm8725 is probably the date code (25th week of 1987). The part number is just 1698-99-0. Very possibly a custom part made for the device?

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 11:48:15 am
content: Quote from: tooki on May 16, 2025, 11:27:41 amI don't know, this is the first time I've come across such a component

author: squadchannel
author_rank: Frequent Contributor
timestamp: May 16, 2025, 11:59:39 am
content: it was probably custommade based on the 698 series.

author: Andy Watson
author_rank: Super Contributor
timestamp: May 16, 2025, 12:05:29 pm
content: I think you may be correct about it being "special".Could it fit an R2R network pattern ?http://ttelectronicsresistors.com/pdf/application_notes/LADDERNETWORKS.pdfhttps://datasheet.ciiva.com/26936/getdatasheetpartid-781803-26936142.pdfI would make a 16x16 table of every possible pin-pin resistance. Tedious but you only have to fill-in half the table.

author: Andy Watson
author_rank: Super Contributor
timestamp: May 16, 2025, 12:08:22 pm
content: Quote from: tooki on May 16, 2025, 11:27:41 amI agree with this. The surrounding chips have date code of 88 or 87.

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 12:29:34 pm
content: Quote from: Andy Watson on May 16, 2025, 12:05:29 pmThanksDo I need to measure it?If you need it please let me know and I will take measurements

author: Haenk
author_rank: Super Contributor
timestamp: May 16, 2025, 03:51:43 pm
content: Quote from: daisizhou on May 16, 2025, 12:29:34 pmIMHO these values are not "crazy off the scale", but rather similar, so likely the resistor array is fine. I would not waste my time on reverse engineering it.

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 09:54:30 pm
content: Quote from: Haenk on May 16, 2025, 03:51:43 pmI want to know the structure of this resistor network.It seems to me that the pin resistance values ​​I measured are irregular.I don't even know which pin is the home pin

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 10:00:56 pm
content: Quote from: Andy Watson on May 16, 2025, 12:05:29 pmPlease see herehttps://www.eevblog.com/forum/repair/micro-switch-pressure-sensor-help-needed/This is an analog differential amplifier circuit.The final analog voltage output

author: tooki
author_rank: Super Contributor
timestamp: May 17, 2025, 12:12:45 am
content: Quote from: daisizhou on May 16, 2025, 09:54:30 pmYou can’t know it’s irregular without knowing what it is supposed to be.The problem is, it could be a structure that is way more complex than you think, and which defies simple analysis by measuring between any two pins.Chapter 4 of this old BI catalog covers all their old standard products, but there’s also a form where you can order custom networks. (So it could be literally anything the customer needed.) And like some of the standard products, they’re not limited to resistors! You can also have capacitors and diodes inside.https://archive.org/details/bi-technologies-corporation-third-edition-1996/page/3-16/mode/2upFor example of a complex resistor network structure, look at page 4-91. The -45 option (TTL to ECL conversion) would be quite difficult to figure out blind.What do you mean by “home pin”. That’s not an expression we use in English for electronics.

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 02:27:58 am
content: Thanks .I mean pin 1.This chip comes from an analog differential voltage output board.Please see the picture

author: Haenk
author_rank: Super Contributor
timestamp: May 17, 2025, 06:57:47 am
content: Quote from: tooki on May 17, 2025, 12:12:45 amIt's marked "R" on the PCB, so I would assume (or now) it's just a resistor network. Maybe check some pin combos for capacitance or diodes, if you find something being "not a resistor" - that would make things impossible to reverse."home pin" probably meant the "common" pin on most of the R-network-devices - however it might just be not that simple, like several separate networks, or one large spiderweb of resistors. But the PCB does not look overly complex, so probably not a lot of magic in there.

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 07:54:26 am
content: Quote from: Haenk on May 17, 2025, 06:57:47 amI used a digital multimeter, Select resistance and diode ranges, to test the pins in the green area and found that the upper and lower rows were independent. I drew a simple illustrationBecause the pressure sensor on this PCB is damaged, I plan to replace the pressure sensor, but I don't know its working voltage and some related electrical performance.So I planned to reverse-engineer the pcb, but the BI resistor network prevented me from doing so.

author: ivo
author_rank: Regular Contributor
timestamp: May 17, 2025, 04:44:31 pm
content: If you say it's a differential amplifier, that would align very well with having 4 equal resistors on the chip (the 74.4k's), as in a differential amplifier design. Additionally they all seem to be near multiples of ~25k. I'd guess the LM346 might be being used as a discrete instrumentation amp. The OP11 at the top might have also originally been specced as an LM346, you can see the last two extra pins in the socket not in use, per the LM346 datasheet they're for an optional extra set resistor that can set internal opamp currents in the LM346, however everything would likely still function fine if replaced with some normal 4-opamp package that doesn't use those pins.Oh yeah and a 10V ref sitting there (REF01). Seems very likely it'll be some classic instrumentation amp design.

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 05:52:57 pm
content: Quote from: ivo on May 17, 2025, 04:44:31 pmYes.A ~3.4k pressure sensor is connected to the PCB.The right side jack is the power interface (+14.3, -14.3), differential voltage output (HI, LO)

author: coppercone2
author_rank: Super Contributor
timestamp: May 17, 2025, 10:11:59 pm
content: measure pin 1 to all pins, pin 2 to all pins, pin 3 to all things, pin 4 to all things.... and so on.. then measure them all with reverse polarity.Then make a table and start eliminating values.permutations512 measurements + excel

author: floobydust
author_rank: Super Contributor
timestamp: May 17, 2025, 10:36:52 pm
content: I would say it is a custom part. Here are the "usual" pinouts. It should follow that but maybe mixed resistance values.There is one more thing to search,. I found a 1698-185-00 on eBay but no data.

author: mathsquid
author_rank: Frequent Contributor
timestamp: May 17, 2025, 11:12:09 pm
content: you'd only need 16C2 = 120 measurements.

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 12:31:07 am
content: Quote from: coppercone2 on May 17, 2025, 10:11:59 pmOK, here is the test data

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 12:41:58 am
content: Quote from: floobydust on May 17, 2025, 10:36:52 pmBased on my test data, I guess the internal structure may be like this

author: coppercone2
author_rank: Super Contributor
timestamp: May 18, 2025, 02:06:08 am
content: I think your test data says something else important that you are sure it looks like that and there does not appear to be any diodes thereWhat isis guessing a custom part because you think you see a pattern instead of knowing there is a patternI think its a good test, there is no assumptions and a clear table, no cowboy engineering

author: coppercone2
author_rank: Super Contributor
timestamp: May 18, 2025, 02:16:45 am
content: And if you REALLY wanna be sure, you gotta get the LCR meter to look for capacitors. Or capacitors and diodes that only effect AC!!!! If its true that they can put capacitors in there, which I seriously doubt. But you can put cap across resistor for some situations.And you can even have R || (C+R) . Like a snubber. I wonder if anyone ever does that for some reason?What is the scale of capacitors they can put inside of a IC anyway? Do they mean on the chip (silicon capacitor), or do they solder a capacitor in there under the plastic?actually this is more like a hybrid then silicon right? ceramic with nichrome? so I guess you could solder 0402 capacitors in there

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 02:27:10 am
content: Quote from: coppercone2 on May 18, 2025, 02:06:08 amThanks.From the data analysis, it seems that this resistor network does not seem to have any rules.The smallest resistance is more than 250 ohms, and most are around 20k-74k.Apart from being able to see that the upper and lower rows are symmetrical, I have not discovered anything else.The resistance accuracy does not seem to be very accurate.This is a traditional analog amplifier circuit board.The pressure sensor is old.A thermal stability failure has occurred，I used 4 4k resistors to form a bridge resistor network for testing,It was found that the PCB amplifier circuit was normal,The root cause of the failure is the pressure sensor itself.I tried to replace it with the current mainstream pressure sensor,But I don't know which type of pressure sensor to choose and how to calibrate it correctlyHere is my testing processhttps://www.eevblog.com/forum/repair/micro-switch-pressure-sensor-help-needed/I tried to draw a circuit schematic,But I encountered this undetermined resistor network.

author: coppercone2
author_rank: Super Contributor
timestamp: May 18, 2025, 02:38:17 am
content: Actually I don't get something. If its a linear divider why is R1 + R2 = 250 ohms. It should be 6kIf 1 and 2 is 3kand 2 and 3 is 2.7k1 and 3 should be 5700 but you measure 250You are measuring out of circuit right??"?? Measuring in circuit is bedlam and only used for gross fault findingIn the drawing you have there is resistors in a line. that means they should add up.If 3000+2700=250 you got some kinda shit going on thereA branch possibly? Y

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 02:47:19 am
content: Quote from: coppercone2 on May 18, 2025, 02:38:17 amMe too。I can't find any mathematical logicI measured it offline because I understand that online measurement is not accurate.There are some errors in the picture, they cannot be connected together, I just want to show that the upper and lower rows are independent

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 02:53:38 am
content: They appear to be symmetrical.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 18, 2025, 03:36:45 am
content: The internals seem to be different from the simple chain.Some parts seem to add up (depending on how accurate the readings are): e.g. a partial chain between pins 1 - 3 - 2 or 5 - 4 - 6.However others don't add up so easy.From the described use it could be a bit like a network for gain switching at a instrumentation amplifier, maybe with additional resistors to keep resistance symmetrical.

author: coppercone2
author_rank: Super Contributor
timestamp: May 18, 2025, 03:49:07 am
content: there is dual terminator network too, someone would need to try to draw itisolatedbusseddividerdual terminator (differential?)mixtures

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 03:59:47 am
content: You mean I try to reverse engineer the PCB,Then conduct a comprehensive analysis to try to infer this resistor network?

author: coppercone2
author_rank: Super Contributor
timestamp: May 18, 2025, 04:20:04 am
content: No I mean draw the values that make sense on the chip for the resistors that are between pins that klienstein said and then try to solve the puzzle for the rest

author: amyk
author_rank: Super Contributor
timestamp: May 18, 2025, 04:58:56 am
content: Based on the measured values, this is my attempt at determining the topology. It looks like there's a 250, a 2k75, a 6k2, and several 24k8 resistors. All the measured values agree within 1%.

author: coppercone2
author_rank: Super Contributor
timestamp: May 18, 2025, 05:06:02 am
content: That looks like it works out mathematically I am just wondering WTF it is doing lolIt makes sense that its weird because its something for the dr's office it looks like, or some weird lab

author: amyk
author_rank: Super Contributor
timestamp: May 18, 2025, 05:33:05 am
content: The right side looks like a 1:4:8 ratio.The left side is more mysterious. 250 (or 251/252 as measured) is just a little over 1% of 24k8, but 2k75 is not 10% of 24k8 either.

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 05:53:24 am
content: Quote from: amyk on May 18, 2025, 05:33:05 amThanks.Give me some time and I will try to draw the schematic.Maybe the reason can be known by combining the schematic diagram.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 18, 2025, 07:22:41 am
content: Quote from: coppercone2 on May 18, 2025, 05:06:02 amIt could be resistors for an INA, with a few options for gain switching.Something like the 250 Ohm (or alternative the 2.7 K) (single, series or parallel) and 2 x 24.7 K for the first stages and than 4 x 24.7 K for the final differential stage. The 6.2 K and additional 24.7 K could be for gain options with the output stage.

author: dietert1
author_rank: Super Contributor
timestamp: May 18, 2025, 07:31:46 am
content: A nice little sudoku. I arrived at the same solution as amyk.The first four pins form a 1:10 or a 1:100 divider. The other pins add more ratios like 1:50 etc. Maybe the feedback network of a switched gain opamp stage, with pin 3 the negative feedback input and pin 4 the output. Pin 1 or pin 2 would be connected to Gnd.Regards, Dieter

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 12:15:53 pm
content: Quote from: amyk on May 18, 2025, 05:33:05 amI have drawn a schematic, but it seems that 1698-99-0 has not fully utilized all the pins.Can you know the functional purposes of R1109 (TC), R1102 (NULL), R1104 (XD BAL), R1116 (ZERO), and R1123 (VB SET)?

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 12:45:03 pm
content: Quote from: Kleinstein on May 18, 2025, 07:22:41 amAs can be seen from the schematic diagram, the PCB circuit board is powered by 29.18v.HI and LO are output signals,The PCB does not have a gear switching circuit.As can be seen from the actual picture, the host flow part has 2 gears,A solenoid valve is used to switchhost manual(https://mega.nz/file/sMYVDYCS#Uezoi3J0ui5RHs7EFoCrBJ3jXdoJ0x2UB1VggLn92Lw)

author: Kleinstein
author_rank: Super Contributor
timestamp: May 18, 2025, 04:01:20 pm
content: For the schematics it looks like they use only a part of the resistor network. Could be as a part also used in other instruments and having enough of them.Different gain options could be with switches in the circuit, but of cause also just using different parts of the chip via a fixed layout or jumper options to populate or not.

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 11:20:52 pm
content: I followed the manual instructions and tried adjusting R1102(NULL)，Connect the digital multimeter to the HI and LO test pins and observe the voltage changes.Rotate the R1102 (NULL) adjustable resistor, and the HI-LO voltage will indeed increase or decrease accordingly,Adjustable to 0 +/-.005vdc ultimately.At the same time, in the host panel, enter "30",View V/F Converter,Can reach 375+10.（I did not adjust the R33）Currently, we only know the function of the R1102 (NULL) adjustable resistor, and the functions of other adjustable resistors are unknown.*Since the thermal stability of the pressure sensor has failed, the final accurate data cannot be stabilized, so I plan to replace the pressure sensor*

author: daisizhou
author_rank: Super Contributor
timestamp: May 23, 2025, 06:06:15 am
content: Hallo everyone.I want to know what changes will occur when adjusting R1109(TC),I tried to analyze the signal and finally the signal went into the 9th pin of "1698-99-0"I'm lost, if anyone can help me, I'd be very grateful

author: ivo
author_rank: Regular Contributor
timestamp: May 24, 2025, 03:37:08 pm
content: It likely stands for Temperature Compensation. Likely related to this in the manual:QuoteI would guess that as long as it was set correctly at the factory and its not aged badly in any way, it's probably still likely very close to its perfect value. Without the Factory / Internal full cal procedure available, or a lot more information / reverse engineering, fiddling with it might do more harm than good.

author: daisizhou
author_rank: Super Contributor
timestamp: May 24, 2025, 10:17:15 pm
content: I took a video, please watch it

author: Terry Bites
author_rank: Super Contributor
timestamp: May 28, 2025, 05:21:38 pm
content: See attached horrible schematic from another posthttps://www.eevblog.com/forum/projects/help-differential-amplifier-circuit-analysis-temperature-compensation/msg5928636/#msg5928636