hybridfree/eevblog-posts huggingface dataset:
First time using current limiting IC - Page 1
Forum section: electronics / beginners

author: Pariston
author_rank: Contributor
timestamp: October 12, 2020, 09:52:31 pm
content: Hi,Thanks for stopping by. I am trying to use MAX4787EXK,100mA, current limiting ic to charge 1.2 V NiMH battery. At the moment, I have 3.3 volt from power supply connected to pins ON&IN, 3kpullup resistor for #FLAG (which is not connect to mcu, basically remain high all the time), everything else is according to provided schematics. IC seems to be working (giving off around 110 mA) when I keep my finger on the ON pin(basically it is constantly forcing ic to turn on due to bitrate), from here, I get a feeling that chip is turning itself off. There is no output current when ON pin is connected straight to vdd or vcc.I am missing something simple...Datasheet:https://datasheets.maximintegrated.com/en/ds/MAX4785-MAX4788.pdf

author: langwadt
author_rank: Super Contributor
timestamp: October 12, 2020, 10:19:48 pm
content: it is not a constant current source, think of it as an electronic fuse. It turns off when the current limit is exceeded which will happen immediate when you connect at 1.2V battery to 3.3Vyou need a charger IC not an IC intended to protect things like a USB port from a short

author: Manul
author_rank: Super Contributor
timestamp: October 12, 2020, 10:25:09 pm
content: This is not a "current limiting ic" and not a current source either. This is a switch with a current limit (for protection). It is not in any way supposed to be used like you use it. And the behaviour which you observe does exactly match the information provided in the first page of the datasheet.

author: pwlps
author_rank: Frequent Contributor
timestamp: October 12, 2020, 11:10:21 pm
content: page 6:"The MAX4785 and MAX4787 do not have the autoretryoption and the switch remains in latch-off mode untilthe ON pin or the input power is cycled from high to lowand then high again. "It seems this is what happens here.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 12, 2020, 11:20:52 pm
content: If you want to charge batteries, then use a battery charger IC.
First Time Using Pull-Up / Pull-Down Resistors, Did I Do It Right? - Page 1
Forum section: electronics / beginners

author: Max Holdcroft
author_rank: Contributor
timestamp: July 28, 2024, 12:08:14 pm
content: Hey all,Basically the title. I have a push button connected to a pin on a microcontroller that I want to be able to detect the pushing of. I've connected this to a pull-up resistor. I'm running the microcontroller off 2.8v input, and the resistor is 4.7K ohms. This is my first time using these, and I just wanted to check I did it right.Thanks in advance!Max

author: ledtester
author_rank: Super Contributor
timestamp: July 28, 2024, 12:10:42 pm
content: Yes you did it right.

author: rich t
author_rank: Contributor
timestamp: July 28, 2024, 12:31:14 pm
content: Many microcontrollers also have built-in pull-ups you can enable in software.In general, the one thing you don't want to do is pull up beyond the microcontroller supply voltage.

author: kevin.gibbs
author_rank: Regular Contributor
timestamp: May 13, 2025, 02:29:20 pm
content: Yes, it will most likely work. However, I would read the microcontroller's datasheet to configure its input correctly. After all, there are built-in pull-up resistors not only for VCC but also for the GND line.

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 13, 2025, 04:13:20 pm
content: As an extra, I would add a small capacitor to ground to debounce the switch. A 100nF capacitor will do the trick.

author: SteveThackery
author_rank: Super Contributor
timestamp: May 13, 2025, 06:16:54 pm
content: Or debounce in software.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 13, 2025, 07:37:52 pm
content: Quote from: pcprogrammer on May 13, 2025, 04:13:20 pmNo. Don't do that.When the switch is pushed, it shorts the capacitor, and a 10nF ceramic capacitor can deliver very high peak currents, much more then a switch designed for "logic input" can handle. As a result, the switch will wear out and fail prematurely. This happens especially with rotary encoders, because they see a lot of actions. The fix for this is to add another series resistor between the capacitor and the switch to limit the current to a safe level.
First time using Ucurrent gold, needs some expert advise :)  - Page 1
Forum section: electronics / beginners

author: Henry_jk
author_rank: Newbie
timestamp: October 02, 2018, 08:00:37 pm
content: Hi Everyone,I just bought an Ucurrent gold to measure Sleeping current one a circuit that I design. The circuit comprised of ESP8266 and Attiny sends a signal to a 2n7000 that turn on or off the power to the ESP8266. The Attiny 84 sleeps majority of the time, while the ESP is powered off.So I bought the Ucurrent gold with the hope to measure the low current of my entire circuit while it's asleep. The problem that I encounter is when I hook up the uCurrent gold according to this setup (please see diagram). It seems like the burden voltage on my DMM still effects the ESP8266. The blue light flickers, but it doesn't seem to perform its actual duty.My circuit has two states, active state (awake and do something), sleep state (almost everything is off except the attiny84). When I use the Ucurrent gold to measure the active state (draws 50-120mA typically when esp is on), the esp doesn't seem to function or connect to the web. The blue light flickers.I have tried to measure the resistance on the Current IN, and Out with 10K 10Ohm and 10mOhm they all seem to read correctly. So I don't think I blew the Shunt resistor.So I draw a diagram to illustrate my setup. I hope I didn't damage anythingAny feedback would be much appreciated.

author: Henry_jk
author_rank: Newbie
timestamp: October 03, 2018, 10:37:06 pm
content: Or perhaps if anyone would able to tell me if my diagram is correct?Much appreciated.

author: piguy101
author_rank: Regular Contributor
timestamp: October 04, 2018, 12:15:38 am
content: I don't own a uCurrent, but it looks like you've got the uCurrent wired up so that your DMM will read negative currents. That shouldn't be an issue, but this is just a heads up.What range do you have the uCurrent on? The burden voltage might be too high when the microcontroller is active. Assuming you have it on uA range (middle range), there is a resistance of 10 Ω. 100 mA through 10 Ω is a 1 V drop in voltage, which is likely unacceptable for your circuit.
First time with mosfets, am I doing it right? (wireless irrigation system) - Page 1
Forum section: electronics / beginners

author: namero999
author_rank: Newbie
timestamp: October 22, 2019, 03:35:36 pm
content: Hello all (and sorry, english is not my native language).I'm working on a personal project, an automatic watering system. It has the following features:- esp8266- analog and i2c ports for sensors (such as temp and soil moisture)- port for water pump (250mA @ 5V)In front of the whole thing, I'm putting a soft latching on/off switch, as described in this eev videoI attach the schematic, where I divided the circuit in logical components (the relevant one being Power and Pump, where the 2 mosfets are circled in red).My questions are:- is it correct to have a mosfet piloting the main power and one piloting only the pump?- how can I calculate the current draw of the soft latching on/off circuit? I'm afraid I can't see how much current will pass through it when the pump (or pumps!) will be on, therefore I'm not sure what components I should choose to implement it.Thanks, generally speaking if you have any feedback on the schematic I'll appreciate it, I'm a beginner on these topics.Best regards.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: October 22, 2019, 04:33:28 pm
content: Which MOSFET are you using for Q4?

author: namero999
author_rank: Newbie
timestamp: October 22, 2019, 04:36:17 pm
content: I still have to decide but I think this is my candidatehttps://www.mouser.de/datasheet/2/308/NTR1P02T1-D-100317.pdf

author: Arjunan M R
author_rank: Regular Contributor
timestamp: October 22, 2019, 04:39:43 pm
content: Also, how much current will the pump draw? The maximum continuous drain current of Q1 is 750mA.

author: namero999
author_rank: Newbie
timestamp: October 22, 2019, 04:40:48 pm
content: The pump draws 250mA @ 5V and the reason why I chose the 750mA is because I might opt to have multiple pumps (2 or 3) attached to it.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: October 22, 2019, 04:48:05 pm
content: If you are going to control 3 pumps using the MOSFET, you might go with another one. You are probably going to heat up the MOSFET if you draw its max current. I recommend only using a max of 2.

author: namero999
author_rank: Newbie
timestamp: October 22, 2019, 04:51:05 pm
content: Thanks, indeed I am way more inclined towards having max 2 pumps (maybe in a second revision of the project).When it comes to Q4 instead (so, the "main" mosfets), generally speaking, is that a design that makes sense? One "power" block with the soft latching on/off scheme, and then the rest with a second mosfet for the pump(s)?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: October 22, 2019, 04:51:31 pm
content: Looks good to me. You could use NDS332P for Q4 if you haven't picked a candidate yet. Have fun
First try at designing a 5A/12V multi purpose mosfet switch - Page 1
Forum section: electronics / beginners

author: bryce1
author_rank: Regular Contributor
timestamp: February 13, 2014, 05:03:07 pm
content: Hi guys,I need your input on this since it is the first time doing something like this.Basically, I want to design a (low side-) "switch" that allows an AVR (5V) to safely switch a variety of 12V loads. This includes LEDs (PWM), SSRs, DC pumps and things I haven't thought of yet (up to 5A).VCC=12VSWITCH1=Atmega pinR5=depends on the LEDR10=pull downR9=limits the current to the MOSFET gate when PWMing (1/8W enough?)The mosfet will be something like this:http://www.irf.com/product-info/datasheets/data/irlb8748pbf.pdfIt will probably need proper cooling.I am not sure yet on how to calculate R9 and R10 and I have not chosen D2 and C3 yet.Can you give me advice/criticism on the schematic? Maybe some layout advice? This is all new to me, so I'd like to learn as much as I can (and hopefully end up with something great ;-) ).Thanks!

author: madworm
author_rank: Frequent Contributor
timestamp: February 13, 2014, 05:13:55 pm
content: The gate resistor should be high enough to limit the peak current on the AVR's pin to about 30-ish mA. Consult the datasheet. I think for some AVR chips, the absolute maximum is 40mA for GPIO pins.So 160Ohm would work for 5V.Using the GS-capacitance, you can calculate the RC-time and see how long it takes for V(GS) to be reasonably high for the mosfet to turn on fully. That will also give you the upper limit for the PWM frequency.For really fast switching you need a mosfet-driver ic, that can charge the gate really fast and avoid thermal loss in the transistion from off to on.The pull-down resistor (bleeder) is not that critical. If you like to conserve power, 10k seems a bit low. Again, calculate the RC-time if you think it matters.
First Velleman kit, TV Tennis - troubleshooting - Page 1
Forum section: electronics / beginners

author: Stonent
author_rank: Super Contributor
timestamp: October 20, 2013, 05:07:25 am
content: So this was my first real soldering kit. I mean I've soldered stuff before, but never a self assembly kit like this.And of course it didn't work. The power light wouldn't come on. I checked all the joints and was reasonably sure I didn't bridge any joints. So I started googling pictures of the board just to make sure there wasn't something that had missed and everything looked good.So then came the systematic tracing out of stuff on the schematic. I checked all parts that were tied to ground and got good continuity on all of them. So then I checked all the things tied to +4.5 and all those were good. I plugged it in again and no power but I shifted my hand across the bottom and the light came on but nothing on the screen.I went back and started checking traces coming from the Pic and found what appeared to be an open connection between the clock pin and the crystal. So I reflowed the solder on those connections and still open. The solder had bonded to the copper pads but there was nothing between them. I finally took a scrap from a resistor and just jumpered it across and it worked! Success!Then I remembered when I was looking at pictures of other kits people had done, there was someone who built one with an 8 year old and had a dead trace that he had to jumper similarly.http://2.bp.blogspot.com/-P50M4bKz32s/TiN2lTSvkuI/AAAAAAAAE0I/OvHXT38-cNQ/s1600/IMG_7417.JPGAnyway I didn't like how the RCA jacks turned out but it looks like they had holes for different form factors, but it worked.So I guess on to my next kit, the Velleman Pic experimenter kit. I wonder if I'll be able to dump the PIC16C505 chip on this board?

author: c4757p
author_rank: Super Contributor
timestamp: October 20, 2013, 05:14:28 am
content: Ugh... I hate that. Shitty PCBs are always a freaking joy.By the way, where'd you get the soldering shovel? I've been looking for one!

author: Stonent
author_rank: Super Contributor
timestamp: October 20, 2013, 09:12:58 am
content: Well I started on the other kit and I kept on turning it off between loading parts, but since the plating was gone off the copper, my tip has actually vanished. This was the 20 year old iron that I dug out from a box from when I was a kid.Normally I would use my fine tip butane iron that I got a long time ago to replace an SMD part, but I'm almost out of butane.

author: Fraser
author_rank: Super Contributor
timestamp: October 20, 2013, 10:01:02 am
content: I suggest you write to Velleman detailing your experience with this kit and the faulty pcb trace. Velleman are actually a very good company to deal with. I detailed a fault on the PC Controlled function generator that I built (noise on teh clock line) and Velleman responded by offering any two kits from their basic range. I received the LCD sign unit and the FM radio receiver kitVelleman kits are usually well tested so if one does not work, they are interested. Many faults are caused by component placement error but yours is a pcb production fault so more serious.
Fish tank - random lights. - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: January 07, 2019, 06:28:12 pm
content: A few months back my fish tank lights started fail. They now only come on randomly. I checked and double checked the timer, even bypassing it and plugged directly into a working wall socket they don't come on. Of course randomly through the week I'll walk into the living room and they are on and working fine. Then the next day they don't come on at all.The fish tank has two fluorescent tubes so I would imagine if it was the bulbs failing one or other would go first not both together.I don't know if they share a starter, but they probably share a ballast.An lid with LED lamps is £145! Nearly as expensive as the fish tank was in the first place.I suppose my first question is...how much of a fire risk is it if the ballast has almost failed?Second question, are ballasts easy to find and replace, bearing in mind I have to crack open the glued enclosure ... before I can do that I need to degunk/dealgae the lid. If I'm going that far surely I should attempt to fit custom LED light strips and use an external power brick/LED driver.
Fishfinder/depth finder Transducer/Sensor - Page 1
Forum section: electronics / beginners

author: jesse405
author_rank: Newbie
timestamp: July 15, 2022, 09:40:13 am
content: I need to confirm that a Transducer is working. I don't know if there is a continuity test or? that will do this.I have an old Hummingbird Smartcast designed for wireless/RF sensor - but also has a compatible jack on the back for a hardwired transducer I have fromanother old unit. I set it all up with the hardwired transducer in the water but the screen keeps saying 'Waiting for Signal' as though it is still waiting for anRF signal from the wireless unit. I went through all the menus, etc that I could find and nothing indicates any use of the hardwired sensor. So... I need toconfirm that the old hardwired one is operational. Any clues out there? I saw where there was someone named David who has some experience in this field?Any info would be greatly appreciated. Attached is a picture. Mine is a 'Hummingbird 455 High Definition Sensor'.

author: CaptDon
author_rank: Super Contributor
timestamp: July 15, 2022, 11:19:40 am
content: If you are handy with a scope and signal generator you may try applying a signal into the transducer through a resistor of perhaps 1000 ohms and then look at the transducer side of the resistor for a change in signal level around 150Khz to 200Khz. I would expect to see a resonance peak at around 180Khz where many of these units operate. As for signal level, a 5vpp sinewave applied through the series resistor should be plenty. When they pulse these sensors they do it with around 200vpp of a nearly square wave. They really hit these sensors hard and some are known to fail if they are not submerged in water while operating.

author: jesse405
author_rank: Newbie
timestamp: July 15, 2022, 07:36:05 pm
content: Thanks! I don't have a scope anymore.... But that detail infowill help when I take it to my buddy who does... And I am thinking you might be right - that someone burned it up out of the water.
Fix lcd display on pcb board with metal  - Page 1
Forum section: electronics / beginners

author: zulunation
author_rank: Contributor
timestamp: September 08, 2023, 06:02:04 pm
content: HI ALL,I am using popular LCD screen on PCB board.I need to fix it somehow. I was using a sticky tape (on both sides) but it doesn't hold for a long time.Maybe there are special metal holders which can be soldered on PCB board?I didn't found any.I have added a picture to illustrate that.I have pictured the fix element with red color.I can made them by myself from thing metal but maybe there is a ready made solution?Thanks

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 08, 2023, 07:58:24 pm
content: Double-sided foam tape.

author: zulunation
author_rank: Contributor
timestamp: September 28, 2023, 04:52:08 pm
content: Yeah,As I said I was using double sided tape but it does not holds well. Maybe it is poor quality.I would like to use metal holders. For reliability.

author: ataradov
author_rank: Super Contributor
timestamp: September 28, 2023, 05:09:35 pm
content: Did you use foam tape or just plain double sided tape?It is really hard to apply necessary pressure with displays for the plain tape to stick properly. But the foam tape (~2 mm thick) can be pressed and it will apply the pressure on its own. With added thickness, ribbon cable has less leverage too.If foam tape does not work, then it is either a really bad tape, or you have some excessive forces in the cables. With the foam tape there is usually the opposite issue - removing it when necessary, it requires some work.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 28, 2023, 05:43:00 pm
content: if you use 3m tape dual sided, some types from them means : once its glued, good luck to remove it, you'll rip the entire thing just trying to loose it upthey where called vhb series i thinkhttps://www.3mcanada.ca/3M/en_CA/bonding-and-assembly-ca/vhb/

author: TimFox
author_rank: Super Contributor
timestamp: September 28, 2023, 05:46:23 pm
content: With rigid objects pressed against each other, regular "double-sided tape", which is a thin tape coated with adhesive on each side, cannot cope with mismatch between the two surfaces and will have low adhesion.Double-sided foam tape (0.5 to 1.5 mm thick, typically) will conform to the mismatch and press against both surfaces for better adhesion.The really good stuff is used to mount rear-view mirrors on automobile windshields,https://multimedia.3m.com/mws/media/402121O/3m-structural-bonding-tape-9214.pdf, but requires a heat-cure after application.

author: Gyro
author_rank: Super Contributor
timestamp: September 28, 2023, 05:54:54 pm
content: If using double sided foam tape, make sure you have clear corner alignment marks on the PCB and use gentle even pressure when attaching. There's nothing worse than a crooked display that is difficult or impossible to remove.
Fix Scratchy-feeling Rotary Encoder - Page 1
Forum section: electronics / beginners

author: yoctoflop
author_rank: Newbie
timestamp: November 21, 2018, 06:27:49 am
content: I recently replaced some glitchy rotary encoders in a piece of equipment with thesehttps://www.mouser.com/ProductDetail/Bourns/PEC16-4020F-N0024?qs=7YHpgRs8DgzaOU2kUEObfg%3D%3D.They are functionally perfectly fine now, but as I turn them, they feel scratchy and gritty, definitely unlike the ones that were previously in it. They felt fine out of the package, so I'm thinking maybe my soldering process could have possibly damaged them. Could this simply be a matter of replacing the grease inside them, or could there be a more severe problem (e.g. a bent shaft)? Thanks.

author: tautech
author_rank: Super Contributor
timestamp: November 21, 2018, 06:35:27 am
content: Welcome to the forum.Most likely your issue results from the knob scraping on the front panel as they're not bottoming on the shaft or rebate. A felt washer behind the knob or a small packing in the knob recess will keep it from scraping on the panel.

author: yoctoflop
author_rank: Newbie
timestamp: November 21, 2018, 06:51:54 am
content: I can visually see that the knobs are ~1mm above the panel when fully pressed onto the shaft, so it's definitely the encoders' fault.

author: tautech
author_rank: Super Contributor
timestamp: November 21, 2018, 07:03:35 am
content: Quote from: yoctoflop on November 21, 2018, 06:51:54 amOK.Is the solder mounting the only way they are secured ?If the solder mounting and a chassis mount are not perfectly aligned there could be stress on the encoder.

author: xavier60
author_rank: Super Contributor
timestamp: November 21, 2018, 07:37:29 am
content: From my experience, new mechanical rotary encoders normally do feel somewhat gritty. They get smoother with use. Also, I always lubricate them with some PAO synthetic oil anyway.I recently purchased a 20 year old HP DSO. It must have had an easy life because some of its encoders felt gritty for a while.
Fixed threshold difference Schmitt trigger? - Page 1
Forum section: electronics / beginners

author: SittingBear
author_rank: Contributor
timestamp: July 15, 2014, 07:59:50 pm
content: I want to change the high threshold level by a potentiometer, or similar component, manually while always keeping the difference of levels between the thresholds equal.Example:Code:High: 2v Low: 1.8vThen change potentiometer to raise high-threshold:Code:High: 5v Low: 4.8vor a ratio (90% low to high ratio as above):Code:High: 5v Low: 4.5vI've tried with messing around with the Vref value, but I'm not sure if that's the proper thing to do.Is this even possible, and if so how? Thanks very much in-advance for any help!Below is the circuit I have drawn up so far (it's a scan so forgive the angle).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 16, 2014, 12:17:57 am
content: That's the basic idea. You don't really need the follower from the pot, if you dimension the pot to be a low resistance relative to the feedback divider. Or if you want the dead band proportional to setting, use a current source to put some voltage across the pot and the pot resistance adds in series with the feedback resistor. (The pot alone, with voltage sources and/or resistors at either end, won't give a linear response; the Thevenin equivalent is lowest towards the ends and highest in the middle.)Tim
Fixing a small SMPS (for dual LM317 split supply) - Page 1
Forum section: electronics / beginners

author: Cliff Matthews
author_rank: Unknown
timestamp: December 04, 2017, 12:59:19 am
content: Sorry for all the pictures... I want to make a split variable 317 supply of +/-24v at 700ma, so I picked-up 2 15-watt 24v SMPS's for use as pre-regulators. I wanted to test the limits of the optional adjust pot to see if I could get 30v stable. It turns out I can, but I pooched one of the units zener by briefly testing its maximum output.Googling ZC 339D gives me nothing. Now I need to know what zener to use, or can I use a 1watt glass type?Also, is there a definitive way to read part numbering like this? (eg: the stepped line around barrel)Googling ZC 339D gives me nothing

author: mikerj
author_rank: Super Contributor
timestamp: December 04, 2017, 10:02:56 am
content: When you say the adjustment pot is an option, I suspect you mean that you can order it with the pot fitted? This being the case, it's almost certain that some of the fixed resistor values are changed when the pot is fitted, which gives the stated adjustment range (and prevents things blowing up when the pot is turned to minimum resistance).

author: Cliff Matthews
author_rank: Unknown
timestamp: December 04, 2017, 11:27:43 am
content: Thanks, makes sense one smd part underneath must be different. On the zener: since I don't need the stock 24v, does it really matter how close I get? As long as clamping doesn't kill the 35v caps, I could test some pulled parts for 30 to 33 volts, right?By its number,ZC339D could mean 33.9v, sure wish I knew(Note: Ideally, I'd like to switch-in 24 or 32v, then I can current limit on another 317 with a few resistors and panel switch)

author: Cliff Matthews
author_rank: Unknown
timestamp: December 05, 2017, 12:57:32 am
content: OK, last 2 digits were a date code and complete part # was 1ZC33. Replaced zener's with33v 5-watt(ITT #1N5364B), and upgraded output el-caps to a more reliable 50v. These will be switch selected to run at 24v-700ma or 32v-500ma).
Fixing Calculator LCD missing pixels - Page 1
Forum section: electronics / beginners

author: sairfan1
author_rank: Frequent Contributor
timestamp: January 24, 2022, 02:14:04 am
content: Please refer to below image this calculator LCD is missing pixels, when i press this ribbon cable it shows correct digits. A quick google shows some people fixed it by applying hot air and some with soldering iron.I want to know what is better option, hot air gun or soldering iron? (i have both tools) I also want to know what temperature should be applied in any case.On some posts i saw that wide face metal is most helpful, any thoughts?

author: mathsquid
author_rank: Frequent Contributor
timestamp: January 24, 2022, 04:07:10 am
content: I’d use hot air and a pencil eraser. Heat the ribbon cable a bit, then take the eraser and press down on the cable and rub the eraser along the direction of the wires. I’ve managed to fix a few LCD issues by doing this.I wouldn’t use a soldering iron. I’d be afraid I’d melt the cable.

author: james_s
author_rank: Super Contributor
timestamp: January 24, 2022, 04:35:15 am
content: Put a piece of paper over the ribbon and rub a soldering iron across that where the joint is. I've fixed the same problem on several Gameboy handheld games that way.

author: rpiloverbd
author_rank: Regular Contributor
timestamp: January 24, 2022, 12:27:04 pm
content: I think a hot air gun is better. But, sorry. I can't recommend any temperature without knowing the model number of the LCD and seeing its datasheet.

author: PKTKS
author_rank: Super Contributor
timestamp: January 24, 2022, 01:04:32 pm
content: Quote from: james_s on January 24, 2022, 04:35:15 amI use a proper TIP for that...Mileage will vary but the proper the tool greater the chance..Paul

author: sairfan1
author_rank: Frequent Contributor
timestamp: January 24, 2022, 03:52:16 pm
content: Any good idea temperature to set on Hot air or soldering iron while using any technics.

author: PKTKS
author_rank: Super Contributor
timestamp: January 24, 2022, 04:15:44 pm
content: Quote from: sairfan1 on January 24, 2022, 03:52:16 pmBoth bad idea... in less than a second a wrong setting will melt the plasticsPaul

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2022, 12:09:26 am
content: The problem with hot air is it just heats everything up but doesn't press the contacts together. You need to apply both heat and pressure to the adhesive to re-bond it.
Fixing H8 LED bulb which sometimes does not shine - Page 1
Forum section: electronics / beginners

author: symbianas
author_rank: Regular Contributor
timestamp: September 10, 2023, 07:59:59 am
content: Hi, I have bought "ebay" H8 LED bulbs for my car (on the right side of the image). I suspect they have big resistor and some kind of CAN BUS attachments to it. The issue is that the bulb sometimes does not shine, mostly on startups. I suspect loose connection to it. I am thinking to remove connectors and solder wires instead (marked in circles on photo). Could this fix the issue?I have another set of LED's for this car (on the left side of the image), maybe I could reuse the bottom part of it or does it contain different resistor if it was rated at bigger wattage and had more LED's?Also what power supply do I need to test loose connection for these bulbs? Would just simple 12V 2A do the trick?

author: MrAl
author_rank: Super Contributor
timestamp: September 10, 2023, 09:16:49 am
content: Quote from: symbianas on September 10, 2023, 07:59:59 amHi,You should try jiggling the wires when a bulb does not start to light up. See if it lights up after you move the wires around and if it does you know you have a loose connection.If that doesnt work then maybe the driver is defective. That means send them back and get new ones from somewhere else.
Fixing Marantz SR1040 - Page 1
Forum section: electronics / beginners

author: mrkva
author_rank: Unknown
timestamp: December 01, 2012, 12:05:13 pm
content: Hey guys,just obtained one beautiful piece of receiver and tuner. The only problem is that it doesn't work. When turned on, I just hear slight hiss in the speakers and very quiet music (almost not noticeable). I managed to get a service manual, but I don't really know how to orient myself there, what to look for. I understand schematics, I have meter and a digital scope, but maybe some of you already have an idea what can be the issue?Thank you very much for your help. I have uploaded the service manual for you here:http://www.sendspace.com/file/rbdk1kJonas

author: w2aew
author_rank: Super Contributor
timestamp: December 01, 2012, 02:18:22 pm
content: Typically, you'd start with the basics. Check all of the power supply voltages to be sure each of them is working, and are clean. Check them at each of the subcircuits/boards.If they're all ok, then start narrowing down the problem. Does the unit work with a Line input or a phono input? How about AM vs FM? This should help you to narrow the problem down to a particular block. Then, work though the suspect blocks, checking bias voltages and functionality (injecting signals and measuring where necessary. Follow any troubleshooting charts that may be in the service manual.That should be enough to get you started.
Fixing QC1920 - Page 1
Forum section: electronics / beginners

author: Jbliss
author_rank: Regular Contributor
timestamp: August 14, 2015, 04:41:07 am
content: Hi Im trying to fix a old oscilloscope the digitech QC1920. the + and -12volt rails were both down I replaced the regulators and there working however there is a separate PCB with a hidden fuse which keeps blowing. I have tried putting a larger fuse for trouble shooting when I did the the 12v rail dropped to 1 v i believe this seperate PCB is loading down the 12v rail but I can't work out whats wrong. The fuse is directly connected to the + and - 12 volts.Can some please helpthis is the only scope i have and would like to try and get it working again.

author: Jbliss
author_rank: Regular Contributor
timestamp: August 14, 2015, 04:43:18 am
content: here are the shematics

author: Jbliss
author_rank: Regular Contributor
timestamp: August 14, 2015, 05:01:45 am
content: here

author: vk6zgo
author_rank: Super Contributor
timestamp: August 14, 2015, 07:53:02 am
content: I have a very similar looking CRO,which died on me on one occasion..I found that V709 or V710 was faulty (can't remember which,but the former seems the most likely).It was some obscure part number,but I replaced it with a transistor of the same package salvaged from a switchmode supply in an old piece of equipment.Would have liked to have replaced both with the salvaged pair,but one of them ended up with a short leg during extraction.It didn't matter---the beastie fired up perfectly!

author: singapol
author_rank: Frequent Contributor
timestamp: August 14, 2015, 08:05:28 am
content: Hi,I don't see a hidden fuse you refer to...unless it's the fuse F701 before 7812. Anyway both 7812 and 7912 are part of switching power supply circuit developing 140V and 220V to feed vertical and horizontal drive circuit for the CRT ( cathode ray tube).Most likely drive transistor V709/710 may have shorted. I hope the transformer is still good...Schotkey diodes V711 - V714 may have shorted. ( They will measure low resistance but they are good,only if they measure dead short from both polarities can you be sure they are defective).So are the high voltage electrolytic filter caps C715/716 respectively. Also check R703 47 ohm and R704 430 ohm.Hopefully you can find the fault. Good luck.Edit: Most likely vk6zgo has confirmed my suspicion...but check the rest of the components anyway.

author: Jbliss
author_rank: Regular Contributor
timestamp: August 16, 2015, 08:55:23 am
content: Hey Guys ThanksI found the shorted Transistor and have replaced it with a new one i could not find the exact one. But It Works !!!! however the new transistor makes really quiet noise Is this a problem
Fkc05-12D12 regulator module... - Page 1
Forum section: electronics / beginners

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: June 06, 2014, 01:06:28 am
content: I was going to use one of these just to get a -12volt rail, but found out that if the rails aren't evenly loaded, they become unbalanced... 60ma load dropped it to -11.8volts.http://www.amtex.com.au/power_pdf/FKC05%28W%29.pdfI've already designed the pcb with this part, but can always change it...Is there another option to easily get -12volts at upto 100ma, from a 15-19volt input voltage?Thanks!

author: jahonen
author_rank: Super Contributor
timestamp: June 06, 2014, 03:43:49 pm
content: If you need just the negative voltage, you can use single output type and connect positive output to your ground. This works because the module is isolated.Regards,Janne

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: June 06, 2014, 10:01:56 pm
content: I already had this part, so I designed the board around it, before I tested what it did with an uneven load
flash memory erase - Page 1
Forum section: electronics / beginners

author: vitUP
author_rank: Newbie
timestamp: January 06, 2015, 12:16:16 pm
content: Why flash memory can only be erased on block level. Is it a convention or something else?

author: IanB
author_rank: Super Contributor
timestamp: January 06, 2015, 12:24:27 pm
content: What mass storage technology do you know of that isnotaddressed at a block level?

author: macboy
author_rank: Super Contributor
timestamp: January 06, 2015, 01:25:53 pm
content: Quote from: IanB on January 06, 2015, 12:24:27 pmFlash erase blocks are different than, say, a hard drive sector (.5 or 4k). The flash erase block can be many MB in size, and the whole thing needs to be erased in one (time consuming) pass.Even NOR Flash, which is byte addressable like any other memory technology, must be erased in large blocks. On smaller (sub Gb) devices, it is not unusual for the erase block to be as big as 1/16 of the total capacity.Wikipedia has a good description of how Flash works at the quantum level. The reason for erasing in blocks is due to the need to put different voltages onto different parts of the storage cell (transistor) for programming or erasure. Individually wiring each byte's worth of cells to allow byte erasure would add too much extra wiring complexity and take away valuable real estate from being used for storage. Instead, multiple cells are wired together so that these voltages can be applied to an entire block at once. There is also the issue of performance. Erasing a cell takes time; erasing a million cells in parallel takes exactly the same amount of time. And this is no small amount of time. We are not talking on the order of micro- or milliseconds, but tenths of seconds per block. That would be per byte if done that way.
Flash memory not compatible or status register settings ? - Page 1
Forum section: electronics / beginners

author: Sjokolade
author_rank: Regular Contributor
timestamp: November 07, 2023, 02:12:11 pm
content: HiI'm replacing the flash chip memory on my netgear router with bigger sizes and now I'm stuck.It orginally came with a32Mb MX25l3205D, I replaced it with a64Mb MX25L6405Dand upgraded it to a128Mb S25FL128working just fine.Now I'm trying to get it to boot a256Mb MX25l25735Ewhich it will not - the chipset supports 256Mb flash but I dont know if this exact memorychip is supported.Can it be as simple as setting the right status registers to get the chip in right mode ?Thanks

author: alligatorblues
author_rank: Regular Contributor
timestamp: November 08, 2023, 07:49:17 am
content: The chipset might support 256 MByte flash, but the system might be configured to a lower maximum by the mcu, the storage bus, or firmware. Also, the 256 Byte flash might be a different density, or bit configuration. The number of bits per bank could be incompatible with the storage controller. So, you need to match all that up in the datasheets.
flashing LED''s - Page 1
Forum section: electronics / beginners

author: BazzaKeen
author_rank: Newbie
timestamp: October 23, 2023, 10:14:34 am
content: Hi allI recently made a led panel from led strips to go over my work bench, all works well most of the time but occasionally they start to flash, I wired them in series and the power supply is ample for the strips,Help required please, as I need the extra light to work from.

author: PlainName
author_rank: Super Contributor
timestamp: October 23, 2023, 11:06:39 am
content: QuoteThe flashing is typical of a supply that isn't quite up to it. Your problem would be much easier to diagnose if you said:* what the LEDs are* what the PSU is* how fast the flashing is (once a minute? second? 5 times a second?)

author: Zero999
author_rank: Super Contributor
timestamp: October 23, 2023, 11:19:02 am
content: It could be a loose connection, or the bond wire inside the LED failing.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: October 23, 2023, 11:29:42 am
content: Hi BazzaKeen,have you checked the voltages (Mains, V-Led, V-PSU)?Have you tried shorting out some LEDs (since series-connected)?More info.Good luck

author: hovadmartin
author_rank: Newbie
timestamp: October 23, 2023, 11:40:27 am
content: It sounds like there are loose wires or solder joints. If not, try rewiring the LED strips in parallel rather than in series. There's a tutorial on theirwebsiteI believe.

author: liaifat85
author_rank: Regular Contributor
timestamp: October 23, 2023, 01:00:01 pm
content: It can be either a loose connection or excessive heat. Have you used any heat sink in your LED panel?LED strips can overheat if they are not adequately cooled. Overheating can lead to flickering. Also, make sure that all components are properly grounded. And just in case, if you ever consider redesigning your panel, you can take a look here.https://www.pcbway.com/project/shareproject/LED_Panel_V2_5b035fa1.html
Flat coil calculations - Page 1
Forum section: electronics / beginners

author: yalect
author_rank: Regular Contributor
timestamp: June 08, 2018, 01:02:33 am
content: Hello,I would like to ask you how to calculate flat BCB inductor value I found some spiral inductor formula but mine is straight not spiralThanks

author: Dukov Ahzrukhal
author_rank: Regular Contributor
timestamp: June 08, 2018, 02:04:32 am
content: Hello, could you post a picture to illustrate the inductor you're talking about? I recently took a class on electromagnetism, I can send you some of my notes if you want.

author: MasterT
author_rank: Frequent Contributor
timestamp: June 08, 2018, 02:25:51 am
content: http://coil32.net/pcb-coil.htmlhttps://www.eeweb.com/tools/rectangle-loop-inductance

author: yalect
author_rank: Regular Contributor
timestamp: June 08, 2018, 06:42:40 am
content: Thank youMaybe flat and square PCB inductor three sides not four

author: emece67
author_rank: Frequent Contributor
timestamp: June 08, 2018, 07:18:58 am
content: .
Flat panel Monitor repair - Page 1
Forum section: electronics / beginners

author: Jamescbarrow
author_rank: Newbie
timestamp: September 17, 2020, 12:15:43 am
content: I am working for someone that refurbs arcade machines, and he was asking me about doing flat panel monitor repair as he has a lot of them, question is what would be the most common issues besides bulging caps, and issues with the backlight, they are all pretty much computer monitors, using vga for a signal. what tools would I need to do basic repairs, besides a multimeter and a esr meter.

author: radiolistener
author_rank: Super Contributor
timestamp: September 17, 2020, 01:04:46 am
content: Quote from: Jamescbarrow on September 17, 2020, 12:15:43 amscrewdriver, tweezers, hot-gun, and soldering station, desoldering pump

author: Jamescbarrow
author_rank: Newbie
timestamp: September 17, 2020, 01:22:54 am
content: Kinda what I was thinking, am I correct in thinking most of the issues will be bad caps due to failed power supplies.

author: MosherIV
author_rank: Super Contributor
timestamp: September 17, 2020, 07:29:59 am
content: HiWelcome to the forum.Yes, most commonproblems with lcd monitors isA. Back light gone end of lifeB. Caps gone badOther issuesDry joint on controller chipController chip died.
Flat ribbon cable -- repair or replace? - Page 1
Forum section: electronics / beginners

author: whatever
author_rank: Contributor
timestamp: January 03, 2024, 06:43:39 pm
content: I need to REPLACE both of these cables. They are from a 1986 Kenwood CD player (made in Japan)PROBLEM: On the quick-disconnect end, the firm (clear) plastic (rectangular) piece to which connector terminations to are attached has fallen off.REPAIR ATTEMPTS: I tried to carefully super-glue, but I can't seem to make connections again. I also tried thick plastic clear tape (see photos). I did try to rig another connector which may or not work; because BOTH ribbon connector are bad, the CD player is not functioning normally, and I have time only to play with the smaller connector.Not sure whether these ribbon connectors are common sizes? One has 8 terminals; the other has 14.Perhaps if any of you know of a source for such cables, that would be ideal.Thanks!BELOW: The plastic laminate fell off; so the used a piece to clear tape to adhere the connection. Note misalignment.BELOW: The plastic laminate fell off; so the used a piece to clear tape to adhere the connection. Note misalignment.BELOW: The soldered end on the CD transport PCB:
Flea Mkt. Purchase. (what is it?) please - Page 1
Forum section: electronics / beginners

author: 6Shooter
author_rank: Newbie
timestamp: January 30, 2017, 06:21:48 pm
content: I think it is a hi voltage DC supply, but Im fairly new to reading schematics.Thank YouDoug

author: calmtron
author_rank: Regular Contributor
timestamp: January 30, 2017, 07:04:55 pm
content: Looks like a big, non-isolated, variable voltage, selectable AC or DC output power supply.

author: james_s
author_rank: Super Contributor
timestamp: January 30, 2017, 07:11:25 pm
content: It's a power supply of some sort, I don't see any transformer in there so it's not going to be particularly high voltage. Probably not very useful as-is but it might contain some potentially useful components.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: January 30, 2017, 07:25:31 pm
content: Hi,bigger pictures of the unit would helpThe circuit diagram is quite hard to read, but I don't see any HV stuff right now, it looks more like somthing that has to do with motors? At least there is a reference to motors at the bottom and middle left part of the diagram and I guess the big black thing in the middle of the inside picture could be a motor.Also, there doesn't seem to be any transformers, so no isolation. Be careful with that thing!Btw, welcome to the forum!

author: Ian.M
author_rank: Super Contributor
timestamp: January 30, 2017, 08:06:43 pm
content: It looks like its got a big 120V 15A motorised Variac - bottom section of cabinet and bottom left of schematic. According to the schematic, there's also a 70 second motorised timer which appears to be wired to ramp down the Variac.The Variac would be worth a bit.%DEITY% only knows what the original purpose was.

author: BrianHG
author_rank: Super Contributor
timestamp: January 30, 2017, 09:26:03 pm
content: Quote from: Ian.M on January 30, 2017, 08:06:43 pmWith a large motorized variac, maybe it's for professional remote control stage lighting. I know large variacs used to be used in professional stage lighting or film sets as well as huge wind blowers. Triac based dimmers were just un-acceptable is such situations where you need the full dimming range, silent non-buzzing lamp filaments with reliable shades all the way down to black.

author: 6Shooter
author_rank: Newbie
timestamp: January 30, 2017, 09:50:16 pm
content: Thanks everyone for the quick responses. I paid 20.00 for the object with the intent of stripping parts especially the variac. But then I thought I better ask around in case it was more usefull as is. Based on the responses I pulled the variac and tou guys were right on. Google the model and it is a motorized variac for motor testing. So now Ive got some vintage parts to play with including what looks like a large heavy duty bridged rectifier and some old style meters.Doug