hybridfree/eevblog-posts huggingface dataset:
Oculus rift connector identification. - Page 1
Forum section: electronics / repair

author: PepiHax
author_rank: Newbie
timestamp: August 07, 2019, 04:00:36 am
content: Hej, i was hoping that someone with some experience could help identify a connector.The story goes that my Oculus Rift has started to get these errors, where it sayes that the HDMI connector isnt attached even though it clearly is, and after some talking with support, buying a new cable, and being frustrated. I did some experimenting and found that by wiggling the connector i can produce this fault.So finally the guestion is if anyone has seen a connector like this before? and possible if a replacement can be bought anywhere?The connector it self sayes TE on it and has a Y160719D1 code, this is the connector that carries both the hdmi connection and the usb.Pictures on imgur

author: AlfBaz
author_rank: Super Contributor
timestamp: August 07, 2019, 04:39:12 am
content: Looks like a pcb mounted mini hdmi connector

author: PepiHax
author_rank: Newbie
timestamp: August 07, 2019, 11:40:59 pm
content: It does look like a mini hdmi, i however can only find them with 19 pins, and this one appears to have 27.
OCXO pinout ID help, OFC 1813-1106 AKA Corning MC857X4-004W used in HP8920A/B - Page 1
Forum section: electronics / repair

author: kj7e
author_rank: Frequent Contributor
timestamp: December 22, 2023, 03:32:05 pm
content: Looking to see if anyone may know the pin out on this OCXO. This is marked as OFC 1813-1106 AKA Corning MC857X4-004W used in HP8920A/B. Not been able to find a datasheet online anywhere.I have attached the 8920A Reference assembly schematic, other than the ground pin, not sure what the other pins are. Id hate to apply 12v to the wrong pins and damage it.

author: kj7e
author_rank: Frequent Contributor
timestamp: December 23, 2023, 02:27:00 pm
content: I think I figured out the pinout, 1 and 2 are in the upper left (close together) and are +12v. 3 is ground, lower left. Not seeing any output unfortunately, either I was sent a bad part of I popped it trying to figure out the pinout. Not sure which is the VCO and output, but I suspect VCO is across from the VCC and the output is across from ground. I can see proper operation of the Oven, no output though.Found a photo of the 08920-61192 OPT REFERENCE card for the 8920A.

author: kj7e
author_rank: Frequent Contributor
timestamp: December 29, 2023, 08:03:43 pm
content: Hopefully, this will help someone someday.Through out some trial and error, here is the pinout.
Odd 220V AC 7805 Circuit - Page 1
Forum section: electronics / repair

author: daneduplooy
author_rank: Newbie
timestamp: November 27, 2021, 07:32:56 pm
content: Hi! Anybody have any idea how the following 220V AC to 5V DC (7805) circuit works?Thanks! :-)

author: mariush
author_rank: Super Contributor
timestamp: November 27, 2021, 07:43:11 pm
content: You have the switching power supply controller right there, labeled U1, by the D3 diode.In very simple explanation, the chip sends pulses of high DC voltage (ac rectified by that bridge rectifier and smoothed by a capacitor) through the transformer and the output gets converted back to DC.The lower voltage then goes to the linear regulator to get 5v.

author: daneduplooy
author_rank: Newbie
timestamp: November 27, 2021, 08:24:32 pm
content: Thanks!!! Makes sense...I was surprised to see the AC Neutral connected straight to the 7805 positive input - so the switching circuit must be generating a "negative" voltage relative to the AC Neutral.So if this is not working (measuring 0V at the regulator input), then likely there is a problem with either U1 or the transformer? Or perhaps the 7805 itself is blown?DC voltage after the bridge rectifier is measuring fine.

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2021, 10:12:40 pm
content: That looks like a non-isolated power supply. Its pretty dangerous for novices to work on as when its connected, just about everything on that board is mains live and could electrocute you. I certainly wouldn't want to work on it powered on without an isolating transformer and all CAT II rated test equipment suitable for making floating measurements, and I've been in the trade for several decades.TLDR: If you need to ask how it works, you don't know enough to work on it safely!

author: m k
author_rank: Super Contributor
timestamp: November 28, 2021, 10:03:56 am
content: Pictures are named Airwave 12.That seems to be misleading.

author: daneduplooy
author_rank: Newbie
timestamp: November 28, 2021, 10:36:32 am
content: https://tvmall.co.za/home/beaumark-airwave-12l-air-fryer-1.html

author: daneduplooy
author_rank: Newbie
timestamp: November 28, 2021, 10:40:07 am
content: Thanks for your concern @Ian.M, but unless working on this whilst in the bath electrocution seems unlikely.
Odd issue with Infiniium 54815A input impedance  - Page 1
Forum section: electronics / repair

author: wastedhotdogs
author_rank: Newbie
timestamp: July 08, 2024, 12:20:05 am
content: I recently purchased this scope and have replaced the CMOS battery, installed software version 4.3, and am now working on getting it to calibrate. Initially it passed all self test but would fail to calibrate all but one channel. I narrowed it down to the attenuators, as the calibration success followed the one attenuator as a swapped it between channels. I have taken the attenuators apart and cleaned and reworked the relay contact springs. I now have three out of four channels passing with a weird issue on channel 4. The calibration fails early in the process and I've found that the input impedance switching is inverted. It reads a near perfect 50ohms with set to 1M and a spot on 1M when set to 50. Has anyone encountered this?

author: m k
author_rank: Super Contributor
timestamp: July 14, 2024, 05:45:48 pm
content: So one inverter in selection line is now a buffer.Are there enough discrete components to check the selection line?
Oil filled electric radiator heater tripping RCD - Page 1
Forum section: electronics / repair

author: Koray
author_rank: Regular Contributor
timestamp: December 15, 2019, 01:47:29 pm
content: Hi all,An oil filled electric radiator in my office trips the RCD as soon as I plug it in. I checked the resistance between Live, Neutral, and Earth on the plug. Between L and N depending on heat setting, my meter measures 50-100 Ohms. When I measure between L and E, or N and E, I receive about 25-30 Ohms reading. I opened the front panel and checked cables and circuitry: everything looks OK. When I disconnected the heating element from the rest of circuitry, I get readings as shown in the image below, where one coil seems to be shorting the earth (casing). This looks like a lost case, right? ---->Thanks!Koray

author: ebastler
author_rank: Super Contributor
timestamp: December 15, 2019, 03:35:56 pm
content: Yes, that would be my interpretation -- the upper coil has a short to ground, about midway. And yes, I don't think it can be repaired in a safe way. Depending on the brand and age of the heater, you may be able to purchase a new heating element, or may be better off replacing the whole unit.

author: SeanB
author_rank: Super Contributor
timestamp: December 15, 2019, 05:09:52 pm
content: Those elements are easy to replace, place heater so element is on top, and unscrew it, and replace with a new one, not forgetting to replace the o ring seal at the base of the threads. You might lose a drop or two of the oil fill, but nothing to worry about. The elements tend to have a very generic size and thread, despite the brand of the unit, as most are made to the same pattern, with only the brand applied being different, along with a slightly different style of side plastic case.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 15, 2019, 06:56:21 pm
content: Similar style of heating element to what is found in electric water heaters. The resistive element is inside of a metal tube which is filled with some type of heat resistant insulating material to isolate the resistive element from the metal tube, which is grounded.What has likely happened is that either by a fault (hot spot) or manufacturing defect, the resistive element has migrated through the insulating material and come into contact with the grounded metal tube.Such a fault is not repairable as the heating element can not be disassembled. The only solution is to replace the heating element.

author: Koray
author_rank: Regular Contributor
timestamp: December 15, 2019, 08:29:35 pm
content: Thank you all for your comments and suggestions! I now checked online if there are replacement heating elements: yes, there are plenty of them at very affordable prices (around $10USD in my home country). I will order one. Thanks a lot, again.K.
OKI reset drum "chip" - what is this component actually? - Page 1
Forum section: electronics / repair

author: evava
author_rank: Regular Contributor
timestamp: August 23, 2019, 07:53:11 am
content: Hello,I wonder if someone know what is this component called "Oki reset drum chip" and sold on alibaba?https://www.alibaba.com/product-detail/For-OKI-B411-B431-FUSE-Drum_60749096957.html?spm=a2700.7724857.normalList.233.128e78c8UtebahIs is some resistor or fuse or what?

author: amyk
author_rank: Super Contributor
timestamp: August 23, 2019, 11:53:11 am
content: 3A Littelfusewith the picture mirrored...Does the printer blow the fuse on the cartridge when it thinks it's empty? That would explain the "reset" terminology.

author: Towger
author_rank: Super Contributor
timestamp: August 24, 2019, 08:08:55 am
content: It is a fuse which blows when the cartage is used for the first time, resetting the required counter.It is a littelFuse "1/16A LF" :https://ie.rs-online.com/web/p/non-resettable-wire-ended-fuses/5413221/I have some new 'Oki' ones somewhere, extracted from new toner belts damaged in shipping. The chips in the toner cartridges are RFID. The printer remembered the last x (8?) used, before deciding the toner is new.On some (all?) models you can tell the printer to ignore the various counters from the service menu. It may still warn on the display, but keeps printing.
Old Boston subwoofer SMPS blowing up MOSFETs - Page 1
Forum section: electronics / repair

author: jjne
author_rank: Newbie
timestamp: March 26, 2024, 01:37:07 pm
content: This one has been annoying me for a few weeks now lol.Aging Boston sub, uses an IR21531s-based dual output SMPS for power. Recently blew the fuse. I get the impression this may be a common issue looking at them on ebay.Both FETs blown, so I bought some new ones and a replacement 21531.With these parts replaced it's still blowing FETs. I noticed that the 21531 only seems to be oscillating with reference to VS on the LO output - I initially thought this was the fault as it seems to be the FET linked to HO that is blowing, but the replacement chip is doing the same thing. If you ground VS then both HO and LO are oscillating at approx 50kHz, but as configured I'm seeing no oscillation at HO, just a constant high signal. This would definitely blow the FET, but I don't think it's as simple as that as the chip does seem to be functioning and I admit I don't really understand how that VS line from the IC (it's a floating supply referenced to HO according to the datasheet but this doesn't seem to be doing anything).I've attached a scribbled diagram of the circuit - this is the same as that on the service data I found online with the not installed bits removed.It has occurred to me that the insulation on the primary winding of the transformer may have broken down but this still doesn't explain the lack of oscillation on one "phase" - would I be right in thinking that I should be seeing a 50KHz square wave on both HO and LO relative to VS, essentially inverted so that only one FET is on at any one time?One other thing, looking at the right of the diagram I can see that this is just a pair of unregulated outputs, I believe one for the preamp one for the power amp, and looking at the caps I'd estimate that the pre is +-15v and the power likely +-24v. These are going to be noisy and unstable due to the lack of regulation that I can see so assuming these are regulated downstream (not checked yet).However, what is the purpose of pin 1 on the lower connector? It appears to be just one leg of the other winding, unrectified and unfiltered. I had thought of replacing this SMPS with a suitable alternative but that line is weird and the service data is less than helpful.Sorry if this is just a stream of nonsense but there's just so much of this confusing me just now!All passives appear to test good BTW.
old B&W crt - Page 1
Forum section: electronics / repair

author: pop982
author_rank: Newbie
timestamp: March 22, 2021, 01:41:28 pm
content: Hi i got a small "gern" crt and no matter how much i adjust the v-hold it doesn't look any better than in the picture.I can't for the life of me find any info about this tv or any kind of manual.Any suggestions for any adjustments i could make?

author: CaptDon
author_rank: Super Contributor
timestamp: March 22, 2021, 01:47:00 pm
content: That is not a vertical hold problem, it is a vertical size or vertical linearity problem. There may be adjustments available on the circuit board. There may also be an out of tolerance resistor or capacitor at the real root of the problem.

author: perieanuo
author_rank: Frequent Contributor
timestamp: March 22, 2021, 02:13:35 pm
content: find on that pcb your vertical deflection chip tracing the deflection coil, then here you have the datasheet/schematic for V deflection, then you can trace why the V isn't okyou're lucky, that's the simpliest in the book

author: jdragoset
author_rank: Frequent Contributor
timestamp: March 22, 2021, 02:42:25 pm
content: Vertical foldover.Had a Toshiba that did that, re-soldering the pins on the vertical amplifier chip fixed it.When it did it again, put #26 Ga. insulated wires from each pin to the foil pattern.
Old eprom programmer repair. - Page 1
Forum section: electronics / repair

author: Rolls1234
author_rank: Newbie
timestamp: March 14, 2024, 04:19:25 am
content: Hello.(sorry about my poor english,also if im posting in the wrong place).I ve got an old elan e9a programmer which i bougthfrom ebay as faulty vintage item,the device is in very good shape very clean ,the problem is when i turn it on there is no beep were i suppose to hear a beep ,keyboard not responding at all, display shows only ffffffff,cfffcfff,..only garbage were i suppise to see the type of eprom.i ve already opened it and checked the power supply rails and noticed that voltages are present.5v 12v, other than that i ve checked mathieu.benoit.benoit.free.fr website for shematics ,i tried to download and burn the firmware given by him and put into the programmer but did nt worked.i attached pictures of the programmer and it main board , i will attach more pictures of power supply and I/O boards. im lost and need help from experts engineers, thanks.Thankyou.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 14, 2024, 11:59:43 am
content: tons of documents and maybe schematics too, lots to checkhttp://matthieu.benoit.free.fr/147.htm#E9A_E13usual suspects, bad contacts on the socket ic's, you have tons of them, voltage issues, you have 5 12 and others voltages to check, normally an 24 - 25vdc voltage too

author: Haenk
author_rank: Super Contributor
timestamp: March 14, 2024, 01:27:42 pm
content: Yeah. I'd estimate the displayed code as a rather good sign, as it does not seem to be garbage. So CPU seems to be kind of working.Carefully pulling all ICs and using a bit of contact cleaner might do the trick.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: March 14, 2024, 02:15:11 pm
content: The step by step troubleshooting guide is in "E series Maintenance manual.pdf",@coromonadalixposted.

author: Rolls1234
author_rank: Newbie
timestamp: March 17, 2024, 04:35:33 am
content: Hello, and thanks to all for replay, i removed all ic , and used contact cleanerSame thing..

author: dobsonr741
author_rank: Frequent Contributor
timestamp: March 17, 2024, 05:19:05 am
content: At voltages all OK?
Old Giavazzi/Pantec analog multimeter. Resistive network ... - Page 1
Forum section: electronics / repair

author: saronno
author_rank: Regular Contributor
timestamp: November 27, 2020, 10:14:41 am
content: I have this old analog multimeter from Giavazzi Pantec. This is the schematic.As you can see, in the middle of the schematics there is a 4-pin resistive network (26 20 025).This component is clearly burned. The point is I have no idea where and how to find a replacement.Any idea?

author: bob91343
author_rank: Super Contributor
timestamp: November 27, 2020, 07:28:54 pm
content: I think you will have to make your own. Unsolder it and make some measurements to see which parts are damaged and just replace those.It will be a lot easier to make up satisfactory resistors than to try to find an original part. Luckily you have the values. I assume 1% tolerance would be satisfactory.

author: saronno
author_rank: Regular Contributor
timestamp: November 27, 2020, 08:13:40 pm
content: Quote from: bob91343 on November 27, 2020, 07:28:54 pmI think this resistive net is critical ... if you are off even just a bit, the multimeter get unreliable.Probably the ratio between the values is most important than the values themselves. This is the reasonthey have a single component. It's easier to build resistive net with specific ratio with very good toleranceif you create a single component.Anyway, I will give it a try to see how off the multimeter is with a DIY net.

author: TimFox
author_rank: Super Contributor
timestamp: November 27, 2020, 10:45:10 pm
content: The resolution of the d'Arsonval movement is on the order of 1%, with similar linearity. Therefore, 1% metal-film resistors are probably sufficient to replace the four in the network. You probably need to use two in series to achieve the values required for some of the resistors. The overall accuracy, including the calibration of the microammeter, can be adjusted with the trimpots for different functions.

author: saronno
author_rank: Regular Contributor
timestamp: November 29, 2020, 10:38:27 pm
content: Quote from: TimFox on November 27, 2020, 10:45:10 pmThanks ... I will give it a try.How many watts could they be ask to dissipate?

author: TimFox
author_rank: Super Contributor
timestamp: November 29, 2020, 11:38:13 pm
content: I believe that that network is only used for ohms. A quick glance shows 3 V from the battery applied in series with roughly 6 + 8 ohms to the circuit. The current through that 14 ohms would be 215 mA (max), or 370 mW in the 8 ohm resistor. You might want to use 2 W wire wound resistors for those small units. 1/2 W metal films should do for the larger units.My cursory glance at the circuit was handicapped by not knowing the input connections.
Old HP Gear - What Kind of RF Connectors Are These? - Page 1
Forum section: electronics / repair

author: fmashockie
author_rank: Frequent Contributor
timestamp: August 13, 2024, 08:46:09 pm
content: Hey y'all! I am in the process of trying to repair my HP 8557A Spectrum Analyzer plug-in. I want to perform some of the performance tests in the manual, which requires me to connect a sig gen up to preamp. However, I cannot for the life of me find what kind of RF connectors HP used for this instrument. They appear to be subminiature, but I am not sure what kind. I tried SMA and SSMA but both were not right. SSMA was definitely closer, but the male and female versions are opposite compared to the HP ones if that makes sense. For example, the HP female connector is a threaded nut, whereas the SSMA connector I bought is a male inside a threaded nut. I took some photos of the HP connectors for reference. Would really appreciate anyone's help!!! So I can stop buying the wrong connectors!!!Thanks!-Frank

author: TimFox
author_rank: Super Contributor
timestamp: August 13, 2024, 08:53:47 pm
content: Those look like "SMC", a threaded connector similar to the snap-on "SMB".Check dimensions with this site:https://www.amphenolrf.com/rf-connectors/smc-connectors.html

author: fmashockie
author_rank: Frequent Contributor
timestamp: August 13, 2024, 09:45:58 pm
content: Thanks Tim! I looked at the diagrams on the link you gave. Measurements seem to match up. For some reason I thought I read a chart stating that SMC was larger than SMA so I didn't think to check those...
Old Lodestar 8202 linear psu massive overshoot on slave channel on power off - Page 1
Forum section: electronics / repair

author: lop734
author_rank: Newbie
timestamp: May 15, 2025, 07:19:55 pm
content: HelloI have recently acquired this old (2003 calibration sticker) Lodestar 8202 triple-channel linear DC power supply.I have noticed some quirks, such as the 5v channel being dead (perhaps a blown fuse). Neither channel can go below 3 volts, which I believe is a limitation of the old LM723AM regulators inside this unit. These are not big problems, and I can deal with them. However, the slave channel exhibits significant overshoot (2x set voltage!) upon turning off the unit by the master power switch (or just unplugging the unit). I have attached the scope pictures below. I note that the master channel doesn't exhibit this overshoot problem. The scope pictures show the output of the slave and master channels without load (other than the 10Mohm input impedance of the 10x probe and scope). For this test, I set the master and slave to around 5 volts. I have found schematics, but I'm unsure if they're applicable to my hardware revision, since mine looks much older than other Lodestar 8202s.https://www.circuittest.com/Media/Data/Schematics/SC-PS-3330.PDFhttps://www.alfaelectronics.com/manuals/PS-8202.pdfBased on what I know so far about circuit components, this reminds me of "inductive kickback" of some kind (from relays?), but given that the overshoot event takes place over a period of roughly 300 ms, I'm not too sure about this. Upon power off, I hear relays click for both channels (master first, slave second).I am comfortable taking this unit apart and probing with voltmeters. (I don't see any energy storing components on the HV side anyway?). I will attach pictures of the unit's internals later. I would appreciate it if anyone could point me in the right direction, since I'm not too sure where to start.

author: m k
author_rank: Super Contributor
timestamp: May 19, 2025, 07:59:37 pm
content: What it does if you add some load?

author: MathWizard
author_rank: Super Contributor
timestamp: May 22, 2025, 12:02:40 am
content: There's a lot of floating supplies in the PSU and some big caps, I'm going to guess it's just the way the regulation circuits work, and/or the BJT's, as the various supply caps discharge, and as the local GNDs move around.That's something else I must try on my own PSU's, and the model of one I'm currently working on. In it, the control rail GND's, are tied to each channel's +O/P, and with no external load, the shunt output resistance is +30k, so it doesn't take much current, to make a big output voltage.The main part of the unloaded shunt O/P resistance on mine, and probably your PSU, is the volts meter, with some 27k in the coil. Ok your's has a 3.9k.
OLD NTB 486 .. 3pin things  : AU34 and CR26 - Page 1
Forum section: electronics / repair

author: PC-maniak
author_rank: Newbie
timestamp: July 07, 2020, 09:47:56 pm
content: Hi, I have an old 486 laptop whose fan doesn't work and the part that controls the fan contains 3 pin components AU34 and CR26 as in the photos .. will anyone help me find out what it is? I searched everywhere.. but it doesn't make sense .. they are old parts

author: fzabkar
author_rank: Super Contributor
timestamp: July 08, 2020, 12:27:49 am
content: CR and AU are probably BJTs or MOSFETs.http://www.smdmark.com/en-US/search/code?id=CRhttp://www.smdmark.com/en-US/search/code?id=AUTry searching for a service manual here:https://elektrotanya.com/showresult?what=486&kategoria=&kat2=all&page=0
Old PCB lacquer gone milky white - Page 1
Forum section: electronics / repair

author: MWP
author_rank: Contributor
timestamp: July 09, 2020, 05:15:02 pm
content: Hi all,I have a few PCBs i made almost 20yrs ago that had a coat of that Jaycar "protective circuit board lacquer" spray on them.They were looking pretty nasty with dust, grime, etc, so i threw them in the ultrasonic cleaner (mentholated spirits as the cleaning liquid) for a few mins.After doing so I gave them a bake at ~70degC for 30mins to make sure all the alcohol was evaporated away.Ive been left with PCBs that are now a milky white colour, and slightly chalky in texture.I havent tried powering up the boards as yet, but i assume the colour of the lacquer wont effect the circuits.It would be nice to have them back to looking like new though.Any ideas on how to clean this up?Thanks in advance!

author: aqibi2000
author_rank: Regular Contributor
timestamp: July 09, 2020, 05:43:37 pm
content: Sounds very much like having a sheet of transparent perspect and then melting the surface with a splash of acetone and then expecting it to maintain the transparent surface finish
Old power supply ripple waveform - Page 1
Forum section: electronics / repair

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 06, 2023, 08:24:25 pm
content: Restored an old 723 based power supply. The +5V output giving an interesting looking ripple waveform under 1.5A load. Solid flat no ripple under no load.Does anyone know what it might signify? The frequency is 60Hz.

author: Mazo
author_rank: Regular Contributor
timestamp: May 06, 2023, 08:31:30 pm
content: Simple PSRR+some funky rectification effects in the internal circuitry?

author: bdunham7
author_rank: Super Contributor
timestamp: May 06, 2023, 08:54:38 pm
content: Can you put the scope on points E20 and E23 and look for switching noise from the rectifiers (short spikes at 120Hz) and get a general idea of what the input looks like? And what is the value of C3, I can't read it.My first thought is that the regulator circuit is not reacting perfectly to rectifer switching noise since there appears to be no RC snubbing of the bridge. Too high a value for C3 might make the system slow.I would observe that your ripple or noise is fairly small, <2mVRMS, so I'm not sure you have an actual defect.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 06, 2023, 10:53:40 pm
content: I agree, it's not a defect. I think it's impressive from an original 1983 supply, with no parts replaced, all electrolytes are original. The ripple, as attached, on C1 is 1V, when at 3A to a resistive load.The shape of the waveform caught my eye, and the phase difference relative to the C1 ripple. The 12V section ripple is much better, interesting enough. Perhaps the 2N3055/TIP31 on 5V is way tooo slow.
Old Sony tv replaced inverter, now turns on but no video - Page 1
Forum section: electronics / repair

author: azigta
author_rank: Regular Contributor
timestamp: May 21, 2021, 04:19:34 pm
content: Hi, I got an old Sony KDL40v2500 with the red light blinking 4 times. I replaced the inverter and now it turns on, steady green light, all the ccfl turn on and I don't see any damage In the lcdHowever, I get no video. It does respond by blinking the green light whenever I push a button so I guess the logic board is ok?Does anyone have any idea on what should I do next? I really want to repair this tv even though it's old...ThanksEdit: randomly pushing the channel + button put the tv into analog mode I guess and I can hear the typical no tv signal white noise through the speakers! And the volume buttons work too! So that kind of confirms it's not the logic board right? Could it be the t-con?
OLED 40x2 modules - Page 1
Forum section: electronics / repair

author: View[+]Finder
author_rank: Unknown
timestamp: February 03, 2025, 05:02:14 pm
content: I find myself in the middle (I hope) of a project to repair my Datron 1271 (non-working right-side display). Thanks to @picburner, and others, there is a path to a proper replacement with PCB's and code for a STM32 solution.Alert: the final product as shown in eevblog posts is a 40x2 OLED display fitting nicely in the Datron 1271.So I ordered Winstar modules from AliExpress. When I saw the tiny components that would need to be soldered to the PCB's, in light of my poor vision, I rewound my project to @picurner 1.0 with a "Bluepill" processor. And, to test the display, a prototype on Arduino. {!@#$%##!!!} 2-days!It turns out there are two (2) types of OLED character displays, one based on WS0010 and the other on HD44780. From China--where the same product finds its way into dozens of "unique" packaging--I did not expect incompatibility. But there it is.The HD44780 is older and by Hitachi; the WS0010 by "Surenoo" and seems to have better documentation (in English).What is missing is a reliable driver for the Arduino. "LiquidCrystal.h" is the most compatible (meaning 'popular') implementation, however NOT with WS0010. Adafruit tried a work-around (not working for me) and there is an evolution to a Russian version for "Winstar" that being the WS0010 that I have.Weary of the blank screen, I ordered a HD44780 from Amazon, just to see.It is likely that the STM32 version will have taken the issues above into account and @picburner end product will work just fine.Meanwhile . . . I will continue to work on a solution using what I have at hand: an Arduino and the Winstar OLED.Why so? Well, the goal is to see the information on the Datron's right-hand screen--currently implemented on a series of paper displays--and since the screen displays are mostly unchanging content for basic functions, there might be another alternative to "sniffing" the character stream in the Datron PCB.NOTE: I know nothing about OLED displays that range from tiny to giant; my task is to get a simple text display for the 1271.

author: tooki
author_rank: Super Contributor
timestamp: April 11, 2025, 10:35:12 am
content: Quote from: View[+]Finder on February 03, 2025, 05:02:14 pmSorta but not really. The Hitachi HD44780LCDcontroller was discontinued years ago, long before OLED character displays came out. Hitachi never made an HD44780 for OLED. Every HD44780-style character display, whether LCD or OLED, on the market now (and for the last probably 20 years) uses an HD44780-compatiblecontroller.The WS0010 is clearly intended to be HD44780-compatible, but needs a slightly different initialization sequence, after which it apparently behaves the same:https://sl-alex.net/embedded/2021/10/08/universal_initialization_of_hd44780_and_ws0010_displays/Quote from: View[+]Finder on February 03, 2025, 05:02:14 pmSo… do you have a concrete question or something?
Oltronix Power Supply B703 repair help - Page 1
Forum section: electronics / repair

author: kirill_maker
author_rank: Contributor
timestamp: October 21, 2024, 08:58:07 am
content: I got one Oltronix Power Supply B703 - myself but it has shorted primary and secondary looks fried - want to try to rewind it.One problem - there is no info about secondary voltages in SM.I will be glad if someone who have it will find some time and measure secondaries voltagesThanks!

author: Harry_22
author_rank: Frequent Contributor
timestamp: October 21, 2024, 09:57:51 am
content: Hi!You do not need to know the voltage when the transformer fails. Just remember the number of turns, the thickness of the wire and the direction of winding.Judging by the photo, your PS provides all the set voltages.

author: kirill_maker
author_rank: Contributor
timestamp: October 23, 2024, 12:03:33 pm
content: Photo isn't mine - just for clarification of device face - mine have dark goo leaked from secondary side + blown off diode rectifier

author: Harry_22
author_rank: Frequent Contributor
timestamp: October 23, 2024, 12:31:16 pm
content: Hi!Could you make some good photos of broken parts as well as a general view of the device intestines.

author: kirill_maker
author_rank: Contributor
timestamp: November 11, 2024, 09:18:43 am
content: Hi! I've disassembled transformer - pretty fried

author: Ranayna
author_rank: Super Contributor
timestamp: November 11, 2024, 09:48:50 am
content: Besides the obviously broken transformer and the cracked rectifier, i see a lot of RIFA caps in the device.I wonder if they contributed to the damage?

author: kirill_maker
author_rank: Contributor
timestamp: November 11, 2024, 06:44:55 pm
content: Rifas were replaced already - ive checked those - cracked but not shorted and ive replaced tantalums as well

author: Harry_22
author_rank: Frequent Contributor
timestamp: December 09, 2024, 01:47:50 am
content: Rewind the transformer. It's not as difficult as it seems. Draw only all the winding data.
Olympus DSLR (E-500, E-520) repair - Page 1
Forum section: electronics / repair

author: MarkMLl
author_rank: Frequent Contributor
timestamp: June 13, 2021, 05:29:22 pm
content: Elsewhere, there's occasionally discussion relating to these cameras which, when they reach "a certain age", start forgetting things like the date and that they shouldn't flash in public.I've determined that they have a Sanyo UT621or similar rechargeable lithium cell buried deep inside, and have posted a blow-by-blow of an E-520 repair athttps://www.dpreview.com/forums/post/65206962. An E-500 was even easier, since the battery was accessible as soon as the camera back was removed.MarkMLl
omron relay - Page 1
Forum section: electronics / repair

author: Farah
author_rank: Contributor
timestamp: September 20, 2023, 10:56:03 am
content: I have a OMRON 6-pin surface mounting terminals relay with code "- V 111" on it. I need its datasheet but I couldn't find the exact part number of relay. what is the complete part number of this relay?
on surface jumper - Page 1
Forum section: electronics / repair

author: abdulbadii
author_rank: Frequent Contributor
timestamp: February 17, 2023, 01:45:14 pm
content: Anyone quite experienced in assembling surface jumpers from ones sold on markets or just point us which of them are quality ones, or even is used to make up his own smd jumper then assembling it ?

author: Gyro
author_rank: Super Contributor
timestamp: February 17, 2023, 05:22:05 pm
content: Your post doesn't convey any meaning. Please post a picture of what you are talking about.

author: Grandchuck
author_rank: Super Contributor
timestamp: February 17, 2023, 06:36:03 pm
content: https://resources.pcb.cadence.com/blog/2022-smd-jumpers-bridging-the-gap(I suppose this is what he refers to?)

author: jpanhalt
author_rank: Super Contributor
timestamp: February 17, 2023, 07:22:04 pm
content: That has to be one of the most worthless "explanations," excepting those from the US CDC, that I have seen in years. A J1 is on the picture, but is not defined, nor is a jumper clearly shown that I can find.As for assumptions, I assumed the TS was referring to "0-ohm resistors," and as usual, the TS will not return to explain.
one case for HP 5071A cesium standard repair - Page 1
Forum section: electronics / repair

author: testpoint1
author_rank: Frequent Contributor
timestamp: March 19, 2020, 11:14:29 pm
content: checked the Ion Pump currecnt is 0 or 0.2 uA, then found the high voltage only +1000V (as usual is +3500V), high voltage module (05071-60216) in malfunction, spent one day to open it, inside fill the silicon glue already, then found one high voltage CERAMIC capacitor in condition will be broken. blame HP, so hard to tear down.
One expert clarify on handphone charger cable please? - Page 1
Forum section: electronics / repair

author: abdulbadii
author_rank: Frequent Contributor
timestamp: June 24, 2022, 02:59:37 pm
content: Why our (old) handphone charger cable is being stranded conductive wires surrounding thin hairy white threads, instead of just usual plain conductive cable ?

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 24, 2022, 04:11:16 pm
content: copper strands can easily snapped to pieces if you pull them.. thread is mechanically strong, fishing braided line is small but can cut your hand if you are not careful.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: June 24, 2022, 04:34:42 pm
content: What that white smooth fibers is made up usually of, it's surrounded by the conductive or the other way around, or else positioning?

author: tooki
author_rank: Super Contributor
timestamp: June 25, 2022, 03:05:38 pm
content: I have no idea what your last reply is supposed to mean. But the reason headphone wire is super thin enameled wire or ribbon wrapped around fibers is a) for strength, as Mechatrommer said (those thin conductor wires would snap at the lightest tug), but also b) flexibility. It takes much less effort to bend a spiral than a wire itself, but critically, it also means the wire itself isn’t being bent at a sharp angle. This means the cable will last much longer in high-flex situations. (The downside is that the conductor strands end up being many times longer than if they were not wrapped.)

author: abdulbadii
author_rank: Frequent Contributor
timestamp: June 25, 2022, 10:34:50 pm
content: Quote from: abdulbadii on June 24, 2022, 04:34:42 pm

author: IanB
author_rank: Super Contributor
timestamp: June 25, 2022, 10:38:37 pm
content: Quote from: abdulbadii on June 25, 2022, 10:34:50 pmWhite smooth fibery stuffI mean seriously, why do you think anyone would know? It will be polyester, or nylon, or something like that.
One way a LED TV dies. - Page 1
Forum section: electronics / repair

author: Housedad
author_rank: Frequent Contributor
timestamp: June 21, 2019, 12:21:24 am
content: My daughters 55" LG 4KTV died one month after the extended warranty and of course, she brought it to me.Turns on, no signal, backlight works, blue screen of death, no sound. no lines.Testing: Power board works as designed. putting out the proper 190v and 13.2v DC. No AC or ripple. Motherboard getting full power power lights on board functioning without flashes, All SMD caps. diodes and trans check for function and ESR if possible.No shorts on the T-con board, Power working fine. All components checked and good. LCD board strip at bottom of display all good condition, parts check out, signal traces all clean and tested for continuity.Now I started figuring it might be a solder point. Started doing tons of traces on the motherboard, all OK. Of course I end up saving the CPU for last.Pull the heat sink and lookie what I found below. The tape was so damn thin it barely touched the IC around the periphery. Barely thicker than scotch tape.Shoddy manufacturing? Planned obsolescence? Some Chinese worker way overworked? Bean counter saving coin in Korea? God knows.I suspected after that a bad solder joint under the BGA and since it was dead anyway, I went over to a friend that had a rework station, added flux and did a reflow profile and seated the heatsink back with tape that was thick enough to fill the gaps and applied enough pressure to make if conform.For right now, the miracle occurred: All is well in LG land.We'll see how long it lasts. I'm not holding my breath.

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 21, 2019, 06:43:15 am
content: Thin adhesive is not necessarily a bad thing, thin means less thermal resistance (if both surfaces are flat enough in the first place), in your case it does look like thicker is needed...Did this BGA have a soft thermal pad between PCB and aluminum frame on the underside?Pressing on BGA's during power-up has become one of my routine checks in flat TV troubleshooting...

author: PKTKS
author_rank: Super Contributor
timestamp: June 21, 2019, 11:35:53 am
content: IMHO These adhesives are crappy stuff.I have found half dozens MOBOs with those adhesives justspread underneath the heat sink as if they had melted.one MOBO rendered useless as the adhesive promotedcorrosion on the already crappy LGA damn small pinswhen the adhesive melts and falls inside the LGA arraythey turn that crappy thing a hell to clean..RELIABLE THERMAL PASTE I NEVER *EVER* HAD SUCH ISSUES.Not even garbage old pastes...2 cents.Paul
Onegraph WG300 Power Evaluation Monitor repair. - Page 1
Forum section: electronics / repair

author: aargee
author_rank: Frequent Contributor
timestamp: April 12, 2024, 07:13:17 am
content: Hi all,I have an old Onegraph WG300 that has decided to short out one of its secondaries in the power transformer.Before I send it to e-waste I thought I'd see if anyone had a service manual or schematic for this device.The PCB mount transformer is part of a linear power supply on board and is a custom part. It has 100-115V and 220-240V primary windings with two secondaries, one of which is shorted internally.Looking at the circuitry hanging off it, it's possibly a 24V winding or there-abouts.
Ongoing Fluke 175 Repair - making progress  - Page 1
Forum section: electronics / repair

author: MC2Short
author_rank: Contributor
timestamp: December 08, 2024, 12:04:07 am
content: Hey guys so a while back I posted about my fluke 175. I accidentally cooked it with a MOT like an idiot. (Yes, I discharged the cap and all.)So at first I wasn't getting any kind of ac voltage readings, and in continuity it just kept beeping with the leads not even connected. I was told to try desoldering 6 SOT23 chips and trying it again. Pictures included here.. So I desoldered them, and then nothing worked. I was then told I probably shouldn't have desoldered the top two. After lots of trying to figure out what those top two SOT23's were, I got some new ones from digikey and soldered those on. Now, it works, kind of. When I measure AC it measures as accurately as I'd need it to, and with DC it also measures right where it pretty much should. Now in ohms mode it also seems good.in continuity mode it seems like it takes its time, but shorting the leads beings the ohms reading down a little slowly and then beeps. If I hold it it'll go - numbers on me. Now the part I don't really understand is I have a brand new 9v battery in there, and when I turn the meter off, after a sec it will display batt on the screen. Once it does that I can move the switch anywhere I want and it will just say batt until I disconnect it. So, after that long rambling post my question is does anyone know why or what to check? And also the 4 other SOT23s just above the bridge I still haven't replaced. They are all marked 6B> I was told they were MMBF5484's. Then another person on here said they were BC817-25's and I think that's correct. What exactly do these 4 SOT23's do, and would they have any effect on the batt coming on when the meter is off? I wouldn't think so but... Hey I really have no idea. Thanks for your help. First picture are the SOT23s I removed. I replaced the top two, then the 6b> ones I still haven't replaced. The rest of it is pretty self explanatory. Thanks again.

author: MC2Short
author_rank: Contributor
timestamp: December 08, 2024, 12:17:26 am
content: If anyone needs more pictures or anything just let me know I got a bunch.

author: MC2Short
author_rank: Contributor
timestamp: December 08, 2024, 03:12:06 am
content: I soldered on the other SOT23s I thought might of been the wrong ones, and it's working now!
Onkyo A-RV401 Surround receiver Wires came off during repair, don't know where t - Page 1
Forum section: electronics / repair

author: smk279
author_rank: Contributor
timestamp: December 14, 2023, 02:34:12 am
content: they connecthttps://imgur.com/a/8v9pRzP

author: darkspr1te
author_rank: Frequent Contributor
timestamp: December 14, 2023, 07:09:01 am
content: in the schematic the yellow/white wire are on A/C input side, see last page of the this manual ,https://elektrotanya.com/onkyo_a-8840_a-rv401_sm.pdf/download.htmldarkspr1te

author: smk279
author_rank: Contributor
timestamp: December 14, 2023, 06:17:14 pm
content: I found a photo I took before disassembly showing where the wire from the transformer goes I still need to know where the loose inline wired capacitor connects to, both of it's wires have been disconnected
Onkyo av receiver woes - Page 1
Forum section: electronics / repair

author: dertoid
author_rank: Newbie
timestamp: May 10, 2020, 08:09:40 pm
content: Hiya all. Long time lurker, avid eevblog subscriber.Here's my problem.Onkyo RZ720 av receiver developed a hiss in L channel, which is volume independent, get a liiiitle lower when 'mute' is pressed, sometimes it starts making rather noticeable random sounds - like hissing gets louder static-like. All other channels are dead silent.Headphones - pronounced hiss in L channel too.So, i whipped out my multimeter and rigol and here's the result --0.35v dc on L channel. All other chans are below 0.01v.Oscilloscope doesn't show anything significant (like ac 50/60hz leak etc) in AC mode, -0.35v steady-ish in DC cpl mode.I have the service manual (can attach on req!) and narrowed it down to +29db PA on the L channel.Yes, i did read info here about leaky mute transistors - but i can see in my device those are before PA stage? Or am i being horrifyingly noobish?I do ok with digital circuits but all those 'class A' and 'offset bias' - and i'm lost.Yes, i understand (looking at diagram) that all channels have 3 protections in place - a) overcurrent b) over DC (!) and c) over voltage (re +-69v getting thru to speakers from amp power rails). Looks like my -350mv are just on the verge of triggering protection b).I also understand that my left speaker's coils are under undue stress (lovely magnat).I would appreciate any tips, input etcetera.Stay well and safe!
Onkyo randomly stops audio - Page 1
Forum section: electronics / repair

author: irondemigod
author_rank: Newbie
timestamp: November 17, 2024, 05:09:39 am
content: I have an Onkyo HT-R390 hooked up to my laptop with the RCA jacks, and when audio is playing, the audio would randomly fade out 15-20mins in (not necessarily in this time), and would only start playing again after turning it on and off after a few times. This happens to all audio sources including optical and HDMI.Tried searching up my issue on Google, but all the videos were about a DSP chip causing issues with HDMI board, such as no sound playing at all.Is there anything I can do to fix this?Thanks!Service Manual:https://data2.manualslib.com/pdf7/240/23962/2396146-onkyo/htr390b.pdf?d13bfffb71506c02afbd37edc2cf1f24

author: calibrationfixture
author_rank: Regular Contributor
timestamp: November 17, 2024, 06:17:17 am
content: Hi irondemigod,Look at the Power Supply/Standby Board. Just fixed a Onkyo TX-NR676 AV Receiver. No Powering Up and Display. I take the aforementioned Board out for inspecting (Electrolytics, Relais etc.). No issues. I had to disconnect a few Ribbon Cables with the Main Processing Board. Putting it back all together gives a Receiver that Powers Up, is Initializing (yes, it is a Computer) and working again.Calibrationfixture

author: fzabkar
author_rank: Super Contributor
timestamp: November 17, 2024, 06:33:08 am
content: This is from the troubleshooting section of a different Onkyo product:Quote

author: irondemigod
author_rank: Newbie
timestamp: November 17, 2024, 09:38:20 am
content: Is the display supposed to show that the protection mechanism has been activated? Mine does not, and apart from no audio, everything else behave as normal.

author: MathWizard
author_rank: Super Contributor
timestamp: November 19, 2024, 07:31:47 am
content: Does it happen to all speaker outputs, do headphones still work, when speakers loose the sound ?If you have a DMM, it shouldn't be too hard to track the audio signal back from the output (plus with the schematic's) and see where the signal normally comes from. Then when it stops working, you should see it missing from those places.If it's just analog audio in, and all outputs cut out about the same time, I'd suspect something like an Analog Input switch IC, or Volume control IC, or something related to them, has a problem. Assuming the power rails are all working, and it's not the actual output drive cutting out, but yeah it could be that too.Or it could be some other muting function kicking in.