Recent Posts

1

Beginners / Re: Oscilloscope advice

« Last post by Xena E on Today at 02:18:52 am »

In English "particularly" means "specifically" and/or "especially". Or are you using another less usual meaning of "particularly? If so, enlighten us.

Your comment may have been meant to help the OP, but it was - as you have "clarified" - wrong.

OK. I sense this seems important to you, so have it your way, though I'm not sure quite what point you want to make?

My meaning was "****** but not meaning exclusively". My apologies, English is a third language, (insert your own word).

Perhaps the 'moisture' affected equipment that I've seen was caused by some other phenomenon being as you have so kindly pointed out that I am wrong.

Regards,
Xena.

2

RF, Microwave, Ham Radio / Re: How do you verify an impedance matching network?

« Last post by AJ528 on Today at 02:15:04 am »

Wouldn't measuring impedance from the 50 ohm side only tell me if that side is 50 ohms? How does that help me verify I have matched the impedance between the amplifier and matching network?

3

Projects, Designs, and Technical Stuff / Small wire joiners

« Last post by Factotum on Today at 02:09:30 am »

Scenario - I frequently need to in-line join pairs of stranded cables around the 24AWG / 0.5mm² size (used for small speakers in temporary installs).

I thought of DC barrel jacks (fiddly) and then moved on to XT30 connectors (no back shells) but all of these require soldering.

I'm looking to avoid having to solder things for repairs or changes in the field. Crimping a ferrule is a lot easier.

I use a ton of ferrules on these cables for other projects when they go in to screw terminal side of other connector systems.

Wago type lever nuts seem to be ferrule compatible. I also see a lot of DIN mounted "spring" connectors but not in-line.

Is lever the answer? These connectors are inside waterproof sections of housing and primary purpose is to make transport modular and infrequent dis/connect easier.

Anything I should be looking at? Thanks!

4

RF, Microwave, Ham Radio / Re: How do you verify an impedance matching network?

« Last post by szoftveres on Today at 02:07:25 am »

How about building your amplifier and matching network, then measure from the 50ohm side? If the output impedance isn't what you're looking for then you can continue tweaking your matching network.

5

Beginners / Re: BM786 continuity beep not latched

« Last post by J-R on Today at 02:00:55 am »

I personally don't like the scratchy sound either.  One solution: Dave can offer firmware version flash options in his store at an extra charge.

Possible, but postage is a killer.

I mean as part of the initial purchase.  Take it out of the box, flash it, then ship it.

6

Projects, Designs, and Technical Stuff / Re: Reverse-engineering misc. avionics (ongoing)

« Last post by D Straney on Today at 01:54:01 am »

Mystery signal conditioner card
I couldn't resist the shininess of this board:



What does it do though??
There's a lot of different part numbers sprinkled around, but the only one that gets any hits in aerospace/military parts supplier databases is 8601260-503 = NSN 6605-00-106-2537.  This is in the "Navigational Instruments" supply group, but there's no other info besides that.  Let's see what we can find out...

The board is full of gold-plated flatpacks with custom part number markings.


You can see how each one is a little "ice cream sandwich" of metal-ceramic-metal:



Luckily, I was able to find records for each of the part numbers, from the same aerospace/military supplier websites.  4x of the 10-pin packages are "hi-rel" versions of the LM110/LM102 buffer amplifiers, and 2x are the same for the classic LM741 op-amp.  Some of the others had more ambiguous descriptions, so I decided to pop their lids and look further:


7118771 = Fairchild 9624

Code: [Select]

NSN 5962-00-735-8092

Supply Group (FSG) NSN Assign. NIIN Item Name Code (INC)
59 31 MAR 1972 00-735-8092 31779 ( MICROCIRCUIT, DIGITAL )

Part Number Cage Code Manufacturer
351-7428-010 13499 ROCKWELL COLLINS, INC. DBA GOVERNMENT SYSTEMS
7118771-1 06481 NORTHROP GRUMMAN SYSTEMS CORPORATION
7118771-1 17863 LITTON SYSTEMS INC GUIDANCE AND CONTROL SYSTEMS DIV
8560220 16170 TELEDYNE TECHNOLOGIES INCORPORATED DBA TELEDYNE MICROELECTRONIC
9624FM 07263 FAIRCHILD SEMICONDUCTOR CORP
DMS 84109B 16236 DLA LAND AND MARITIME
HL50058 07263 FAIRCHILD SEMICONDUCTOR CORP
SL10971 07263 FAIRCHILD SEMICONDUCTOR CORP
U31962451X 07263 FAIRCHILD SEMICONDUCTOR CORP
U3I962451X 07263 FAIRCHILD SEMICONDUCTOR CORP

Characteristic Specifications
OUTPUT LOGIC FORM TRANSISTOR-TRANSISTOR LOGIC
DESIGN FUNCTION AND QUANTITY 2 CONVERTER, INTERFACE
INPUT CIRCUIT PATTERN DUAL 3 INPUT
VOLTAGE RATING AND TYPE PER CHARACTERISTIC -0.5 VOLTS MINIMUM POWER SOURCE AND 5.5 VOLTS MAXIMUM POWER SOURCE
OPERATING TEMP RANGE -55.0 TO 125.0 DEG CELSIUS
TERMINAL TYPE AND QUANTITY 14 FLAT LEADS
TERMINAL SURFACE TREATMENT GOLD
INCLOSURE CONFIGURATION FLAT PACK
INCLOSURE MATERIAL CERAMIC AND GLASS
BODY LENGTH 0.240 INCHES MINIMUM AND 0.260 INCHES MAXIMUM
BODY HEIGHT 0.080 INCHES MAXIMUM
BODY WIDTH 0.225 INCHES MINIMUM AND 0.250 INCHES MAXIMUM
MAXIMUM POWER DISSIPATION RATING 400.0 MILLIWATTS
STORAGE TEMP RANGE -65.0 TO 150.0 DEG CELSIUS
FEATURES PROVIDED HERMETICALLY SEALED AND MONOLITHIC AND POSITIVE OUTPUTS
III UNPACKAGED UNIT WEIGHT 0.26 GRAMS
III PRECIOUS MATERIAL GOLD
III PRECIOUS MATERIAL AND LOCATION TERMINAL SURFACE GOLD


It took me a look at the bare die to figure it out, but this is a standard part, the Fairchild 9624 "dual CCSL-to-MOS translator".  Bitsavers came to the rescue here; see page 220 of this PDF of their 1970 catalog - there's even an internal schematic on the next page.  "CCSL" stands for "Compatible Current Sinking Logic", Fairchild's name for their DTµL (diode-transistor), TTµL (transistor-transistor), and LPDTµL (low-power diode-transistor) logic families - these are all bipolar-transistor-based digital logic, from before everything somewhat standardized on either CMOS or LS-TTL.

7118777 quad switch

Code: [Select]

NSN 5962-00-489-2884

Supply Group (FSG) NSN Assign. NIIN Item Name Code (INC)
59 17 MAR 1972 00-489-2884 31778 ( MICROCIRCUIT, LINEAR )

Part Number Cage Code Manufacturer
7118777 06481 NORTHROP GRUMMAN SYSTEMS CORPORATION
7118777 17863 LITTON SYSTEMS INC GUIDANCE AND CONTROL SYSTEMS DIV
M1010 15818 TELCOM SEMICONDUCTOR INC
SM9867 27014 NATIONAL SEMICONDUCTOR CORPORATION

Characteristic Specifications
DESIGN FUNCTION AND QUANTITY 4 SWITCH, ANALOG
INPUT CIRCUIT PATTERN 4 CHANNEL
VOLTAGE RATING AND TYPE PER CHARACTERISTIC -35.0 VOLTS MINIMUM POWER SOURCE AND 35.0 VOLTS MAXIMUM POWER SOURCE
OPERATING TEMP RANGE -55.0 TO 105.0 DEG CELSIUS
TERMINAL TYPE AND QUANTITY 14 FLAT LEADS
TERMINAL SURFACE TREATMENT SOLDER
INCLOSURE CONFIGURATION FLAT PACK
INCLOSURE MATERIAL CERAMIC
BODY LENGTH 0.380 INCHES MAXIMUM
BODY HEIGHT 0.065 INCHES MAXIMUM
BODY WIDTH 0.240 INCHES MINIMUM AND 0.260 INCHES MAXIMUM
MAXIMUM POWER DISSIPATION RATING 200.0 MILLIWATTS
STORAGE TEMP RANGE -65.0 TO 150.0 DEG CELSIUS
FEATURES PROVIDED HERMETICALLY SEALED AND MONOLITHIC AND W/SWITCH
TEST DATA DOCUMENT 17863-7118777 DRAWING
III UNPACKAGED UNIT WEIGHT 0.4 GRAMS

This one turned out to have 4 (identical) discrete MOSFETs inside.


These MOSFETs (confirmed with diode-check) are interesting because they have a lateral arrangement and a separate substrate connection.  The typical discrete MOSFETs you'd buy these days, packaged, have a vertical construction where the current flows from top to bottom (drain to source), and the substrate and source are tied together to add the "body diode" and prevent certain parasitic effects.  With these MOSFETs though, the current flows laterally along the surface just like in the simplified diagrams that textbooks show to illustrate basic operation; the substrate (which serves as the "reference potential" for the gate voltage) isn't internally connected to the source terminal, and so all 4x MOSFETs share the same substrate connection from the gold-plated base plate, which is connected externally to pins 1 & 8.

Here's an annotated view of the MOSFET structure.  You can see how the gate winds back and forth between the source & drain terminals: this creates a low on-state resistance, by creating a short but wide path (like a short piece of very thick wire).

There's also a small silicon-substrate resistor in series with the gate terminal.

7104104 dual switch

Code: [Select]

NSN 5962-00-491-4863

Supply Group (FSG) NSN Assign. NIIN Item Name Code (INC)
59 18 MAR 1972 00-491-4863 31778 ( MICROCIRCUIT, LINEAR )

Part Number Cage Code Manufacturer
7104104 06481 NORTHROP GRUMMAN SYSTEMS CORPORATION
7104104 17863 LITTON SYSTEMS INC GUIDANCE AND CONTROL SYSTEMS DIV
8560045 15818 TELCOM SEMICONDUCTOR INC
8560045 16170 TELEDYNE TECHNOLOGIES INCORPORATED DBA TELEDYNE MICROELECTRONIC

Characteristic Specifications
DESIGN FUNCTION AND QUANTITY 2 SWITCH, FIELD EFFECT TRANSISTOR
INPUT CIRCUIT PATTERN DUAL 2 INPUT
VOLTAGE RATING AND TYPE PER CHARACTERISTIC -40.0 VOLTS MINIMUM POWER SOURCE AND 35.0 VOLTS MAXIMUM POWER SOURCE
TIME RATING PER CHACTERISTIC 150.00 NANOSECONDS MAXIMUM PROPAGATION DELAY TIME, LOW TO HIGH LEVEL OUTPUT AND 150.00 NANOSECONDS MAXIMUM PROPAGATION DELAY TIME, HIGH TO LOW LEVEL OUTPUT
OPERATING TEMP RANGE -55.0 TO 100.0 DEG CELSIUS
TERMINAL TYPE AND QUANTITY 14 FLAT LEADS
TERMINAL SURFACE TREATMENT SOLDER
INCLOSURE CONFIGURATION FLAT PACK
INCLOSURE MATERIAL CERAMIC AND GLASS
BODY LENGTH 0.395 INCHES MAXIMUM
BODY HEIGHT 0.075 INCHES MAXIMUM
BODY WIDTH 0.275 INCHES MAXIMUM
STORAGE TEMP RANGE -65.0 TO 150.0 DEG CELSIUS
FEATURES PROVIDED HERMETICALLY SEALED AND MONOLITHIC AND NEGATIVE OUTPUTS AND POSITIVE OUTPUTS
TEST DATA DOCUMENT 17863-7104104 DRAWING
III UNPACKAGED UNIT WEIGHT 0.4 GRAMS

This turned out to be a full hybrid module, with resistive traces and multiple bare dies mounted to a ceramic substrate:

The bare dies also catch the light really nicely at the right angle:

Here's the contents:

The larger dies with the semi-dogbone-style pattern are diodes, while the smaller dies with the interdigitated patterns are JFETs used as analog switches.  This is the internal schematic:

You can see how it makes a nicely-self-contained dual analog SPST switch.  Each JFET gate has a resistor to pull the gate up to the source voltage by default (turning the JFET on, with Vgs = 0V), but with a diode so that an external voltage can pull the control pin low to turn off the JFET without having to exactly match the source voltage.  There's also a small resistor optionally in series with each drain terminal, but it isn't used here.

7118781 resistor array

Code: [Select]

NSN 5905-00-481-7705

Supply Group (FSG) NSN Assign. NIIN Item Name Code (INC)
59 11 MAR 1972 00-481-7705 32068 ( RESISTOR NETWORK, FIXED, FILM )

Part Number Cage Code Manufacturer
7118781 06481 NORTHROP GRUMMAN SYSTEMS CORPORATION
7118781 17863 LITTON SYSTEMS INC GUIDANCE AND CONTROL SYSTEMS DIV
7118781 57027 INTERNATIONAL RESISTIVE COMPANY OF TEXAS LP
8560705 16170 TELEDYNE TECHNOLOGIES INCORPORATED DBA TELEDYNE MICROELECTRONIC

Characteristic Specifications
ELECTRICAL RESISTANCE 10.000 KILOHMS
IDENTICAL VALUE RESISTOR QUANTITY 4 EACH RESISTOR
RESISTANCE TOLERANCE IN PERCENT -10.000 TO 10.000
POWER DISSIPATION RATING IN WATTS 0.020 EACH RESISTOR
AMBIENT TEMP IN DEG CELSIUS AT FULL RATED POWER 25.0
AMBIENT TEMP IN DEG CELSIUS AT ZERO PERCENT RATED POWER 100.0
TEMP COEFFICIENT OF RESISTANCE IN PPM PER DEG CELSIUS -100.0 TO 100.0
TEMP RANGE OF TEMP COEFFICIENT IN DEG CELSIUS -55.0 TO 100.0
SCHEMATIC DIAGRAM DESIGNATOR 5 SERIES NETWORK
INCLOSURE METHOD ENCAPSULATED
STYLE DESIGNATOR 219 FLAT PACK
BODY LENGTH 0.275 INCHES MAXIMUM
BODY WIDTH 0.395 INCHES MAXIMUM
BODY HEIGHT 0.075 INCHES MAXIMUM
TERMINAL TYPE PIN
TERMINAL QUANTITY 6
RELIABILITY INDICATOR NOT ESTABLISHED
TERMINAL LENGTH 0.250 INCHES MINIMUM

This is the least exciting of the custom parts - just a resistor array, so I didn't bother opening it up and instead probed the terminals with sewing needles to pierce the conformal coating and measure the internal continuity.

Schematic!
Because the PCB is only 2 layers and the circuitry is sparse, the connections were easy to trace by overlaying photos in an image editor.  The real "meat" is going on in the analog section:

There's three separate signal sources that can get selected on a single output pin (# 20, at the right-hand side).  Two come from identical sample-and-hold circuits, and one comes from a buffer-then-offset circuit, which can itself take its input from two separate sources (4 separate selectable signal sources total).  Interesting points are:

• Having multiple analog input channels multiplexed like this suggests to me that this is meant to feed either a computer's ADC, or a single-channel telemetry transmitter, each of which can only sample a single analog input at a time and therefore need to cycle through each input individually.
• The sample-and-hold capacitors are non-polarized tantalum caps so that the input can be either positive or negative.  These are usually constructed as two back-to-back polarized caps, as electrolytic types will act (approximately) as a short when reverse-biased.
• Both sample-and-hold sharing a common "sample" and "discharge/reset" signal suggests that this might be used for reading the quadrature signals from a mechanical synchro-style encoder.

As all this circuitry involves conditioning analog signals, the "SC4" on the frame of the card might stand for "Signal Conditioner (#4)":


The digital side is less interesting, and just involves generating all the control signals to drive the analog switches, using those Fairchild 9624 ICs discussed earlier:

The fact that the digital signals had to be converted from DTµL/TTµL makes me think that the digital control circuitry in the rest of this mystery navigational equipment was a "discrete processor" built from individual logic ICs, or just a bunch of state machines (also built from individual logic ICs).  Commercial single-chip "integrated" CPUs like the Intel 8008 were all CMOS at the time, as far as I know - it's also unlikely it used an integrated CPU for other reasons.  The date codes on the ICs here are from 1977, but this board was likely designed at least a few years before that, considering all the qualification testing that a high-reliability design has to go through.  The first commercial single-chip CPUs had only just arrived in the early 70's, and took a lot longer to catch on in high-reliability applications.  The Texas Instruments SBP9900 become popular for avionics & military electronics, but that was released too late (1978+) to be involved in this particular design - although you can see a similar one in a tank's fire control computer I took apart.

Let me know if you have any other insights.

Oh, and let's take one final magpie-like look at all that gold:

7

General Technical Chat / Re: SPICE Generates nonsense with near-zero resistor values.

« Last post by amyk on Today at 01:52:24 am »

It's a good example of low-level details leaking to end-user. And the key finding is that this is unavoidable. It leaks anyway, they can just choose how:

1) They can choose higher precision numbers, and loss of performance. Nearly 100% of users would be pissed and complain, or,
2) They can choose performance over numerical correctness in rare corner cases. But in some cases users accidentally (or purposely) create those conditions and are pissed.

It's a lose-lose situation.

They could also choose to dynamically increase precision from hardware FP to software arbitrary-precision when they detect it's necessary, like some programming languages do, but that's even more complexity.

8

RF, Microwave, Ham Radio / How do you verify an impedance matching network?

« Last post by AJ528 on Today at 01:51:14 am »

If I have an RF amplifier where I know it's source impedance, I can either use math or simulations to find a theoretical matching network to turn it into 50 ohms. However, reality is often different than theory, so once it is built, how can I verify this matching network to make sure the components are optimal? If I replace the RF amplifier with an SMA jack, is it as simple as hooking up a VNA, measuring the impedance, and verifying it is the complex conjugate of the RF amplifier source impedance?
If that is a good approach, how do you make sure your measurement plane using the SMA jack matches the RF amplifier?

Is it also possible to verify the matching network by having the amplifier output a continuous wave, measuring the 50 ohm side, and verifying you are seeing the max power being output?

Essentially, I am thinking of making a test PCB with 2 identical circuits, except replacing the RF amplifier with an SMA jack on one (see attached image). Will this work how I think it will? Is there a better way to verify impedance matching?

9

Test Equipment / Re: LCR Tweezer Fnirsi ST-1 versus Zoyi MD-1

« Last post by DaneLaw on Today at 01:48:42 am »

I don't think I have tested either of them on diodes yet, It's kind of an uphill battle with 0.3v and 0.6v.

Just how ?
Any half decent diode test will display Vf regardless of value.

As emphasized, haven't tested diodes with either of these, so what it does and doesn't do in regards to diodes - and if its a half-decent diode-tester after your perspective of "decent".

You could get one and find out - if these 19.5$ LCR tweezers are "half decent" diode-tester after your own criteria of half-decent....I somewhat doubt it... do also recall an obs-notice in the manual about the use' when testing diodes. (*manuals posted above)
I usually turn to other items when testing diodes, but that's another matter.

// Here buddy...https://www.keepontesting.com/post/zoyi-zt-md1-bonus-review   
I found an article who tested numerous diodes with the Zoyi MD1, so you can go and read his feedback, and see if its your "half-decent" diode tester.

I haven't tested diodes with it, so cant help you, though, do have in mind, its not the ST1 as Skander36 refers to, but the other MD1 model in this thread..
The article do highlight limited current when dealing with diodes... 

10

Thermal Imaging / Re: FLIR PathfindIR (Version 1) command set ?

« Last post by Neo1487 on Today at 01:47:36 am »

I also have flir pathfindir v1 model 334-0001-00PS. This is the standard version without full features. I tried communicating via serial but no response. I measured with oscilloscope and saw signal on digital video pins but I can not decode.