hybridfree/eevblog-posts huggingface dataset:
Battery change in converted 732A to 12V gone wrong - Page 1
Forum section: electronics / repair

author: alligatorblues
author_rank: Regular Contributor
timestamp: February 09, 2024, 07:00:11 am
content: In 2016 I purchased a 732A, which needed batteries, so I thought I'd convert it to (2) 12VDC 5Ah batteries vs the original (4) 6VDC 4.5Ah's. It was time for a battery change, so I pulled the batteries out the bottom of the holder, put the new ones in, and I forgot how to reattach the spade connectors. I know I used (2) black connectors for one, and the other one was was turned with the terminals opposite, and I used (2) red leads for that one. The small PCB on top has 4 pairs of wires, one red, one black, All the black are one side, and all the reds on the other. Each pair connects to the same battery, so the serialization is in the PCB.I decided to move toward Fluke's intention of having each pair of leads connected to one battery. So I flipped a black lead over to the red side, and a red lead to the black side, since the terminals on the 12V 5Ah's are on the same side, thereby connecting the same battery to a pair of red and black leads, like it originally was done with the 6V batteries, and let the PCB do the serializing. But now I have 2 wire pairs just sitting open, connected to nothing. And I'm not getting voltage at the points on the PCB that connect to the external connector.Battery switch is on, and tested for continuity. Batteries test out at 13.8VDC ea. So, I've got (1) connection between the batteries, and the (2) terminals back into the PCB. But the board is expecting something connected to the (2) pairs of dangling wires.So, I think I should short the leads to the missing batteries (2 vs 4), and so that the polarity on the last connection to the PCB is opposite the first one. (2) of the dangling leads are continuous , but the other two are not. This leads me to believe the (2) that are open are the final terminals to the PCB, which must connect to the other pair that are continuous, or shorted. Then I think the expected DCV signals will be present, and the circuit will close.I just can't believe how the whole concept escaped me. So, that's why I'd like an extra brain or two for this one. Thank you for any commentary.

author: alligatorblues
author_rank: Regular Contributor
timestamp: March 03, 2024, 08:02:24 pm
content: No worries. I figured it out. I guess my mind slowed a bit the last 8 years.
Battery charger, no output - Page 1
Forum section: electronics / repair

author: Simon_a_s
author_rank: Newbie
timestamp: July 03, 2024, 06:18:02 pm
content: Repairing a 60V battery charger for an electric scooter. Circuit board is called "JYHK 34" and "JY-PCB-0012 v1.10". Found that a SCR (BT151) was blown. It measures ~100 ohms between gate and cathode. Anode, cathode junction is open. Measured 62 volts at the capacitor connected to the positive leg of the output so it appears to function ok till that point. The SCR is connected between the negative lead at the capacitor and the negative output lead.Replaced the SCR with a new one but it's still dead. There doesn't seem to be a trigger signal at the SCR gate. The Q6 PNP is fine. Traced the gate lead to a component I can't identify. There's no diode junction, infinite resistance if you measure over it with a DMM. I first thought it was a zener but it doesn't got a polarity marking. The markings on the PCB are "DZ1" and a there's a TVS diode (?) symbol. The presumed diode is marked "BP 3 D" - unknown in which order.Made a simplified circuit diagram (see attachment). What's this diode? What can I replace it with. I'm by no means an electronics expert and I don't understand fully what this <diode> is supposed to do.

author: RoGeorge
author_rank: Super Contributor
timestamp: July 03, 2024, 06:34:14 pm
content: Most probably it's adiac, often used to open a thyristor or a triac.https://en.wikipedia.org/wiki/DIAC

author: Simon_a_s
author_rank: Newbie
timestamp: July 04, 2024, 12:42:09 pm
content: Thanks! Found a DIAC called DB3. Might be the correct component.
Battery charger starting behave weird so reversing polarity - Page 1
Forum section: electronics / repair

author: marhuum
author_rank: Contributor
timestamp: November 03, 2024, 01:08:48 pm
content: This'd be a discussion only now, not repair technicalityA cheap low quality, standalone 4.4 V Li-ion battery charger for light torch is starting to get old. It's made for 2 loads in parallelIn the past 4 months it behaves weird, the polarity suddenly get reversed while every other thing is functioning normally!So simply reverse the load, ie. battery, polarity which simply works charging them till full. But on other time before being full while charging in reverse, it gets back to normal, ie. original, polarity. So if not checked for too long beyond the usual full charge time limit, the charge result just getting back to reduce the battery voltages!So one expert or kind enough to shed lights on it for all of us ?

author: temperance
author_rank: Super Contributor
timestamp: November 03, 2024, 02:02:24 pm
content: It could be as simple as the hamsters in the charger got tired of running in the same direction. But it more sounds like quantum computing to me.Where what and how did you measure those voltages?
Battery Connector Identification - Page 1
Forum section: electronics / repair

author: grue42
author_rank: Newbie
timestamp: June 21, 2021, 03:24:37 pm
content: Hi all,I've come across a clever battery connection for a battery that gets inserted into a tube.The battery terminals are wired to these posts, and the receptacles are panel mounted in the housing at the base - so when the battery is slid in, the posts plug into the receptacles and connection is made. (The mechanism is keyed, so no concern of plugging it in incorrectly)I'd love to use these in an upcoming project, but I can't seem to identify the parts.The posts seem to be akin to an unthreaded car battery bolt with a birdcage on it, but with a matching receptacle? Does anyone recognize them?Thanks!!!Edit: Sorry, I forgot I took an exploded pic of the plug, too!
Battery eliminator vintage ohmmeter - Page 1
Forum section: electronics / repair

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: June 27, 2019, 10:14:12 pm
content: I recently aquired an old KS-8455 volt/ohm meter used for telco cable testing. It appears in excellent working condition minus I do not have the proper 45 volt battery to power it normally. The Eveready No. 455, NEDA 201, 45 Volt is available but pricey. Would there be any drawbacks to using a step-up boost dc to dc module that has ability to go up to the 45v or close. I know switching frequency is very high but imput impedance of this meter is 430 ohms. Would needle deflection even be suceptable to that fast of frequency if boost module is used?

author: Gregg
author_rank: Super Contributor
timestamp: June 28, 2019, 12:07:54 am
content: Stack some 2032 lithium coin cells until you have 45 volts, they are cheap in lots of 20 to 50 cells on Amazon. You will have a cheaper higher power density battery than the old carbon zinc one. If you are lucky they may even fit into the old battery wrapper and look like they belong.

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: June 28, 2019, 01:41:43 am
content: I would but the meter didn't come with battery. Just made more sense to me to use li-ion or lipo cells and boost converter. I think the original 45v battery was only around 300-500mah. Average single lipo is probably 1500-2000mah.Also my meter has a metal battery holder mounted to the gauge which is removable to allow more room if needed. I haven't seen any pics posted online with this feature.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 28, 2019, 02:16:52 am
content: I think it could actually work.The best way to find out is to actually purchase a cheap e-bay converter and do some testing.Do you have any idea of the expected current load @ 45 volt?

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: June 28, 2019, 02:23:33 am
content: Just checked and across the leads measures 100k ohms. So .45 milliamps or .02 watts I believe worst case scenario with shorted leads. I think any module that can output 100mA should work a treat.

author: bob91343
author_rank: Super Contributor
timestamp: June 28, 2019, 02:41:43 am
content: Consider the use of a salvaged wall mount supply. They aren't usually well regulated but a little TO-220 style cheap regulator has worked well for me.I use them on my old fashioned analog VOMs for the Ohms ranges. The only down side is loss of portability.
Battery for American Arium ML4400 logic analyzer - Page 1
Forum section: electronics / repair

author: OldieButGoldie
author_rank: Newbie
timestamp: October 06, 2020, 09:43:41 am
content: Hello,I bought an American Arium ML4400 logic analyzer on eBay.The device basically works, but (as usual with such old equipment), the (important) NVRAM storage does not workThere seems to be little to no information on the INET about this device. The only information I could find, was an old thread on this forum (https://www.eevblog.com/forum/repair/arium-ml4400-logic-analyser) with an link to the operating manual and some rom files (was very helpful though).So I opened it to replace the battery. As I thought, the battery was completely flat and also started to leak. Fortunately no traces or components have been damagedBut unfortunately, the search for an replacement battery is more complicated than I thought, because they used an unusual type (see attached pictures). It was manufactured by Plainview, and it's part no is PMB 2.4 B.There are not many referenced on the INET about this type, but I finally found some information in an old PostScript document about a "RT284 mass memory cared". Basically it seems to be an NICD pack with an Voltage of 2.4V. But there are no information about it's capacity, and also no datasheets.My questions are:- Does anyone know this type of battery? Have datasheets?- Can it be replaced by an 2.4V NIMH battery, without modifying the charging circuit?- Has anyone a service manual for the American Arium ML4400 logic analyzer?

author: Haenk
author_rank: Super Contributor
timestamp: October 06, 2020, 09:55:17 am
content: So that's 2 NiCd cells in one hotshrink case.As the cell needs to be soldered in, you might want to try something like this:https://www.ebay.de/itm/153877726128(I'm in no way attached to this seller, probably other and better offers out there - but you get the idea...)

author: OldieButGoldie
author_rank: Newbie
timestamp: October 06, 2020, 10:28:29 am
content: Thanks for the reply HaenkYes, I already thought of something like that. But without a datasheet from the original battery, I can only guess it's capacity.And with no schematics from the charging circuit, I just don't know, if using a higher capacity could impact it's performance.Probably, I just have to try some random 2.4V NICAD battery, and see if this works in the long run.

author: Haenk
author_rank: Super Contributor
timestamp: October 06, 2020, 01:43:27 pm
content: I don't expect any complex charge logic being implemented (probably none at all), a small capacity (smallest you could find) should work flawlessly as a replacement.
Battery ID / Transistor ID? - Page 1
Forum section: electronics / repair

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 16, 2023, 12:09:37 pm
content: My central heating controller has packed in....... it works (i.e. the timer part works but it doesn't seem to switch)... I tested the relays...One thing I did notice is that the battery is horribly corroded...No mention of voltage on the case and googling V10RT VARTA didn't work for me.Any idea of a suitable replacement?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 16, 2023, 12:23:29 pm
content: I also did a wander around the transistors.... There is one that shows slightly weird voltage drops on diode mode...I get 0.7V between the top and the bottom left and 0V the other way around... but between top and bottom right I get around 2V in either direction... doesn't sound right?What sort of transistor would this be? [ Specified attachment is not available ]

author: wasedadoc
author_rank: Super Contributor
timestamp: June 16, 2023, 12:25:30 pm
content: That looks like a backup battery/cell to retain settings during power failures. If the timer is working I doubt that cell would stop the relays opearting.What voltage do you measure on the vacant cell connection points on the PCB?Looks likehttps://www.ebay.co.uk/itm/392045818698though part number is different but I'd be fairly confident that your one is also a single cell.https://www.ebay.co.uk/itm/393083617381is cheaper equivalent.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 16, 2023, 12:36:21 pm
content: I don't have the device powered since it is 240V and I have no nerve.I agree the battery backup is probably a red herring but it would nice to be able to replace it as I go.I suspect the transistor above... I'm thinking this is a NPN and shouldn't measure as it does. I ordered some BC847B from EBay and will try to replace it when they arrive in a few days.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 16, 2023, 12:39:05 pm
content: @wasedadoc That battery looks perfect. Ordered... now waiting for that too. Thanks!By the way... in case anyone is wondering... I have actually just replaced my central heating controller with a new one... the later ones was far better in that they know about daylight savings... I'm just toying with this as I have some lights that need a timer (with an advance button).
Battery phone connector - Page 1
Forum section: electronics / repair

author: time27
author_rank: Contributor
timestamp: September 19, 2022, 12:13:29 am
content: I have repaired a unindent phone using a BT-446 AAA NiMH 3 pack battery.The battery end is female connector that is okIt connects to a inline connector Male fro the phone.I thought initially it was JST-PH but its not .Can any one suggest the connector type?purchase location?Thank you//Nick
Battery powered lawnmover doesn't start - Page 1
Forum section: electronics / repair

author: teslinius
author_rank: Regular Contributor
timestamp: September 07, 2021, 07:58:57 pm
content: I have a battery powered lawnmover which has stopped working, when i press the start button only the fan starts spinning, but the motor doesn't start, i took it apart and didn't find any visible damage measured that none of the mosfets aren't in short circuit, then i connected it to my bech supply to 35V and it didn't draw any current when i noticed it has +5v pin on the back so i connected it to +5v supply and the onboard led blinked and the pcb started drawing current. So i think there is a supply problem, there is a lm317 voltage regulator and a 5V regulator, when i power the pcb through the battery input , there isn't any voltage on the lm317 so i think there is a problem somewhere in the part where that transistor is.I tried replacing it with a similar pnp bjt and when connected to battery the pcb led blinked and the board booted, but immediately as i connected the battery the fan started spinning (normally the fan starts when the start button is pressed) and the motor didn't start, also after some time the pcb led started blinking multiple times like it sensed an error. Any ideas what might be the problem, what else to check?, there is no problem with the battery.

author: bob91343
author_rank: Super Contributor
timestamp: September 07, 2021, 09:10:36 pm
content: I neveer saw one of these but I am guessing that some of the TO220 units are transistors or FETs that supply power to the motor. One is the regulator. The others are drivers maybe. The motor may be a dc motor that gets driven by the above. So trace out the motor wiring to see where it's supposed to obtain power.

author: andy3055
author_rank: Super Contributor
timestamp: September 07, 2021, 10:50:08 pm
content: Have you checked the motor on its own to see if it spins at all?
Battery-Powered Soldering Iron Issue – Gravity Sensor Malfunction - Page 1
Forum section: electronics / repair

author: Pcaiman
author_rank: Contributor
timestamp: March 09, 2025, 12:35:15 pm
content: I know that battery-powered soldering irons are often considered more like toys than proper tools, but I work a lot in the field, and for automotive applications, having a portable soldering iron is quite useful.I have a battery-powered soldering iron that is having issues with its gravity sensor. The sensor is supposed to put the iron in standby mode when not in use, but it is intermittently activating even when I’m soldering, which is quite frustrating.I’d like to disable or bypass the sensor to keep the iron on while I’m using it. Has anyone dealt with a similar issue? Any advice on how to fix or modify it?Thanks in advance!

author: BILLPOD
author_rank: Frequent Contributor
timestamp: March 09, 2025, 06:31:59 pm
content: Good Morning Pcaiman, Would you share with us the make and model of your battery powered soldering iron?

author: Pcaiman
author_rank: Contributor
timestamp: March 11, 2025, 12:59:34 am
content: Quote

author: coppercone2
author_rank: Super Contributor
timestamp: March 11, 2025, 01:26:02 am
content: for some reason thinking about a accelerometer as a gravity sensor is interesting, from the point of a what is gravity question

author: Whales
author_rank: Super Contributor
timestamp: March 11, 2025, 01:57:52 am
content: I can't see any parts in those photos that look like an accelerometer chip. Those are typically in little LGA packages (small black square with no pins on the sides).Does the iron make a rattle noise when you shake it? It might have a mechanical tilt switch in the case somewhere. My current iron does and it's a PITA, I have to flick the iron up to a silly angle once per minute to stop it turning off.

author: Pcaiman
author_rank: Contributor
timestamp: March 11, 2025, 11:12:12 pm
content: It doesn't make any noise, it just turns on and after reaching the operating temperature it simply goes into standby mode, and no matter how much I move it, I need to make AWG14 cable connections. At first it worked, but then when it goes into pause it's annoying.

author: thm_w
author_rank: Super Contributor
timestamp: March 11, 2025, 11:42:41 pm
content: U1 - charger ICU2 - I assume mcuU3 - regulator?It could be on J2 as there are 4 connections there.Ergonomics on this thing look like crap, I would just get a bench C115 iron.
Battery Rating - Page 1
Forum section: electronics / repair

author: bobcat2000
author_rank: Regular Contributor
timestamp: January 04, 2021, 01:08:41 am
content: Happy New Year All,I am trying to replace the Li Ion batteries in some of my gadgets.I have a Monster Clarity HD speaker with a dead battery inside. I have a spare digital camera battery. So, I cut the old one out and soldered one of my camera battery to the speaker. Mickey mouse job but my speaker works again.I am thinking to buy a Lipo from Amazon. Oh man oh man. They have so many selections.How do you know the rating printed on the battery is what they claim it is?Like this one the size of a piece of chewing gum (59 x 26 x 9mm), they say it is 1600mAh. I bet it maybe just 200mAh the most.Thanks!

author: ledtester
author_rank: Super Contributor
timestamp: January 04, 2021, 03:00:44 am
content: Compare it to a 18650 cell -- 18 mm in diameter, 65 mm in height:59*26*9 / (pi*9*9*65) = 0.835And 1600/0.835 =~ 1900 which is well within the ballpark for an 18650 cell.High quality 18650 cells are around 2500 mAh - maybe even 3000 but not much more.The only sure way to find out is to buy one and test it.

author: bobcat2000
author_rank: Regular Contributor
timestamp: January 04, 2021, 05:04:38 am
content: Thanks!You gave me the idea to verify the rating.So, take the size of a standard 18650 as the base. Compare the ratio and estimate the rating.So, this one claims to be 600 mAh. The size is 40 x 25 x 8 mm = 8000 mm38000 / 16540 mm3 ~ 0.482000 x 0.48 ~ 960 mAhSo 960 mAh if we are counting the chemical alone.Let take half of 960 mAh ~ 480 mAh.So, 600 is pretty close.

author: ledtester
author_rank: Super Contributor
timestamp: January 04, 2021, 05:18:52 am
content: Weight is also a good indicator of whether you are getting the real deal...See beginning at 4:12 in this video:https://youtu.be/j4RfYufeFhc?t=4m12s
Battery replacement for GPS Logger (Columbus V990) - Page 1
Forum section: electronics / repair

author: T_guttata
author_rank: Regular Contributor
timestamp: August 03, 2024, 07:01:48 pm
content: HiAfter 9 years I would need to replace the battery of my GPS Logger (Columbus V990). Sounds simple, but: how do I find a suitable battery?I only know the size, which is 49x39x4.7mm. I'm not familiar with the details of batteries and standardization. Could anyone help me to find a suitable battery?Thanks for your help.
Battery replacement HP 8901B - Page 1
Forum section: electronics / repair

author: Crambone
author_rank: Frequent Contributor
timestamp: December 09, 2022, 01:38:14 pm
content: The 2.8v battery in the HP 8901B is said to be, “Non Volatile Memory” it is a 4331DE number battery.Question is can I replace without jumping in a power source and just remove old and replace with new?

author: Tony_G
author_rank: Super Contributor
timestamp: December 13, 2022, 07:17:33 am
content: I'm pretty sure that there is nothing held in RAM that relates to calibration data (i.e. the RAM is just working memory) - The service manual doesn't mention anything more than just disposing of the battery correctly - I've had my 8901 for almost a decade and haven't experienced any issue with the battery (it is only used I believe when the power drops to the unit).TonyG

author: TheDefpom
author_rank: Frequent Contributor
timestamp: December 17, 2022, 04:18:18 am
content: I did a couple of repair videos on the 8901B, I have included them below in case they are of help to you, I don't think I showed the battery replacement in them though.Part 1:Part 2:
Baxandall CCFL inverter transformer ? - Page 1
Forum section: electronics / repair

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 13, 2021, 01:46:18 am
content: I'm trying to repair a LeSiglent toy DSO that has cooked the BJT's and control MOS on its single CCFL inverter's primary side.Replacing the transistors restored backlight but transistors are running much too hot.Anyone know of a cheap source (disassembling a ready made module is an option) for these Baxandall (/Royer) inverter transformers?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 13, 2021, 01:59:04 am
content: Do you know that the transformer actually has a fault?Those circuits usually just run hot. 150°C isn't much of a problem for semiconductors, if not great for lifetime. Even at merely 80°C it'll feel very hot (too hot to touch) while being quite reliable -- I don't know what metric you're using to evaluate the thing here.To improve reliability, it might help to simply add some heat spreaders/heatsinks and thermal (gap) pads to reduce peak temperatures.Tim

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 13, 2021, 10:28:58 am
content: I'm not absolutely certain the Xfrmr is defective.I know these Baxandall converters have low efficiency at the best but within a couple of minutes the TO-251 transistors are at 90°C (measured with thermal camera), current consumption is 2.2A (@6V).Letting the inverter run 10 minutes led to one of the transistors shorting.Any clues on where to find such transformers?Thanks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 13, 2021, 12:13:32 pm
content: Can you measure the transformer's small signal parameters, say with a signal generator and AC voltmeter or scope?Tim
B&C Microsystems 1409C Programmer - Page 1
Forum section: electronics / repair

author: ehobby
author_rank: Contributor
timestamp: May 11, 2020, 11:22:52 pm
content: This might be a long shot but...I have a couple of old 1409C programmers from the late 80s. I want to make some modifications to the hardware but cannot find any documentation for the 1409C. There is a manual floating around the Internet for the earlier 1409 version but it is electrically and PCB layout different from the 1409C. I know these were popular in the 80s so wondering if someone still has the manual/scan for the C version. Schematically, I would expect five ZIF sockets and a dip switch labeled S7. The 1409 only had two ZIF sockets and no dip switch.If you have a schematic or the whole manual, please let me know if you can provide a scan.Thanks
B&D MM525 electric mower motor repair - Page 1
Forum section: electronics / repair

author: orbanp
author_rank: Regular Contributor
timestamp: June 11, 2020, 12:22:41 pm
content: Hello Everyone,I have the above electric mower, it uses a 3.5HP permanent magnet DC motor, running from 120VAC, using a big rectifier block.The mower must have ingested a small stone, one of the magnets in the stator cracked, about 1/4 of it broke off into a few pieces, the rotor jammed.A replacement magnet ring is quite pricey:https://www.ereplacementparts.com/magnet-ring-p-95757.htmlAs I have all the pieces, any chance of gluing up the broken magnet - or is it totally hopeless?Would I use epoxy as glue, or something else?Thanks for any comments!Peter

author: CaptDon
author_rank: Super Contributor
timestamp: June 11, 2020, 01:00:33 pm
content: If you have a way to make each piece stay where it needs to becyano super glue may work best. There should be enough of acrystalline type structure on the broken surface that super gluewill hold up well even in the modest heat inside the motor. Myexperience with broken magnets is that they sometimes wantto push away the broken piece. You often see the broken piecespun around backwards and sticking to where it came from.One thing is that the magnetic field will be weaker than it oncewas and the motor torque will be reduced, how much is anyone'sguess. Re-gluing cracked magnets on magnetron tubes shiftstheir operating point far enough that it is usually a death sentence.
B&D Smart 12v Battery Charger SMPS Repair - Page 1
Forum section: electronics / repair

author: tango17
author_rank: Regular Contributor
timestamp: November 19, 2019, 08:20:01 pm
content: Black & Decker VEC1093DBD automotive battery charger runs at 4 to 40A continuous with short bursts to 100A.While charging at 40A, it blew the switchmode section.The PWM control chip is a TL494CN that controls four irf640n n-channel mosfets in an H bridge. The driver circuit for each mosfet is identical, and includes a two resistors, 6R8 and 1K1, an smt driver transistor marked "1P" and a diode (no marking).The PWM control drives a transformer with 4 output pairs, each connected to the base of its corresponding driver 1P transistor.The first failure occurred while 40A charging for a few hours. Two of the mosfets on one side of the H bridge blew, taking out the main FWBR, the main fuse, and a cap at the input filter as well as one 1P driver transistor, a diode and a 6R8 resistor in one of the driver circuits.I repaired with misc. components I had. I looked up 1P and decided it was a 2n2222. I had a thru hole 2n2222a which I installed. The diode I guessed at and stuck something in from another smps. I had no irf640n but found an old irf640 and used itAfter repair, it worked. I ran it at 4A to charge a small battery overnight. That worked. Then I tried a 20A charge. It worked for a while, and also at 40A for a while (a few minutes) then I left it charging at 20A. As I walked away, it made a bang and released the magic smoke.This time it left major black marks where the 2n2222a repair was installed. That transistor was disintegrated. It also took out a second 1P (same side of the H bridge) and a couple resistors in the driver circuit. I believe the two new irf640's may be damaged, too, but they didn't leave as much black as in the first failure - maybe none.I'd appreciate comments on where to go now. The substitute diode is fine. Was the 2n2222a substitution for the 1P smt a bad idea? How about the irf640 for irf640n sub?I'm mostly interested in learning a bit more about smps repair. Would you suspect anything upstream closer to the pwm control, in my mosfet subs or in the driver circuits?The mosfets are from a no name source.Would it make sense to make the same repair again and then check out timing with a scope? Could a cap cause an issue at the tl494? (The charger is prob about 10 years old or more).Thanks for any comments or suggestions.
BD636 replacement ? alternative ? - Page 1
Forum section: electronics / repair

author: Overspeed
author_rank: Frequent Contributor
timestamp: October 10, 2024, 09:15:33 am
content: HelloI have circuit with PNP BD636 which is ? non availablemaximum current collector is 1 Ampload voltage Vceo is 12 Voltfrequency 500 kHzbest is a TO220 foot printany idea in commonly available transistor ? TIP32 perhapsRegards

author: coromonadalix
author_rank: Super Contributor
timestamp: October 10, 2024, 12:39:04 pm
content: you have a search toolhttps://alltransistors.com/crsearch.php?mat=Si&struct=PNP&pc=30&ucb=60&uce=60&ueb=5&ic=3&tj=185&ft=3&hfe=25&caps=TO220&cf=oncheck the results

author: Overspeed
author_rank: Frequent Contributor
timestamp: October 14, 2024, 11:52:15 am
content: Quote from: coromonadalix on October 10, 2024, 12:39:04 pmHelloThanksOK , but all resistor listed are obsolete transistors , Mouser ''alternative'' is a better tool as components are available , base on data of the BD636 .RegardsOS
Beats solo 3 no sound on right speaker - Page 1
Forum section: electronics / repair

author: Pama77
author_rank: Newbie
timestamp: March 12, 2025, 06:42:19 pm
content: First off thanks for any help and input. I have a Beats Solo 3 headphone that the right speaker has stopped working. The left speaker works fine. The right side speaker has the 3.5 jack while the left has the USB charger. The headphone turns one, charges and works although there's no sound on the right side.I took the speakers apart and looked at the wiring. It uses very small gauge stranded wire. I did notice that the red wire that should be for the right speaker was kinked. This is the wire I cut, see pictures, in order to solder a new wire between the cut ends.When I cut the wire I notice that it looks like a single strand and then branches to two strands a positive and ground. To me it looks like the red wire is solid inside the red sleeve and I was just going to solder a new wire. But when I got some scrap wire and touched both ends to the red cut wire the speaker is still not working.My first question is that really a single strand wire that has two leads to the + and -. All speaker wire I'm familiar with has two wires, I have never seen a single strand used like that, so am assuming there's a core inside and I would be able to just bridge the red wire.Before I cut the red wire, I tested the negative test point on the speaker to the ground screw terminal on the left and there was no continuity. Now when I touch the red end, the short end on the right, and the terminal screw I get ground. This seems correct as i believe the red wire was previously kinked and not making a full connection.The issue is when I use a scrap wire to bridge the red, I'm just touching it, the speaker is not working. I have yet to solder and connect the red wire but it seems like its not going to work. So how would I fix this issue, to i need to same type of wire and instead solder to the solder point on the board ? Where can I get this wire, am not sure the guage and wire type.Any input would be helpful.TIA,P

author: tom66
author_rank: Super Contributor
timestamp: March 12, 2025, 09:00:13 pm
content: Yes this is a pretty common type of wire to use for the speaker, they would not want to share the ground for the USB as it could create a noise path whilst charging (if the headphones support playback whilst plugged in).

author: Pama77
author_rank: Newbie
timestamp: March 12, 2025, 11:37:20 pm
content: Is there a name for this type of wire. I was trying to find it on Amazon. Is it save to assume I can't just solder from broken end to broken end ?thanks for your reply.

author: amyk
author_rank: Super Contributor
timestamp: March 13, 2025, 12:17:50 am
content: Tinsel wire. I'd find where the other end goes and replace the whole thing....this is assuming that you've already checked that the speaker coil isn't open and the other end is actually outputting a signal.

author: Pama77
author_rank: Newbie
timestamp: March 13, 2025, 01:03:25 am
content: Amyk, thank you. I will look into this.
Beatspill loudspeakers sytem not charging - Page 1
Forum section: electronics / repair

author: Cornboats
author_rank: Newbie
timestamp: June 02, 2020, 04:17:06 pm
content: [ Specified attachment is not available ]Trying to troubleshoot this system. Batteries aren't charging -no charge light indicator on when plugged into usb.Usb is 5v but when connected .6v across + & - at Beatspill end.I removed the micro usb socket as I thouught this was faulty- hared wired connections by following the traces. Theres only 4 out of the 6 pins being used.Could be the batteries are dead and pulling down the voltage but I don't know enough to know for sure. How do I rule out batteries without buying a new pair?

author: floobydust
author_rank: Super Contributor
timestamp: June 03, 2020, 11:02:06 pm
content: Beatspills are notorious for breaking at the micro-USB connector, shearing it right off the PC board.Or, the daughter board cracks the solder joints to the main board (under the green glue). It's a terrible design and fragile.When it is plugged in to a charger, you should be able to measure 5V underneath at the main board connection, the 4-pins.If the micro-USB has sheared off traces and lifted them, too hard to fix. Instead people are selling Beatspill replacement USB connector boards. I did a PCB layout a long time ago and I think it's an oddball thickness laminate so I left it.

author: Cornboats
author_rank: Newbie
timestamp: June 04, 2020, 08:03:52 am
content: Thanks for the reply. Your usb board is exactly the same as mine except yours has diodes D300 & D301 missing & link L300 missing. On mine the 2 middle traces of the usb socket go to left side of D300 and right side of D301. I wondered if I'd got these connected the wrong way round and that was causing the low voltage.I did hot wire the + & - direct to my 4.5v voltage regulator but as well as the voltage across + & - being less than 1v at the pcb end, the component marked as U7 which googles as a voltage booster converter was getting really hot. As the charging led wasn't showing I decided this wasn't the way to go.

author: mikerj
author_rank: Super Contributor
timestamp: June 04, 2020, 09:11:57 am
content: Check for internally shorted MLCC caps, seen this on a couple of different brand bluetooth speakers.

author: Cornboats
author_rank: Newbie
timestamp: June 04, 2020, 02:53:12 pm
content: Thanks for your reply- I'll check and also solder pins previously suggested and come back with results.Much appreciated.

author: floobydust
author_rank: Super Contributor
timestamp: June 04, 2020, 05:37:22 pm
content: U7 on mine is aTPS61175boost-converter. Note there are also quite a few Beatspill firmware updates.
becker_BE1100 - Page 1
Forum section: electronics / repair

author: david69
author_rank: Regular Contributor
timestamp: September 26, 2025, 01:59:49 pm
content: Hello,Is it possible to see a schematic for this radio somewhere? The processor is somethingsimilar to an 8051 with an EEPROM 8582 or 24C02. Functional entries into the EEPROMdo not affect the I2C bus? from which the TDA7300 audio processor is controlled.The codes are not a problem, but the main error is in the I2C bus, when I want to regulatethe volume and the bus is without clock and without data, other input from the keyboardworks even if I swap the keyboards. The MUTE button and volume control do not work.Otherwise, both keyboards send a code to the processor, I have not read it yet, butthe audio processor control is inactive, only balance and sound color work.I do not know why the volume control is disabled when the TDA7300 is a SLAVE receiver.Does anyone have experience with this? The 5V and 8.5V power supplies are repaired.Thanks

author: coromonadalix
author_rank: Super Contributor
timestamp: September 26, 2025, 04:34:18 pm
content: this maybehttps://elektrotanya.com/becker_europa_2000_be1100.zip/download.html#dlattached filemaybe here toohttps://www.eserviceinfo.com/index.php?what=search2&searchstring=becker+be1100https://github.com/Florin4226/Becker-Europa-2000-BE-1100?tab=readme-ov-fileOriginal 85C82 EEPROMs that are corrupted cannot be rewritten.You must replace them with a compatible 24C02 memory chip

author: david69
author_rank: Regular Contributor
timestamp: September 28, 2025, 03:11:06 pm
content: firmware version 2 is OKbut it doesn't change the problem with the sound. FM radio plays weaklyand it is not possible to amplify via I2C bus, there is no signal on the bus.
BECKMAN CIRCUITMATE AM12 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: October 27, 2022, 08:19:11 am
content: Hi there! I am looking for the diagram of the BECKMAN CIRCUITMATE AM12 multimeter: could someone help me?? Thanks in advance! (view the photo)

author: lionelkjh
author_rank: Frequent Contributor
timestamp: November 05, 2022, 09:16:51 am
content: sniff

author: Gyro
author_rank: Super Contributor
timestamp: November 05, 2022, 10:01:39 am
content: I can't see whether this is a passive moving coil multimeter or whether it has active electronics to increase the ohms-per-volt input impedance. The image is low resolution so trying to scale up the image doesn't help.Analogue meters lilke this are usually fairly simple internally (single or double sided PCB, through hole components) and it is relatively easy to reverse engineer the schematic. If you are trying to debug specific problem, eg, current, voltage or resistance functions then tracing those specific areas should reduce the task.Edit: A quick web search revealed some information, it is an active meter using a pair of descrete jfets in a bridge configuration...https://worldradiohistory.com/hd2/IDX-UK/Technology/Technology-All-Eras/Archive-Practical-Television-IDX/90s/Television-Servicing-UK-1993-03-OCR-Page-0036.pdfNon of the usual manual sites seem to have anything and I can't find any internal photos.

author: Chris56000
author_rank: Frequent Contributor
timestamp: November 05, 2022, 08:38:29 pm
content: Hi!This meter is a clone of the Huang Chang HC–5050E & you can get a booklet with a circuit diagram and component list in the back from Elektrotanya here :–https://elektrotanya.com/altai_hc-5050e_analog_multimeter_sm.pdf/download.htmlChris Williams

author: lionelkjh
author_rank: Frequent Contributor
timestamp: November 06, 2022, 05:48:14 pm
content: THANKS A LOT!!
Beckman Industrial/(later Wavetek) Digital Multimeter DM27XT - Page 1
Forum section: electronics / repair

author: mholin
author_rank: Newbie
timestamp: August 18, 2024, 05:51:48 pm
content: Was testing to see if a bug zapper grid voltage (=< 2800VDC) had discharged yet. Set meter to highest range (1000 VDC) and probed across the grid. Heard an audible arc so voltage must have discharged into something in the front end of the meter. Now all functions that use the V-Ohm/Com input just reads "OL" (over range). Even the continuity test with the probes shorted reads OL with no beep. Opened it up and found input resistor R31 47 ohms, completely open. Replaced with new resistor but meter still reads "OL". Any insight into what other component to check much appreciated.

author: floobydust
author_rank: Super Contributor
timestamp: August 18, 2024, 06:16:50 pm
content: I would say it's killed, dead.https://www.eevblog.com/forum/testgear/broken-wavetek-dm27xt
beginner advice on led disco light SMPS repair - Page 1
Forum section: electronics / repair

author: src1989
author_rank: Contributor
timestamp: January 27, 2022, 11:23:09 pm
content: not sure if this belongs in beginners or repair:i need advice with repairing a SMPS from a cheap led disco light. it's not the design that has separate power, logic and IR/RF modules - they're combined into one.initial diagnosis:inrush 1Ω resistor & plug fuse are blown. caps don't test as short or with resistance, no sign of bulging or leaks, test within tolerance. resistors, tx coil, diodes and bridge rectifier beep out as normal and not shorted/open. the light functions as normal when i hook my bench PSU into the unused 12V fan output on the secondary side.bear in mind i'm using cheap meters - a Mercury MTM01 and an "Ultrics":the mystery switching chip measures as a dead short between pins 3 & 6 (GND and current sense as i understand), and a diode drop between pins 1 & 7/8, 6/3 & 2 and 3 & 1.schematic so far:what i need advice on:By using a switching chip webpage that another member recommended, I found a couple of ICs that kinda look pin-compatible and power/voltage compatible - these are the SDC603 and the THX203H.the first thing that bugs me is that pin 4 on my board does not appear to be connected to anything, but the schematics for both the chips i mention say something about a picofarad-value timing capacitor. all other pins match up however. is there a chip which is N/C on pin 4 or will this one work?second: when testing (i'm utterly terrified of loud noises eg KABLAMMO) - should i use a much larger value resistor at the inrush position (several kOhms?), or wire an incandescent lamp in series with the whole thing? (I don't own a variac or a bench PSU that goes over 30V). I have a step-down 120V (actually 135V) isolating transformer if thats an idea?thanks.

author: src1989
author_rank: Contributor
timestamp: June 07, 2022, 09:40:08 pm
content: UPDATE: I managed to fix it using the THX203H SMPS IC. the cap appears to be optional, but I don't have an oscilloscope to conduct in-depth tests (yet).video here:I got cocky and had a go at fixing another SMPS, this time with a sagging voltage output under load. I replaced the output caps, and now the thing gets stuck in hiccup/startup mode. d'oh....

author: strawberry
author_rank: Super Contributor
timestamp: June 08, 2022, 06:29:36 am
content: check RCD clamp or secondary rectifier . could be TL431/zener
Beginner Question - Repair of 8.4v lithium battery PCB - Page 1
Forum section: electronics / repair

author: brooko
author_rank: Contributor
timestamp: February 05, 2024, 06:07:44 pm
content: Hello, I have removed the PCB from a lithium battery used to power cycle lights. 8.4v 18650 8cellsI believe that the PCB is damaged as the lights on the power source won't stay on, but will for other battery packs.Can anyone advise how I check the PCB please. The equipment I have is...Bench powerUNI-T volts, amps and resistance meterPic attachedThanks, Andy

author: tunk
author_rank: Super Contributor
timestamp: February 05, 2024, 06:10:35 pm
content: Could be an BMS. Any markings on the ICs?Edit: What's the voltage of the two cells?

author: brooko
author_rank: Contributor
timestamp: February 05, 2024, 06:31:59 pm
content: Hi, thanks for looking at this.The chip has 8205A Y105220F on it. The batteries are putting out 7.4v.Andy

author: SeanB
author_rank: Super Contributor
timestamp: February 05, 2024, 07:00:41 pm
content: Could be the one cell is failing, and thus the pack shuts off. Put it in, and run till it cuts off, and measure each cell block voltage. Likely one will be just under 3V when the BMS cuts off the pack.
BEHA Amprobe Hexagon 120 Problem  - Page 1
Forum section: electronics / repair

author: martin_072
author_rank: Newbie
timestamp: May 03, 2023, 08:26:34 pm
content: Hello from BulgariaI have a multimeter that has broken resistor and varistor elements and I am looking for their parameters, please if anyone has the same multimeter, write to me personally or in the topicThe multiset is branded BEHA Amprobe Hexagon 120

author: martin_072
author_rank: Newbie
timestamp: May 03, 2023, 08:54:30 pm
content: image urlfree image uploader
Behlman ACP-250 user and reference/repair manual - Page 1
Forum section: electronics / repair

author: Grubi
author_rank: Contributor
timestamp: June 19, 2021, 03:06:43 pm
content: Hello,looking for schematic and user/reference/repair manual for Behlman ACP-250 AC source.It is generally starting, but display is dark (not really, there is some very low brightness initial message, I hope it is not broken display).One of two power boards is quite hot around some resistors, plus some burn marks around them. Still did not measure any votages or did not change any components. Otherwise seems clean and not broken-burn marks on any of the boards. All fuses are fine internally, external 10A fuse has broken body, but function well.Only thing that works for sure is clicking relays, when change the output ranges.Thanks in advance!
Behringer BX4500 voltage issues.  - Page 1
Forum section: electronics / repair

author: average joe strummer
author_rank: Newbie
timestamp: December 16, 2019, 11:09:43 pm
content: Hello allGot a problem with the power amp board on this lovely (sarcastic) bass head. Power rail voltages are miles out. See attached schematic. All measured voltages are in red.So far, Ive had odd continuity readings across D4 & D6 but the tested good out of circuit, checked pretty much all other components and seem to be OK. I'm guessing there is a short to ground, but cant seem to track it down. I've re-flowed solder to all the transistors & filter caps.Tks for any pointers anyone mat have.CheersAJS
Behringer EP 4000 EUROPOWER - clipping too early - Page 1
Forum section: electronics / repair

author: xavlaur
author_rank: Contributor
timestamp: July 21, 2021, 04:35:16 pm
content: Hello ! I have 2 Behringer amplifiers with below problems:Behringer EP 4000 EUROPOWER - no.1 - premature clippingIt enters clipping too early (red LED clipping on), at around 15W, it starts to distort, if I reduce the potentiometer the red LED still stays on for a few seconds and still distorts - after a few seconds the red LED goes out and no more distortion , but only at low signal.There is no DC on output and no idle current.DIP_SWITCH does not change the premature clipping behavior.Behringer EP 4000 EUROPOWER - no.2 - distortionsThe left channel distorts stronglyTransistors checked as diodes = ok. Currently, some of the diodes checked = ok. I'll check the rest.There is idle current - 0.5 A and DC on 3.5V output, without the possibility of adjustment from the 3 semi-adjustable.If I turn on the load, the DC output drops to 0.05V and I have an audio signal on the X21 / pin 7.No load, no audio signal on X21 / pin 7.As you rotate the VR4 upward, the distortion disappears for a second as if the transient mode were to ensure proper polarization.

author: lazyman
author_rank: Contributor
timestamp: August 30, 2021, 01:52:00 pm
content: Check Mosfets for rail switching, 50n06
Behringer mixer board, flakey power up - Page 1
Forum section: electronics / repair

author: CaptDon
author_rank: Super Contributor
timestamp: February 14, 2025, 02:41:59 pm
content: I have had several Behringer mixers in the shop all with a similar symptom. No power, intermittant power etc. As we have discussed lately on several threads about the ply-o-bond rubberized resilient glue becoming conductive with age, this is the very problem with the Behringers. You have to open up the mixer unit and then fully dis-assemble the power supply module. On the under side of the SMPS power supply module is a disk ceramic capacitor swimming in a heavy coat of cream colored glue that is turning a milk chocolate color. Removing all of the glue with a dental pick has restored every unit with this power supply symptom back to life. Cheers!!

author: darkspr1te
author_rank: Frequent Contributor
timestamp: February 15, 2025, 06:46:01 am
content: Another thing with these mixers are dry joints, I cannot tell you how many i have repaired where all audio drops because of a primary ground or power rail.darkspr1te