hybridfree/eevblog-posts huggingface dataset:
waveform output with gate drivers - Page 1
Forum section: electronics / beginners

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: August 27, 2019, 08:45:33 pm
content: Are gate drivers such as the type depicted capable of driving gates with sines, ramps, triangles or other arbitrary waveforms other than squares?The capacitive and opto isolated drivers cannot reproduce the input waveform thereby them being intended for switching only however - this is about the TC4420/TC4429 gate driver.

author: senso
author_rank: Frequent Contributor
timestamp: August 27, 2019, 08:58:49 pm
content: Thats a NOT Schmitt trigger in the signal path, so it will only output square waves.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: August 27, 2019, 09:18:27 pm
content: There are many driver varieties, are there any capable of arbitrary waveform output?Maybe a class ab power opamp but those are only for audio frequencies.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 27, 2019, 11:34:03 pm
content: No. No one needs linear gate drivers (for better or worse).If you want to make a MOSFET amplifier, you probably need more than just an analog isolator, rather a high side current control.Hmm, I drew up an amp along such lines years ago, don't know if I have it handy...guess I'll have to print off a copy, here:https://www.seventransistorlabs.com/Images/Power_OTA2_Sch.pdfIt's a diffamp, level shifter (constant currents), local diffamps (sets current through respective transistor), output. Common mode current sets quiescent bias, differential input voltage sets output current sets output voltage. So it's a transconductance amplifier first and foremost hence the name, with voltage feedback to give a fairly ordinary voltage gain response.The simulated bandwidth is quite good, something like 10MHz, but the phase shift is quite large at cutoff (>180°?) so can't run in a voltage feedback loop nearly so quickly. It's not clear if a real version would actually achieve that much bandwidth, but 100s of kHz seems likely.Note the 6V "batteries"; I was going to use a pair of DC-DC modules for that.Never did build it, but made most of a PCB, IIRC.For higher voltages, the high side level shift will be that much more sensitive to voltage swing; a differential stage should be used. A contemporary digital example is here:https://www.seventransistorlabs.com/Images/CMBuck_Output.pngBut anyway, the point is, by putting some control circuitry at the transistor, you can solve one of the harder problems otherwise, which is setting current in a reasonable way. A traditional audio amp structure (diffamp, gain stage, follower) assumes the output follows the gain stage voltage, which is necessarily the case for BJTs, but not with MOSFETs, and isn't easy to adapt for N-channel types (P-channel types aren't available in high voltages, or high speeds now that SiC MOS is an option too). This control can be integrated as part of the level shifting so you dilute the impact of not having an explicit isolator, or don't much care in the first place.Tim
Wavetek DM27XL No display - Page 1
Forum section: electronics / beginners

author: Steve1851
author_rank: Newbie
timestamp: June 23, 2019, 12:50:07 am
content: Hello everyone.I have a Wavetek 27XL multimeter with no display. I was wondering if anyone out there is familiar with the UM7108F chip. On pins 5 & 6 there is a crystal that doesn’t seem to be oscillating. Does anyone know what the function of this particular clock circuit is?The clock on pins 41, 42, and 43 is working.The clock input on pin 36 is not connected. Just as the print shows.This is the closest print I can find:https://320volt.com/wp-content/uploads/2011/05/Unit-UT70A-UT70A-schema-UT70A-circuit-Digital-MultiPurpose-Meters.gifThanks for your help in advance.Steve

author: Steve1851
author_rank: Newbie
timestamp: June 23, 2019, 05:48:01 pm
content: The correct model is Wavetek 27XT. Sorry for the wrong model.From the Data sheet I can't tell if the LCD frequency's come from the clock input on pin 5 and 6 or the other clock input. Is anyone out there familiar with the UM7108F DMM IC?

author: retiredcaps
author_rank: Super Contributor
timestamp: June 24, 2019, 02:38:21 am
content: This thread and the links within it might give some clues?https://www.eevblog.com/forum/testgear/broken-wavetek-dm27xt/

author: Steve1851
author_rank: Newbie
timestamp: June 28, 2019, 05:00:47 pm
content: The prior thread provided no help. I couldn't find anything on the web to answer this question. However, to answer my own question, the crystal oscillator does provide the signals to "excite" the LCD. Without it working you will get random segments, some lit and some not.

author: mholin
author_rank: Newbie
timestamp: September 25, 2025, 11:57:38 am
content: Hello. I know this is an old post but I have the same issue with my DM27XT. I over voltaged it and blew a couple resistors as well as the UM7108F. Got a replacement on ebay but think they might be counterfeit parts as the display is random and fades out after the power is applied. Was wondering if you had any more insight into the display issue?Best, Mark
wavetek/stabilok si4015 memory card wanted - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: August 24, 2025, 10:06:08 am
content: Can anyone point me in a direction where i can buy beg steal or borrow memory cards for a wavetek si4015 comunication monitor? thanks.

author: ME
author_rank: Frequent Contributor
timestamp: August 24, 2025, 10:29:07 am
content: I an after an SRAM card of between 32K and 128K. It needs to be a 34-pin one if that helps.

author: ME
author_rank: Frequent Contributor
timestamp: August 26, 2025, 07:55:57 am
content: this is what the guy told me:You’re after an SRAM card of between 32K and 128K. It needs to be a 34-pin one, most are 68-pin PCMCIA ones. Unfortunately they’re a bit of a thing of the past and go for a lot of money, sometimes hundreds on ebay and most are untested as no-one has the means to do so.Best Regards,Does anyone know what a 34 pin connector that will plug into these is called and where can i find them?, regards.

author: ME
author_rank: Frequent Contributor
timestamp: August 27, 2025, 09:55:58 am
content: Well i found 2x 32kb used cards for £23 inc postage , now need a way to write a bin file to them!.

author: ME
author_rank: Frequent Contributor
timestamp: August 29, 2025, 06:49:18 pm
content: I found 4 of these now and they are enrout so search over.
Way(s) to use SMD LED/resistor on breadboard - Page 1
Forum section: electronics / beginners

author: Jaunedeau
author_rank: Regular Contributor
timestamp: November 24, 2015, 08:17:21 am
content: Hi,I needed a way to test some SMD components on a breadbord. I came up with a solution that is so clean and easy to do that I now prefer to use SMD instead of thru hole on breadbord when possible.I wrote atutorialwith some (hopefully) helpfull hints, but the attached picture almost says it all. Since this tutorial got few views and people IRL seems to encounter this problem, I try to give it more visibility.Do you know other interesting ways to use SMD on breadboard ?John.

author: macboy
author_rank: Super Contributor
timestamp: November 24, 2015, 03:39:47 pm
content: Very clever.It seems to me that you could also shear the top pins clean off and solder the component directly onto the remaining stubs. This may be easier than air-mounting the component between the pins.

author: Jaunedeau
author_rank: Regular Contributor
timestamp: November 24, 2015, 03:44:59 pm
content: Good idea, I have to try that !

author: Cloud
author_rank: Regular Contributor
timestamp: November 24, 2015, 08:24:33 pm
content: I use solder bread board like thishttp://s2.electrodragon.com/wp-content/uploads/2013/07/Breadboard-Style-Soldering-Prototype-Board2.jpgto solder LEDs on and if I am feeling rich I also solder a header othervise I use just wiresWill send you an example of this when I came home.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 24, 2015, 10:12:07 pm
content: I do similar things but with right angle headers like these oneshttp://www.ebay.fr/itm/10pcs-1X40pin-Yellow-90-degree-Right-angle-Male-2-54mm-Pin-Header-connector-/291308780150?hash=item43d35b3a76:g:~JYAAOSwkNZUdur4I put the smd component on the small part of the pins, which you can turn to reach any smd size.Edit: Sorry the above link is not correct. You need the plastic part on the long side of the header, like thiesehttp://www.ebay.fr/itm/5Pcs-Pitch-2-54mm-40-Pin-Male-Single-Row-Right-Angle-Pin-Header-Strip-/170842981516?hash=item27c709048c:m:mtm3riM-5vQ4tc90001vhxAso you can rotate the pins to make the two short parts come close to each other if needed.

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 24, 2015, 11:39:32 pm
content: Very smart, thanks for sharing!
way to split one trigger signal to multioutput - Page 1
Forum section: electronics / beginners

author: broier
author_rank: Newbie
timestamp: October 06, 2017, 01:17:52 pm
content: Hello i have maybe dum question but i have one Trigger signal (12V, 10ns, 10Hz) and i need to split it for maybe 10 other devices i am thinking just some fast mosfets or transistors without any amplification and put them on 12V and be done with that but on the other hand its weird when i put it on paperIs there some more elegant way how to do this or some box which already do this stuff (there is a lot of bmc sma splitters but just for tv) and in the future there will be probably need for MHz so ...thanks for any advice...Vojta

author: katzohki
author_rank: Frequent Contributor
timestamp: October 06, 2017, 05:43:34 pm
content: Trigger what? An oscilloscope? Trigger a circuit to turn on? How? Little more detail what you're trying to accomplish would help answer better.
Ways to measure idle power on an SBC? - Page 1
Forum section: electronics / beginners

author: bhj99
author_rank: Contributor
timestamp: March 19, 2023, 10:10:46 pm
content: Hello, a beginner at electronics here. I am interested in ways to measure the idle power of an single board computer (SBC), which takes in 12V, 5V and 3.3V power outputs from a motherboard. The voltages are used for various different circuits on the SBC. What are some of the simplest options, like using a DMM or current probes to an oscilloscope? Using software may not always be accurate. Would like some opinions here, thank you!

author: Benta
author_rank: Super Contributor
timestamp: March 19, 2023, 10:52:41 pm
content: Just use a DMM. What's the complication?

author: bidrohini1
author_rank: Contributor
timestamp: March 20, 2023, 01:35:47 pm
content: You can use a DMM to measure the voltage and current going into the SBC. To measure current, you can place the DMM in series with the power supply or with the SBC itself. However, keep in mind that measuring current in series requires breaking the power connection, which may not be feasible in some setups.

author: shapirus
author_rank: Super Contributor
timestamp: March 20, 2023, 01:54:08 pm
content: For the USB-powered ones, here's probably the most convenient method:

author: waoj
author_rank: Contributor
timestamp: March 22, 2023, 12:47:59 am
content: I'm tempted to say just measure current on the negative rail. But by what would you multiply it to find wattage? Interesting conundrum.I suspect you will actually need three DMMs. One for each power rail's amperage. And if you really want to be precise, another three to measure voltage.Personally, i'd measure on the 'other side' of the power supply, monitor the AC going into it, because that's what you pay for. But I assume you are trying to ignore the losses of your power supply in your measurements. I think the only way to pull that off is to measure current and voltage on each rail.There are DC amp-clamps also, btw. kind of rare. kind of flakey. But for the low amperage setting you're looking at, I'd go in-line if I was you.I'm also assuming you want to monitor power usage over time. If not, then:use a single DMMinstall stress-ng, to create a worst case system load situation.One by one, measure voltage and amperage of each rail while under full load from stress-ng

author: james_s
author_rank: Super Contributor
timestamp: March 22, 2023, 01:17:32 am
content: DC clamps aren't rare, I bought mine from Amazon, wasn't even all that expensive, $60 or so I think.Measuring the negative rail won't work, you need to measure each of the positive rails and then add up the power. I suspect you'll find that one of the rails accounts for the vast majority of the power and the other rails will be just a few mA.
Weak ground vs strong, solid ground (A/V application) - Page 1
Forum section: electronics / beginners

author: CkRtech
author_rank: Regular Contributor
timestamp: April 10, 2014, 01:02:27 am
content: Hey All -First post. Been dabbling in electronics since around 1999. I've also watched Dave for awhile and only now arrived here and registered. I imagine I have quite a few things I could ask, but the first will be this -What sort of issues would you experience in analog video if your ground was say... a haphazard of cold solder joint with the absolute thinnest wire you could find vs a nice, thick wire with good connection to its two points? What sort of difference does it make?Are you looking at something where the video signal either works or it doesn't, or can you have all sorts of things in-between? How is it manifested? Can you see what appears to be interference on the screen if your ground isn't as good as it could be?Thanks!CK
Web access ID to login into AVCOM SPECTAN - Page 1
Forum section: electronics / beginners

author: bigzuma
author_rank: Newbie
timestamp: May 10, 2015, 03:47:48 pm
content: I am currently workong on AVCOM SPECAN, serial num. SNG-2150C, but i can login because i don't have the username and password. even though i have the ip address.Help...
Web site help - Page 1
Forum section: electronics / beginners

author: broderp
author_rank: Regular Contributor
timestamp: April 29, 2015, 12:45:52 am
content: I hope this is real easy, but I can't seen to figure out how to unsubscribe from a thread?Sorry for the noob question.

author: apelly
author_rank: Unknown
timestamp: April 29, 2015, 01:11:20 am
content: This?

author: broderp
author_rank: Regular Contributor
timestamp: April 29, 2015, 01:32:43 am
content: Quote from: apelly on April 29, 2015, 01:11:20 amOne would think so, but I don't get that unnotify button.I've posted on this thread:https://www.eevblog.com/forum/chat/special-price-for-eevblog-members/?topicseenand requested notification, but I don't get the button you show. Just the 'notify' button.Every time I check in, I see there's a post to that thread and it shows up in my "show new replies to your post" link.??

author: apelly
author_rank: Unknown
timestamp: April 29, 2015, 02:24:17 am
content: Ah. Apparently that's a feature.You're looking for the "ignore topics" mod which was installed recently.Dave posted instructions for enabling it the other day, but I can't find them now, sorry.something like:profile > modify profile > look & layout > show quick moderation as checkboxesthenyou should see checkboxes and an ignore topic button on the right on the replies screen you refer to.

author: broderp
author_rank: Regular Contributor
timestamp: April 29, 2015, 11:17:36 am
content: Quote from: apelly on April 29, 2015, 02:24:17 amFound it! Thanks a million!
Webpage with electronic circuits to analyze - Page 1
Forum section: electronics / beginners

author: nForce
author_rank: Frequent Contributor
timestamp: November 03, 2018, 04:25:48 pm
content: I would like to know if there is a webpage with electronic circuits (op-amp, 555 timer, and other supporting analog electronics) to analyze?It's for learning purposes so it would be welcome if it starts with basic schematics and progresses to more difficult ones.Thanks.

author: JackJones
author_rank: Regular Contributor
timestamp: November 03, 2018, 04:33:32 pm
content: I'm not sure if this is exactly the kind of thing you're looking for, but the falstad simulator has several basic circuits (including various 555 configurations):http://www.falstad.com/circuit/Click on the "circuits" tab on the top right.
Website for parametric searches for bench gear? - Page 1
Forum section: electronics / beginners

author: usao
author_rank: Newbie
timestamp: May 22, 2018, 02:13:19 pm
content: Ive seen many of Daves videos comparing bench meters, generators and oscilloscope, and he also identifies things to search for in bench gear.However, I don't know the best way to actually compare the options, features and precision/accuracy of the gear.Is there any websites out there which can be used to compare the search parameters side by side to aid in gear selection?

author: The_Boots
author_rank: Contributor
timestamp: May 22, 2018, 08:28:32 pm
content: It doesn't work for ALL bench gear, but there are some really great spreadsheets for Oscilloscopes and DMMs (if you haven't already seen them).Here:https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/and Here:https://www.eevblog.com/forum/testgear/digital-oscilloscope-comparison-chart/

author: Terry01
author_rank: Frequent Contributor
timestamp: May 22, 2018, 08:54:03 pm
content: Google!
Website Technical Support/Assistance - Page 1
Forum section: electronics / beginners

author: Infrared_Fred
author_rank: Regular Contributor
timestamp: October 30, 2020, 02:35:25 pm
content: Hello!I am a complete newbie to eevblog and I was wondering where I could get technical assistance for eevblog account settings.I did a search but I did not see any specific members to message or a forum to post such questions on. Can anyone tell me where I could send my question?Thank you!
Website to download schematics - Page 1
Forum section: electronics / beginners

author: daneck
author_rank: Contributor
timestamp: April 02, 2015, 02:30:59 pm
content: I occasionally need to download a schematic for repair purposes, currently for a Samsung Syncmaster 910MP. What is a good, trusted website for schematics? I am even willing to pay a nominal fee. Most that I come up with on Google searches look "suspicious" and I won't risk downloading anything from them.
Websites to download or purchase schematics and boardviews - Page 1
Forum section: electronics / beginners

author: mcinque
author_rank: Unknown
timestamp: November 17, 2021, 03:45:39 pm
content: I was wondering if anyone had any suggestions for sites that make available (free or paid) schematics and board views of various devices.I don't have any specific devices to fix (the last one is a Wouxun transceiver that doesn't power up completely), just that in the last years with miniaturization and multilayer pcbs, every time I get something that doesn't work and I try to fix it, I go crazy trying to figure out what is connected to whom.Having schematics would be very helpful, not to mention the board view!From what I see on YouTube, there seems to be a specific market (like the laptopschematics site) and in some cases even banned (like Apple schematics that theoretically shouldn't leave Apple).What sites do you recommend? If I'm getting into a topic that is somehow banned, tell me right away and I'll stop asking.

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 17, 2021, 04:36:30 pm
content: I guess you haven't visited places likehttps://elektrotanya.comhttp://www.ko4bb.com/getsimple/index.php?id=manualshttps://w140.com/tekwiki/Forgot the boat anchor manualshttps://bama.edebris.comAlso mostly Tek and HP manuals in good quality scans:https://artekmanuals.com

author: mcinque
author_rank: Unknown
timestamp: November 19, 2021, 11:28:12 am
content: Thanks!Louis Rossman tells that he "knows" where to purchase Apple schematics and of course he doesn't reveal his source for obvious reasons.I don't need Apple schematics but I would like to have access to those kind of "not public" schematics: I wonder if there are specific markets or websites to look for other than the ones you told me.Maybe it's necessary to go on the dark web?As before, if this is not allowed on this forum, just told me and I'll stop right now.
Wein Bridge Curve Tracer Followup - Page 1
Forum section: electronics / beginners

author: Zielsziek
author_rank: Contributor
timestamp: March 12, 2025, 06:43:07 pm
content: A while ago I posted a problem I had with a curve tracer build. Now I have made some adjustments to the design and I was able to confirm that I was shipped some fake integrated circuits. The 150 Hz part is working fine but I cannot get the higher frequency part to oscillate. For some strange reason I am getting a 1 Hz sine wave. On a breadboard I was able to get the circuit to oscillate with 68 nF caps for the high frequency range. I tried using such capacitors here but to no avail.I have tried fiddling around with the values for the resistors but I cannot make it work. I am sure I used the values in the schematic for the caps and resistors. Solder defects have been ruled out. I am aware that by design is not optimal but I do not require high stability for the frequencies. All I want is to have a high frequency range and a low frequency range.Thank you for your time.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 12, 2025, 07:16:38 pm
content: My guess would be on a mix up with the capacitors, like 10 µF instead of 10 nF.Another possibilty could be the virtual ground oscillating: the LM358 may not be that happy with all the capacitve load (2 x 10 µF).

author: Zielsziek
author_rank: Contributor
timestamp: March 16, 2025, 02:24:30 pm
content: Thank you very much for your answer. Indeed the virtual ground was oscillating. 1 nF fixed it right up. Sorry for the late answer and than you for your patience!
Weird Arduino Due SPI glitches in logic capture - Page 1
Forum section: electronics / beginners

author: NotionalLabs
author_rank: Unknown
timestamp: November 19, 2014, 01:37:25 am
content: Hey all,I'm working on a project to reimplement the control protocol for a toy quadcopter using an Arduino Due (Cortex M3) and a SPI-driven 2.4GHz transceiver, but I'm experiencing some odd behaviour from the Due's hardware SPI. I noticed a problem when I was test-flying the quad and it would be fine and stable, then all of a sudden it would go nuts - I performed a logic analyzer trace and found that there appears to be transmission corruption in the 16-byte control packets sent to the Tx.The SPI glitches seem to take 2 forms:- Clock glitches where it will just hang high for the duration of the byte transmission:- Phase glitches where the MOSI transitions seem to be out of sync with the clock (the flagged byte should be \x00, not \x01):Because the glitches are evident in the traffic from the Due, I don't think it's a problem with the transceiver (an AMIC A7105). I wondered if it could be interference on the bus, but the lack of unexpected logic transitions in the capture makes that seem unlikely. The SPI clock speed is 4MHz (default), which is under the 10MHz limit of the A7105.I'd really appreciate any advice or troubleshooting tips, I'm at a bit of a loss!Thanks,Jim
Weird audio voltage - Page 1
Forum section: electronics / beginners

author: starplayer
author_rank: Contributor
timestamp: November 30, 2014, 09:08:38 pm
content: Hello. I'm trying to build a simple transistor amplifier which I know usually suck, but it's just for the experience.Anyhow, after figuring my amplifier doesn't work, I tried measuring the voltage that is coming from my computer audio jack which is enough to drive a pair of 32 ohm earphones, the ones you plug in your ear. However, the voltage I get is very low, about 20 mV at maximum volume. I'm generating a sine wave at 60 Hz and my multimeter is TRMS, so I believe that should work. On the internet people say the voltage should be about 0.4 V, or even 1 V maximum (2 V peak to peak).Is my multimeter just bonkers or is this normal?

author: Yansi
author_rank: Super Contributor
timestamp: November 30, 2014, 09:18:21 pm
content: Probably you measure it wrong.Usual audio levels for consumer electronics are about -10dBV which is about 300mVrms, for professional equipment it is around 0dBu (0,775Vrms) up to +4dBu (1.5Vrms) for long-distance cabeling.Decent soundcard can output at least those 300mV. What was your exact measurement setup? What amplitude of test signal (on the digital side) did you use? Was the card's output loaded somehow? With 32R load you will sure get decreased voltage, the output impedance can be anything around let's say 100 ohms.

author: IanB
author_rank: Super Contributor
timestamp: November 30, 2014, 09:38:52 pm
content: Are you sure you didn't damage the audio output from any previous experiments?Assuming you didn't, you should get an AC signal in the order of 1 V RMS, which is sufficient to drive headphones at decent volume.Try a higher frequency than 60 Hz. The output amplifier may be rolling off lower frequencies, especially if it is a lower quality audio source rather than a high quality sound card. Try 200 Hz or so.

author: Simon
author_rank: Unknown
timestamp: November 30, 2014, 09:49:51 pm
content: How about 1KHz as pretty much most things are specified at 1 KHz

author: IanB
author_rank: Super Contributor
timestamp: November 30, 2014, 09:51:28 pm
content: Playing regular music, the headphone socket on my sound bar is producing ~400 mV AC at maximum volume.

author: starplayer
author_rank: Contributor
timestamp: December 01, 2014, 08:39:05 am
content: Hey guys thank you for your answers.I figured it out, I should have said the audio out was from my laptop. When I measured the line out of a sound system (to be used with big headphones), I measured about 400 mV. Turns out laptop jacks really output low voltages.

author: Simon
author_rank: Unknown
timestamp: December 01, 2014, 08:49:07 am
content: laptops will have the same output as PC's as they have to drive the same headphones.
Weird backplane pattern - Page 1
Forum section: electronics / beginners

author: jassuncao
author_rank: Newbie
timestamp: April 17, 2014, 09:10:50 am
content: Hello all,While I was tidying up my workshop I found an backplane PCB from an old computer with the following pattern (sorry for the crappy photo)I assume these are ground guards to avoid crosstalk but it's the first time I saw this kind of pattern in a motherboard. Is my guess correct?Thank you in advance.

author: Simon
author_rank: Unknown
timestamp: April 17, 2014, 09:17:06 am
content: can I hazard a guess that this is on the back of an ATA port ? 80 pin ata ports go up to 133 MB/s rather than the 33mB/s on the 40 pin ports simply because every other wire is a ground and avoids cross talk like you say.

author: jassuncao
author_rank: Newbie
timestamp: April 17, 2014, 10:42:15 am
content: This is not an ATA port. From the type of connectors I assume it's a ISA or MCA backplane from a late eighties server. I guess the designer made an extra effort to minimize cross talk in a <20MHz bus

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 17, 2014, 11:45:09 pm
content: Yeah, reduces electrostatic coupling a little. Wouldn't be great for rise times in the < 2ns range, but would be fine for anything CMOS/TTL back in the '90s or earlier.Tim
solved: Weird banana plug? - Page 1
Forum section: electronics / beginners

author: incf
author_rank: Frequent Contributor
timestamp: March 25, 2025, 05:54:21 pm
content: While planning out out how to build some custom test cables I ran across this E-Z-Hook 8703 stack-able banana plugWhy is it constructed this way? What is it used for? (I know what stackable banana plugs are used for, but this one is different)It looks like they wrapped a spring around the barrel and expect you to connect to it somehow? (Is the spring removable? Is this for standard "sta-kon" ring terminals?)

author: ataradov
author_rank: Super Contributor
timestamp: March 25, 2025, 07:13:48 pm
content: Likely for alligator clips or any other type of clip.

author: CaptDon
author_rank: Super Contributor
timestamp: March 25, 2025, 08:25:25 pm
content: It is a bit difficult to get the wire started into the coil, however, when you insert a piece of wire with about 5/8" of insulation stripped back through the hole in the side pushing it down through and slightly out the lower hole (near the flared end) you can then begin to turn the coil and convince a portion of the coil to act as a locking mechanism holding the wire in place without solder. And of course the little ring is a great place for gator clips and EZ-Hooks to attach. (After inserting the wire through the upper hole you begin turning the coil and the first loop of the coil should pass on the opposite side of the wire from the rest of the coil. you end up with about two loops of the coil on one side of the wire and the rest of the coil on the other side and it 'sort of' locks the wire in place without soldering)

author: CaptDon
author_rank: Super Contributor
timestamp: March 25, 2025, 08:30:52 pm
content: And as mentioned above, you now have a wire connected, a place to hook gator clips AND you can still stack another plug on the butt end. Pretty handy eh? This style of device is not cross drilled with an internal captivating screw like most banana stackers we think of.
[SOLVED] Weird behaviour in motherboard repair - Page 1
Forum section: electronics / beginners

author: mlefe
author_rank: Regular Contributor
timestamp: April 22, 2018, 09:01:31 pm
content: Hi guys, i'm trying to repair a laptop that has a fan that doesn't work.When I measure resistance between an IC pin and the VFan_OUT pin on the fan connector I have a short (as expected) but when I connect the fan and measure again I can read more than 50K and raises until it OLs the meter (like if I was measuring a cap)... this is completely unexpected as I don't see how adding something can change the previous short... what am i missing? Thanks!

author: Shock
author_rank: Super Contributor
timestamp: April 23, 2018, 02:04:09 am
content: Quote from: mlefe on April 22, 2018, 09:01:31 pmSo are you saying, you're measuring a low resistance trace on the PCB and getting an odd measurement when you connect the fan?Do you have a link to the schematic and is there any power/battery connected to the circuit or charged caps etc?

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: April 23, 2018, 06:43:05 am
content: Sounds like a residual voltage upsetting the meter.

author: amyk
author_rank: Super Contributor
timestamp: April 24, 2018, 03:11:25 am
content: You have the leads touching something slightly different, and a cap is being charged up by the meter's test voltage.

author: mlefe
author_rank: Regular Contributor
timestamp: April 24, 2018, 06:47:45 pm
content: I feel embarrassed, it was a very dodgy connection, nothing elseThank you all!
weird BJT push pull directly coupled amp design. - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: July 17, 2022, 03:39:57 pm
content: [ Attachment Invalid Or Does Not Exist ]what does V16 and V17 diodes + V4 V5 BJTs are meant to do here? the diodes have a forward voltage of 1 volt.is it like a redundant biasing circuit?doesn't seem to do much in LTC but I don't know what to look for really...also, if it's using a zener diode for some kind of biasing (V15, 6.8V zener), then why does it seem to also have a Vbe multiplier (V8)?

author: magic
author_rank: Super Contributor
timestamp: July 17, 2022, 03:47:16 pm
content: Current limiting. They forward bias and activate when voltage across one of the 0.22Ω output resistor reaches ~1.2V.IIRC it is advised to also have some resistance in series with this circuit, to limit how much current may flow through BE junctions of the transistors, particularly in the event of output devices failing short.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 17, 2022, 03:48:49 pm
content: V16,V17,V4,V5 provide some current limiting / short circuit protection. The implemantation is a little confusing, but OK.P.S.: the part around V15 is indead strange. It is only weakly coupled to the bias adjustment. It looks more like some way to extend the output voltage range a little with bootstrapprapping the current source and still trying to get a constant current through the VBE multiplier.

author: magic
author_rank: Super Contributor
timestamp: July 17, 2022, 03:51:21 pm
content: Because when the output is shorted the amp will turn on hard one of the darlingtons. It would take a lot of series resistance to prevent it from smoking in such case and maximum output swing under load would be crap.

author: David Hess
author_rank: Super Contributor
timestamp: July 17, 2022, 09:06:27 pm
content: I agree with the others, those circuit are for current limiting the output. More sophisticated designs include foldback current limiting tailored for the safe operating area of the output transistors rather than a hard current limit.There is also an optimum value for R54 and R55 for least crossover distortion from modulation of the output transistor's transconductance, so increasing them has other disadvantages.
Weird board short solved; to do: always look at gerbers - Page 1
Forum section: electronics / beginners

author: jolshefsky
author_rank: Regular Contributor
timestamp: April 01, 2015, 06:46:33 pm
content: I just got some boards back from OSHPark. They are test-jig boards with a couple card-edge connectors for attaching the board-under-test.I was doing a little continuity testing to make sure they were what I designed and discovered a short between a bunch of pads. I couldn't see the problem with a visual trace, so I went back to the board design in KiCAD and confirmed the nets were not connected. Taking a microscope view of the board, I discovered the problem: I had included the board outline on the copper layers and OSHPark tried to subtract the outline from the copper but missed 1 mil or so on the left side, front. This hairline was the resulting short. Fortunately I can just grind a bit of a bevel on the board and remove the offending copper.The lesson here is,always look at your gerbers. I would have immediately seen the outline layer and went back to remove it before I sent the gerbers to the fab. Even though OSHPark does a render of what the board will look like—which I counted on to be correct—there is no sense in sending them files that have such obvious bugs.

author: amyk
author_rank: Super Contributor
timestamp: April 01, 2015, 09:50:27 pm
content: Does this mean they can actually do 1mil traces?Fusing these slivers open with a large charged capacitor might be faster than trying to grind them off...

author: jolshefsky
author_rank: Regular Contributor
timestamp: April 01, 2015, 10:10:52 pm
content: Quote from: amyk on April 01, 2015, 09:50:27 pmIf you tried to make 1mil traces, they'd be broken, but for this, of course they're solid!As for the cap, I did think of that while troubleshooting to quickly identify the source of the project. Unfortunately there are 2 card-edges with 15 pins on each side ... and some of the pins are supposed to be shorted. 30 seconds with the Dremel worked a treat.

author: EEVblog
author_rank: Unknown
timestamp: April 01, 2015, 11:00:45 pm
content: Nasty!

author: zerorisers
author_rank: Regular Contributor
timestamp: April 02, 2015, 01:30:02 pm
content: "The More You Know"try to do something it doesn't work, you do it unintentionally where you don't want it of course it will work. Its just fundamental physics! The laws of nature itself!

author: free_electron
author_rank: Super Contributor
timestamp: April 02, 2015, 02:54:27 pm
content: your fault. Should not have included the board outline on the copper layers...Board outline is a separate layer.NEVER-EVER ! merge gerber layers.
Weird capacitor pinout - Page 1
Forum section: electronics / beginners

author: IO390
author_rank: Regular Contributor
timestamp: March 17, 2014, 09:59:34 am
content: Hi,I found some of these capacitors at collegehttp://uk.rs-online.com/web/p/aluminium-capacitors/0104382/?searchTerm=104-382&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3130342D33383226They've got a really weird pinout (5 pins) and I can't seem to find what each one is.There's a datasheet on that RS page, but it doesn't seem to have any info as to what each pin actually does, so if anyone can help that'ddd beee great.

author: Andy Watson
author_rank: Super Contributor
timestamp: March 17, 2014, 10:11:19 am
content: The extra pins are for mechanical anchorage. As the datasheet says: pin 1 i is positive, 5 is negative, the remaining pins are not connected but may be at the same potential as pin 5.

author: IO390
author_rank: Regular Contributor
timestamp: March 17, 2014, 11:57:22 am
content: Thanks for the quick reply. I guess that will teach me to read the datasheet a bit better...

author: Psi
author_rank: Super Contributor
timestamp: March 17, 2014, 12:05:28 pm
content: I've seen large multi-pin caps which are actually multiple caps in a single cap package. Usually it's obvious though as there's multiple uF values written on the side.

author: MLXXXp
author_rank: Frequent Contributor
timestamp: March 17, 2014, 05:06:50 pm
content: Another weird and rare capacitor type is the four terminal axial electrolytic. It's a single capacitor that actually has just two leads, but each lead goes all the way through and comes out both ends. It's sort of a combination axial and radial. You treat the two ends as input and output but it doesn't matter which end is which. Polarity is still important, though. These capacitors are designed for low ESR and inductance.I've attached a picture of a couple of old ones that I have.Here's the manufacturer's web page:http://www.vishay.com/capacitors/list/product-42040/
Weird IGBT Please help - Page 1
Forum section: electronics / beginners

author: 13
author_rank: Contributor
timestamp: August 23, 2016, 10:20:25 pm
content: Howdy folks,Recently a friend and I took apart a Prius inverter module for the IGBTs that drive motors. As much as we have succeeded in getting the parts we have not succeeded in getting them to work. In fact, they seem to be backwards! We hooked up a negative lead to the possible gate and the IGBT turns on and when we hooked up a positive lead the thing turned off. We would really like to use the IGBTs in parallel to maximize the current capability as we switch around 4ka for the coilgun. Does anyone know how to work these? See the picture attached.Thanks,13

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 24, 2016, 12:08:53 am
content: They'll probably turn on once, at 4kA. Then stay on.Tim
weird NE555 circuit, found in a cordless drill... - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: March 28, 2021, 04:59:07 am
content: I took apart the switch in a cheap broken cordless drill I had... this one wasn't potted in epoxy surprisingly. reverse engineered the circuit... and drew a shematic...I could've gotten the NE555 pins wrong by 180degrees... idk, it had no notches on it and I'm not too familiar with IC's, or SMD stuff for that matter...the SOT package too... it had 'A73' writen on it, so I asumed it was some 2SA73- BJT, and for that too I could've gotten the wrong BJT with a diffrent pinout, since it makes no sense how there's like no grid leak, no collector supply, no emitter drain... it just seems like it it wrong af....I don't know where the pins connected to the mosfet and the big diode since it fell apart when I got it open.if it helps the diode was a 6A4, and the fet was a 50N06[ Attachment Invalid Or Does Not Exist ]

author: retiredfeline
author_rank: Frequent Contributor
timestamp: March 28, 2021, 05:16:16 am
content: 2SA transistors are PNP. The VCC feed to the 555 doesn't look right.

author: mvs
author_rank: Frequent Contributor
timestamp: March 28, 2021, 11:02:49 am
content: A7* is BAV99, two diodes in series.https://assets.nexperia.com/documents/data-sheet/BAV99_SER.pdf

author: retiredfeline
author_rank: Frequent Contributor
timestamp: March 28, 2021, 12:39:29 pm
content: It seems to be some kind of PWM circuit. You should move the resistor network and switch to the left to make it clearer.

author: Zero999
author_rank: Super Contributor
timestamp: March 28, 2021, 03:10:49 pm
content: Yes, it's probably a dual diode package, rather than a transistor.The circuit doesn't look quite right. Pin 4 should go to +V.Here's a schematic of a PWM circuit with a potentiometer. It should be similar to that, but with a switch and discrete resistors.
Weird old capacitor values - Page 1
Forum section: electronics / beginners

author: qoole
author_rank: Contributor
timestamp: March 13, 2013, 08:37:16 pm
content: Hi again,Whilst rummaging through the old A-Level kit at the school I work at I came across a lovely stash of old electronic components including some caps (I assume they're caps) with rather odd markings.They're all RS components branded with the following values "100nW" (100 nano farad), "100nZ" (100 nano farad) and "10nW" (10 nano farad).I have never seen caps with 'W' or 'Z' on them before. Is this some kind of tolerance value.Attached is a photo of the caps.Anyone seen anything like this and know what it means?

author: Kaluriel
author_rank: Contributor
timestamp: March 13, 2013, 08:43:49 pm
content: could be tolerance

author: qoole
author_rank: Contributor
timestamp: March 13, 2013, 08:46:21 pm
content: I can find 'Z' as a tolerance, but not W...

author: Alana
author_rank: Frequent Contributor
timestamp: March 13, 2013, 09:26:49 pm
content: Encoded max voltage?

author: MartinX
author_rank: Regular Contributor
timestamp: March 13, 2013, 09:38:51 pm
content: Maybe an indication of the type of dielectric, Z maybe stands for Z5U.

author: komet
author_rank: Unknown
timestamp: March 13, 2013, 10:36:58 pm
content: Here you gohttp://my.execpc.com/~endlr/markings.html

author: qoole
author_rank: Contributor
timestamp: March 13, 2013, 11:27:14 pm
content: @komet Thanks! That is one VERY useful resource!
Weird pad resizing in Eagle - Page 1
Forum section: electronics / beginners

author: gregallenwarner
author_rank: Regular Contributor
timestamp: February 12, 2015, 08:31:48 pm
content: I've got a problem in Eagle. (Besides using Eagle itself as the problem!)I made a part for a USB micro B socket by following the dimensions in a Hirose datasheet. The shielding pads and TH anchors are supposed to be 1.9mm tall, according to the dimensional drawing in the datasheet. So I created SMD pads of 1.8 x 1.9 and TH pads with diameter 1.9mm. In the library footprint view, everything looks ok. All the pads are the same height.Soon as I import my part into a schematic and go to place the part on the PCB, things look different. The TH pads are a bit bigger than the SMD pads. I tried creating a via directly in the PCB using the same parameters as the TH pads in the library part, just as a sanity check, and it seems like the TH pads match on the PCB, yet to me, I could swear the TH pads look like they've been enlarged on the PCB.Does anybody know what's going on here, or what's causing this issue? It's a problem because the extra width of the TH pads violates the copper-to-board-edge clearance of 15mils in my DRC file. If it truly matched what I created in my library file, it would not be violating this measurement.I've attached renderings of the part in the library view, as well as on the PCB. Thanks.

author: Christopher
author_rank: Frequent Contributor
timestamp: February 12, 2015, 08:39:21 pm
content: Have a look at restring(sp?) in the DRC. This has been a problem for me in the past when I wanted really tiny pad sizes

author: gregallenwarner
author_rank: Regular Contributor
timestamp: February 12, 2015, 08:52:04 pm
content: I've attached a screenshot of my restring window. I'm not really sure what most of this means. All I know is the minimum annular ring of my board house is 7mil, and by my calculations, a 1.5mm hole with a 1.9mm diameter pad just meets this requirement. So I don't think the pad should've been resized at all, as it meets the 7mil minimum.
Weird PCB design - teardrop, mechanical or...? - Page 1
Forum section: electronics / beginners

author: daqq
author_rank: Super Contributor
timestamp: June 18, 2014, 08:03:34 pm
content: Hi guys,I found this on one PCB from a TV. The triangular patern from the connector. Any clues as to what it is and why it's there? My guess was teardrops, but it seems really big for that. Impedance black magic? Seem small for that.Any suggestions?Thanks,David

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 19, 2014, 02:33:39 am
content: Interesting, it's cut back sharply in the surrounding polygon too, well beyond what a clearance rule would suggest.No obvious electromagnetic purpose -- assuming the designer/layer-outer knew what they were doing.Stylistically, it has kind of a heavy metal appeal to it, huh?Most likely a wave soldering feature. Note the extra wide pads on the end of the SMT chip nearby.Tim
weird reverse LED? - Page 1
Forum section: electronics / beginners

author: dentaku
author_rank: Frequent Contributor
timestamp: October 29, 2014, 06:04:42 pm
content: I recently tested out some pink lensed red LEDs from an old Pioneer stereo and at first I thought they didn't work but then I realised that they are simple backwards LEDs.What I mean is that looking inside the lens you can usually tell the anode from the cathode of a regular LED (thin bit and thick bit) but this one was the other way around.Does/did this happen alot? You'd think that LEDs have been standardized for many years now and a stereo from the 90's would have LEDs that are all the same.By the way, these are horribly dim red LEDs. One has a concave conical lens and the other pink one is just regular shaped but they're both backwards.

author: mikerj
author_rank: Super Contributor
timestamp: October 29, 2014, 08:27:40 pm
content: This is fairly common with more modern LEDs, you can't reliably tell just by looking through the body any more.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 30, 2014, 01:07:47 am
content: LED pet peeves:- Which lead is the cathode? The shorter? Yeah, triple-check the datasheet on that one.- Which lead is the cathode, the thicker one (internal view; the one the die is mounted to) or what?- Round LEDs with flats (which side!?)- Round LEDswithout any flats- Bicolor LEDs with three leads and any of the above concerns- SMT (chip) LEDs, with- Microscopic or invisible polarity markings,- Or markings that are completely wrong (dot means..?)Let's not even start with other optoelectronics, like LCD module pinouts...Tim

author: dentaku
author_rank: Frequent Contributor
timestamp: October 30, 2014, 01:20:21 am
content: I guess people with more experience than me have seen it all.