hybridfree/eevblog-posts huggingface dataset:
LG SR906SB: Sound stopped working on receiver, powering on fine. Please help! - Page 1
Forum section: electronics / repair

author: wilruf
author_rank: Newbie
timestamp: August 31, 2022, 10:12:41 pm
content: Hi all,My receiver has been working perfectly, I changed most of the capacitors on the power board about 3 months ago and had no issues since.Most recently working was playing PS4 through it. Had been using a racing wheel plugged into the PS4, sound was working fine throughout and when turning everything off. Next day turn on and no sound from any speaker.From what I can see all capacitors look fine on the speaker board, as well as everywhere else.Any suggestions on what could be causing this?To clarify I’m not being a dum dum, I’ve checked sound settings on receiver and PS4 and now using the test tone function to check speaker output!Thanks for help in advance!https://imgur.com/a/MMxnNle

author: manicdoc
author_rank: Unknown
timestamp: September 01, 2022, 03:56:32 am
content: I presume you have done all the visual/basic multimeter type checks and know how to be safe around mains powered equipment:- power light comes on- power being delivered to the main board (check the 2 LHS connectors off the power supply board, looks like there is a pin out to work with top left)- is the fuse in the low right corner good?If its getting mains and looks dead, check the small elec caps on the power supply, one of them might well be the bootstrap reserve to start the switcher - you will need to get pin outs for the chips on there and work back from the sample usage schematics on the data sheets to work out how the power supply starts up. An ESR meter will be your friend here, but make sure all the caps are discharged first..
Lg Tv 32LB5820-TB Power supply-intermittent power (EAX65391401) - Page 1
Forum section: electronics / repair

author: brandnew2000
author_rank: Newbie
timestamp: August 28, 2022, 02:20:41 pm
content: My tv (32lb5820) has this issue where it powers only occasionally. Other times the standby led just blinks. I opened it up, disconnected the main board , probed the voltages and discovered a normal 3.6 volt line. However, when I connect the 3.6v line to the pwr-on line (without the main board attached), the 3.6 v rail drops rapidly to 0 volts before returning to 3 volt and resuming the cycle. Similar behaviour can also be observed on the 24 and 12 volt line.This leads me to believe that the 12/24 volt circuitry on the power supply is faulty. Something may be internally shorted tripping the power supply’s failsafe. Any ideas where to start my diagnosis?

author: inse
author_rank: Super Contributor
timestamp: August 28, 2022, 04:42:33 pm
content: Maybe it‘s the common startup capacitor issue.I suggest heating it up with a hairdryer and see whether it‘s more willing.
LG TV fault codes - Page 1
Forum section: electronics / repair

author: coppice
author_rank: Super Contributor
timestamp: August 08, 2021, 05:22:04 pm
content: Our LG 55UB8500 TV froze, and after cycling the power it won't start up at all. The red standby LED flashes 3 times when you try to start the TV, and if you leave it on for about a minute an orange LED on the power supply board starts giving bursts of 5 flashes. I assume these flashing patterns indicate the nature of the fault, but Googling hasn't flushed out their meaning (although it did get me a couple of hits of people asking about exactly the same 5 flash bursts from the LED on the power supply board). Does anyone know what this flashing means?

author: Mario87
author_rank: Frequent Contributor
timestamp: August 08, 2021, 05:54:07 pm
content: Check the service manual (linked below). If there is no info regarding flashing leds in there then it’s nothing worth noting, if it’s an error code of sorts it should be in there.https://data2.manualslib.com/pdf6/124/12391/1239056-lg/55ub8500.pdf?3c8c136eb8a3e094ef1a1b32cecd8a72

author: coppice
author_rank: Super Contributor
timestamp: August 08, 2021, 09:22:11 pm
content: Quote from: Mario87 on August 08, 2021, 05:54:07 pmThanks. I can't see a reference to LED flashing patterns, but that's really helpful. Like most current "service" manuals the fault finding information only tries to locate the fault to a particular board, although it does have the detailed schematics.
LG TV Repair - Page 1
Forum section: electronics / repair

author: vidarr
author_rank: Frequent Contributor
timestamp: November 03, 2022, 12:09:53 pm
content: Hey guys, I want to resolder this pin back into the circuit, but want to know if there is a way to test the component it belongs to to see if it is still working. Or, should I just resolder the pin and turn it on?The TV is old, so it is no major loss. But, if I can fix it, that would be great.Thanks!

author: wasedadoc
author_rank: Super Contributor
timestamp: November 03, 2022, 04:11:11 pm
content: That appears to be a transformer in a switch mode power supply. Question is why has that pin become unsoldered? If it got too hot because of excessive current, most probably the transformer itself is not the culprit.

author: inse
author_rank: Super Contributor
timestamp: November 03, 2022, 07:13:14 pm
content: Mechanical and thermal stress…Just resolder it

author: vidarr
author_rank: Frequent Contributor
timestamp: November 03, 2022, 10:32:20 pm
content: OK, I will do it. Thank You for your input!(Just FYI for others, I actually rolled back the solder away from the pin to get a better look at what happened. It was originally just a <0.5 mm gap around the pin. It appeared to just have melted away.)Thanks Guys!

author: TheMG
author_rank: Frequent Contributor
timestamp: November 03, 2022, 10:33:44 pm
content: If it was overcurrent the weakest part of the trace would go first, not the pad itself.Likely solder joint cracked as a result of thermal stress and if this is in the high voltage side of the transformer the resultant arcing is what burned the pad away.Solder it up and see what happens.

author: vidarr
author_rank: Frequent Contributor
timestamp: November 03, 2022, 10:42:23 pm
content: I am on it. Will post the results tomorrow.Thank You!

author: vidarr
author_rank: Frequent Contributor
timestamp: November 04, 2022, 01:59:13 pm
content: Unfortunately, it did not work. But, now, I have a lot of parts.It was worth a shot.Thanks!

author: slbender
author_rank: Regular Contributor
timestamp: November 04, 2022, 08:24:09 pm
content: Hi,It looked to me like that pin may have intentionally been bent out of the way (last photo) and is not used - is that a possibility? Therefore, the fault lies elsewhere in the set.Steven

author: inse
author_rank: Super Contributor
timestamp: November 04, 2022, 09:43:22 pm
content: Maybe the arcing also killed the power semiconductor…

author: vidarr
author_rank: Frequent Contributor
timestamp: November 05, 2022, 12:57:14 am
content: Yeah, I think the component is fried. The TV is too old and not worth the time/money to buy new parts for, so I disassembled it and made a giant light table out of it for my daughter.Thanks!
LG TV T-CON board help - Page 1
Forum section: electronics / repair

author: raf11011
author_rank: Newbie
timestamp: December 12, 2023, 03:37:14 am
content: I need to replace the T-CON board in my lg tv. I have found this one. Can anyone that knows more about these board than me (literally no knowledge at all) tell me if the replacement board will be compatible?My board is the one with the ribbon cables attached. Replacement board is on dark surface.

author: m k
author_rank: Super Contributor
timestamp: December 16, 2023, 04:18:19 pm
content: It's pretty close.Can't see the exact model type of the replacement board.Much is programmable, so probably much must be programmed after a change also.Do you know that replacement is ok?Its center has been hot, maybe even not healthy.
LG Xboom XO3 360 - blown voltage reg? problem with identyfication - Page 1
Forum section: electronics / repair

author: Dimon
author_rank: Newbie
timestamp: July 28, 2024, 09:19:11 pm
content: Hello All.I have an LG Xboom 360 XO3 speaker which doesn't power up, just a red LED lights up and that's all. I found a broken component in the sot23-6 package but have a problem with identification, I believe it's some kind of voltage regulator. Would appreciate any help with it.ThanksDamian
LG55 LED TV HDMI INPUT PROBLEM NEED HELP - Page 1
Forum section: electronics / repair

author: Shopy
author_rank: Contributor
timestamp: December 05, 2020, 05:28:47 pm
content: hello experts.i have a strange problem with my LG 55 led tv HDMI INPUTS.when i connect the cable tv HDMI to the HDMI input of the lg led tv .the tv says NO SIGNAL .but if i connect to the same inputs a china tv box all is working fine. all the HDMI inputs are the same. non of them work with cable tv but work well with the china tv box.this happens only on this specific tv another tv i have work fins with the cable tv and with the china tv box.i cant figure way it happens in this tv only.thanks, to the helpers?

author: Digorion
author_rank: Contributor
timestamp: December 06, 2020, 09:45:11 pm
content: Hello!Check the output resolution on your cable tv box. If your LG tv can handle only 720p, and cable tv box output resolution is 1080p (for example) it may cause this problem. If it so, try to set lower output resolution on your cable tv box.
Li-Ion UPS BMS error - Page 1
Forum section: electronics / repair

author: jordanz82
author_rank: Newbie
timestamp: March 03, 2025, 05:24:23 pm
content: Hi folks,I have a Li-Ion ups, I had an extensive power outage onsite where the battery pack was completely drained. When the power revived and the ups started back it gave me a 'bad bms error'. I since bought new cells and have replaced them. The voltage on the pack is strong and consistent, however, once installed and the ups has been online for a couple of minutes the 'bad bms error' returns. The pack will still have good voltage, but due to the error, the ups refuses to charge the pack. Any ideas on how to reset the bms on something like this? Thanks

author: benj38
author_rank: Frequent Contributor
timestamp: March 03, 2025, 09:50:36 pm
content: Some BMSs cannot be reset. Once tripped, even if you put in new cells they never get out of the tripped state. Dyson vacuum cleaners' battery packs are notorious for that.The only solution in such cases is to replace the BMS.

author: Swake
author_rank: Frequent Contributor
timestamp: March 07, 2025, 09:00:04 am
content: Makita batteries have a similar protection. The BMS stops the house from burning down when one of the cells fails However replacing the cell is not enough, you need another BMS too.It is also causing some trouble when one tries charging the batteries in freezing temperatures (which is really not a good idea with li-ion): you get en error, at the third try you can say bye bye to the BMS in the battery and throw it away. Agreed that it should stop the charging in freezing temperatures, but it should allow the charging again ones temperatures have normalised and not 'fail' definitively.
Liebherr freezer with deffective front panel controls and temp indicator - Page 1
Forum section: electronics / repair

author: conducteur
author_rank: Regular Contributor
timestamp: August 11, 2019, 09:36:15 am
content: Hello,We got this Liebherr freezer from someone. The problem is that the temperature indicator and the controls on the front panel doesn’t work... (the compressor is presumably always on).It’s not clear to me how to open this thing.

author: soldar
author_rank: Super Contributor
timestamp: August 11, 2019, 11:07:20 am
content: Ha! I got a two compressor refrigerator + freezer combo and the freezer has the same problem. In fact, I started a thread about it.For now I have figured out how to disconnect the freezer compressor and have it on a timer. As soon as I get a new refrigerator I will attempt to repair this one. I am guessing it may have a stuck relay or a PCB that needs repair. If I cannot repair the original control I will just replace it with a cheap thermostat from eBay.I will be following this thread.

author: conducteur
author_rank: Regular Contributor
timestamp: August 11, 2019, 12:24:35 pm
content: I suspect that there’s a power supply pcb in it that’s Not working... I have no experience with repairing freezers and fridges but the led and temperature control must operate from a lower voltage I think... I think there’s a relay in this thing to switch the compressor Off, but because the psu is brokken this control loop with the temperature sensor and the indicztor doesn’t work

author: conducteur
author_rank: Regular Contributor
timestamp: August 11, 2019, 02:03:17 pm
content: I’m in. It’s just a system with clips above the door to open it. The relay is rated at 24 volt... there’s a bridge rectificer next to the relay, but I only get 14 volts across it

author: floobydust
author_rank: Super Contributor
timestamp: August 11, 2019, 05:34:44 pm
content: It uses a capacitive-dropper. Check the value of the big gray film capacitor, they go low value with age. The zener diode next to it can also fail.But it might be short on the LED/control board which makes it draw too much current from the power supply. There should be around 24V unless the relay is on all the time, then 14V is OK.
LIEBHERR GNw 1360-5 index 20B  - Page 1
Forum section: electronics / repair

author: BY-74-MINSK
author_rank: Newbie
timestamp: September 29, 2024, 01:12:34 pm
content: Good afternoon, collegium. THERE is a charge from the LIEBHERR GNw 1360-5 index 20B refrigerator. The atmega324 short circuit is a hole.I'm looking for the firmware. Thank you in advance
lifecycle 6500 exercise bike repair - Page 1
Forum section: electronics / repair

author: zenelec
author_rank: Newbie
timestamp: September 27, 2024, 05:53:20 pm
content: Two photos attached. Does anybody know what is this component or part number? Is it a big resistance?I know a little bit electronic and try to repair my bike, but wondering how exercise bike works.Thanks.

author: thm_w
author_rank: Super Contributor
timestamp: September 27, 2024, 11:21:17 pm
content: Yes a very large 1 ohm resistor. Could be 100-300W rated.You can measure the resistance of it with a multimeter.
light bolt 1 phase connection logical problem - Page 1
Forum section: electronics / repair

author: john23
author_rank: Frequent Contributor
timestamp: November 05, 2024, 04:24:21 am
content: Hello ,an AC light bolp has needs two wires , while AC power in the wall has three wires.So how am i supposed to connect the lightbolp in the power in the wall?Thanks.

author: CaptDon
author_rank: Super Contributor
timestamp: November 05, 2024, 01:16:15 pm
content: It is so obvious, The lamp gets connected to the brown (hot) and blue (return) and if you have a metal fixture the green (earth ground) goes to the metal frame of the fixture. If this wasn't obvious to you from the start then let someone else do the wiring.
Light pen phototransistor recommendations ? - Page 1
Forum section: electronics / repair

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 28, 2023, 11:09:46 am
content: I need to replace a 3mm transparent case phototransistor in a light pen for the Thomson TO / MO series computers, what should I be looking for or avoiding?

author: Gyro
author_rank: Super Contributor
timestamp: February 28, 2023, 11:17:59 am
content: Depending on the screen resolution (pixel frequency) you might find a photodiode more appropriate, are you sure the original was a phototransistor?

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 28, 2023, 11:25:03 am
content: I'll edit this when I've checked the resolution but it's low.The schematic shows a phototransistor, no reference in the parts list though.Edit: "Highest" resolution is 320x200

author: Kleinstein
author_rank: Super Contributor
timestamp: February 28, 2023, 11:29:02 am
content: The electric internals tend to be quite similar. The main difference is likely with the optics. Chances are that a more focussed type is best suited. One should not get a type with IR fitler, but that should be obvious. If in doubt one may have to test a few, as the normal plastic case phototransstors are cheap.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 28, 2023, 07:32:51 pm
content: In the 3mm / T1 models looking at lowest possible centre wavelength or broadest spectrum and best focus, unfortunately most devices seem to peak in the I.R. even unfiltered.I've selected a few readily available references, whatever the original was could be EOL now, the design is from mid '80s:Vishay BPW85: 50°, Peaks at 860nm, 50% sensitivity at 620nm.Vishay TEPT4400: 60°, Peaks at 560nm, poor focus with 72% sensitivity on axis and 100% when 13° off-axis...Osram SFH-309: About 30°, peaks at 860nm, 50% sensitivity at 560nm.LiteOn LTR-209: Well focused at less than 20°, no data for wavelength...I'm leaning towards the SFH-309 or LTR-209 in the end it also depends on how cheap I can find them postage included.Any suggestions for better models?

author: Kleinstein
author_rank: Super Contributor
timestamp: February 28, 2023, 08:50:11 pm
content: The SFH 309 looks good and they even specify the speed. Some others seem to be slower (e.g. 15 µs).There seems to be a balnce with speed and sensitivity, though not that much difference. If one has the choice probably test both a low and high sensitivity bin.Having a peak wavelength of some 850 nm is normal for silicon sensor (phototransistor or photodiode). The phototransistors with a 550 or similar peak wavelegth would have an exter IR blocking filter to get closer to the human eye response. This is not really needed. The screen may also emit some IR that can be used.I faintly remember using phototransistors as a light pen with the C64. AFAIR this were just the normal types, nothing special and it usually worked OK, provided the screen was bright enough and the cable not too long. If there is no amplifier in the pen, the cable capacitance could be an important point.
liitokala charger - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: December 03, 2020, 06:15:16 pm
content: hi all ive a liitokala lii-500 charger thats died,does anyone know where i can find a schematic for it?,cheers Paul m3vuv.

author: shakalnokturn
author_rank: Super Contributor
timestamp: December 03, 2020, 08:21:30 pm
content: No schematic, I have the same charger.The 12V adapter supplied with mine went intermittent very soon.Have you checked yours?

author: m3vuv
author_rank: Super Contributor
timestamp: December 03, 2020, 09:24:36 pm
content: yup my adaptor is fine,just the charger wont power up

author: Miwer
author_rank: Contributor
timestamp: March 07, 2021, 11:17:36 am
content: I have one of those too. Also looking for a schematic.Mine died after being dropped on the floor from a table. I replaced a TL431 vref and a transistor on the power input to make it work again, but now it seems a bit "wonky" as it does not correctly measure the voltage on the batteries. I can't seem to find any other faults on it, but it's not easy without a schematic. No visible damages, but I'm not sure if the drop could have caused a pcb via to crack, and make bad connection.

author: Miwer
author_rank: Contributor
timestamp: March 17, 2021, 10:24:49 am
content: Quote from: m3vuv on December 03, 2020, 09:24:36 pmJust wanted to follow up on this, with some pictures.You need to check the voltages around U2 and Q27 - you can see my measurements in the pictures. The 5v regulator in this charger is more or less directly copied from the TL431 datasheet (apart from the resistor values).I had to change both the TL431 (U2) and the NPN transistor (Q27) in mine.Now beware- the chinese "431" marked part is actually not pin compatible with the TL431 from Texas Instruments, that I had. The pinout actually matches TL432 instead, so I had to flip my TL431 around, and connect a wire from anode to ground, as you can see in the picture.From the datasheet:"The TL432 device has exactly the same functionality and electrical specifications as the TL431 device, but has different pinouts for the DBV, DBZ, and PK packages."If I had to purchase a replacement, I would get the TL432 instead, but I already had the TL431 so I couldn't be bothered.As for the NPN transistor (Q27), I believe any generic NPN transistor will work, as long as it can handle the current draw of the Liitokala (only the logic/display/etc., not the charging) - I just used whatever high current NPN transistor I could find. In my case I used a ZXTN19100CFF - maybe overkill, but it works.
LIN bus help need - Page 1
Forum section: electronics / repair

author: Chriss
author_rank: Frequent Contributor
timestamp: April 03, 2022, 11:03:32 pm
content: Hi!I'm repairing my car power windows system cos the back door power windows left and right are working very funny.The back door left windows can be controlled from the driver side door switch but not from the door switch.The back right door windows is not working from the drivers door switch, but is stepping up and down by the switch from the back right door.The switches are tested and ok.No diagnostic trouble codes set in any ecu.And here I'm coming to my question:The doors have a sort of control module in each of doors.They are interconnected through LIN Bus, but the switches have nothing to do with the LIN Bus.The switches are going to the door control module in each door.If the LIN Nus would be in some way compromised a DTC would be set I assume.Am I'm right?If the LIN Bus wire would be disconnected or broken, let's say in the right back door, would the switch still control the windows up and down?How is affected the system like a power windows module if his LIN line is broken?Will the modul still be usable locally or would it stop to response to his local I/O's?Thank you for any suggestions and help.

author: eurgenca
author_rank: Regular Contributor
timestamp: April 04, 2022, 05:54:44 am
content: Hello.Which car are you working on?Did you check common wiring failure between door and chassis?

author: Chriss
author_rank: Frequent Contributor
timestamp: April 04, 2022, 07:44:15 am
content: Yea, I checked the wirings, no cracks or any damages.Also checked with dmm continue test...Hypothetically if I would extract the window motor which is integrated with the door module, and I would try to setup it on my bench with the switch etc, but without the LIN bus connected, would the motor react based to the switch position?I think it should work without the LIN attached.I assume the LIN is in this case just for reading the error or state of the electronic and mechanics part in the door and has nothing to do with the locking/unlocking, power windows etc.Am I right?The car is a Seat Ibiza 1.4 2008.
Line 6 DL4 Repairs - Page 1
Forum section: electronics / repair

author: fmashockie
author_rank: Frequent Contributor
timestamp: October 05, 2023, 03:18:19 pm
content: Hey everyone! I recently did some repairs on a few Line 6 DL4 pedals. Figured I would share the outcomes on here for anyone's reference. These guitar pedals are a staple on most pedal boards, but they are notorius for having tons of issues. I'm sure anyone who uses one religiously has at least gone through more than one of these due to some kind of issue. So I put some videos of the repairs onto my YouTube channel. Also, I will attach a full schematic that I found online. This schematic also includes instructions for putting the DL4 into test mode which can be helpful for troubleshooting. Be advised this schematic is for the older revision DL4s. At some point they revised the PCB on the newer models. The most noticable changes are to the power supply section, the microcontroller, and the cirrus logic audio codec. But the schematic is still helpful even for these versions.Repair #1 - Bad audio output stage due to faulty precision op-amp. Would not even bypass a clean signal.Repair #2 - Flashing low battery when battery is not low. Due to interruption in battery life signal path to U6 ADC TLV0838Repair #3 - Malfunctioning switches and LED upgrade.Hope this is helpful to someone!

author: Calambres
author_rank: Frequent Contributor
timestamp: October 05, 2023, 05:35:33 pm
content: I have a DL-4 that suddenly failed many moons ago. It was a real favourite of me. I still keep it.Thanks a lot!

author: fmashockie
author_rank: Frequent Contributor
timestamp: October 06, 2023, 04:54:39 am
content: It's one of my favorites, too! Has always had a place on my board. Feel free to reach out if you need help fixing yours!

author: BarbarianATX
author_rank: Newbie
timestamp: December 20, 2023, 08:29:10 pm
content: Piggybacking from theALL 4 LIGHTS FLASHING (LOW BATTERY) FAULTwhich I successfully repaired just now, and also replied on the Youtube video for reference:"Reporting back on the repair unit...R38 (220k) resistor had totally blown open circuit! Replacing it (simply used a 1/2-watt through-hole part soldered to the smd pads), then reflowing all the toasted solder joints on R52/R53/D13/D14, and making sure U6 pin6 was soldered nicely restored functionality. Also did the common fix of removing, cleaning socket, replacing the EEPROM chip.That was done after previously rebuilding the Power Supply section:Electrolytic caps (C40 : 1000uF/25V) and (C48, C58, C59 : 220uF/25V)Diodes (D11, D12 : 1N4002 Schottky)D16 (1N4729 3.6V 1-watt Zener) new diode raised about 1/2" off the PCB and tilted away from the 1000uF cap...so that it won't toast the nearby pads like before.Unit is happy again, as will be the customer. Cheers!"- Paul @GREMLIN Machine Shop FXandBARBARIAN Electronicsin Austin, TX.
Line 6 Helix No Backlight For Main Display - Page 1
Forum section: electronics / repair

author: -KAI-
author_rank: Newbie
timestamp: June 01, 2025, 02:40:24 am
content: My friends Line 6 Helix had a blown power supply. There seemed to be no other damage on the unit so I replaced the PSU, the unit booted, and operated normally - but there was no display. I found a replacement display (https://static.chipdip.ru/lib/291/DOC006291203.pdf) on the EEV form but a replacement did not fix the issue.I think the only issue is that the backlight is not being told to turn on. I have attached picture of a crude schematic I drew up and the area of the unit I think the problem is in.Troubleshooting steps I have taken:If I plug in the data cable from the unit into the display and power the display from a 9v battery I can see the backlight turns on. So the screen is good.There is a test pad called TP_BL_K on the PCB that is connected to the WHITE wire of the display and measures 5v. If I ground this pad or the WHITE wire the backlight turns on.WHITE is connected to two MOSFETs (https://componentstree.com/wp-content/uploads/2024/12/LN2302LT1G-Datasheet.pdf) called Q4 and Q5. If I put 12v on the gate pin the backlight turns on. Therefore I think that Q4 and Q5 are good.Connected to Q4 and Q5 is two NPN transistors (https://www.alldatasheet.net/datasheet-pdf/view-marking/226196/BILIN/MMBT4401.html) called Q6 and Q7. This is where things start to act funky but I don't see where the problem is specifically. If I put 12v on the base of Q7 the collector goes from 90mV to 5mV. To me this seems unexpected because we would want the collector of Q7 to go hi in order to have Q4 and Q5 pull WHITE down to GND and turn on the backlight.I can't find where R42 goes...I spoke with an engineering buddy and he thinks Q4 and Q5 are bad. ChatGPT thinks that Q6 is bad. Neither party has given me a good reason for their opinion.Any help would be appreciated!

author: -KAI-
author_rank: Newbie
timestamp: June 01, 2025, 02:44:03 am
content: Re-uploading the schematic since it was rotated...

author: Vicus
author_rank: Regular Contributor
timestamp: June 29, 2025, 03:23:40 pm
content: Something is missing in your schemastic. Look for a pull up resistor. Maybe R55? By the way apply voltage straight to a bjt base is the right way to kill it. BJT are current device so only a very small current have to be use in the base.

author: -KAI-
author_rank: Newbie
timestamp: July 02, 2025, 10:54:23 pm
content: Thank you for trying to help but we have sold this unit for parts. I may have been causing my own problems by connecting 12v to different spots on the board...
Line filter assembly in a Tektronix 2235 - Page 1
Forum section: electronics / repair

author: Matthew H
author_rank: Newbie
timestamp: February 20, 2024, 02:42:30 am
content: I was able to pick up a Tek 2235 AN/USM-488 for a real reasonable price. I'm going to replace the RIFA caps before I do anything else, and I was considering replacing the line filter assembly while I'm at it. My question is how critical are the values of the components in the filter assembly?The verison of the 2235 I have has line filter 119-1788-00 which is a ZUB2203-00 made by TDK. Specs are: 3A, L=1.0mH, X2=0.1uF, Y=2x2200pF.It looks like the Schaffner FN9222 series is a close match. The cap values are teh same, but the inductance is 2.5mH for the 3A part and 0.78mH for the 6A inlet. Will this make any difference?Thanks in advance!

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: February 20, 2024, 03:03:30 am
content: Inductor, and capacitor values I would guess will have not much significance. Just make sure the new line filter can handle the power consumption of the scope.
Lineage Power CP2000AC54TEZ issue - Page 1
Forum section: electronics / repair

author: dk5ya
author_rank: Contributor
timestamp: December 27, 2019, 09:20:57 am
content: I love to use Lineage Power CP2000AC54TEZ PSU (48V, 2KW) for my Ham Radio stuff running high power LDMOS-Amps. They are silent, stable and solid like a rock.I bought 2 Lineage last week but both are showing a weird behaviour. Last year I've built 2 LDMOS amps (70 MHz and 23cm) with these fine und low noise PS and they are working flawlessly.The 2 PSU I bought last week in the bay won't come up with the proper DC voltage. After enabling the PSU via Pin 3A/4C (Logic GRD to Enable) via a 10 KOhm resistor the PSU starts working (blowers running slowly) but both show just 2.52V DC at the output instead of 50V. The two I bought last week are from a rather new production line of late 2015. Both PS show exactly the same behaviour. Pin 5C to 3A via 10 KOhm Pot in order to regulate POut doesn't work either.These PSU are sold under several different brand names like GE, Tyco, ABB etc.Datasheet:https://www.alldatasheet.com/datasheet-pdf/pdf/568847/LINEAGEPOWER/CP2000AC54TEZ.htmlAn idea?

author: dk5ya
author_rank: Contributor
timestamp: December 27, 2019, 05:28:34 pm
content: Got it! A total reset of the device via I²C Bus was healing the issue which seems to be some kinda weird firmware mess :-)Udo
Linear encoder check - Page 1
Forum section: electronics / repair

author: Zielsziek
author_rank: Contributor
timestamp: June 03, 2025, 11:50:43 am
content: Hello, I need to diagnose a Heidenhain LS623 Glass tube linear encoder. There are two of these on a Darley Pressbrake. My machine isn't calibrating on Y axis and I suspect that there might be a reference point on the encoder. The encoder was jolted and I suspect that if such a calibration point exists mine isn't working. I have never worked with these glass tube encoders and I find the datasheet a bit cryptic. The machine diagram does not help either. I do not understand the purpose of pins 2, 11 and 17, Sensor Power and Uas.Thanks!

author: benj38
author_rank: Frequent Contributor
timestamp: June 03, 2025, 10:54:29 pm
content: Indeed, there is a special scale inside carrying a reference mark for absolute positioning information. Ua0 and its inverse (pins 3,4) are the ones you want to monitor to see the reference mark pulses.Pin 7 (Uas) is a fault detection signal. It will pulse low if certain faults are detected (like a failed light source).Pins 2,11 are the power supply pins for the sensor. The main supply pins (12,10) are connected to the light source. One usually connects pin2 to 12, and pin 10 to 11.

author: benj38
author_rank: Frequent Contributor
timestamp: June 03, 2025, 11:06:31 pm
content: One more thought (and I apologize if I am stating the obvious here): if you are lucky to have long enough wires, you can plug the y-axis connector to the x-axis encoder, and vice-versa. Then, if the problem shifts to the x-axis on the display (obviously, mechanically it will stay with the Y-axis) then the problem is the encoder, and if it stays with the y-axis on the display then the problem is somewhere else in the circuit.

author: Zielsziek
author_rank: Contributor
timestamp: June 04, 2025, 09:54:08 am
content: Thank you so much !
Linear multicode gate opener schematic needed - Page 1
Forum section: electronics / repair

author: emptech
author_rank: Regular Contributor
timestamp: June 07, 2021, 08:38:23 pm
content: I have a linear multicode gate opener with poor sensitivity, could be off frequency. It works but only when the transmitter is up close, the issue is not the transmitter. I can spend some time reverse engineering the pcb but hoping somebody else has already done it. I don't care about the codes, I'm interested in the rf area. It is on 300 MHz.For what it's worth, the part number on the pcb is 221421-01DJim

author: emptech
author_rank: Regular Contributor
timestamp: December 31, 2024, 05:02:32 am
content: It's only me again, this time working on another receiver, low sensitivity. Schematics anywhere? jim
Linear PSU question - Page 1
Forum section: electronics / repair

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: November 09, 2024, 02:19:22 pm
content: Hi!I have purchased for a cheap (20euros) a power supply made by unknown brand. The unit has a 1 analog instrument which shows voltage/current.So the main question is why does my psu behave like shown in a video? I mean, why voltage jumps to the max. value during the powering the unit off?https://easyupload.io/g4favkThank you and sorry for shaky video.Hrvoje

author: IanJ
author_rank: Unknown
timestamp: November 09, 2024, 02:30:38 pm
content: No video, just a bunch of Ads and a link to some dodgy software.Try YouTube or Odysee.Ian.

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: November 09, 2024, 04:00:32 pm
content: Hi Ian!Try it download fromhttps://files.fm/u/f2x6wgwzbghere.Thank you!Kind Regards,Hrvoje

author: tunk
author_rank: Super Contributor
timestamp: November 09, 2024, 04:31:40 pm
content: There may be stored some energy in a capacitor.Try to put a load on it, e.g. an 1k resistor.Photos of the inside may help understanding how it works.

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: November 09, 2024, 04:56:48 pm
content: Quote from: tunk on November 09, 2024, 04:31:40 pmI agree! Tomorrow i will post some pics

author: u666sa
author_rank: Frequent Contributor
timestamp: November 10, 2024, 11:24:14 am
content: Quote from: Hrvoje_CRO on November 09, 2024, 02:19:22 pmBroken. My YaXun PS-1501A from the times of before Noah's ark slowly goes down to 0 when turned off. That's what yours should be doing. Most likely some caps are bad on yours. Easy to check visually. If nothing seen visually, LCR or replace everything.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: November 10, 2024, 11:42:03 am
content: HiQuite a number of bench power supplies go well over set voltage at either swirch On or Off.There are a number of well know and expensive makes that do so, disconect load before switch On or Off.G Edmonds

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: November 10, 2024, 12:07:45 pm
content: Quote from: u666sa on November 10, 2024, 11:24:14 amHi George!Agree, but partially, psu works fine otherwise. But it is old cca. 30yrs. I will post some pictures in a few moments.Regards,Hrvoje

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: November 10, 2024, 01:19:32 pm
content: Here are the some pics of the unit itself:
Link-Miles DC Amplifier - Page 1
Forum section: electronics / repair

author: djrm
author_rank: Contributor
timestamp: March 19, 2025, 08:59:48 am
content: I recently bought a piece of vintage test equipment which contains a Link-Miles DC amplifier of which I can find no information. I'm starting to reverse engineer it to get an idea of how it works and I see that it may be a chopper amplifier.There are a pair of neons arranged as a multivibrator lighting a light dependant resistor. With power applied it oscillates at 151 Hz and generates an approximately square wave. I hadn't seen this configuration previously but a search shows similar configurations being used in chopper amplifiers.I have seen HP amplifiers with multiple LDRs used for chopper signal path selection, this design uses a single LDR and a pulse feed from the neon circuit. I'm trying to understand how this could be configured in the circuit, any help much appreciated, David.Amplifier board and neon multibrator with photo-resistor:Neon-LDR multivibrator module:

author: MathWizard
author_rank: Super Contributor
timestamp: March 21, 2025, 09:50:02 pm
content: So why do they use the bulbs? Do they have have very consistent turn-on voltages or something ? Or are they more stable or drift less than caps ? And then I guess they use the light for feedback or signal path, without loading the circuit ?At 1st I thought the circuit had BJT's too, like a BJT multi-vibrator, but wow it doesn't.I have a bag of little Neon bulbs, I know they barely use any current and ~100V, and I just made an adjustable, low current 200V supply. So I should try some experiments with them. How do they do at higher frequencies I wonder.LTSpice has these bulbs too, I must try them too.

author: TimFox
author_rank: Super Contributor
timestamp: March 21, 2025, 09:59:57 pm
content: Before LEDs, the only small light sources were incandescent and neon bulbs.For photochoppers, the incandescent bulbs were far too slow to pulse at the required rate.I have an old -hp- 425A sensitive voltmeter that used incandescent bulbs with a motor-driven chopping wheel (steady excitation of the bulbs) and photoresistors.Photoresistors (at the other end of the chopper) come with different chemistry, some of which are fast enough for chopping: compared with photodiodes, they are symmetric for current flow.I did see a photograph in an electronics magazine of a magic-eye tube (with linear display) used to control a photoresistor for variable attenuation.
Linn ftp directory? - Page 1
Forum section: electronics / repair

author: Chris56000
author_rank: Frequent Contributor
timestamp: December 18, 2023, 09:56:51 pm
content: Hi!There's quite a lot of what look like Linn Sondek mechanical drawings and manuals for Linn products that keep appearing on Google searches – how did Google manage to crawl these?Is there known to be an access to this? The links are named "FTP Directory Listing", but all of them appear to be dead!Chris Williams
LINN MAJIK-IL Integrated Amplifier issue - Page 1
Forum section: electronics / repair

author: hifiramr
author_rank: Newbie
timestamp: January 30, 2020, 09:38:50 am
content: Hi guys I need help to resolve issue on LINN MAJIK-IL Integrated Amplifier.I got amplifier from my relative as non working condition.When i swich on the amp its just a number 7 on the display nothing else that also some time glows some times in dim light status.What will be the issue i can see that viedo controler ic getting hot might be LM317T issue non proper voltage.Please let me know your inputs

author: hifiramr
author_rank: Newbie
timestamp: January 30, 2020, 10:52:17 am
content: please find the display image photo

author: goaty
author_rank: Regular Contributor
timestamp: January 30, 2020, 11:37:18 am
content: Looks to me as if "7" is not fully lit. Lower segment seems darker.Maby start by checking the power rails in the amp.I have not found schematic.
Linsn card with flickering problem - Page 1
Forum section: electronics / repair

author: nonkeldw
author_rank: Newbie
timestamp: December 16, 2019, 05:32:00 pm
content: HiI'm busy with reverse engineering of a LISN card, RV905H.I use the card in standalone mode without any connection to a "server", when I push the button the LEDWALL steps to predefined patterns, this works!But sometimes there is a white flickering noise... I measured already the power rails this rails looks good and stable.When measuring the CLK (this CLK is generated by the FPGA and go through all the LED panels.)I found some strangs signals... See picture below.Have any of you suggestions how to future investigate this problem?

author: StillTrying
author_rank: Super Contributor
timestamp: December 16, 2019, 05:41:18 pm
content: A silly question would be have you got the scope probe on X10.

author: nonkeldw
author_rank: Newbie
timestamp: December 16, 2019, 05:59:08 pm
content: Yes, it's standard for me
Lipo battery reversing polarity ? - Page 1
Forum section: electronics / repair

author: Carl E
author_rank: Regular Contributor
timestamp: September 24, 2021, 12:38:08 am
content: Hi,Something I've never seen.....My hand vac died in mid use. Reading 14v on an 18V pack I found a Lipo battery ( 18650 ) with reversed polarity. It was the last battery in a series string. I removed the cell, tested it again, .500 volts reversed polarity. Anybody ever run across this? Once I replaced the bad battery the pack was good again.

author: BradC
author_rank: Super Contributor
timestamp: September 24, 2021, 12:43:47 am
content: Charge reversal can happen to the weakest cell of pretty much any battery chemistry in a string under the right circumstances. I've never seen it on a lithium cell, but only because the BMS usually shuts things down before it gets that far. As you've demonstrated, it's clearly possible.

author: feedback.loop
author_rank: Frequent Contributor
timestamp: September 24, 2021, 02:53:39 am
content: http://liionbms.com/php/wp_cell_voltage_reversal.php

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2021, 04:56:17 am
content: Does the unit have a proper BMS that monitors each cell? You probably already know this, but don't attempt to revive the reversed cell, it has been damaged and charging it could be dangerous.

author: amyk
author_rank: Super Contributor
timestamp: September 24, 2021, 06:53:08 am
content: A lot of cheaper designs don't have balancing and rely on the cells being matched in capacity and charge initially. They tend to last longer if you don't deep-discharge the whole pack before charging it each time.

author: magic
author_rank: Super Contributor
timestamp: September 24, 2021, 06:45:36 pm
content: I guess you are also supposed not to overcharge, thenSounds very cheap and dodgy

author: Carl E
author_rank: Regular Contributor
timestamp: September 24, 2021, 09:26:02 pm
content: Thanks to all who replied. I have already put the defective cell in the recycle bin.The battery pack does monitor each cell for balance, HOWEVER, this particular vacuum is a B&D Pivot that has a design flaw that shut off the vac after a few seconds. Once it did that and the switch was turned off then on again, it would run a little less time before stopping again. This could be repeated several times. I put a jumper from ground at the battery to ground at the switch and that solved the problem. Apparently there is some circuitry that broke the ground from the battery pack to the switch and once it shut off, the connection was restored but the switch had to be turned off and back on to get it to run.. I could never catch the open with a DVM. I originally thought there was a thermal cutoff in the motor but that was not the case. It will be interesting to see if another cell reverses polarity. I wish I could see a schematic for it.Will let you know what happens in the future.
Liteon PA-4291 SMPS repair gone wrong after a complete reverse engineering - Page 1
Forum section: electronics / repair

author: Zanot92
author_rank: Newbie
timestamp: December 30, 2020, 09:10:29 pm
content: Hi all, I'm Fabio from Italy. I take this opportunity to wish you all a happy Christmas ad a happy New Year.I've got a faulty Toshiba TDP S8 projector laying around for a while so I've decided to try troubleshooting it during these winter holidays.Before I've taken apart, the projector was not powering up, even the led indicators on the fort panel were off. Since at a first visual inspection the lamp seemed ok and also it's driver, I focused on the PSU, a Liteon PA-4291.It's suppoded to deliver 385V for the lamp ballast, +13V, +5V and +3.3V for the rest of the projector circuit. I've tested it apart and there were no output voltages.Since I'm (unfortunatly) plenty of time I've reverse-engenieered the board, see attachment (I named only the components that have a silkscreen on the PCB). I think it's quite comprehensive.I've deeply tested apart all the major components, the two mosfets with a basic switching circuit, measured inductors and their saturation current (not needed, just for fun!), checked the ML4800 control IC feeding the right voltages with external supplies to see if it was still good and it was so.The only things I found wrong were two:a faulty electrolytic cap C206 rated at 3.3mF but measuring only about 26uF (I didn't measured ESR)R125 PFC current sensing resistor shorted.Reading R125 color, red-green-white-gold-green, I think It was a 25.9Ω 2WBUTI've ignored, and here I think I've made a mistake, trusting silkscreen on PCB that says 385V @ 0.65A max. So according to ML4800 datasheet page 8 I've calculaded the new sensing resistor value as 1V/0.65A chosing 1.5Ω. After replacing those two component the PSU was running fine at no load but when I've connected the lamp ballast I saw the magic smoke..As result, the new R125 was shorted, the 10Ω SMD 1206 resistor marked on the schematic completly carbonized, also the 3 1n4148 clamping diodes protecting pin 3 I_Sense of the control IC were shorted. Also the ML4200 has been damaged because now it's draining over 60mA at 12V Vcc becoming very hot. Mosfets instead are still fine.I suppose, and here I'm asking your kind advice, that only a dead short between the 385V connector and GND could had cause such a failure, making the voltage on ML4200's pin 3 too negative blowing the resistors and clamping diodes and IC too.What it's confusing me is that I've also started the reverse engineering of the ballast, an Osram PT VIP4AC 380, and for what I can see now It's power stage is basically a buck converter feeding a H bridge for switching the lamp. All mosfet here are good (tested outside pcb) and there are no short at the input 385V connector!