hybridfree/eevblog-posts huggingface dataset:
Tektronix 465B DMM44 restoration - Page 1
Forum section: electronics / repair

author: krisztian_andre
author_rank: Newbie
timestamp: October 16, 2014, 11:25:41 pm
content: Hello,I'm repairing and cleaning a tek 465b that I bought recently. I couldn't find a partslist for the dmm44, does anyone know the part number of the knob on the multimeter? Mine is broken. Also, what kind of bulb is in the grid illuminator?

author: krisztian_andre
author_rank: Newbie
timestamp: October 17, 2014, 12:18:03 am
content: All the service manuals I found have mussing parts on the left and right sides of it's pages. If you have a manual with full unclipped diagrams please let me know.

author: coppice
author_rank: Super Contributor
timestamp: October 17, 2014, 01:48:34 am
content: Thanks. You've reminded me of a weird piece of history. I never understood why anyone would buy one of those overpriced, clumsy to use, poor performing multimeter add ons for a scope. There were quite a few around at one time, though.

author: David Hess
author_rank: Super Contributor
timestamp: October 17, 2014, 04:50:40 am
content: Quote from: coppice on October 17, 2014, 01:48:34 amI never really liked the idea either but some of them doubled as the delay time and delta delay time readout on oscilloscopes which had delayed dual sweep and delta delayed dual sweep timebases. You can tell which ones support this because the delay time control will not have a mechanical readout.As far as the service manual goes, try contacting Artek Manuals. I am sure they have complete scans for a low price.
Old MiniScribe 8438, 30 MB Hard Disk Repair - Index Pulse Not Detected - Page 1
Forum section: electronics / repair

author: Unknown
author_rank: Unknown
timestamp: October 17, 2014, 04:02:56 am
content: Hi guys,This post comes off the back of a previous post I madehere.I'd like to try and get this drive working (as finding a suitable replacement for a reasonable price is proving difficult). The error that is being generated is "Code 4 - Index pulse not detected during spin up". The manual describes the following power-up procedure:+12 VDC powers the spindle drive motor. The microprocessor verifies that the disks are spinning at 3600 rpm and then activates the automatic Track Zero positioning. -TRACK ZERO, -SEEK COMPLETE, and -READY will become true upon completion of the Track Zero positioning sequence.Further on down the manual, it goes on to specify:-INDEX This 300 microsecond (typical) interface pulse is provided by the drive once each revolution (16.67 ms nominal) to indicate the beginning of the track. Normally, this signal is a high level and makes the transition to the low level to indicate -INDEX. Only the transition from high to low is valid.In my case, the motor is spinning fine. I can physically see it make several full rotations upon power-up before shutting off with the error code. There are other error codes which relate to the actual speed:Code 5 - Unable to reach 3600 rpm in 30 secondsCode 6 - Unable to stabilize spin speed in 10 secondsCode 7 - Unable to maintain spin speed to 0.5%As I'm not getting these errors, this indicates to me there is absolutely no output from the sensor at all.One of the forum members, Chris, posted this:QuoteI've pulled the PCB off the drive and found what appears to be the index sensor. There is a small silver circle (A) on the edge of the motor which passes a small black piece (B) as it rotates. Now I'm stumped at where to start troubleshooting. What kind of sensor is this?Unfortunately I don't have a scope to probe around with (Dave, interested in a repair video?)

author: SeanB
author_rank: Super Contributor
timestamp: October 17, 2014, 04:46:23 am
content: 6 wires on the motor, so likely 3 are the phases, with a star point, and the other 3 are for the hall sensor that detects the index pulse. Look on the board where it plugs in, there will be 3 heavy traces going to the motor driver, and a trace connected to ground and another going to 5V, with the last thin one going to the motor control and the MCU. Solder a test wire to it, put the drive back together and power it up. There should be a pulse on that wire, if not either the pull up resistor is faulty or the sensor is bad. As you have to dismantle the drive to get to the bottom of the motor hope it is the resistor. If the sensor you can get a new one and break off the original one and epoxy one to replace it to the magnetic shield, and route the 3 wires to the connector.
HP1740A Vertical preamp hybrid - Page 1
Forum section: electronics / repair

author: DmitryL
author_rank: Regular Contributor
timestamp: October 13, 2014, 09:11:28 pm
content: I bought recently HP1740A scope in a quite pity state.. After fixing its PSU and re-soldering a hundred of cracked solder joints it turned out that its vertical preamplifier hybrid (HP part 5081-3030-1) is half deadChannel A 5mV balance is completely out of order and a quater of ranges simply don't workThe input attenuator/amplifier worrks OK.Is it possible to get such hybrid somewhere or they are completely unobtanium ?It would be very pity to throw away this scope, it doesn't have much use with ony one channel..

author: tautech
author_rank: Super Contributor
timestamp: October 14, 2014, 06:17:35 am
content: Be patient something will turn up.I have a 1740 too waiting for some spare time, my second one.Looked athttp://www.sphere.bc.ca/test/hp-parts/hpparts3.html, they had one but now sold.But probably worth an email to them to book their next arrival for you.Keep looking on the "bay" for one being wrecked.Put an add in the forums Buy/Sell Wanted too.

author: DmitryL
author_rank: Regular Contributor
timestamp: October 14, 2014, 08:55:02 am
content: Hi! Thanks for the reply..Do you know what you need for your 1740 ?If I don't find that hybrid, I might dismantle my scope and donate its organs, anyway it will be collecting dust if not repaired.

author: tautech
author_rank: Super Contributor
timestamp: October 14, 2014, 06:24:35 pm
content: No not at this time. I have seen a waveform on the CRT, but it is an intermittent fault.I'm not at all worried about the repair(when I get around to it) having repaired a good few CRT scopes in the past.I have all the HV test gear needed and access to a 100 MHz pulse generator for calibration checks if required.For my last one I got a donor from our NZ HP agent, but sold it with the last one for spares not thinking I might get another or be able to help you for example.Again be patient, you will find a donor or mainboard or the hybrid IC.
Siglent SDG1025 Self-Cal Failure - Page 1
Forum section: electronics / repair

author: sggtav
author_rank: Newbie
timestamp: October 13, 2014, 10:07:14 pm
content: Hi!This is my first time posting on this forum!I tried to run a self-adjust procedure on my Siglent SDG1025 Waveform Generator, and after it was done I found that the device stopped working correctly. When I turn on any of the 2 channels it looks as if they were "saturated", and if I change the voltage reference it modifies the level of that saturation but the signal never has the expected waveform.And to make things even worse, I later found that my serial number was like "erased" during the process, because now it says "sdg000", while it should be like 14 digits long.It seems as if I had lost all the configuration files or something like that. I wanted to know if this has ever happened to any of you, because I would really appreciate avoiding having to send it to Siglent.I'll leave you a picture of the screen, where it shows the serial number problem.I would really appreciate any piece of advice you can offer!Thanks in advance!Santi

author: tautech
author_rank: Super Contributor
timestamp: October 14, 2014, 06:02:17 am
content: Santi, I will point Siglent China to you post.Add your country flag to your profile.

author: sggtav
author_rank: Newbie
timestamp: October 14, 2014, 12:43:27 pm
content: Thank youtautech, i appreciate your help.Hope to have any answer from them.
Pop 3 Tablet repair - Page 1
Forum section: electronics / repair

author: electrolux
author_rank: Regular Contributor
timestamp: October 06, 2014, 09:37:29 am
content: Recently I got a Android 7 inch tablet from China/Ali express it's called Pop 3, anyway, While messing about with the settings I tried to change the resolution since the the screen has turned blank and the back light stays on, any idea how to fix this? Tried the reset button.

author: electrolux
author_rank: Regular Contributor
timestamp: October 07, 2014, 11:43:24 am
content: Too late fixed.

author: Zucca
author_rank: Unknown
timestamp: October 07, 2014, 01:51:50 pm
content: Cam´on... tell us how you fixed that...Are you not an E/E addicted?

author: electrolux
author_rank: Regular Contributor
timestamp: October 08, 2014, 08:58:42 am
content: Quote from: zucca on October 07, 2014, 01:51:50 pmMy brother did it ('abdullahseba' is his EE user name) something to do with pressing all the buttons on the side to bring up the boot menu and resetting to factory default it deleted all the apps but that didn't matter as we'd only just got it and hadn't many installed.

author: miguelvp
author_rank: Super Contributor
timestamp: October 09, 2014, 05:19:10 am
content: All the buttons or just holding volume up and power up?Although some other devices is just holding volume down and then power up.

author: electrolux
author_rank: Regular Contributor
timestamp: October 14, 2014, 09:12:16 am
content: Quote from: miguelvp on October 09, 2014, 05:19:10 amDunno, PM 'abdullahseba' and ask if you want!
Isn't it ESR Meter showing correct? - Page 1
Forum section: electronics / repair

author: Savetheday
author_rank: Regular Contributor
timestamp: October 11, 2014, 09:32:10 am
content: HiI buyed an used ESR Meter from ebay.After turning the device on.it shows the number 1 in display.When i try to measure capacitors it allways shows numbers greater then 1.3 or higher. Isn't it suppose to show numbers below 1 ?thanks.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: October 11, 2014, 09:47:03 am
content: Note the position of the 1. The 1 you are seeing is not the number 1, but means "overload", too high resistance to measure (open circuit).1.3 ohm is a reasonable ESR value for some capacitors. Which type of capacitor did you probe? (Value and voltage rating.) What happens if you short the probes?

author: kripton2035
author_rank: Super Contributor
timestamp: October 11, 2014, 11:30:56 am
content: seems to be the elektor esr meter from september 2002here is a link to the original article and the method for calibrating.http://kripton2035.free.fr/commercial%20esr/esr-elektor-sept.html

author: Savetheday
author_rank: Regular Contributor
timestamp: October 13, 2014, 12:21:45 am
content: Quote from: kripton2035 on October 11, 2014, 11:30:56 amThanks but i didn't get it.Is It still working and usable?

author: kripton2035
author_rank: Super Contributor
timestamp: October 13, 2014, 06:05:49 am
content: Quote from: Savetheday on October 13, 2014, 12:21:45 amyes first link in the description - just downloaded again it's working.
HP 3200B how to restore front panel label/marking - Page 1
Forum section: electronics / repair

author: johnh
author_rank: Regular Contributor
timestamp: October 11, 2014, 10:27:15 pm
content: What the best way to restore the front panel labels/markings?

author: valvedude
author_rank: Contributor
timestamp: October 11, 2014, 11:52:16 pm
content: hi what i do is i get a sharpie pointy permanent marker and retrace the writingthey come in a really fine tiplook at office works make sure all hand oils are wiped off it will look like new when done i did some of my 1950 hp test gearhttp://www.sharpie.com/enAU/Products/Pages/ProductDetails.aspx?pid=SharpieFinePointPermanentMarker(Sharpie%20Catalog)

author: PaulAm
author_rank: Frequent Contributor
timestamp: October 12, 2014, 12:38:19 am
content: That works very well for embossed legends.Be glad you don't have white silkscreened legends on plastic.

author: rhost
author_rank: Newbie
timestamp: October 12, 2014, 04:30:00 am
content: I've always had good luck with Markal lacquer sticks for engraved panelshttp://www.amazon.com/gp/aw/d/B002BYWUMO/ref=mp_s_a_1_1?qid=1413088051&sr=8-1
PSU question - Page 1
Forum section: electronics / repair

author: angelothewolf
author_rank: Contributor
timestamp: October 10, 2014, 02:13:38 pm
content: Hi there!! im working with this power supply that is delivering 38VDC where it's supposed to be 25VDC. Should R205 adjust this voltage? got 35VAC coming out of the transformer and 41VDC after rectifier on filter caps... ??

author: angelothewolf
author_rank: Contributor
timestamp: October 10, 2014, 04:26:25 pm
content: nobody?

author: w2aew
author_rank: Super Contributor
timestamp: October 10, 2014, 05:32:27 pm
content: Quote from: angelothewolf on October 10, 2014, 02:13:38 pmPerfectly normal to see a larger DC voltage after the bridge rectifier, so no sweat there.If everything was operating normally, then yes, R205 should adjust the regulated output. However, it is possible that he pass transistor T201, or the regulator IC itself have failed. Measure the voltages around the pass transistor. Do they make sense? What voltages do you see on the regulator IC pins - do they make sense?
Anyone have manual/schematic for Power Designs 2020? - Page 1
Forum section: electronics / repair

author: motocoder
author_rank: Unknown
timestamp: October 10, 2014, 04:51:19 am
content: Does anyone have a manual/schematic for the Power Designs 2020 Precision Power supply? I have the manual for the 2020B, but this unit is labeled 2020, not 2020B.

author: tautech
author_rank: Super Contributor
timestamp: October 10, 2014, 08:41:54 am
content: Quote from: motocoder on October 10, 2014, 04:51:19 amCheck this post fromrobrenz:https://www.eevblog.com/forum/testgear/looking-for-goodinexpensive-bench-power-supply/msg103781/#msg103781

author: motocoder
author_rank: Unknown
timestamp: October 10, 2014, 12:57:14 pm
content: Quote from: tautech on October 10, 2014, 08:41:54 amThanks, but I already PMed robrenz before I posted this thread. As it turns out, he does not have a manual or schematic for the 2020, only the 2020B. The 2020B appears to be significantly different (it evens appears to have an IC). Just looking at the components in this thing it looks a lot like the 2005 as robrenz mentions in that post, but ther are differences and the components are spread out over 3 circuit boards versus the single board of the 2005. I was hoping to get the manual as this one apoears to be in need of repair.
fluke 87-5(V) beeping on me when not set on Amp meassuring  - Page 1
Forum section: electronics / repair

author: eevblogfan
author_rank: Frequent Contributor
timestamp: October 09, 2014, 03:58:39 pm
content: HeySo my dear fluke 87 was exposed to black smoke about half A year ago , i havn't used it ever since , he is beeping when power on , it's clear that was the probe detect , so i cleand with air preassure , and yay ! The beeping has stoped ! , 5 sec after , the beeping began again ..I need your help to solve it , since i have no spare time lately , i'll be glad if someone will share with me hes experiance with such A problem , unless , i'll be stuck without my 87 for now .. witch is feeling so bad not to use it ..Thank you in advance

author: retiredcaps
author_rank: Super Contributor
timestamp: October 09, 2014, 07:43:30 pm
content: Suggestions.1) Take a strong bright flashlight and see if there is any debris in the A input jack.2) Take a qtip dipped with IPA and clean the input jack.3) Flip the pcb upside down so the backside is exposed. Measure the resistance of the A split input jack. It should read 0L (infinite ohms).I included pictures from modemhead's website for examples. The two pads circled in red are the solder points for the V/ohm input jack on Fluke 87 series I. You need to measure the equivalent for the A input jack.PS. All pictures are from modemhead's website athttp://mrmodemhead.com/
NIKKEI-NCLCD4O CIRCUIT BOARD - Page 1
Forum section: electronics / repair

author: BONGOJERE
author_rank: Newbie
timestamp: October 09, 2014, 12:32:52 pm
content: Hi. I'm seeking help for an unusual problem. I have a Nikkei-NCLCD40 TV with a bad circuit board. (T.MS6M181.1B 11223) that uses the NTSC format. I have searched formonthsfor a replacement board. The ONLY board available is one that uses PAL. That obviously won't work and converting NTSC TO PAL is way too complicated (& expensive). I know this board exists because I'm looking at it. The tag says GDCwww.gdc.com.hkwhich of course is in Hong Kong. But when I go to their site, all they have is the PAL board. This isdefinitelyNTSC.These televisions are sold here in the Dominican Republic. No one here can find it either. HELP!Thanks,J
PC Video Cards - Page 1
Forum section: electronics / repair

author: geartechbrandon
author_rank: Newbie
timestamp: October 02, 2014, 02:06:48 pm
content: Hello,Been a long time lurker and watcher of EEVBlog. Recently I've wanted to make use of the piles of video cards I've accumulated after years of upgrading to delve deeper into cuda parallel processing. That project is fine and running but one of my Nvidia cards seems to be faulty as it causes the system to lock up.I've isolated it and, thought I don't need it for the project, want to know more about what's going wrong. I would like to attempt to fix it and am wondering if anyone has any tips of diagnosing what the problem with it is. I've tried other forums for answers but the usual response is: buy a new one. That would be easy but what I want is to delve deep into what makes these cards work and how to keep them working. For instance if it's just a bad ram chip I could just pop it off and replace it.The challenge and experience are more valuable to me than just having a working video card. Any thoughts would be greatly appreciated.

author: Rasz
author_rank: Super Contributor
timestamp: October 03, 2014, 12:41:23 am
content: my diagnosis: its broken

author: jmoreland79
author_rank: Regular Contributor
timestamp: October 03, 2014, 07:55:54 pm
content: You're talking about an embedded system with tens of thousands of lines of code running on hardware at extremely high frequencies.You would need copious amounts of proprietary information as well as a custom test setup to properly diagnose what's wrong with it.Other than checking for overheating and some low level tests of a few components, the best advice is to just buy a new one.

author: videobruce
author_rank: Frequent Contributor
timestamp: October 09, 2014, 10:19:00 am
content: There is also the fact these are grossly out of date. Too slow, limited memory, surely are useless for gaming. A card under $50 would outperform any of these probably.You also didn't state the interface. PCI, AGP or PCI-E?
Keithley 225 current source: -136V output voltage - Page 1
Forum section: electronics / repair

author: fedora_88
author_rank: Newbie
timestamp: October 21, 2014, 05:40:51 pm
content: Hello,yesterday I recognized that my Keithley 225 current source shows about -136V output voltage at the output under the following conditions:- polarity: +- compliance voltage: 10V (it doesn't matter if it is 10V or 100V position)- filter: on or off doesn't matter- 100mA range- all current-knobs in zero position (00,0mA)- no load on the output, only a 10MOhm Multimeter in voltage modeWhen I short the output with a second multimeter, the flowing current is only -10uA. When I open the short again the voltage slowly rises until -136V. When I set current to 1mA or 10mA the voltage rises to the selected compliance voltage (+10V).Beside of that it works perfectly normal. So I don't know if there is an error, or if that behavior is normal. So to all Keithley 225 owners, can you please check if your device shows the same issue.kind regardsThomas

author: Vgkid
author_rank: Super Contributor
timestamp: October 21, 2014, 08:06:02 pm
content: Have you tried measuring it across a load.

author: jlmoon
author_rank: Unknown
timestamp: October 22, 2014, 08:59:14 pm
content: Quote from: fedora_88 on October 21, 2014, 05:40:51 pmThomas,I suspect you have a problem with the differential amplifier section (drive amplifier) I have fixed a few of the calibrators similar to this one, check the current limiting resistors that are at the top and bottom power supply rails. These resistors are what feed the supply to the bipolar differential amplifier to establish a balanced supply. Best of luck!JLM
Trinitron Monitor Repair - Page 1
Forum section: electronics / repair

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 03, 2014, 12:55:28 am
content: I repaired my 21" Trinitron (CRT) monitor the other day:http://seventransistorlabs.com/Monitor/index.htmlJust pictures right now, more notes to come. Short story: intermittent horizontal failure. Seemed like a cold solder joint or something like that. What was it actually? An 0805 chip resistor, no kidding.Board design and construction is excellent, a well crafted instrument that everyone should get a chance to see!Tim

author: SeanB
author_rank: Super Contributor
timestamp: October 03, 2014, 04:43:24 am
content: I hope you resoldered all the pins on the LOPT and the line output transistor while you were in there, cracked joints on those along with the flyback tuning capacitors and the wiring and connectors to the scan coils are very common as well.

author: HighVoltage
author_rank: Super Contributor
timestamp: October 03, 2014, 08:20:45 am
content: In those days, the high end Trinitron monitors had such a high quality, they were used for the commercial airport radar screens.They were built in the Sony San Diego, California and just across the border in Mexico in Sony facilities.I had the opportunity to visit the factory by the end of the 90's.The quality was just amazing.Some of these monitors even came with a RGB sensor that could be placed on the front screen to calibrate the color.And this was in 1995!Just amazing machines.Thanks for sharing your teardown and repair.It is really something special to look at these pictures.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 05, 2014, 09:55:11 am
content: Annotated:http://seventransistorlabs.com/Monitor/index.htmlor hit refreshCheers!Tim
Looking for NEC PS2561-W opto-isolator equivalent - Page 1
Forum section: electronics / repair

author: Agent24
author_rank: Regular Contributor
timestamp: September 28, 2014, 11:03:43 pm
content: I need a new NEC PS2561-W opto-isolator, having accidentally broken a lead off one. The W represents the CTR (current transfer ratio) which in this case is 130 - 260%I can't find any PS2561 anywhere in New Zealand, let alone the W version.Another problem is this Opto has Vceo of 80v, and the maximum I can find in Farnell or RS is 70v.Does anyone know of a suitable replacement that isn't made from unobtainium? - or even someone who has some and would be willing to sell me one?

author: David_AVD
author_rank: Super Contributor
timestamp: September 29, 2014, 12:30:34 am
content: Try the parametric filters on the Digikey web site to narrow down your list. It should have filters for Vceo and CTR at least.

author: Agent24
author_rank: Regular Contributor
timestamp: September 29, 2014, 02:40:09 am
content: Thanks, didn't think of that since Digikey doesn’t ship here (cheaply) but it did lead me to this (the only) one:http://nz.element14.com/sharp/pc817x2nsz0f/optocoupler-phototransistor-5kv/dp/2420048?Ntt=PC817X2NSZ0F(Aside from the PS2561 itself and the PS2501)Unfortunately I don't know if it will be suitable, it has lower diode forward current rating (50mA vs 80mA) also Veco is 6v vs the 2561's Veco of 7v.

author: MarkL
author_rank: Unknown
timestamp: September 30, 2014, 01:26:55 pm
content: Here's someone selling the W version with VDE rating on ebay:http://www.ebay.com/itm/261351421896There may be others. You can also search for "NEC2561" (some sellers are just reading the top of the chip).

author: Agent24
author_rank: Regular Contributor
timestamp: October 04, 2014, 11:25:00 pm
content: Quote from: MarkL on September 30, 2014, 01:26:55 pmThanks, I did actually see those before, but I am very wary of Chinese sellers. Maybe I will risk it if I can't find anything else.
Repairing some clippers - Page 1
Forum section: electronics / repair

author: trevwhite
author_rank: Frequent Contributor
timestamp: October 02, 2014, 11:55:25 pm
content: A friend has asked me to look at some clippers she uses on her horses.I have found the page detailing the clipper partshttp://www.peasridge.co.uk/acatalog/Wolseley__Harrier__clipper_parts.htmlI looked inside and the part that has blown up is the following which can be found on the page.Wolseley "Harrier Mk III" - Condenser Ref: 50584Sorry, I did try to figure out how to insert better information. It seems the part that has blown up is a condenser for the the clippers. I cant find any information though on the actual components inside the condenser and their configuration. I was wondering if I can replace it with some cheaper parts or even improve it. The replacement part seems quite expensive really.Anyone got any ideas?ThanksTrev

author: lowimpedance
author_rank: Super Contributor
timestamp: October 03, 2014, 03:11:56 am
content: The 'condenser' is an RFI suppressor it would seem. Consisting of a 0.1uF type X and two 2.4nF (2400pF) type Y capacitors.Type X are rated for connection across Active and Neutral, and type Y are lower capacitance value usually and rated for connection from Active to Earth and Neutral to Earth. You will find plenty of info for these.This unit has all three combined into the single package, hence the three leads, ie Active , Neutral and one to Earth (green). Now perhaps you can get the same unit some where else (who is the manufacturer on the 'condenser' itself if not completely barbecued, do a search) . But for this repair I would be using the same rated unit even if it appears a little expensive, since operator safety is priority.Substitutions will have to be of the same rating and connection and be such that its also done electrically safe too. (if using 3 individual caps)And there would be no improvement to be gained here from any other alternative component change, so just buy the spare part.Make sure you clean any carbon/soot and debris liberated from the death of the original 'condenser'.

author: SeanB
author_rank: Super Contributor
timestamp: October 03, 2014, 04:40:23 am
content: You could most likely get it from a white goods parts wholesaler, as these are a common part often used on universal motors to reduce noise fed back into the mains. They might have the same item at wholesale price, otherwise you will have to buy oem.

author: trevwhite
author_rank: Frequent Contributor
timestamp: October 03, 2014, 08:21:26 am
content: Thanks for the replies. I think I will buy the original as its more convenient and will fit, etc. I was wondering about trying to save some money as my friend doesn't have much but safety is most important.Thanks again
transistor  help please  - Page 1
Forum section: electronics / repair

author: Napalm2002
author_rank: Regular Contributor
timestamp: September 30, 2014, 02:45:47 am
content: Hello allI apologize for asking such an easy question but I am working on an old akai receiver aa-6600 and I need to replace a bunch of 2sc458 transistors. I had read somewhere awhile ago that 2sc2240 was a suitable replacement. So I bought a bunch very cheap and started to replace them. Then I had printed out a data sheet and I saw that the specs are quite different. Now I am far from an EE so if some of you guys could tell me if you thinks that the 2sc2240 is a close enough replacement or do I need to buy another part no.ThanksMike M

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 30, 2014, 02:54:24 am
content: At a very good guess, absolutely any crap will work. 2SC945, 2SC1815, PN2222...2SC2240, specifically the GR grade will be a closer fit, but yeah, I doubt it matters at all.Tim

author: liquibyte
author_rank: Frequent Contributor
timestamp: September 30, 2014, 02:56:55 am
content: Someone else will probably answer your question better than this but I wanted to throw this site out there for you:http://alltransistors.com/It helps to narrow down replacements and substitutions but I have to admit that I've only used it a couple of times. It did work well for those times though.

author: kjn4685
author_rank: Regular Contributor
timestamp: September 30, 2014, 03:30:24 am
content: I would Google it and get the datasheets then compare.

author: Napalm2002
author_rank: Regular Contributor
timestamp: September 30, 2014, 04:37:53 pm
content: I did do that I just do t know how important the specs are and don't know what is ok and what might be too much.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 01, 2014, 04:53:38 am
content: Quote from: T3sl4co1l on September 30, 2014, 02:54:24 amPretty much my attitude Tim--if it's got 3 legs you are halfway there!A tip for the OP---------manufacturers like to use the same transistor as much as possible,so if something does look critical,take a look around to see if they use the same device in a non-critical spot.Steal that one,& replace it with a 2N22?,BC10? or whatever!

author: IconicPCB
author_rank: Super Contributor
timestamp: October 01, 2014, 05:28:26 am
content: Try BC546 although 2sc2240 is also a good choice being a low noise audio device.

author: denelec
author_rank: Regular Contributor
timestamp: October 01, 2014, 10:25:22 pm
content: Why use the Internet when you can dig in old dusty reference guides?According to myRadio-Shack Semiconductor Reference Guide 1988 Edition:The equivalent of 2SC458 is Radio-Shack transistor 276-2009.http://www.radioshack.com/product/index.jsp?productId=2062608It's a MPS2222A equivalent.
Need Help Identify This Diode or What for AirCond Split Unit (w X21 Mark) - Page 1
Forum section: electronics / repair

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 30, 2014, 03:06:19 pm
content: my fren sent me split unit blown pcb. in the picture, its in neutral (mains) line, so every current used by the split unit pcb, compressor and cooling fan etc need to go through this guy, now its blown to pieces (with other components on board i deal with them later). i tape this guy together for picture...i'm suspecting this is a diode? please confirm, thanks.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 30, 2014, 03:25:39 pm
content: The 102oC makes me think it is a temperature fuse.

author: 4thDoctorWhoFan
author_rank: Regular Contributor
timestamp: September 30, 2014, 03:30:58 pm
content: I second the previous poster that it's a thermal fuse.

author: mij59
author_rank: Frequent Contributor
timestamp: September 30, 2014, 03:51:54 pm
content: Agree it,s a PSE JET thermal fuse

author: Shock
author_rank: Super Contributor
timestamp: September 30, 2014, 03:56:43 pm
content: Thermal Cutoff, 3a 250v 102 Degree X21 X Series

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 30, 2014, 04:32:24 pm
content: yahalelu! its easier than i think. thank you all!
TDS 644A probe gain compensation fails - Page 1
Forum section: electronics / repair

author: resistor
author_rank: Regular Contributor
timestamp: September 29, 2014, 05:02:41 am
content: I recently finished recapping a TDS 644A. The startup self-check now passes, as does the signal path compensation. But when I try to perform a probe gain compensation cal operation, it fails. Interestingly, it only fails when my probe is in 10x mode. 1x mode appears to work. I'm using cheapie 100MHz probes from eBay.Question: Is this some lingering issues with the scope, or is it just that my probes are too crappy? If the latter, is there any way to set the attenuation factor in the scope's software manually?

author: nctnico
author_rank: Super Contributor
timestamp: September 29, 2014, 11:14:03 pm
content: Maybe you missed the caps in the calibrator circuitry. IMHO I would skip the gain calibration.

author: macboy
author_rank: Super Contributor
timestamp: October 01, 2014, 12:34:13 pm
content: Quote from: resistor on September 29, 2014, 05:02:41 amIt fails in 10x because the scope does not know that you have a 10x probe. See all those contacts surrounding the BNC jack on the scope? Even the simplest passive 10x Tek probe will contact one of those (probably grounding the biggest contact to ground) telling the scope that it is a 10x probe. You wan-hung-lo probe doesn't have those contacts.Do yourself a favor and get some faster probes. Even if all you can afford is cheapie generic 250 MHz passive probes, get them. Then replace those with better as money and opportunity arises. Those 100 MHz probes are crippling a very nice fast scope.
Mains wiring question - Page 1
Forum section: electronics / repair

author: radhaz
author_rank: Regular Contributor
timestamp: September 28, 2014, 07:15:19 pm
content: I'm working on a Jung Jin 1051B RF signal generator that appears to be dead.I've got the power supply out, and measuring the voltages, things appear off.It looks like the unit might be wired incorrectly for the 120 vac for my area. Thoughts?I should add that these values are with the loads disconnected. With the loads, there is sag of the DC voltages.

author: radhaz
author_rank: Regular Contributor
timestamp: September 28, 2014, 08:12:04 pm
content: Issue solved. This unit has a Corcom J series input module with a small PC card to select the input voltage. It was set to 220 vac. Set it to 120 vac and I have front panel lights.In case anyone runs into a similar issue:http://www.mouser.com/ds/2/418/J-12416.pdf
How do I test a LM3886TF power amp chip? - Page 1
Forum section: electronics / repair

author: LektroiD
author_rank: Frequent Contributor
timestamp: September 29, 2014, 11:51:52 am
content: I have a faulty Tannoy Precision 8D speaker, I've replaced the regulators & rectifier (I had these in stock so I thought I'd replace the parts I had before spending money). It's looking like it could be one of the power amplifiers that have failed. So, I bought some from evilBay, but they all have different manufacture codes. They look unised, but I would like to test them before soldering them in, as they are real bastards to remove.Any ideas how I could test them before commiting them to the PCB?

author: diyaudio
author_rank: Frequent Contributor
timestamp: September 29, 2014, 01:02:48 pm
content: Quote from: LektroiD on September 29, 2014, 11:51:52 amyes, if you really paranoid just build a bread board test jig it requires some effort from your side, if you lazy, remove the old one, and just resolder the new one, set-up with a cheap speaker to verify its operational.

author: macboy
author_rank: Super Contributor
timestamp: September 29, 2014, 01:03:40 pm
content: LM3886 is commonly suspect of being counterfeit. Best bet is to buy them from big distributors (Digi-key, Mouser, etc.) or direct from TI. If you want to talk to people very experienced in such things, head over to the chipamp forum at diyaudio.com .

author: LektroiD
author_rank: Frequent Contributor
timestamp: September 29, 2014, 02:49:41 pm
content: Quote from: macboy on September 29, 2014, 01:03:40 pmCounterfeit meaning they do not work, or made by a unregulated manufacturer?

author: SeanB
author_rank: Super Contributor
timestamp: September 29, 2014, 05:08:01 pm
content: Both, or they may be so poorly made that they work at low power, but fail ( often in a spectacular way) when you start to turn up the volume.

author: dundee
author_rank: Regular Contributor
timestamp: September 29, 2014, 10:16:43 pm
content: I bought this little PCB to test them:http://www.ebay.de/itm/DC-20-28V-LM3886TF-68W-Sound-Audio-Amplifier-Mono-Digital-Puissance-AMP-DIY-Kit-/321482294033?pt=FR_YO_MaisonJardin_Bricolage_ElectroniqueComposants&hash=item4ad9d68311Very cheap.Soldering of the LM3886 is not necessary for a short test
Videonics Equalizer (VE-1) RGB colorizer issue - looking for help on fix  - Page 1
Forum section: electronics / repair

author: doodark
author_rank: Newbie
timestamp: September 24, 2014, 08:57:50 pm
content: Hello,I've got two videonics equalizers from the US that both have an issue with the colorizers. The colorizer sliders should tint the entire image, but although they do change the image, it appears only more faded or darker in grayscale. There's no change of colour whatsoever.Demo video i took of the issue:https://www.youtube.com/watch?v=mY1y_uKgavY&feature=youtu.beHow it should be functioning:http://www.infinitelooper.com/?v=bdmWLlMfA5s&p=n#/57;104I've checked I am using the right USA to UK transformer and polarity etc, so its definitely an internal issue.Can anyone could give me some pointers on what might need replacing in terms of parts (see pic of internal)? OR point me in the direction o a video hardware electronics repair service in London, UK?Ive included some pics of the circuit board.. Any help much appreciated

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 25, 2014, 12:34:55 am
content: errrmmm... that's a NTSC box? You're in the UK? Are you feeding in NTSC video? You sure the colorburst is at the right frequency?
Connector identification - Page 1
Forum section: electronics / repair

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 22, 2014, 02:42:44 am
content: Anybody know what these things are called/who makes them? I'm in the middle of a repair job with about 4 billion of these connectors and there's a few I'd like to replace while I've got access. It occurred to me though that I've never actually come across these before and searches so far haven't helped me find them. There's a few different pin counts and two different pin pitches on these, but they all share the same flat pins and big/small tabs on opposite sides.

author: JSnyder
author_rank: Contributor
timestamp: September 22, 2014, 03:20:56 am
content: http://www.digikey.com/product-detail/en/0903250012/WM9239-ND/404183Is this close to what your looking for? It's the Molex "picoflex" series of connectors.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 23, 2014, 01:48:18 am
content: Legend! Thanks mate

author: Neilm
author_rank: Super Contributor
timestamp: September 23, 2014, 06:14:51 pm
content: Picoflex is a ribbon cable connector that is a bit of a pain to crimp without the correct crimp tool. The easiest way is to line it up and use a fine pair of needle nose pliers to press each contact down.

author: Christopher
author_rank: Frequent Contributor
timestamp: September 23, 2014, 06:37:39 pm
content: I like this series of connectors as they do premade ribbons in a variety of different pin counts & lengths.Crimping is a massive bitch from looking, though. In cases where I need to crimp I look at MicroMatch connectors.
Hameg  HM 205-3 Ocilloscope disorted screen. - Page 1
Forum section: electronics / repair

author: Isad
author_rank: Frequent Contributor
timestamp: September 12, 2014, 10:24:49 am
content: So i got a oscilloscope from ebay andok the seller told me it was bad and the picture sad sobut i am trying to reapir this thing and anyone knowwhat it could have.Pls if anyone had this problem and they repaired thispls leave a commen on what it could have .Thanks.

author: tautech
author_rank: Super Contributor
timestamp: September 12, 2014, 10:49:22 am
content: You need this PDF:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdfDo you have a Service manual?Maybe you can find one from the links in this thread:https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/msg477909/#msg477909First check the PSU is exactly to manual specs.

author: David Hess
author_rank: Super Contributor
timestamp: September 15, 2014, 06:18:12 am
content: Is there any evidence that the oscilloscope was dropped? Are there loose pieces rattling around inside the CRT?That kind of display is what I would expect if the internal CRT elements were damaged and it looks like the screen phosphor has been scraped off from the inside by loose debris. The curved display of straight lines can be caused by dents in the scan expansion mesh.

author: mij59
author_rank: Frequent Contributor
timestamp: September 15, 2014, 01:38:54 pm
content: Is the picture on the oscilloscope static, or does it wobble a bit ?Please post some photo's of the boards.

author: fww
author_rank: Contributor
timestamp: September 17, 2014, 02:42:05 am
content: There are two possibilities:1. The chassis is magnetic and need demagnetization.2. Due to the use of time is too long, the CRT has been aging.

author: tautech
author_rank: Super Contributor
timestamp: September 17, 2014, 03:01:45 am
content: Quote from: fww on September 17, 2014, 02:42:05 amWrong & wrong.There may be more than one problem.PSU voltages and/or ripple LV & HV.

author: fww
author_rank: Contributor
timestamp: September 17, 2014, 03:58:36 am
content: @Isad, could you provide more phenomenas for analysis.To convert to" x-y", try to move the bright spot up and down and left and right, whether it can be moved out the screen? The bright spot's luminance can be completely closed?You can also open the chassis, view the CRT, whether there are poles touching together?

author: kjn4685
author_rank: Regular Contributor
timestamp: September 20, 2014, 08:48:32 pm
content: I go with tautech

author: N2IXK
author_rank: Frequent Contributor
timestamp: September 23, 2014, 03:26:00 pm
content: Have to go with David Hess here. This looks like a case of severe misalignment of internal CRT elements, likely as a result of the scope being dropped.Do the horizontal and vertical position controls move the display purely vertically or horizontally? If not, you likely need a new CRT (or a new scope at this point).
b&k precision 820 capacitance meter inop - Page 1
Forum section: electronics / repair

author: Napalm2002
author_rank: Regular Contributor
timestamp: September 23, 2014, 01:37:57 am
content: Hello everyone,I was using my beloved 820 capacitance meter and I needed to change batteries. However being tired I didn't pay attention to the sticker directly on the battery compartment stating that the unit may receive internal damage if batteries are installed incorrectly. Can anyone help me try and fix this thing. I have no manual or schematics.ThanksMike M

author: tautech
author_rank: Super Contributor
timestamp: September 23, 2014, 09:56:54 am
content: This should help:http://www.ko4bb.com/Manuals/09)_Misc_Test_Equipment/B&K/B&K_Precision_820__Capacitance_Meter__Service_Manual.pdf
Help IDing a potentiometer - Page 1
Forum section: electronics / repair

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 14, 2014, 05:35:36 am
content: This is the position feedback pot from a mini servo. It was chattering a lot.It's about 10mm x 11m in size. Anyone recognize the brand? Or can suggest a similar part? I've ordered a replacement servo but I want to see if I can fix it. I'll try cleaning the pot and checking again.

author: miguelvp
author_rank: Super Contributor
timestamp: September 14, 2014, 05:57:41 am
content: Sounds like apple talk to me.Can you measure the resistance, that might help narrow it down.

author: fww
author_rank: Contributor
timestamp: September 15, 2014, 04:35:26 am
content: There are marked the potentiometer type on it? Or any other word?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 15, 2014, 01:00:26 pm
content: Quote from: fww on September 15, 2014, 04:35:26 amYou see the CF logo in the photo. That's it.I just wanted some spare pots but I need the exact part or else it won't fit. I can repair the pot but it's a plastic case, I can't do this often.

author: kjn4685
author_rank: Regular Contributor
timestamp: September 17, 2014, 12:55:23 am
content: Could it be central semiconductor
Monitor Problem (No Signal) - Page 1
Forum section: electronics / repair

author: bauhaus
author_rank: Newbie
timestamp: September 15, 2014, 05:47:51 pm
content: Hi!A friend of mine gave me an old monitor (hitachi cml158xw) which has a problem.When I connect it to a desktop, the monitor powers on (power light turns green) but I get only a blank display. When I disconnect the vga cable, I can see the known messages (no signal, etc) and the light turns yellow. If I reconnect the cable, the light turns green again.As I presume, the monitor receives signals from the vga card (I've also checked the continuity of its pins, and it is ok).Also, because I can see the info messages (e.g. no signal) I think that the fluorescent lamp is ok..I've also checked (visually) the monitor's board and I didn't see any burnt caps/diodes/resistors/etc.Do you have any idea what to check next? What would be the fault?Any help would be very much appreciated!!

author: tautech
author_rank: Super Contributor
timestamp: September 15, 2014, 11:28:14 pm
content: Welcome to the forum.Confirm backlight is working when connected by shining a flashlight at the screen and looking for info illuminated.Maybe this screen won't display you current PC settings.Are the PC video settings set to default monitor to start with?

author: bauhaus
author_rank: Newbie
timestamp: September 16, 2014, 08:14:03 am
content: Thank you for your reply!I'll check the backlight this afternoon. I also forgot to mention that I cannot even see the osd menu, although I can see the "no signal", "connect the cable", etc messages.If there is a problem with the backlight, these messages couldn't be displayed, right? or not?I'm confused.I've tested the monitor even in 1024x768 pixels display resolution. Nothing.

author: tautech
author_rank: Super Contributor
timestamp: September 16, 2014, 08:38:46 am
content: QuoteYou are correct, you would not see the messages.Are you trying to use the monitor as a second monitor?Try connecting it alone and see if the video card identifies it on boot up.

author: Psi
author_rank: Super Contributor
timestamp: September 16, 2014, 08:39:52 am
content: Does the monitor have any other inputs you can try? VGA / DVI / DisplayPort / Composite etc.

author: bauhaus
author_rank: Newbie
timestamp: September 16, 2014, 03:58:55 pm
content: No, I try it as a primary monitor (alone). It only has the standard d-sub (vga) plug.