hybridfree/eevblog-posts huggingface dataset:
TTi QXP1200 PSU repair - help me understand a bit of the circuit?? - Page 1
Forum section: electronics / repair

author: max_torque
author_rank: Super Contributor
timestamp: January 31, 2025, 10:35:27 pm
content: Hi all PSU guru's!I have a TTi QX1200 psu (60V/50A) that i blew up and i'm in the middle of the fix, when a bit of the circuit has me puzzled, nothing to do with the repair, but i'm curious!The PSU uses a pretty normal PFC front end, generating a 400vdc dclink from 240VAC, that is fed into a ZVS resonant push-pull converter, and that is followed by a low votlage drop linear stage to improve regulation and noise etc. So far, nothing surprising. The circuitry is an interesting mix of analogue and digital and obvisouly dates from a while back, 'cause you'd just do it all in a dsp now and save a lot of messing around with op-amps etc. However, the bit that i can't really work out is a chunk of transistors sat on the gate drive for the linear stage:The bit that i can't quite work out is what looks like some sort of current mirror on the far rhs of that diagram, where the gate voltage for the linear power stage fets (Q3,Q4,Q5,Q6) is passed through R109 (10k) and into Q34 (PNP), via R106 (10K).V+SEC is a voltage from a linear reg that comes from +LTPSUPPLY generated by Aux windings on the transformer and is referenced to +VOUT (+ve DC output of linear stage)-8VSEC is a generated from a negative charge pump and diode, and is, funnily enough, 8 volts negative to +VOUT0V is the negative DC output busIn the very top rh corner, Q37 and R49 are clearly fairly heavily loaded, being a 100w power resistor and a pretty chunky T0-220 well heat sinked PNP transitor.NOTE: despite being shown R1 is NOT FITTED so there is no connection at this point.As the output linear power stage is made up of NFETs, then clearly GATE is going to be well above +VOUT, meaning the -8VSEC rail is going tp be well negative to those fets sourceSo, can anyone help me out, what is this doing and why?(i'm currently stuck between its a negative clamp to keep the linear fets off, or it somehow is used to discharge V+SEC if the gate voltage zero?sorru, i'm sure it's pretty obvious, but it's been a long day so far, so any insight appreciated!BTW, full circuit diagram can be found here:https://www.farnell.com/datasheets/319866.pdf

author: Harry_22
author_rank: Frequent Contributor
timestamp: February 01, 2025, 09:23:22 pm
content: Hi!Seems this is a mistake in circuit diagram.Let us make the logic chain.Q37 has 0.5A maximum continuos current. 0.5 A*100 Ohm (R49)=50 VSo "V+SEC" should be around 50 volts. Like your PSU output voltage.If you connect R49 to +VOUT instead of V+SEC then it will make sense.Circuit R49 Q37 discharges C18 when the source output voltage is turned off.Correct?

author: max_torque
author_rank: Super Contributor
timestamp: February 03, 2025, 10:02:53 pm
content: HI, thanks for that. Yes a circuit to pull down +Vout when the output linear stage is off makes a lot more sense! I'll have to find a minute to pin out the actual pcb and see what is connected to R49Thanks!
TTI / Thurbly Thandar TSX3510 Repair - Page 1
Forum section: electronics / repair

author: TheBay
author_rank: Unknown
timestamp: January 22, 2014, 10:28:43 am
content: I have had this power supply for some time and has served me really well. It is a Mixed mode design based on SMPS but precision.It's just the Standard non programmable TSX3510 35v 10amp, the version that has a dark grey case, not the recent white one.Recently I was trying to charge some SLA batteries and forgot I had one trickle charging, ever since then this PSU has been playing up.The fault is, if anything draws over 800ma+ the Constant Voltage light flickers on and off (Does not go to constant current, which is correct), and the LED segment display shows a brief drop in Voltage, If I have a multimeter attached it constantly shows the voltage the the display drops to, not what is displayed on the PSUConstant Voltage/Constant current switch over is working correctly.If I connect a dummy load at say 500ma it all works correctly and the multimeter reads correctly.Also when it is not working correctly it makes an awful buzzing/whine from one of the SMPS transformers, this PSU was near silent previously.I think an SLA has backfed or shorted out causing damage. I do have the schematics for this PSU, any help will be gratefully appreciated.I love this PSU and would love to get it back in action.

author: macboy
author_rank: Super Contributor
timestamp: January 22, 2014, 03:56:00 pm
content: Do you have the full service manual or just schematics? I can share the service manual with you if needed.

author: TheBay
author_rank: Unknown
timestamp: January 22, 2014, 05:59:41 pm
content: I've been sent a service manual from TTi.I guess that's the same as what you have?

author: djsb
author_rank: Super Contributor
timestamp: December 24, 2022, 09:43:50 pm
content: Did you ever get this fixed? Just curious. Thanks.

author: TheBay
author_rank: Unknown
timestamp: December 24, 2022, 10:21:02 pm
content: Quote from: djsb on December 24, 2022, 09:43:50 pmIt was the large capacitors in the primary side.
Tube radio. - Page 1
Forum section: electronics / repair

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: September 12, 2019, 11:01:04 am
content: what is the value of this inductor, it's 2 ferrite core inductors in one and it has a lot of windings! there isn't a value for it labeled anywhere, maybe I could bypass it somehow.the radio is called 'rigonda stereo' I plan to use it as a guitar amp but first I need to make it work so can anyone help?

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 12, 2019, 11:33:11 am
content: Please do NOT doublepost! I'll ask a mod to remove this thread.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 12, 2019, 11:39:18 am
content: Quote from: ELS122 on September 12, 2019, 11:37:24 amhttps://www.eevblog.com/forum/projects/tube-radio-help!/

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 12, 2019, 11:47:03 am
content: Quote from: ELS122 on September 12, 2019, 11:42:03 amThat's just BS, please show me the differences, here is the schematic from the other thread:

author: Andy Watson
author_rank: Super Contributor
timestamp: September 12, 2019, 12:10:52 pm
content: Quote from: ELS122 on September 12, 2019, 11:37:24 amReally? I must be suffering severe déjà vu. I've seen exactly the same question about the same circuit with at least half-dozen replies.
Tunable inductor for Moog Theremin - Page 1
Forum section: electronics / repair

author: EugenioN
author_rank: Contributor
timestamp: June 11, 2024, 09:31:26 pm
content: I've got a Moog Theremin and I need to replace this tunable inductor because its ferrite core is cracked and can't be rotate:It's a SLOT TEN5-10 from Coilcraft:https://www.coilcraft.com/getmedia/90724f9c-b8a9-4867-9507-a749f251f08c/slot10.pdf47uH nominal (20uH-60uH range) with a fairly low Q=32.Unfortunately I can't find it: it was quite uncommon at its heyday, discontinued by manufacturer and no longer available.No one is selling nos parts on ebay (Europe).Any suggestion?

author: indeterminate
author_rank: Regular Contributor
timestamp: June 11, 2024, 10:12:18 pm
content: Do not be to fussyUsually sumthing that is ruffly the same will work , even if you just swap the slug out of one of the following you should be okhttps://au.mouser.com/c/passive-components/inductors-chokes-coils/variable-inductors/?inductance=450%20nH~~550%20nH&instock=y&rp=passive-components%2Finductors-chokes-coils%2Fvariable-inductors%7C~Inductance

author: EugenioN
author_rank: Contributor
timestamp: June 12, 2024, 04:48:29 pm
content: Yea, I've been definitely to fussyJust bought a new tunable inductor like this one:Removed the wire and cut away the base with pins, the ferrite core and its plastic sleeve fits perfectly inside the original tunable inductor.The inductance range is close enoughGreat advice, thank you!
Tunnel Diode is it dead??? - Page 1
Forum section: electronics / repair

author: Zenwizard
author_rank: Regular Contributor
timestamp: March 01, 2019, 02:47:36 am
content: I am working on a Tektronix 284 pulser and the tunnel diode is acting strange. There was a very intermittent short in it and I have seen it pulsing a little. In digging further ALL the biasing resisters are out of spec. The 2 series resisters in the back of the air line are 739.9 Ohms they should be 660 Ohms 5% the front resister is 797.0 Ohms it should be 750 5% closer but still out from the 5% spec. The air line termination resister is spot on at 54 Ohms. With the bias controls the wave shape will change but the square wave is messy not a clean step I would expect. My question, is the tunnel diode is still good? I did a diode check on it and I got .6 V in both directions so it is not dead shorted. But this is to be expected from a TD. This is the infumas D180 from Tektronix. I can source a new part if it need to but it is $250.00 Each Yikes. Is this worth fixing or should I put it up to a learning experance?

author: Zenwizard
author_rank: Regular Contributor
timestamp: March 01, 2019, 03:56:17 am
content: Attached is the drive voltages for the diode. From the service manual this looks a little light especially on the top side. The second attachment is the scope with measure turned on. From the service manual it looks like there should be a + 13 V and a - 13 V square wave that are in time in a push pull config in to the diode.

author: NWerner
author_rank: Contributor
timestamp: August 14, 2020, 08:17:29 pm
content: Just my 2ct:- those biasing resistors are very drifty. Yours look perfectly fine.- check whether the termination resistor module is fine (seehttps://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/284.html)- to test your tunnel diode :- mount it in some kind of spring loaded test fixture- apply a 1KHz square wave with eg. 10% duty cycle and cyrying amplitude. You should experience a Ip of approx. 20mA.- a diode tester is useless as a tunnel diode conducts in both direction.If youre tunnel diode is fine you should be able to resurrect your pulser back to life by fiddling with drive voltage amplitude.

author: srb1954
author_rank: Super Contributor
timestamp: August 15, 2020, 01:14:27 am
content: Check the internal connections within the air-line. These are prone to tarnishing and that may be affecting the resistance values or tunnel diode currents
Turnigy Accucel 6 Calibration - Page 1
Forum section: electronics / repair

author: user119_
author_rank: Newbie
timestamp: July 17, 2021, 11:41:30 am
content: Hi all,I have Turnigy Accucel 6 charger that does not have a calibration mode. My multimeter suggests that it is off by 0.7v, which is very concerning.Is there a way to calibrate it by changing anything on the circuit board?I really want this to be as accurate as possible to check capacity of li ion and lipo batteries.TIA.
Turntable speed control anomaly - Page 1
Forum section: electronics / repair

author: Ingenia
author_rank: Newbie
timestamp: January 27, 2024, 09:51:08 pm
content: Hello everyone. I usually find a strange thing in this speed control card of an EMT turntable.When in Stop, if the circuit is cold, the motor rotates slightly. The mechanical brake stops the engine, but sometimes it can slip and the force of the engine overcomes the brake. After a few minutes pass, the electronics increase the temperature and the anomaly disappears.I think the thing appears in the last exit stage. When hot there is 0v, but when cold it can exceed 1v.Any suggestions?

author: shakalnokturn
author_rank: Super Contributor
timestamp: January 27, 2024, 11:07:34 pm
content: No experience with this particular model but it's very common that low value (0.1 - 10μF) electrolytic capacitors cause trouble in servo controlled turntables.It may be worth checking the lot but if you must start somewhere start with the 1μF ones.

author: Ingenia
author_rank: Newbie
timestamp: January 28, 2024, 12:41:50 pm
content: All electrolytic capacitors have been replaced.It seems like a characteristic of the design. A blast of air and a brake that slips cold makes the engine move slightly for a few minutes.I would like to improve that situation.

author: Tim88
author_rank: Regular Contributor
timestamp: January 28, 2024, 04:22:42 pm
content: I have a Marantz SD9000 that had a bug in the circuit that had a fluctuating playback speed, could not get a steady rpm out of the motor. I chased that off and on for over a year. It turned out to be a dirty switch that either supplied the power or ground, can't remember. So, trace the supply lines to it and see if they run through any switches...

author: Ingenia
author_rank: Newbie
timestamp: February 16, 2024, 10:58:34 am
content: Now I think it's not a temperature problem, it's because of the humidity.
TV backlight LED strips - zener diodes? - Page 1
Forum section: electronics / repair

author: Peabody
author_rank: Super Contributor
timestamp: July 27, 2022, 09:34:36 pm
content: A friend's Samsung TV (UN55HU6840FXZA) began to fail at turning on the backlight when the TV was first turned on. It had audio, and passed the flashlight test, but no backlight. Then after minutes to hours, the backlight would suddendly come on, and would stay on until he turned off the TV for the night. When it wouldn't come on after waiting all day, he brought it to me. But of course, no sooner than it arrived, it started working perfectly again, and it's tough to diagnose a problem when it's working perfectly. So I'm stuck.But in researching this TV, I find that it has 91 LEDs in series. If one of them fails short, there's no problem other than the loss of the light from that LED. The others still work, and if the LED brightness is current controlled, there isn't even any additional stress on the remaining LEDs.But if an LED fails open, no current can flow, and the entire string goes dark. It seems to me that manufacturers could deal with this by putting a zener diode across each LED - one with a moderately higher reverse voltage than the forward voltage of a working LED. So if one LED fails open, the spice would continue to flow, as it must.It turns out that the connections between the LED strips and the backplane they plug into are known to go intermittent for whatever reason, and that may be the problem with this TV. But it could also an individual LED's connection to the strip, the power board, or the main board. I just can't tell until it stops working. But I wanted to ask about the zeners because it seems to be a completely workable solution. But perhaps LEDs always fail short, so adding zeners wouldn't make any difference.

author: TheMG
author_rank: Frequent Contributor
timestamp: July 28, 2022, 12:36:59 am
content: It would be doable, of course the zener diodes would have to be able to dissipate the same amount of power (actually, slightly more) than the LED it is bypassing.However, as manufacturers try to shave off every penny they can from the manufacturing cost of consumer products, there's no way they'll do something like that.You're right that most of the time LEDs fail short, though they can also fail open especially if they are the type with bond wires, the bond wires can sometimes break from thermal cycling. However I do believe manufacturers are leaning more toward "flip chip" LEDs these days which have no bond wires to avoid this particular problem.
Tv boards swap firmware chips - Page 1
Forum section: electronics / repair

author: Hornnumb2
author_rank: Regular Contributor
timestamp: December 08, 2019, 09:46:59 pm
content: I have a Vizio 651-a2r that the main board has failed, I am unable to find the exact board but have found a similar board that does work in the unit. If I go into system info it list the model number of wrong unit. The boards look the same other than firmware version. Could I swap the firmware chips to correct the info. The board is out of an 501-a2r. How do I tell which chip it is? Thanks Michael

author: fzabkar
author_rank: Super Contributor
timestamp: December 09, 2019, 08:54:10 am
content: A photo of the board would help.

author: Hornnumb2
author_rank: Regular Contributor
timestamp: December 09, 2019, 03:16:09 pm
content: Here are some pics of the board front and back, if you need a higher res of a certain part I can take one. Thanks Michaelhttps://www.shopjimmy.com/vizio-91-75q10-c01g-main-board.htm

author: pepona
author_rank: Contributor
timestamp: December 09, 2019, 07:08:17 pm
content: Hi Hornnumb2, if the boards looks the same it will work.The best practice is first to save the content of the memories in case of a failure.Often the firmware is the same so you only must swap the eeprom wich contains the data configuration to that specific TV model.Hope you can understand me.Sorry for my bad English.RegardsMarcos.

author: fzabkar
author_rank: Super Contributor
timestamp: December 09, 2019, 08:20:49 pm
content: I think the flash memory at U4 (on the underside) would hold the firmware.

author: Hornnumb2
author_rank: Regular Contributor
timestamp: December 09, 2019, 08:44:39 pm
content: This is the board I purchased, I was told by seller that it wouldn't work because firmware was different so I am not positive about that. Just when you go into system info on the tv it list it as an M501D-A2R instead of M651-A2R. So I am not sure what I need to change, or just leave it alone...https://www.ebay.com/itm/VIZIO-M501D-A2R-Main-Board-92-75Q10-A01G-55-75Q01-001/362783733124?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

author: Hornnumb2
author_rank: Regular Contributor
timestamp: December 09, 2019, 09:37:23 pm
content: I will check the firmware tonight when I get home and see if the version numbers are different.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 10, 2019, 01:09:27 am
content: A few weeks ago, I opened up an old TV that was having intermittent problems, problem was the user settings ("NVRAM") in Flash got corrupted, I just cleared it from the bootloader and it seems to be working fine. In short, there's the chance the Flash contents are the cause of the problem. If it works fine, just let it be.

author: Hornnumb2
author_rank: Regular Contributor
timestamp: December 10, 2019, 02:28:46 am
content: Looks like I can update the board to the same firmware by just getting it on the network. It will just have the wrong serial number and model unless that’s a easy swap. Thanks Michael
TV HAIER 55DS2 does not turn on - Page 1
Forum section: electronics / repair

author: ggc161169
author_rank: Newbie
timestamp: July 09, 2021, 02:22:26 pm
content: Hi, I have thisTV HAIER 55DS2which does not turn on, it only marks the standby led on fixed, it does nothing when pressing the button or using the remote control. The voltages that are marked on the boards from what I see are correct. The led strips are discarded, since I was able to bypass them and turn them on with the PSU itself (in fact months ago it had problems with the backlight and I know that the TV turns on even by disconnecting the LEDs). I also discarded the button and the IR reception. When disconnecting the T-CON it does exactly the same thing, nothing. The main card isCV59SH-Kand uses aTSUMV9XUSchip, the latter I changed it, being guided by someone who had a similar problem, but remains exactly the same without reacting. I believe and it is what I want to confirm that it is the bios chip (I don't know if they call it that) which is the25Q32FVSIGbut it is clear that you have to have the firmware or software to flash it ... I have the interface to do that, but obviously I don't have the necessary file. I like to confirm someone the problem I would appreciate who has the supposed file, or failing that, some idea of ​​what I could do. Thanks in advance.
TV has noisy picture, and wont do 1080p after blown fuse. - Page 1
Forum section: electronics / repair

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: November 18, 2020, 08:23:09 pm
content: I bought an older 50inch Vizio on craigslist and it was working fine for about 2 months, then one day I was watching it and all the sudden the picture went out and the menu buttons lit up but wouldn't work. It turned out that a surface mount fuse between the psu and main board blew, it was the one for the 5v rail.Not having any smt fuses around I just removed it from the board and boged in a glass fuse which I soldered wires to the end of and heat shrinked.When I turned the tv back on the picture looked weird like someone added sharpening noise in photoshop. I noticed it was only bad in 1080, so I just watched it for a day in 720p. The next morning it wouldn't even switch to 1080 and after an hour the noise was really bad in 720 also.All the caps look fine but the way the problem slowly got worse I'm wondering if caps could be the issue? Or maybe the wires and glass fuse is acting like an antenna or something causing noise? Or does this sound like the chip that handles hdmi is dying? The issue is the same on all hdmi ports no matter what input device is plugged in to them.
TV LCD SONY KDL 40EX407 - Page 1
Forum section: electronics / repair

author: quinoara
author_rank: Contributor
timestamp: September 13, 2019, 02:42:50 am
content: Estimados foristas, tengo el inconveniente con este TV LCD que no prende, al enchufarlo a la red de 110, el led del Staby prende normal y se queda sin parpadeo, sin embargo el led de audio digital prende momentáneamente y se apaga. Al darle encendido prende el Led verde se apaga y se prende el Stanby con siete destellos, indicando temperatura en el procesador. Se reviso la fuente colocando la en simulación y dejando desconectada la main board, para activarla con el inversor conectado y asi comprobar el funcionamiento de fuente y lamparas con resultados positivos.Revise voltajes en tcon inyectando los 12V externos para comprobar el estado de las subfuentes con resultados positivos.Llegue a la conclusión que había fallos en la main board, la reemplace con otra que funciona bien y me encuentro con que esta board también presenta el mismo síntoma.Cambie la fuente por otra, con resultados negativos.Consegui de nuevo otra main board y lo mismo.Compañeros agradezco de antemano una sugerencia.
Tv Philips 32 " does not light up, not even the stanby led - Page 1
Forum section: electronics / repair

author: filippo04
author_rank: Newbie
timestamp: December 20, 2019, 05:59:24 pm
content: With reference to the attached diagram, I found initially and visually broken the 9101- 0.27 ohm resistor and the 9126 capacitor 100pf .I changed so the T6A65D and also the following other components as you recommended in another post( nForce of August 2019) :U9101(PF6005AS),D9104,R9109,R9110,R9113.I have reassembled and fixed the board on the chassis, reconnected the two connectors, pressed the power button but i have verified only the rectified voltage on the primary capacitor without no other voltage on the CN 9101 connector. To read these voltages 12v and 5.2V, do I need some enable signal from the motherboard or do I need to make other checks or replace other components on the power supply board? Thank you in advance.

author: filippo04
author_rank: Newbie
timestamp: December 22, 2019, 03:47:33 pm
content: Sorry, the 220v power cord has not been completely inserted. Therefore, all the components replaced above have solved the problem with turning on the TV again.
TV PHILIPS 55OLED754/12 doesn't receive remote signal - Page 1
Forum section: electronics / repair

author: Watth
author_rank: Frequent Contributor
timestamp: February 15, 2024, 04:42:07 pm
content: Hey EEVFolks,The issue regards a PHILIPS 55OLED754/12 that doesn't react to the remote anymore. The remote is a simple IR model (no smart thing).My phone's camera does detect the remote IR signal.The TV works with the button on its back.I unplugged the TV, held its power button for 15 - 20 seconds, and waited a few minutes before plugging it again: still doesn't work.Before I look inside the TV, any idea?Thanks for reading!
Tv power supply problem - Page 1
Forum section: electronics / repair

author: szevlin
author_rank: Newbie
timestamp: November 24, 2020, 08:58:22 pm
content: I got a Philips tv from the trash (40PFL5606H/58), it looked like it was in pretty good condition, at first I couldn't power it on, only the standby led was on, and the capacitive touch buttons didnt work, also it drew 20 watts,then when i restarted it, it started working, and it worked normally on 1 occasion, then i restarted it and it didnt work again, not a single time,so it seemed like it is completely random if it worked or not, then i saw that I needed to heat up the main chip with a halogen lamp to make it work so i gave it a try,(i covered the other components with aluminium foil to shield them from the heat)it didn't fix the problem but the tv only draws 12 watts now for some reason, and the standby led doesnt power on anymore, did I kill the tv?I measured the power supply voltages and they all seemed fine, except the standby voltage which was 2.6 volts when I removed the psu from the main board and it dropped to 1.4 volts when i connected it back, but strangely there wasnt any current going in the wire, i could measure it with a clamp meter with 1mA resolution and it was 0.also there was a "3v3stndby" pin as well and i was measuring 3.3 volts on it so it seems fine, something I dont understand is why are there 2 seperate voltages for standby?I dont know where to look for problems, it can be a power supply issue or maybe a main board issue? (but again why did it work completely fine on 1 occasion, then it can't be the power supply right?)(sorry for my bad english)

author: Haenk
author_rank: Super Contributor
timestamp: November 26, 2020, 09:18:44 am
content: A lot of Philips TVs share a common problem in the PSU (you need to replace 2 diodes). That's the first place to check.

author: szevlin
author_rank: Newbie
timestamp: November 26, 2020, 10:19:56 am
content: thank you i will check it, but i wasnt suspecting the power supply since it worked fine 1 time

author: szevlin
author_rank: Newbie
timestamp: November 26, 2020, 03:11:29 pm
content: i checked every diode there arent any of them which are shorted, but i could measure that 2.6volts are coming out of the standby transformer? isnt that low?the "3v3stndby" pin is 3.3 volts but the "standby" pin is only 2.6 volts
TV Power Supply Repair (Vestel 17IPS20) - Page 1
Forum section: electronics / repair

author: smilgy
author_rank: Newbie
timestamp: August 18, 2022, 08:31:53 pm
content: Hi,I was wondering if you perhaps could help me troubleshoot a TV power supply that has failed.In my process of troubleshooting, I have found the main fuse, bridge rectifier diodes (D112, D113, D114 and D115 on the attached schematic), as well as D101, D512 and D513 in S/C. I replaced the fuse, and the mentioned diodes, however all of the above failed again, as there is probably still another short somewhere? However, I am unable to find it (relatively inexperienced in this subject). Any thoughts what I should be checking next?Thanks,David

author: inse
author_rank: Super Contributor
timestamp: August 18, 2022, 09:21:18 pm
content: This is the nastiest schematic I've seen for as long as I can remember.It is not a document to support repair, it's an obstacle!A dead Q301 might kill D512/513.Only D101 broken, but not 102 and 506 (who made those references???)Are D104 and the bridge rectifier diodes (D112, D113, D114 and D115) in parallel, or am I too stupid to read this schematic?

author: smilgy
author_rank: Newbie
timestamp: August 18, 2022, 10:18:11 pm
content: It took a bit of effort to remove q301, but I did. Would I be right in saying that it is dead judging by the tester?

author: wasedadoc
author_rank: Super Contributor
timestamp: August 18, 2022, 11:03:34 pm
content: Quote from: smilgy on August 18, 2022, 10:18:11 pmYes.

author: smilgy
author_rank: Newbie
timestamp: August 19, 2022, 08:27:02 am
content: Replaced the mosfet with a close similar, and TV powers on! Time to get the correct replacement.

author: inse
author_rank: Super Contributor
timestamp: August 19, 2022, 08:32:34 am
content: Double thumbs up

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: August 19, 2022, 12:01:41 pm
content: Training book for psu if anyone else drops on to this page ,it may help

author: smilgy
author_rank: Newbie
timestamp: August 19, 2022, 03:22:57 pm
content: Quote from: FIXITNOW2003 on August 19, 2022, 12:01:41 pmThanks, I'm sure this will help someone. I had initially thought Q301 had failed, but was not 100% sure with the component in circuit. I had forgotten I had the component tester as pictured, and once removed and tested, it seemed obvious, especially the S/C path taken.I'm by no means an expert at repair, so was fun to fix this, even if with the help of others!
TV power supply repair - Page 1
Forum section: electronics / repair

author: klazaridis1
author_rank: Newbie
timestamp: April 21, 2022, 09:28:28 pm
content: Hi my old tv is fried, I was trying to fix it but when I desolder a component to measure a voltage something released the magic smoke. The MOSFET, a resistor and maybe this component are fried up. Unfortunately, I am not able to find it, does anybody knows what is it? I can't find any info for the specific component. It is the R12K H8

author: PKTKS
author_rank: Super Contributor
timestamp: April 22, 2022, 12:55:32 pm
content: I have wasted so many hours looking these insane markings...years and years ranting these shitty codes...Anything i can remotely associate with H8 is a ZENERPaul

author: madires
author_rank: Super Contributor
timestamp: April 22, 2022, 01:52:10 pm
content: R12K: fast recovery rectifier, 600V, 1.2A (https://www.alldatasheetde.com/datasheet-pdf/pdf/851341/GOOD-ARK/R12K.html)

author: klazaridis1
author_rank: Newbie
timestamp: April 25, 2022, 01:56:34 pm
content: do you know were I can find them, or a similar component?

author: madires
author_rank: Super Contributor
timestamp: April 25, 2022, 06:31:33 pm
content: Choose the next best fast recovery diode with similar specs. They are pretty much standard, nothing special.

author: fzabkar
author_rank: Super Contributor
timestamp: April 26, 2022, 06:06:40 pm
content: Quote from: madires on April 22, 2022, 01:52:10 pmThe datasheet says 800V for the "K" version.
tv power supply - Page 1
Forum section: electronics / repair

author: glinjik
author_rank: Regular Contributor
timestamp: August 19, 2021, 05:38:37 am
content: Hi I'm having trouble getting this power supply to work going left side ac input the two caps are good x2 cap good bridge good elec cap good thermistor good that filter next to the bridge is burned so I just bypassed it. it's there for the photo only but that ruddy fet keeps popping diodes are good it's like the is a short somewhere could the big transformer be burned?

author: shakalnokturn
author_rank: Super Contributor
timestamp: August 19, 2021, 09:43:09 am
content: SMPS transformers can fail (more often small ones and they'll fail open) but it is quite rare.The most common is that the FET will short due to bad capacitors, overload if there is no OCP, bad solders, dead opto or TL431....Anyway the odds are that once the FET has blown it has also destroyed the PWM IC which will also need replacing to not blow replacement FET.First of all try to identify the initial cause of failure.

author: aqibi2000
author_rank: Regular Contributor
timestamp: August 19, 2021, 06:29:42 pm
content: Build a ring tester or use a curve tracer

author: glinjik
author_rank: Regular Contributor
timestamp: August 19, 2021, 07:33:34 pm
content: so having a look a lot closer i found the pwm controller (FAN7602) pic below with suspect gunge below it the other pic is the filter completely burned no idea what could cause the filter to burn up
Tv PSU LED backlight rail at wrong voltage yet stable - Page 1
Forum section: electronics / repair

author: Thebitwielder
author_rank: Newbie
timestamp: December 02, 2024, 02:21:56 pm
content: Hello everyone, I've been working on fixing a TV that has been gifted to me broken , it kept power cycling so i replaced the smoothing capacitor that was blown to smithereens, I've put in a 47uF 450V one as it was one that seemed to make sense to put in due to the first one not really existing anymore , now my issue is the LCD itself is working as i could see the no signal marker when putting light though it , but the backlight refuses to work with the built in PSU , I've powered the led bars externally with my adjustable PSU and they work , to note is that they only turned on at ~31V , more probing around later i found the PSU even if its marked as 32V 220mA on the label which checks out with the led bar when powered externally but the rail when measured with a multimeter it gives me ~12V , which at first i would have blamed on a faulty MOSFET for PWM control of the brightness ( NCE6050K as attached below) , but for the sake of it ive tried powering a 12V filament bulb off of it and while it wasn't bright it was definitely providing power and at a stable 12V output and now I'm lost on what could be wrong and how to fix it.Im not particularly new to electronics but I still have plenty to learn and im just now geting into the nitty gritty of it.I've also provided photos of both sides of the board (pretty unpopulated i must say) and close up shots of the 2 visible IC's on the back side.

author: MathWizard
author_rank: Super Contributor
timestamp: December 09, 2024, 08:02:59 am
content: It looks like it has a 12V output, the 5V rail is missing, and then the 12V output goes through an inductor, and off into the section w/ the SMD IC, that must control the current to the LED's. I don't see any other inductor, so is that series inductor, the big black one, part of a step-up converter from 12V to 32V ? What is that IC, I'd want to map out that circuit, see if that chip is happy or not, and if the parts around it have a problem.Or is that IC just doing PWM for the brightness, and it really is only 12V max ??.......Ok it's the BIT3260, a PWM boost converter IC. So what voltage is on pin 2?Quotehttps://u.dianyuan.com/upload/space/2012/02/16/1329362322-600862.pdfSo with no load attached, what DC voltages do you get out ? The main switching transformer, the yellow thing in the middle, should step down the rectified mains voltage, to about 12VDC after those 2 big diodes. If there was a problem on the primary side, that voltage would be off, or it would go off once a load is on the output.IDK if your replacement cap is the right size, but maybe it's too small if the output side is lacking current.
TV Repair 1960's Style - Page 1
Forum section: electronics / repair

author: EEVblog
author_rank: Unknown
timestamp: July 07, 2021, 02:02:28 am
content: MYER TV SERVICING FLEET. 1960/61Fleet of Myer FB/EK Holden Panel Vans belonging to the TV Service Division.Australia for those who don't know.

author: bob91343
author_rank: Super Contributor
timestamp: July 07, 2021, 05:52:53 am
content: Probably all right-hand drive.

author: gbaddeley
author_rank: Regular Contributor
timestamp: July 07, 2021, 12:31:26 pm
content: Trying to work out where photo was taken. Albert Park?

author: themadhippy
author_rank: Super Contributor
timestamp: July 07, 2021, 01:11:36 pm
content: And tv repair 2021 style

author: med6753
author_rank: Super Contributor
timestamp: July 07, 2021, 06:15:38 pm
content: That's only about 4 years after you Aussie's finally got TV (September 1956).

author: aargee
author_rank: Frequent Contributor
timestamp: July 08, 2021, 02:31:49 am
content: Those Holdens would be worth a pretty penny now too.

author: VK5RC
author_rank: Unknown
timestamp: July 08, 2021, 05:20:03 am
content: The early tv's were pretty unreliable - our tv repair man from the late 1960s visited so many times - I can recall his name and face.

author: med6753
author_rank: Super Contributor
timestamp: July 08, 2021, 01:07:31 pm
content: Quote from: VK5RC on July 08, 2021, 05:20:03 amUnreliable for sure. My Father owned a TV Repair shop in Queens, NYC with the help of the "GI Bill" after getting out of the US Coast Guard around 1950. I was born in '53 and shortly after that in '54 he was recruited by IBM and closed the shop. I am currently rebuilding his 1951 Heathkit V-5 VTVM. That's the only piece of his original test gear that has survived all these years.

author: Kerlin
author_rank: Regular Contributor
timestamp: July 09, 2021, 03:19:20 am
content: Quote from: EEVblog on July 07, 2021, 02:02:28 amHiIs there a picture that goes with that, not seeing it, would like to. Thanks.

author: Gyro
author_rank: Super Contributor
timestamp: July 09, 2021, 08:34:38 am
content: Yes there is. It appears in your quote too.The link is (deliberately not using a URL tag)https://pbs.twimg.com/media/E5nHf5SVgAAEsVO?format=png&name=900x900

author: tggzzz
author_rank: Super Contributor
timestamp: July 09, 2021, 08:43:29 am
content: Quote from: VK5RC on July 08, 2021, 05:20:03 amThat's one reason why, until the early 70s, it was more popular to rent a TV than buy one.

author: login
author_rank: Contributor
timestamp: July 10, 2021, 12:33:12 am
content: Quote from: gbaddeley on July 07, 2021, 12:31:26 pmprinces park apparently
TV repair - episode 2 - Page 1
Forum section: electronics / repair

author: TheMG
author_rank: Frequent Contributor
timestamp: October 07, 2020, 12:58:02 am
content: Panasonic TC-P65S1. Previous repair was to replace film caps on one of the sustain boards which were failed and shorting out, causing the TV to essentially not come on (trip instantly on power-up).While I was at it, I also checked all electrolytic caps and replaced anything that was out of tolerance or close to being out of tolerance, so I'm pretty confident capacitors are not causing this different problem.The TV works absolutely great except for one issue - random glitches and signal loss on the HDMI ports. This only happens when the input signal is 1080p at a refresh rate greater than 24Hz, and the higher the refresh rate the more glitches. All 3 HDMI ports behave exactly the same way. This TV officially supports up to 1080p60 display mode, so that's not the issue.Weird thing is the amount of glitches seems to vary based on the length of the HDMI cable used. Counter-intuitively: longer cables work better than shorter ones!!! I've tested this extensively with a multitude of different cables and source devices.Would it be correct to suspect an issue with the HDMI 3-way switch IC, since it's the first thing the signal passes through and cable length affects the behavior? The IC is a Sony CXB1444R, for which I can not find a datasheet.Anyone seen anything like this before?

author: fzabkar
author_rank: Super Contributor
timestamp: October 07, 2020, 04:42:46 am
content: Do you have a circuit diagram?Is there an array of low capacitance ESD protection diodes on the HDMI port?Edit:If the problem occurs on all HDMI ports, then I suppose that rules out the ESD arrays.
TV Samsung UE55HU8500L (2014) – service menu + firmware reflashing advice needed - Page 1
Forum section: electronics / repair

author: Robby-Gr
author_rank: Newbie
timestamp: September 27, 2025, 05:40:19 am
content: Hi all,I’m trying to recover a Samsung UE55HU8500L (curved UHD, 4K model from 2014) after replacing the panel. The new panel is a 55A1UU8EH, which produces excellent image quality — very close to the original.However, since the swap, the TV enters a boot loop (Samsung logo → restart) unless I enter the service menu and perform a reset.The service mode had been previously modified — possibly by a technician or during the panel swap — and I suspect some key settings are mismatched for the European (Greece) market.Additional issues:- The HDMI ports behave incorrectly: port order seems scrambled (e.g., HDMI 1 acts like HDMI 2)- No audio output over HDMI, even though video worksHere’s what I’ve tried so far:- Adjusted Type, Local Set, Front Color, Panel Display Type, Model, Tuner, EDID Write, etc.- Compared values with other HU8500 units- Verified internal connections and performed factory resetsDespite this, I haven’t found the correct configuration that allows the TV to boot normally and restore full HDMI functionality. The image looks fine after reset, but the boot loop returns after power off.📸 I can share screenshots of the current service menu settings if helpful.👉 I’m specifically looking for the correct service menu values for this 2014 4K model in Europe/Greece, especially after a panel replacement with 55A1UU8EH. If anyone has experience with HU8500 servicing or knows the right configuration for this region, I’d be grateful for your help.🛠️ As an alternative solution, I’m also exploring firmware engineering and reflashing. If I can reflash the firmware successfully, I may be able to reinstall the latest version (1410) cleanly and potentially resolve the boot/audio issues. If anyone has experience with reflashing on this series or knows whether this approach could help, I’d love to hear your thoughts.Thanks in advance!Kostas
TV service manual?? - Page 1
Forum section: electronics / repair

author: jknightandkarr
author_rank: Contributor
timestamp: January 17, 2020, 10:35:30 am
content: Hope this is the right area, but I am looking for a service manual for an Action Industries Model ACN-5501 5" color rv. It hasn't been plugged in for a good while, but even so, I know how to discharge the high voltage side. Searching on internet won't even get me any tv from this brand as fat as manuals go, just similar ones to buy on amazon or ebay. The tv works, but its got an issue in the signal input on the input a/v connectors. Got it for a friend for a project of his and want to fix it. Thanks.

author: PKTKS
author_rank: Super Contributor
timestamp: January 17, 2020, 11:35:48 am
content: CRT?Depending on how much time it was left aside...You will also probably need to do AFTER REPAIRS ALIGNMENTS.With a proper alignment function generator.The ELCOs are certainly out of spec in the Horizontal sectionPaul

author: jknightandkarr
author_rank: Contributor
timestamp: January 18, 2020, 10:38:17 pm
content: Yes it is a crt from 1994
TV Tuners of days gone by...  - Page 1
Forum section: electronics / repair

author: KD4CCF
author_rank: Contributor
timestamp: August 14, 2019, 08:14:52 pm
content: 35+ years ago, rather than muck around with aligning and repairing rotary type TV tuners, both tube and transistor, I'd send them off to a place called PTS.PTS always did a super job at a price that made sense to outsource the tuners.When they came back, they were spotless, lubricated and aligned.Question is, how and what did they use to clean them?The solvents had to be plastic friendly yet aggressive enough to get rid of corrosion, dust and other contaminates.I would think that they also had an ultrasonic cleaning stage.Anybody know someone who worked there?

author: PKTKS
author_rank: Super Contributor
timestamp: August 16, 2019, 09:50:58 am
content: Well nobody risk some hints....About 30y ago FREON based solutions were very commonThey are better, more aggressive and dry faster promotinga much better cleaner action on rotary switches.But those hairy heads promoted FREON based spraysas something odd (the same hairy heads on LEAD FREE...)and the sprays without FREON are not as fast not as good as theold ones... (much like LEAD FREE will never replace LEADED)nevertheless the very same brands and products still existadvertised as FREON free - of course they not even close thesame results...Paul

author: syau
author_rank: Frequent Contributor
timestamp: August 16, 2019, 10:57:32 am
content: Just like trichloroethane, excellent solvent to clean PCB after soldering.
TVS Diode selection - Page 1
Forum section: electronics / repair

author: jerryk
author_rank: Regular Contributor
timestamp: March 07, 2024, 11:20:43 pm
content: I'm trying to replace a failed TVS diode in this small RYOBI 40V battery charger. It's a friends unit and he said the battery would not charge. A small burn mark inside the cover led me to TVS1 on the board in the photo. It was slightly fractured but still had a readable marking code. Rather than write it down I plugged the battery into the charger and poof went the diode top. Now I'm in the dark on how to select a replacement other than the size seems to be DO 214AC and the voltage across the diode is around 42V and change. I have charged the battery a couple of times without the TVS and all seems correct.Any help/wisdom on how to determine the proper replacement TVS would be greatly appreciated.Jerry

author: fzabkar
author_rank: Super Contributor
timestamp: March 08, 2024, 12:11:59 am
content: FWIW, I can see a small TVS2 component near the bottom battery terminal (?).

author: jerryk
author_rank: Regular Contributor
timestamp: March 08, 2024, 01:24:11 am
content: There are 5 TVS diodes on this board but I was reading the silk screen wrong and thought TVS5 was the small diode directly above it. I ruled all the others out because of their small size. But now that I'm reading the silk screen correctly TVS5 is an SMAJ51A which is the correct package size and seems like it might fit. Voltage across TVS5 is also 42V.Thanks,Jerry
TV’s LCD Panel is coming unstuck along the edge… - Page 1
Forum section: electronics / repair

author: NoDowt
author_rank: Newbie
timestamp: April 07, 2024, 01:01:27 pm
content: I had this happen to another TV (same brand) and was replaced under warranty… however this tv is about 4-5yrs old now so unlikely to be covered.Basically along one edge, the panel in the middle is lifting away from the tv… at the center of the right edge there is maybe 3-4mm gap. You can push it back and it stick temporarily, but then comes loose again.Wondering what the best way to stop this getting any worse might be… do I try to get some double sided tape in there & press it back… or maybe a couple dabs of silicone/polyurethane or something…The TVs this has happened on are wall mounted, and do angle forward/down very slightly… so I think it’s a combination of gravity + Aussie heat softening the factory adhesive. When the first TV was replaced, the service tech did mention it was a common issue on that particular model… this one though is different (but bought around the same time, maybe a year later than the other)Kinda worried the replacement TV might end up doing the same, it seems ok for now though.
Two separate Focusrite Scarlett's cannot connect to 88200 - Page 1
Forum section: electronics / repair

author: musicTechie
author_rank: Newbie
timestamp: December 19, 2020, 07:46:13 pm
content: My friend has a 2nd gen Focusrite Scarlett 18i20. It is unable to when trying to connect with scarlett mixcontrol at 88200 it switches to 96000. It will connect to 44100 and 48000. This behavior is consistent with connecting to qjack on linux. (441100, 4800, 9600 all ok, while 88200 will not connect)I have been using my 1st gen Focusrite Scarlett 2i2 with success switching between all 4 sample rates. I was working on linux (as i have always done for years with this devise) connected at 88200 successfully. I disconnected from jack and later in the day trying to connect it now will not connect at 88200 (it switches to 96000 and all other sample rates work).This leads me to believe that possibly there is a component responsible for switching that has failed. I was wondering if anyone has further knowledge of what would be causing this problem or how to investigate it.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 19, 2020, 08:12:57 pm
content: I somehow doubt this is a hardware issue.I would be looking at drivers/firmware etc.

author: musicTechie
author_rank: Newbie
timestamp: December 19, 2020, 09:56:18 pm
content: How would it be a firmware or driver error when it was working, disconnected and reconnected and is now not working? The software is the same?

author: musicTechie
author_rank: Newbie
timestamp: December 20, 2020, 01:18:48 am
content: After trying to connect through command line to jack I am now able to with both devices and it also works with qjack control now. (though my saved settings for each sample rate have not been changed which was previously not working for 88200) I have not confirmed 88200 on my friends mac.