hybridfree/eevblog-posts huggingface dataset:
POWER SUPPLY WIRING - Page 1
Forum section: electronics / repair

author: aleeeeaaa
author_rank: Newbie
timestamp: December 04, 2022, 05:53:10 pm
content: i HAVE A POWER SUPPLY WITH 5 WIRES THAT NEED TO BE SOLDERED TO THE BOARD. THE WIRES COMING OUT ARE ONE YELLOW WHICH I KNOW IS GROUND. TWO GREEN WIRES THAT HAVE 19 VOLTS ON EACH ONE AND 2 RED WIRES WITH ABOUT 40 VOLTS ON EACH ONE. I DO KNOW THE FIRST HOLE ON THE LEFT OF THE BOARD IS GROUND. wHERE DO THE RED AND GREEN WIRES GO. i HAVE ENCLOSED A SCHEMATIC OF THE BOARD.

author: feedback.loop
author_rank: Frequent Contributor
timestamp: December 04, 2022, 07:50:23 pm
content: Your keyboard needs fixing.

author: R-1125F
author_rank: Regular Contributor
timestamp: December 04, 2022, 11:35:14 pm
content: I would really help to know what the equipment is. Brand and model?

author: AkibUddin
author_rank: Contributor
timestamp: December 05, 2022, 03:32:56 am
content: Quote from: aleeeeaaa on December 04, 2022, 05:53:10 pmPlease try to attach your device photo

author: Swainster
author_rank: Frequent Contributor
timestamp: December 06, 2022, 01:38:51 am
content: My best guess - see pic (look for the rectifier diodes on the board)
Power switche Oscilloscope Rigol 1052 - Page 1
Forum section: electronics / repair

author: GGMM
author_rank: Frequent Contributor
timestamp: September 16, 2023, 04:51:41 pm
content: Hello,I anticipate a push button troubleshooting of this type on a Rigol oscilloscope.Where do you think i can buy this piece?If you have a reference.see pictures capted from youtubethank you

author: GGMM
author_rank: Frequent Contributor
timestamp: September 18, 2023, 01:43:17 pm
content: hello,Something that starts to look likeSmall adjustment to makeIt's 50v 0.5A, some others models. to be seehttps://www.chinadaier.com/ps-12e01l-maintain-spring-return-switch/cdt

author: tunk
author_rank: Super Contributor
timestamp: September 18, 2023, 02:56:00 pm
content: If it's on the primary side, it needs to be at least 230V.

author: GGMM
author_rank: Frequent Contributor
timestamp: September 18, 2023, 03:14:48 pm
content: Hello,I know. That’s an example. You can probably find for 230V.I have some old TV shackles. I’m sure I have a similar switch. It may have 6 pins?Anyway, I have to go to see the case.We can imagine a poultice. LOLcdt

author: GGMM
author_rank: Frequent Contributor
timestamp: September 20, 2023, 03:04:56 pm
content: hello,i have foundsee herehttp://szbej.com/en/index.php?r=article/Content/index&content_id=931it's the sameI think it is possible to repair it with an equivalentGet the part that holds the button, it should be fine

author: GGMM
author_rank: Frequent Contributor
timestamp: September 23, 2023, 05:55:18 pm
content: the switch has been reattached and it works very welcdt
Power Wise 28115 G04 E-Z-GO Golf Cart Charger Schematic (Ferroresonant) - Page 1
Forum section: electronics / repair

author: Kugelsicher
author_rank: Contributor
timestamp: May 12, 2024, 08:23:38 pm
content: Traced out the circuitry for an EZ GO golf cart charger, Power Wise model 28115 G04, while attempting a repair. I thought it was interesting and perhaps it will be of help to someone.The charger and cart aren't mine. In spite of the charger being covered in mud, nothing is wrong with it. There is an 8-bit micro-controller that checks for a minimum voltage that the cart battery apparently isn't meeting. The charger doesn't indicate this in any way.It's a ferroresonant transformer that is powered from the mains through a relay; however, all of the electronics are powered by the DC output side (or the golf cart battery itself when not charging).

author: SeanB
author_rank: Super Contributor
timestamp: May 12, 2024, 08:54:37 pm
content: Most common fault with ferroresonant devices is that resonating capacitor going low value, which results in poor regulation, though you also will have to be aware the voltage across that capacitor is very much higher than mains, and is dependent on load current. Capacitor 10% low in value change it, and preferably with a 440VAC rated motor run capacitor over the 370VAC rated one, as it will last longer there. Have seen them burn those capacitors out, with the converter working fine just with lots of noise and smoke. Otherwise the diodes failing, though normally they are pretty reliable, as the limiting results in a very long conduction angle as the secondary coil saturates and presents a almost square wave output, so the diode conducts over a larger portion of the sine wave. that and inherent voltage limiting within limits, so the lead acid batteries get to float voltage and stay there.

author: Kugelsicher
author_rank: Contributor
timestamp: May 12, 2024, 11:19:04 pm
content: Thank you for the advice. The unloaded output measured 44V. I don't know what's normal and I only energized it briefly as I suspect it isn't designed for no load. The cap measured right on 20uF but it was on a multimeter not an LCR meter; so I don't know what the ESR is and I know leakage looks like extra capacitance. Given your comment that they're often the point of failure; I'll go ahead and replace it before returning it. The spade connectors were so rusted on that cap terminals that I had to break them off and replace them; so that probably should've told me to just replace the cap
Powerland Battery Charger - Page 1
Forum section: electronics / repair

author: Poroit
author_rank: Frequent Contributor
timestamp: August 23, 2024, 03:55:25 am
content: I am doing a teardown of a Powerland 48V Li Battery Charger.The Charger contains a MC9S08PA4 which I assume is the charging controller.I have traced connections from to battery connector back to Pins 7 & 9 of the MC9S08PA4.Can anyone suggest the type of signals I should measure on these pins as I can only measure DC Voltages at the battery connector?

author: indeterminate
author_rank: Regular Contributor
timestamp: August 23, 2024, 06:33:23 am
content: Its just a 8 bit cpu with the usual add-onshttps://www.nxp.com/docs/en/data-sheet/MC9S08PA4.pdfpin 7 & 9 are labeled as data ports so you could expect 3.3 / 5v & 0 v depending on what voltage it is running onit may be data from the BMS or it could just be simple logic levels .
POWERTEC OEM II Model 2B5-3 B 5 VDC supply schematic wanted - Page 1
Forum section: electronics / repair

author: wd5jfr
author_rank: Regular Contributor
timestamp: November 08, 2022, 10:17:49 pm
content: Smoke has gone out of one of the resistors and I need a schematic with parts values but can't find one googling.Any help appreciated.Hank

author: mariush
author_rank: Super Contributor
timestamp: November 08, 2022, 10:31:22 pm
content: Maybe post pictures of the circuit board?

author: wd5jfr
author_rank: Regular Contributor
timestamp: November 08, 2022, 11:02:47 pm
content: I added the circuit board pic but the resistor is under the 10000 ufd cap and I can't get a pic. I'm not going to tear into it unless I can find a schematic because I don't want to waste anymore time and end up with a basket case. I'll have to let it waste gravity as is.Hank

author: coromonadalix
author_rank: Super Contributor
timestamp: November 09, 2022, 03:05:31 am
content: standard psu with lm723 ic, they are not complicated to reverse engineer ..

author: wd5jfr
author_rank: Regular Contributor
timestamp: November 09, 2022, 03:18:39 am
content: It takes time and effort to reverse engineer and the burdens exceed the benefits and at 82 that means less real fun with greater benefits vs burden.

author: UtahMikey
author_rank: Newbie
timestamp: November 09, 2022, 06:23:05 pm
content: These are old linear standards. Probably don't need a schematic? Download uA723 IC data sheet. There is usually a 2N3055 pass transistor, or some in parallel?I have many of these in the junk bin from the old days.The 723 data sheet should show typical schematics. Check the electrolytics. Change them?
Powertech MP-3087 (Jaycar special) dual tracking repair - Page 1
Forum section: electronics / repair

author: w0lfie
author_rank: Newbie
timestamp: October 02, 2020, 12:45:30 am
content: Hi all,I bought a Powertech MP-3087 dual PSU from Jaycar many years ago (before I knew better) and it has been running largely well enough. One issue I've noticed is the voltage tracking in series mode is pretty bad. Sometimes it's pretty close (20-40mV) and sometimes the left PSU is 1-2+ volts off. I've confirmed with a meter that the outputs actually are wrong and not just being displayed as such.I've searched around trying to find any schematics or a service manual but haven't found anything. Before I go down the rabbit hole of doing that myself, I wanted to check with the wider EEVBlog community whether anyone else has done this before me, even partially?Does anyone have an inclination of what could cause the issue to happen or where it may reside? Any advice here would be really helpfulI'm happy to provide more information, just let me know what would be helpful.
Powertech MP3090/Manson SPS9400 - Page 1
Forum section: electronics / repair

author: raistlin119
author_rank: Newbie
timestamp: April 21, 2020, 11:27:51 pm
content: Good morning, I have used the powertech MP3090 also sold as the Manon SPS9400 successfully for many many years.Went to switch it on the other day and nada, nothing, the unit won't power on.The fuse is fine.Could I get some guidance as to what to look for? All the tracks look fine, no burn marks and none of the caps are bulging.Here's a generic pic of the unit.Thanks!

author: Manul
author_rank: Super Contributor
timestamp: April 22, 2020, 12:03:06 am
content: I would say it is not very common for SMPS to fail so silently and calmly. Does AC really come to the main board (I assume PT1 and PT2)?

author: coromonadalix
author_rank: Super Contributor
timestamp: April 22, 2020, 12:48:10 pm
content: maybe some "startup" electrolytic capacitors near the pwm icSchematichttps://eevblog.com/files/SPS9400_ServiceManual.pdfdo you have a voltage on the cathode of d2 in the section of u1you psu has a small power supply section to feed the other one, its called auxilary power supply, its in the section D1 thru D6, it feeds the displays and the main power supply section.You have a Dave eevblog video #272
Powerware Prestige 3000 UPS repair - Page 1
Forum section: electronics / repair

author: MetalHead
author_rank: Contributor
timestamp: December 06, 2022, 11:25:52 am
content: Hi guys!I have Powerware Prestige 3000P3HV double conversion UPS to repair. Pretty old one..There is an I*R module (see photo) that I can't identifyDoes anybody know part number and what is that?

author: TheMG
author_rank: Frequent Contributor
timestamp: December 06, 2022, 02:22:41 pm
content: Most likely a custom hybrid module, containing several IGBT and/or MOSFETs.

author: MetalHead
author_rank: Contributor
timestamp: December 06, 2022, 02:40:30 pm
content: Yes, i think so too. Too much legs for diode bridge and while it sits on heat sink it deals with hight currents.. (2000kw inverter or so)Wondering if I can find a replacement, but as fas as no part number on it chances to find replacement are low

author: wasedadoc
author_rank: Super Contributor
timestamp: December 06, 2022, 07:11:28 pm
content: Quote from: MetalHead on December 06, 2022, 02:40:30 pmI doubt that.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 07, 2022, 02:51:56 am
content: If the module is defective it might be possible with a bit of reverse-engineering to replace it with discrete parts. Might even be able to pop the lid off the hybrid and see the individual dies and internal configuration/wiring.

author: MetalHead
author_rank: Contributor
timestamp: December 07, 2022, 07:05:21 am
content: great!will try that

author: coromonadalix
author_rank: Super Contributor
timestamp: December 09, 2022, 11:23:30 am
content: Maybe inquire at IR Internation Rectifier ... they could answer youOr it's an custom partcould be a mix of parts IE:mosfets, triac, scr, igbt, rectifier diodes ...Some UPS are very cheap on Ebay ??
PPVIS SOFTWARE REQUIRED FOR CHLORIDE UPS - Page 1
Forum section: electronics / repair

author: DURBUGTI
author_rank: Newbie
timestamp: July 07, 2024, 06:14:52 am
content: Can Anyone Have PPVIS software File For CHLORIDE UPS.Kindly share link

author: coromonadalix
author_rank: Super Contributor
timestamp: July 07, 2024, 06:26:36 am
content: please do not write in capital letters it is considered yelling, you may not be appreciated

author: DURBUGTI
author_rank: Newbie
timestamp: July 07, 2024, 06:28:24 am
content: Thanks post has been modified

author: coromonadalix
author_rank: Super Contributor
timestamp: July 07, 2024, 02:11:36 pm
content: what i've found so far from the web ppvis 1.817 ppvis 2.0 read the text files, one has a password and the other as a readme txt file with a codehttps://file.io/muKgxeZjONnNalive for 7 days, i thinknot sure they are active / activablebattery reset, com cable wiring etc ...
Pragmatic 2202A With No Display - Page 1
Forum section: electronics / repair

author: jasonshepherd19
author_rank: Newbie
timestamp: November 06, 2020, 04:51:39 am
content: Hey guys, I've found a Pragmatic 2202A that I'm considering buying. The only problem is that it's broken. I don't have any experience with test equitment repair and I can't find anything online about this device, so I thought I could find some advice here. The Pragmatic 2202A is described as having no display. How difficult do you guys think it would be to repair this? What are the chances that the display isn't the only thing that is busted? And you guys have any info on this machine, like a manual, because I can't seem to find anything online? Thanks in advance, you guys are always so helpful!

author: Stray Electron
author_rank: Super Contributor
timestamp: November 06, 2020, 01:52:44 pm
content: I have a 2414. Unless you can get it for no more than $10 and just want a challenge, I wouldn't recommend buying it. Particularly since you have no experience repairing electronics. AFIK there is no service information available for them and Pragmatic is an uncommon brand so it's unlikely that you'll find anyone that can give you any advice.IF you still want to buy it, look at it closely first and if it shows any signs that anyone has already tampered with it, then DON'T buy it! There's no telling what was done in a previous repair attempt.

author: jasonshepherd19
author_rank: Newbie
timestamp: November 06, 2020, 05:13:52 pm
content: Yeah, that's pretty much what I was thinking. The back of it looks crusty and it's missing a bevel around the front panel, so it has probably been tampered with. Thanks for the advice!
Pre-Compiled Memtest86 v3.3 installable from Windows and DOS - Page 1
Forum section: electronics / repair

author: GGMM
author_rank: Frequent Contributor
timestamp: February 14, 2025, 06:12:23 pm
content: Hello,Someone has this version made for floppy disk to test with DOS. Pre-Compiled Memtest86 v3.3 installable from Windows and DOSI wouldn’t want to get into image unzipping, etc.I have to test the memory of an old PC, and I lost my afternoon with Vxd errors no3...So, it’s true, I’m looking for ease, but I have a little enough for today. LolThis no longer appears on the official website, unless I’m mistakenThank you

author: JohanH
author_rank: Frequent Contributor
timestamp: February 14, 2025, 06:23:53 pm
content: https://web.archive.org/web/20130722051627/http://memtest.org/download/old/

author: GGMM
author_rank: Frequent Contributor
timestamp: February 14, 2025, 07:20:55 pm
content: Thank you Johan,I have downloaded the file.Test on saturday.cdt

author: asis
author_rank: Frequent Contributor
timestamp: February 15, 2025, 03:28:52 am
content: Hi,If it comes to the stage of localizing a defective chip, keep in mind that the data bus and address bus lines on the memory bar may not be laid out in strict accordance in the classical sense with the binding to the pins of the existing chips, but in an arbitrary order.That is, mixed up both in the address line zone and in the data line zone.Here, everything is decided by the manufacturer himself from the point of view of optimizing the wiring of connections.In any case, access to the entire data array is provided, but it is very misleading when localizing the chip.-In this case, the best practice would be to first reverse engineer the memory bar, this will help a lot.Believe me.

author: GGMM
author_rank: Frequent Contributor
timestamp: February 15, 2025, 07:28:17 am
content: hi,I think I would find by elimination, I have several bars ahead.This is the most conventional method.Well after, some clean the contacts, reinstalls, etc. It is quite sensitive.cdt
Precision Standards AC-DC Differential Voltmeter 360A - manual - Page 1
Forum section: electronics / repair

author: calin
author_rank: Regular Contributor
timestamp: April 18, 2024, 03:58:40 am
content: I recently got anPrecision Standards Corporation AC-DC Differential Voltmeter, model 360A which I literally got it just because I've put a low ball offer and I got it for the price of a coffee.Now I kind of want to restore the thing but I cannot find the manual anywhere. Does anyone have by any chance a hint from where I can find the manual ?Either my Google fu is very low these days .. or really there is nothing I can find on the interwebs.Here is a picture of the thing .. maybe it helps to identify a manual

author: donlisms
author_rank: Frequent Contributor
timestamp: April 23, 2024, 12:23:21 am
content: Does it seem to work? I wonder if you can get by without the manual.

author: factory
author_rank: Super Contributor
timestamp: April 23, 2024, 10:10:48 am
content: Quote from: donlisms on April 23, 2024, 12:23:21 amGive it a visual inspection inside before trying it, to make sure there are no burnt parts, or any of those leaking wet tantalum capacitors that were commonly used in some 60s & 70s test gear.David

author: calin
author_rank: Regular Contributor
timestamp: April 28, 2024, 03:09:26 pm
content: Does look like working / turning on somewhat without releasing any magic smoke. But that's about it, the dial indicator just sticks to the max when I try to measure anything and that is it.I am a tad weary sticking my fingers too much in, when this thing is running, as it does produces internally some high tensions especially on the higher ranges.At worst I can gather some really nice precision resistors from the innards and end up with a nice project box if nothing better comes out of it
PreSonus Eris e66 audio amplifier problem - Page 1
Forum section: electronics / repair

author: duzycinek
author_rank: Contributor
timestamp: May 09, 2023, 02:48:53 pm
content: Hello, I got problem with PreSonus Eris e66. It has missing audio amplifier for mid tones. Right one is TDA7294 for high tones. Anyone know what amplifier should be placed there? Looking forward to hearing from you!

author: Audiorepair
author_rank: Frequent Contributor
timestamp: May 09, 2023, 08:53:43 pm
content: I would guess it's another TDA7294.But that's a guess.Does it have the same number of pins?

author: duzycinek
author_rank: Contributor
timestamp: May 09, 2023, 09:40:28 pm
content: Hey, thank you for yours response. It has same layout. I tried to place here TDA7294 but it died after powering up, so I am not sure if it is same amplifier.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: May 09, 2023, 10:06:09 pm
content: Where did you buy the TDA7294 from?

author: duzycinek
author_rank: Contributor
timestamp: May 10, 2023, 10:26:40 am
content: From local online store. I checked it before placing, measurments were same as original TDA.

author: wasedadoc
author_rank: Super Contributor
timestamp: May 10, 2023, 10:39:28 am
content: Did you check whatever the chip is feeding its power output into?If the original was missing, someone removed it. Solder bridges or other damage?

author: duzycinek
author_rank: Contributor
timestamp: May 10, 2023, 11:10:11 am
content: I did not check. It died instantly so was not even able to measuements. No bridges, no missing components, no other damage, board is clean, thats why I am guessing there will be different audio amplifier.
Prevent future problem of KORAD3005p - Page 1
Forum section: electronics / repair

author: Inno_Dim
author_rank: Newbie
timestamp: April 01, 2019, 12:59:04 pm
content: I have korad3005P psu and while I opened it for this projecthttps://www.instructables.com/id/Remote-Sensing-for-Korad-Power-Supply/where I enable remote sensing for the psu, I noticed that the resistor R1 gets overheated, (top left of the image)..Somewhere (maybe here) a person mentioned that replaced this resistor. So maybe I need to take precautionsTill now I think that this resistor is part of voltage divider that drives the cooling fan. When the fan is at idle speed most of the energy is consumed in this resistor. When cooling fan is running (under load) the resistor gets cooler as now most of the energy is consumed by the fan. (For those note having this psu I should mention that the cooling fan does not blow on this resistor by any means).I think that the resistor when fan is at idle speed operates constantly at its power limit, so I am afraid that sooner or later it will need replacement.Can anyone verify it? Could be bad design?

author: Bashstreet
author_rank: Frequent Contributor
timestamp: April 02, 2019, 08:26:10 pm
content: Quote from: Inno_Dim on April 01, 2019, 12:59:04 pmIf it gets hot just replace it with beefier resistor.

author: rodcastler
author_rank: Regular Contributor
timestamp: December 02, 2019, 11:56:42 pm
content: I managed to connect a Lipo battery for direct charging -against common sense and probably some manuals-Even more, I realized I had the polarity reversed after hearing the loud pop and the magic smoke smell.Upon inspection before fixing this little unit, I found two things that called my attention:First, the casualty was D1 (the largest diode visible at the bottom right, below the current sense spring wire). It had blown into pieces.Mi question is, how much protection is there after the diode has blown and the circuit gets open? I could not find the schematics for this board to check the protection circuit.Second, I am pretty sure that the silkscreen for that diode shows a reverse orientation, showing the cathode to the left side!!. Am I missing anything? I'm just glad I double checked against pictures on the internet before soldering the replacement diode. Otherwise I would have soldered it wrong.
Price & source of the axial capacitor - Page 1
Forum section: electronics / repair

author: syau
author_rank: Frequent Contributor
timestamp: November 30, 2019, 04:02:57 am
content: During the repair of old equipment, I encountered an issue of sourcing axial capacitor, Digi-key has limited availability, RS has better choice but expensive.Using radial capacitor may be a solution but required gluing it and extending the lead.Anybody know where I can find a good source of axial capacitors ?

author: Martin Hodge
author_rank: Unknown
timestamp: November 30, 2019, 07:06:01 pm
content: Did you try mouser and taydaelectronics.com? Amazon? Aliexpress? Not much demand for axial components these days.

author: Dacke
author_rank: Regular Contributor
timestamp: November 30, 2019, 07:40:15 pm
content: I was trying to find a good source myself in another thread. Digikey, Mouser, and Newark still seem to be the best bets for axial electrolytics with the biggest selection that I've found and used. For any axial electrolytic caps above 450V, I've used Antique Electronic Supply or Justradios.com before as well.
Pro Breeze® Air Purifier 5-in-1 with True HEPA Filter Repair - Page 1
Forum section: electronics / repair

author: csaszykj
author_rank: Newbie
timestamp: July 17, 2022, 07:04:39 pm
content: HelloCould anybody help to repair my Air Purifier?The Ionizer switches off the device after a minuter or so once it's switched on.The Fan only part of the Purifier faultless, works as it should.The manufacturer replaced the whole unit under warranty, and I don't want to throw away the "old one".Also it has touch sensitive buttons.Here are more detailed pictures:https://imagizer.imageshack.com/img923/8939/r233L0.jpghttps://imagizer.imageshack.com/img924/1911/91EWMi.jpghttps://imagizer.imageshack.com/img922/3352/tLl5sz.jpghttps://imagizer.imageshack.com/img923/3690/iTgG94.jpghttps://imagizer.imageshack.com/img924/593/E6O50V.jpghttps://imagizer.imageshack.com/img924/3031/6yjDNG.jpghttps://imagizer.imageshack.com/img923/5782/Qao5SB.jpghttps://imagizer.imageshack.com/img924/7999/jW1sU0.jpghttps://imagizer.imageshack.com/img923/2654/SxDH6d.jpghttps://imagizer.imageshack.com/img922/2970/N4iCfw.jpg

author: wraper
author_rank: Unknown
timestamp: July 17, 2022, 07:08:36 pm
content: This circuit apparently uses capacitive dropper, so check if the large yellow 1.5uF cap still has it's rated capacitance. Also be cautious as this circuit is directly connected to mains voltage.

author: csaszykj
author_rank: Newbie
timestamp: July 17, 2022, 07:10:14 pm
content: I've checked out with multimeter all the bigger parts, all the caps were empty/discharged.Obviously I not gonna plug in while the PCB is "naked" in my hand.Update:- the large yellow :https://imagizer.imageshack.com/img923/8751/YeuJY9.jpg- the smaller yellow is start from high and slowly discharges- the 3 other black cap - do i need to desolder them to get a good read? as I can't measure itThe back of the PCB has some shiny coating on, and as far as I can see - the Large Yellow cap has been replaced - as I can see flux residue on the joints.
Probem with monitor AOC i2369vm (LG IPS panel LM320WF3) - Page 1
Forum section: electronics / repair

author: ketrba
author_rank: Newbie
timestamp: February 01, 2021, 12:03:34 pm
content: Hi,I have probem with monitor AOC i2369vm (LG IPS panel LM320WF3).Half of display has defect on every other line.I checked it on problem lines:- red subpixel is OK- green subpixel is darker- every other blue subpixel is darkerI am added a microscope photo for the displayed white image.On board LCD panel I verified voltage on:VGH ~ 28VVGL ~ -7and this loks ok.Is there a chance to repair the panel?

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 01, 2021, 03:53:09 pm
content: hi,I doubt the result, if ribbon cable soldering is in question
Probing an AC circuit with an Oscilloscope - Is this feasible and safe? - Page 1
Forum section: electronics / repair

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: May 27, 2023, 03:52:46 pm
content: Let's say you had an SMPS you were wanting to probe with your oscilloscope.Obviously, incorrectly using non isolated probes could cause serious damage to the oscilloscope or worse.So most people opt for an isolation transformer or something like the Micsig DP10013 High Voltage Differential Probe (or both)But why wouldn't the following method be just as safe?Using an inverter that is powered by a battery, to power either the oscilloscope or the SMPS circuit?That way, the Earth is never directly connected to both the Oscilloscope and the SMPS circuit at the same time.I am not certain this will work, it is a question?Thanks

author: EE4all
author_rank: Regular Contributor
timestamp: May 27, 2023, 04:28:59 pm
content: That can add a safety factor sure, but there a other vectors and aspects to the safety. Yes, that is a vague answer on purpose, to make you think. Maximum limits on the scope itself are an aspect too. Safety for the gear AND MOST importantly, your health, is good to think about. An isolation transformer used wrongly can actually make things much more dangerous.

author: bdunham7
author_rank: Super Contributor
timestamp: May 27, 2023, 04:33:08 pm
content: Quote from: EE4all on May 27, 2023, 04:28:59 pmThe same goes for screwdrivers...

author: bdunham7
author_rank: Super Contributor
timestamp: May 27, 2023, 04:36:47 pm
content: Quote from: ThermallyFrigid on May 27, 2023, 03:52:46 pmA battery powered inverter may functionally take the place of an isolation transformer, but there is a possibility of an increased hazard when you selectively ground a part of the DUT (SMPS in your case) to take a measurement since the whole inverter and battery may become live relative to ground.

author: EE4all
author_rank: Regular Contributor
timestamp: May 27, 2023, 04:41:52 pm
content: LOL! Too true on the screwdriver. I put one all all the way through my hand not too long ago when it slipped.Accidents can happen... try to avoid them with safety precautions and correct usage of the tools at hand.

author: J-R
author_rank: Super Contributor
timestamp: May 27, 2023, 10:05:14 pm
content: Perhaps do you have enough channels to use the scope's math function as a differential probe?
Problem between electronic card and lcd tablecloths - Page 1
Forum section: electronics / repair

author: Mevpedro
author_rank: Newbie
timestamp: June 05, 2023, 09:20:26 am
content: Hello,After doing research on internet, I did not find anything conclusive.I would like to know how we repair the lcd tablecloths on a electronic card.I tried with silver flow and classic flow, it doesn't work.If any informed opinions can help me...Cordially

author: tooki
author_rank: Super Contributor
timestamp: June 05, 2023, 03:28:23 pm
content: God I hate machine translations…If you’re going to use one, at least use a good one.Search for “lcd hot bar bonding” and similar. Those keywords should get you some info.
Problem black screen Tektronix TDS210 / 220 - Page 1
Forum section: electronics / repair

author: OP27
author_rank: Newbie
timestamp: January 22, 2020, 09:39:58 am
content: Hi allI have a problem with oscilloscope tektronix TDS210/220.It had a problem with BNC connectors, they were broken off. It was common mistake. Anyway, it was fully functional.The problem was when:- I carefully disassembled the device.- I comply with rules of ESD.- I exchanged BNC connectors.- I assembled the device, but display didnt working (nothing showed and black screen)I checked:- charging power supply voltages are OK- display backlight is OK- processor CLK is OK- output for calibration probe is OK- I pull out display cable and I measured signals on the connector J202 and it is OK too.I am thinking, that it has bad display (problem with display). But I dont understand, how it can be broken only with disassembled device.May you help me with this problem? Where may be the problem?thank you for help.

author: gkmaia
author_rank: Frequent Contributor
timestamp: January 31, 2020, 05:50:50 pm
content: Is the display back light working?

author: OP27
author_rank: Newbie
timestamp: January 31, 2020, 05:58:51 pm
content: yes, display backlight is OK.I have suspicion bad signal display connector.

author: george.b
author_rank: Frequent Contributor
timestamp: February 07, 2020, 04:29:30 am
content: OP27, take a gander:https://www.eevblog.com/forum/repair/tektronix-tds210-repair-oscillator-help-needed/msg2796252/#msg2796252
problem dimming led with EUROLITE EDX4RT  - Page 1
Forum section: electronics / repair

author: iperzipsp
author_rank: Newbie
timestamp: February 03, 2023, 09:14:56 am
content: Hello, I'm tryin to use this EUROLITE EDX4RT with led light, but with dmx signal at 0, lights remain still a little bit on; at about 30% they start flickering. Seems that someone opened it yet ( 2 Triac BTA16, 2 Triac BTA139). Can u guys suggest something?( I can't put an incandescent lamp to solve this situation)video:https://files.fm/f/utg33j78dthanks!

author: MathWizard
author_rank: Super Contributor
timestamp: February 16, 2023, 05:25:04 pm
content: So I see the unit is rated 1150 W per channel, max. 3680 W total. What LED unit or whatever it is called, do you have connected up ? Is there some minimum load the Eurolite is expecting, and putting out too much power for your lights to be "off" ?Is it a new Eurolite? Did it work right before or with other LED units ?
Problem Identifying a chip - Page 1
Forum section: electronics / repair

author: mrm2007
author_rank: Contributor
timestamp: September 27, 2020, 09:40:44 am
content: Hello,I'm trying to repair a Bluetooth handsfree, after opening it, on the board there is only a chip, 2 leds, 3 microswitchs and PCB antenna.I'm trying to find the main chip datasheet or at least the manufacturer with no luck.I attached the best picture of chip that I could get.Can anyone help?Thanks.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 27, 2020, 10:22:12 am
content: All I could quickly find is this, check if it makes sense, the numbering is a bit weird:

author: mrm2007
author_rank: Contributor
timestamp: September 28, 2020, 12:15:01 pm
content: Checked and seems to be correct.Thank you for your help.
Problem in tektronix 2445 oscilloscope - Page 1
Forum section: electronics / repair

author: Yaya122
author_rank: Newbie
timestamp: January 25, 2021, 08:21:46 am
content: Hello,I have a problem in ch1 of my scope that it show 5KV/d at the full scale. If you put a signal you can see that the scope show results in proper to 5V/d, at mean it's looks like there is a definition of 1:1000 probe that conected. But I do not recognize any definition like that in this analog scope.Someone know and can help me with this?Thanks

author: Miti
author_rank: Super Contributor
timestamp: January 25, 2021, 12:31:01 pm
content: That scope has a probe detection ring. If that ring is shorted to GND, your scope thinks you attached a 1000X probe.https://w140.com/tekwiki/wiki/BNC_connector_with_readout_ring

author: Yaya122
author_rank: Newbie
timestamp: January 27, 2021, 08:16:25 am
content: Thank you for your comment.I red the link but I didn't know where is this ring exactly in the BNC connector. I didn't find also any mention for this at the 2445 service manual. That seems there no option for detecting probe at this scope.Do you know where is exactly its located than I can check the short if exist??

author: Miti
author_rank: Super Contributor
timestamp: January 29, 2021, 11:05:58 am
content: Can you post a close up picture of the BNC input?

author: Tom45
author_rank: Frequent Contributor
timestamp: January 29, 2021, 02:40:53 pm
content: Quote from: Yaya122 on January 27, 2021, 08:16:25 amSee the photos here:
problem measurement part frequency victor vc97 - Page 1
Forum section: electronics / repair

author: electronium
author_rank: Newbie
timestamp: December 20, 2023, 06:14:24 am
content: i guys...Good time everyoneI have a vc97 multimeter whose frequency meter does not work, what should I do? I used the power transistor of the hot part to measure the peak city electricity. I wanted to measure the switching frequency from the transistor, but the device had a problem in the frequency meter part.

author: jebem
author_rank: Regular Contributor
timestamp: June 06, 2025, 04:35:37 pm
content: Thanks for the detailed pictures of the internal PCB, showing the DM1106BEN processor and AT24C02B eeprom in use.Did you manage to find out the issue?Most probable the processor was damaged. However the fault could be caused by on other component, like a resistor, ptc, or active limiter devices.

author: MathWizard
author_rank: Super Contributor
timestamp: June 07, 2025, 02:00:08 am
content: What do you mean "I used the power transistor of the hot part to measure the peak city electricity. I wanted to measure the switching frequency from the transistor" ? What power transistor ? What hot part ? As in 120VAC ?

author: Gertjan
author_rank: Frequent Contributor
timestamp: June 07, 2025, 05:56:53 am
content: Hey guys, you are answering to an already banned AI bot.....

author: Steno
author_rank: Newbie
timestamp: July 10, 2025, 02:35:27 pm
content: Sorry for off topic.Hello Gertjan, can you please contact me via PN? I have a problem and unfortunately can't send you a PN, I've just registered. It's about a circuit diagram.Best regards, Steffen
Problem with BG7TBL GPSDO - Page 1
Forum section: electronics / repair

author: DH2FA
author_rank: Newbie
timestamp: November 07, 2022, 12:10:29 pm
content: I have a BG7TBL 10MHz GPSDO (pcb version 2018-02-10) which was always on and working fine for about 4 years. A couple weeks ago I noticed that the green LED PWR is off.I noticed that the red LED ALM comes on for about 6 seconds, then the green LED PWR shortly blinks with the ALM still on. Then both LED are off shortly and it starts again with the red LED ALM.I checked the 12V supply, it is OK.I opened up the GPSDP and noticed a blue LED D2 near the antenna connector which also comes on shortly when the red LED ALM starts to light up.I appreciate any input how to get the GPSDO working again.There is a little battery next to the TCXO which shows less than 1V instead of 3V nominal. A Google search showed that this battery seems to hold last settings of the satellites for a quick warm start. Could it be the culprit?

author: thinkfat
author_rank: Unknown
timestamp: November 07, 2022, 12:40:34 pm
content: I think not. You could replace the battery or just remove it entirely, if your use case is "always on". The GPS is not doing any warm starts anyway.There are only few things that "wear" on a GPSDO. One is the oscillator itself, OCXO's have a limited service life,Or it could be the antenna or cable. Eventually, moisture will creep in.Are there no diagnostic outputs that you could use apart from a few LEDs?

author: Runco990
author_rank: Frequent Contributor
timestamp: November 07, 2022, 04:38:24 pm
content: ALWAYS start with the power supply!!! These little switching plugs are crap and don't last long. I crack them open and change the bloated capacitors every few years at minimum. Have been thinking of making a true linear power supply for mine.

author: DH2FA
author_rank: Newbie
timestamp: November 09, 2022, 08:47:23 pm
content: Thanks for your input. Unfortunately there are no fault messages other than the LEDs.The 12V wall wart was my first suspect. I used a linear bench power supply with the GPSDO but it didn’t change anything. The GPSDO draws 250mA at start up and after a few minutes it goes down to 120mA. This probably shows that the OCXO has reached its operating temperature.Unfortunately I can’t find any contact info for BG7TBL. Otherwise I would ask him.

author: thinkfat
author_rank: Unknown
timestamp: November 10, 2022, 07:35:27 am
content: Provided all the supply voltages are good, these are the next steps I'd do for diagnosis:I would start with trying to find a debug UART. Failing that, I would check if the EFC voltage of the OCXO has run towards a limit: then the OCXO is likely end-of-life. In that case - just replace it. Those GPSDOs use surplus OCXOs of unspecified quality anyway.Next I'd try finding the serial output of the GPS and the 1PPS output. The GPS UART output is likely NMEA and should be easy to decode. This will give you an idea if there's a problem with the antenna.
Problem with CROSSOVER RANE AC23...capacitor..operational.... - Page 1
Forum section: electronics / repair

author: Taso
author_rank: Newbie
timestamp: November 16, 2023, 02:07:10 am
content: Hi, I purchased an analog electronic crossover, i.e. non-dsp, Rane Ac23.It has a couple of power caps that are a little swollen, so I wanted to change the 6 power caps there.The power supply is equipped with a voltage multiplier. 10.5+10.5vac enters the crossover (external transformer) which is multiplied by two and then passes through the 7815 and 7915 regulators. The crossover operates at dual voltage +-15 Vdc.Do you think I can use Panasonic FC for all 6 capacitors even if in different positions? I have the Panasonic FCs in my drawer, but if they don't work well I can buy the ones you recommend.I attach the diagram.I ask because I seem to have read that low ESR capacitors, downstream of the regulators in question, can generate oscillations or in any case not be optimal.I also noticed that one of the operational quads has been replaced with a TL074.Originally there was one like all the others, namely a 4741cp.Apart from the 4741cp there are TL072 (double OP), these on sockets.As per the diagram and are used for input and output.The TL072 at the input is used partly as an input stage and partly as a subsonic high-pass filter at 20Hz (as per the user manual and declared specifications).The TL072 is also on the outputs, I think they say it works as a "buffer". Maybe I'm wrong.In fact there are 3, being 3 ways...6 exits.So, in total, there are 5 TL072s. Three used for the 6 outputs and two used for the two inputs + two subsonic filters to follow.Going back to the problem of the TL074 instead of the 4741cp.... From the diagram this opamp works entirely on one channel (right) and therefore I find the asymmetric crossover!This is certainly not a good thing.The crossover is 30 years old (maybe 40!). There will also be better opamps.I would like to intervene to have all the operational ones, obviously the same, I would say BASIC and essential solution.I would like to mount the sockets for them too and choose which op amps to mount.I wanted to ask if you can advise me on which quadruple operational amplifiers to mount that are clearly compatible with the scheme and with what they are called to do.I don't want OPs other than the originals to make the crossover work badly, I don't know... maybe with different cuts from what I set with the knobs!Thanks for any help.I have a good desoldering station. It takes me very little to plug the integrated circuits.I attach some photos of both the original ops and of the TL074 which was placed in place of an original. no good! no good!I also attach the diagram.Greetings!
Problem with CRT display in Rohde & Schwarz 804.8010.52 spectrum analyzer - Page 1
Forum section: electronics / repair

author: Filip SP9GMD
author_rank: Newbie
timestamp: March 12, 2024, 02:53:57 pm
content: I repair R&S spectrum analyzer. I can't find any service manual for the CRT part - if someone has a link to one, please share.I have successfully repaired many measurement equipment devices, but I have zero experience with CRTs - I just know which parts I shouldn't touchThe problem is as follows:https://youtu.be/dH4SEtppOHk. The image on the screen moves from left to right and becomes more and more skewed over time. I opened the analyzer, and here's what I checked:Capacitors seem to be okay; I chose a few random capacitors, and they're good.The unit responds to turning the adjustment potentiometers.I resoldered the board with flux so there aren't any cold joints.Here's a link to a photo of the video board on Google Drive:https://photos.app.goo.gl/n4jJ1TzB8Kp9xngP8.One potentiometer and capacitor were unsoldered for testing.TDA2653A and TDA2593 are used on this board.If you carefully rotate the HFREQ potentiometer, you can prevent the image from moving to and fro; also, it becomes less skewed.This potentiometer is very sensitive to touching - if you set it up after some time, the image starts moving again. I don't know how to adjust the CRT in this device - if someone could explain the function of those potentiometers, maybe I would be able to fix my analyzer. Maybe it's simply misaligned and has no hardware issue?Any help will be appreciated!

author: Kilo Tango
author_rank: Regular Contributor
timestamp: March 12, 2024, 04:30:13 pm
content: the display rolling from side to side suggests the CRT display line sync is not "synced" to the video signal line sync. Generally the line scan circuit free runs a bit slower than the intended video signal, and it pulls in when the video signal is applied. I would check for a video or line sync signal signal at the line scan chip input. It looks like it will be around the TDA2593 line scan chip, the TDA2653A is the vertical deflection driver chip.Things to watch in CRT monitors, the EHT is generally well insulated and fairly safe,and you can see and hear if its breaking down. Its things like 200V on the tube base that can be a surprise !.Cheers Ken
Problem with Hantek DSO1102B - Page 1
Forum section: electronics / repair

author: azemati
author_rank: Contributor
timestamp: February 13, 2024, 12:45:34 pm
content: Greetings friendsI have a Handheld oscilloscope model DSO1102B, which unfortunately freezes on the boot screen when it is turned on for a few days and does not come up anymore.I got the firmware of the device and plugged it into the device with the USB port, but it didn't show any reaction.Please guide me to fix my problem.Thank you
problem with fluke 8000A - Page 1
Forum section: electronics / repair

author: patan107
author_rank: Newbie
timestamp: April 28, 2019, 02:58:47 pm
content: Hi ,As a retired person , I will start again with the electronic hobby.And as an old radio amateur , you need to have your equipment up and running and in good condition.I need some help to repair an unit with emotional value , the Fluke 8000A-01 which has the following problem.After power up the unit , the display works , however it does not comes down to zero , regardless in which position the switches are. (AC,DC,A,Ohms)Also when the input port of analogue IC U3 , SC408-2 is grounded , the readout is still high , where it should come down to zero.So it seems that the compensation in U3 is not working correctly and just gives a readout depending on the temperature of the IC.I assume that the first part of the IC is broken , also because there is no protection for higher input values to this IC.Lately I saw in younger units that they used another A/D convertor U3 IC , SC522 and I like to know if this IC is technically the same the same as the SC408 , because I saw no differences on the pc board.The same components are around.Both IC's where custom-build for Fluke by Siliconix.The only difference I see is the ceramic housing for the SC408 and a plastic housing for the SC522.Looking forward to any reply.All help is welcome and highly appreciated.Thanks , Adrian(PA0APB)