hybridfree/eevblog-posts huggingface dataset:
Old HP 181A storage scope repair - Page 1
Forum section: electronics / repair

author: DXing
author_rank: Newbie
timestamp: August 03, 2014, 06:42:07 pm
content: Well hello all. I'm just getting my feet wet in the world of old oscilloscopes. I have this old HP 181A that was working pretty well after cleaning all the contacts but then began buzzing and arching. Pulling the covers I found this old ribbon type cable arching. I found a lot of what seems like carbon deposits? I began to clean the ribbon with a Q-tip with IPA and as I lightly brushed it, the ribbon began to delaminate and basically just fell apart. I've attached a photo. Manual lists this as the "HV CONN Block", "P/O A9" where P/O is "part of" A9 assembly. Assembly HP part # 00181-61103. I suspect this is a unique HP ribbon? For those scope restorers out there, any hope of either repairing the ribbon or finding an equivalent part? I guess another old HP 181 part would be just as fragile.

author: tautech
author_rank: Super Contributor
timestamp: August 03, 2014, 08:37:53 pm
content: I have seen a very similar HV cable in old B&W TV sets.How long is it, I might have some in my cable rats nest.

author: DXing
author_rank: Newbie
timestamp: August 03, 2014, 08:52:24 pm
content: Wow, that would be fortunate! Looks like its 6-8 inches. Don't have the tube out yet to see how much further it goes behind the housing, but it's very near the Grid already, so I don't expect it goes much further. According to manual circuit description it seems to be carrying 156 volts to the collector mesh and erase function. Should have tube out soon...

author: DXing
author_rank: Newbie
timestamp: August 03, 2014, 11:34:20 pm
content: This thing wasn't designed for disassembly!but here it is. Pic attached. It's 7 inches, 3 wire. Any chance anyone has seen one of these? Anyone think I could re-laminate with an iron or some kind of adhesive?

author: lowimpedance
author_rank: Super Contributor
timestamp: August 03, 2014, 11:46:06 pm
content: Cannot say I have come across this style before in vintage gear (HP and others), but that may be because I have not had the pleasure of a faulty 181 !.What about just using suitable insulated wire and some tubing ?.Or may be use a document laminator and pouch.best of luck

author: DXing
author_rank: Newbie
timestamp: August 03, 2014, 11:58:02 pm
content: Yep, that was my thought as we'll. although I've been salivating over all the premium parts in this thing as I've disassembled. If it doesn't work out, I can certainly use the parts in other projects, but hoping I can jury rig this, I really liked this four channel scope with great time base/sweep/delay module.

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2014, 12:43:01 am
content: Pic of old CRT TV cable attachedRGB type15 mm wide by 400 mm longIf you really need it I will post it, PM me.
Panasonic SA-HE70 Amp - Page 1
Forum section: electronics / repair

author: tazelikechickn
author_rank: Regular Contributor
timestamp: August 02, 2014, 09:38:17 am
content: Hey Guys,I am repairing a Panasonic SA-HE70 amp, but am having a hard time of trying to find a wiring diagram. I have tried all the usual sites, but can't find that specific model.Can anyone direct me to a schematic for that model?Cheers

author: tautech
author_rank: Super Contributor
timestamp: August 02, 2014, 10:18:37 am
content: This is close:http://www.electronic-circuitry.com/e/DownSys/DownSoft/?classid=61&id=414719&pathid=0They had the correct one but it would not download for me.But also take note of this one, translation needed:http://elektrotanya.com/?q=hu/content/panasonic-sa-he70-sa-he90-f70-hibakod

author: tazelikechickn
author_rank: Regular Contributor
timestamp: August 03, 2014, 08:13:35 am
content: Yeah I tried to download it too previously and it came back as malicious. But thanks for putting me on to the SA-HE75.I was able to easily download a good quality PDF service manual with all the schematics etc., so hopefully I will be able to put the magic smoke back where it belongs!I had seen the other link before, but I have an overload code now after I have fixed the F70. I think I might have done it testing the diodes.Thanks for your help

author: tautech
author_rank: Super Contributor
timestamp: August 03, 2014, 08:39:06 am
content: Good luck with it.The more stuff you search for the more cunning you get with included terms to get the results you need like * to get similar models.

author: tazelikechickn
author_rank: Regular Contributor
timestamp: August 03, 2014, 09:08:13 am
content: Thanks, will keep that in mind for next time.

author: David_AVD
author_rank: Super Contributor
timestamp: August 03, 2014, 09:35:18 am
content: PM me for a link

author: tazelikechickn
author_rank: Regular Contributor
timestamp: August 03, 2014, 10:36:11 am
content: So David are you saying that you have a SA-HE70 service manual with schematics?

author: David_AVD
author_rank: Super Contributor
timestamp: August 03, 2014, 10:19:50 pm
content: It means PM me for a link.
Fluke 189 has beep with LEADS displayed - Page 1
Forum section: electronics / repair

author: johnwhite1000
author_rank: Newbie
timestamp: August 02, 2014, 11:09:53 pm
content: My Fluke 189 meter displays LEADS and beeps when any position except current is selected. I checked the fuses and leads and they are good. Any help would be appreciated.

author: xwarp
author_rank: Frequent Contributor
timestamp: August 03, 2014, 02:45:40 pm
content: Thanks for posting that.I have a 189 and no problems so far.

author: bookaboo
author_rank: Frequent Contributor
timestamp: August 03, 2014, 03:03:57 pm
content: Had this on an 87, dried it with a heat gun but plan to strip and clean it properly someday. Wonder how it affects accuracy even when its not enough to trip the meter into thinking there's a lead attached.
Help me identify stereo amplifier - Page 1
Forum section: electronics / repair

author: dimkovic
author_rank: Newbie
timestamp: July 30, 2014, 02:28:09 pm
content: I'm repairing an old CD/FM stereo player with 2x (8W/4Ohm+3w/4Ohm) speakers. The amplifier integrated circuit is cracked so I can't read the number on it. As far as I can tell pin 1-VCC, 2-R(out), 11-L(out), 12-GND. If it helps near the amplifier there's a transistor D2012.Can someone tell witch IC is this or a replacement for the same speaker configuration. Thanks

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 30, 2014, 02:48:58 pm
content: BA5406?http://rohmfs.rohm.com/en/products/databook/datasheet/ic/audio_video/audio_amplifier/ba5406-e.pdf

author: ctz
author_rank: Contributor
timestamp: July 30, 2014, 02:52:28 pm
content: There are tons of stereo amps in SIP12 like this (starting points: Panasonic AN7156N, Philips/NXP TDA* series).Are there any other markings on the other side of the package?

author: dimkovic
author_rank: Newbie
timestamp: July 30, 2014, 02:55:09 pm
content: I thinks that's the one, thank you so muchWhat do you think, that is the cause of it cracking?

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 30, 2014, 02:57:43 pm
content: Quote from: dimkovic on July 30, 2014, 02:55:09 pmIt's the built in timer that should make you buy a new player

author: dimkovic
author_rank: Newbie
timestamp: July 30, 2014, 03:07:33 pm
content: Thank you anyway
Tape Library PSU failure - KM 88-LCL/PF - Page 1
Forum section: electronics / repair

author: pbgben
author_rank: Contributor
timestamp: July 30, 2014, 04:24:16 am
content: Hey everyone,Some time in the early morning our tape library died, I have narrowed it down to the PSU in the unit but am not sure where to start with fixing it.Have any of you had any issues with this type of PSU before? and give me a few tips? Else I may just mail in

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 30, 2014, 05:16:11 am
content: That is a switch-mode power supply (SMPS, aka "switching power supply") When they are operating, they are great. Small, lightweight, versatile, flexible and efficient.But when they go bad, they are HORRIBLE to work on. Many people with decades of experience wouldn't even dream of trying to diagnose or repair them at the component level. There are a few specialists who have the equipment and experience and information to repair them. For example....That power supply is apparently so popular (and/or blows up so frequently?) that you can even buy refurb replacement units on Amazon.http://www.amazon.com/Samsung-KM88-LCL-Autoloader-supply-KM88LCLPF/dp/B0061YKCF2No offense intended, but if you have to come here and ask what this is, you probably aren't in a position to attempt to repair it.Get a replacement and just swap it out. If there are refurb units available, that would seem to indicate that the "dud" might be worth something.

author: Zucca
author_rank: Unknown
timestamp: July 30, 2014, 07:18:07 pm
content: I agree with the wiseRichard Crowley. If you still have the desire to fix it just to build up some experience in fixing a board the first thing to check is the ESR of those electrolytic capacitors. Here Dave shows how to do that:

author: pbgben
author_rank: Contributor
timestamp: July 31, 2014, 01:08:09 am
content: Thanks for the replies guys,The unit looks like its already been repaired, take a look at the residue on the bottom of the board and also there are CAP's that are different and have also had the "white stuff" cut away.I'm just going to salvage parts from this board, I don't want to mess with the mains until I get more experience.I'll take a look at that video, thanks

author: SeanB
author_rank: Super Contributor
timestamp: July 31, 2014, 08:15:30 pm
content: I would guess the start up supply has gone open circuit. That likely is the load of brown cooked resistors in the middle of the board, and if only 2 go open it will not work. Primary side CrapXon as well, replace those and see if the power devices are not blown and it will work again.
Fluke 77 lucky repair! - Page 1
Forum section: electronics / repair

author: VintageTech
author_rank: Contributor
timestamp: July 30, 2014, 08:30:47 pm
content: A few weeks ago I acquired a Fluke 77 that was not working. Naturally, I took it apart, hoping to find something obliviously wrong. After several hours of poking around with my other multimeter, I decided to try to re-solider the SMD chips. And then... it worked! The only thing that doesn't work is the diode/continuity tester. Does anybody know why that is?So, if any electronic device is not working, check the solider joints. Unless something is obliviously broken.Thanks for reading my long and pointless post!-VintageTech

author: retiredcaps
author_rank: Super Contributor
timestamp: July 30, 2014, 09:37:21 pm
content: Quote from: VintageTech on July 30, 2014, 08:30:47 pmBy not working do you mean it doesn't make a sound/beep when you do a continuity test? If yes, make sure the contacts for the buzzer are clean on the backside of the pcb (two solder dots behind the range switch).

author: VintageTech
author_rank: Contributor
timestamp: July 30, 2014, 10:01:51 pm
content: It just starts beeping when I try to test something then doesn't stop. The contacts are clean and there seem to be no issues with the surrounding circuitry. Also, this seems to be an intermittent issue as It went away then came back. It seems to have gone away... at least for now.

author: lowimpedance
author_rank: Super Contributor
timestamp: July 30, 2014, 11:49:48 pm
content: Perhaps the PCB needs a good IPA clean with a brush (a tooth brush work well) , even if it actually looks clean now.My first DMM was a 77 and is still going strong, and most likely long after I am gone!!.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 31, 2014, 04:53:25 am
content: Quote from: lowimpedance on July 30, 2014, 11:49:48 pmI concur with an IPA bath. Tips from modemhead ...http://mrmodemhead.com/blog/dirty-multimeter-clean-up/
TI 83 calculator - broken screen - Page 1
Forum section: electronics / repair

author: Bodgewire
author_rank: Newbie
timestamp: July 30, 2014, 05:01:59 am
content: Just picked up a ti-83 off the side of the road. Since it's halfway through the summer, I imagine some recent highschool grad may have celebrated by throwing it out the car window. Totally smashed up and "crusty". The LCD is broken, but I measured 6 volts on the LCD module. Presumably, nothing else is broken. I know the flex ribbon can be hacked with mod wire, but not finding any replacement lcd's online so I'm wondering if there are any interesting hacks that can utilize the existing circuitry. Anyone have any ideas on this one or is it trash? I hate to throw away a great device like this, but maybe not worth the effort.

author: miguelvp
author_rank: Super Contributor
timestamp: July 30, 2014, 05:21:49 am
content: If the screen view connector is still functional you can get the projection screen displayhttp://www.ebay.com/itm/like/400289458350?lpid=82not sure if it needs software too

author: amyk
author_rank: Super Contributor
timestamp: July 30, 2014, 09:18:48 am
content: http://ripitapart.wordpress.com/2013/03/02/making-use-of-an-old-ti-83-plus-lcd-screen/According to this, any LCD module compatible with Toshiba T6A04/T6K04 should work.

author: Vgkid
author_rank: Super Contributor
timestamp: July 30, 2014, 10:28:23 pm
content: You could always search ebay for a multitude of TI-83 parts donors.
DS-1052E Frequency Adjustment - Page 1
Forum section: electronics / repair

author: Po6ept
author_rank: Regular Contributor
timestamp: July 29, 2014, 06:42:51 pm
content: After reviewing the "service manual" for the DS-1052E, I am still in the dark about how to adjust the internal frequency reference. The scope reads all frequencies a bit low and I would like to calibrate it to my 10 MHz standard.I thought I'd ask on here because I hate to take it apart if the oscillator is not adjustable - or if it drifts enough that I'd be wasting my time.Thanks!Bob

author: Matje
author_rank: Regular Contributor
timestamp: July 29, 2014, 10:47:35 pm
content: Quote from: Po6ept on July 29, 2014, 06:42:51 pmIt is unlikely there is anything to adjust, it probably just has a bog standard crystal as frequency reference.Any device meant to actually have an accurate frequency reference will have an input for one, nowadays for 10 MHz, so you could just plug in your ref. signal, alternatively these will contain a quite expensive OCXO.Oscilloscopes (at the low end at least) are not meant to be used to actually measure stuff (as in well-defined high accuracy, low drift etc.) anyway, see the specs for that.

author: Po6ept
author_rank: Regular Contributor
timestamp: July 30, 2014, 07:08:40 am
content: Thanks for the reply. It's not that far off but I figured if I could get it on frequency a bit closer, I could take my equally inaccurate frequency counter off the bench.Bob

author: tautech
author_rank: Super Contributor
timestamp: July 30, 2014, 07:34:25 am
content: Typical frequency counter accuracy of low cost DSO's is + or - 0.01%.This can account for noticeable error at high frequencies.DSO's shouldnotbe considered as a high accuracy frequency counter.

author: Po6ept
author_rank: Regular Contributor
timestamp: July 30, 2014, 08:05:46 am
content: Quote from: tautech on July 30, 2014, 07:34:25 amI fully agree. I have high accuracy and precision test equipment for the tasks that need it. Still, if the frequency adjustment was available it would be worth doing.
1979 Rank-Arena (NEC) no raster - Page 1
Forum section: electronics / repair

author: C_Munns
author_rank: Newbie
timestamp: July 28, 2014, 08:59:52 am
content: Hello there people of the EEVBlog Forum!I have a 1979 Rank Arena which isn't happy with me at the moment, I had it working one morning, then I came home to it with no raster and just a grey screen with electrical noise coming through the speaker! I suspect it's a dead IC as the tuner and everything else seems fine.Help would be appreciatedThanks

author: wagon
author_rank: Frequent Contributor
timestamp: July 28, 2014, 01:27:53 pm
content: Get yourself a service manual / schematic for the old dear and get to work! I would expect lots of bad electrolytic capacitors and such, for a start. If you inject composite video in (at the output of the tuner) do you get a picture?

author: C_Munns
author_rank: Newbie
timestamp: July 29, 2014, 02:56:55 am
content: I'd get a service manual if I could, but there is no information on the Rank-Arena C-2616I haven't tried feeding composite into the tuner yet, but the capacitors may be a problem

author: vk6zgo
author_rank: Super Contributor
timestamp: July 29, 2014, 04:58:59 am
content: A neat trick to see if you have EHT is to turn the TV on,wait a few seconds,then place your forearm close to the front of the screen.If the set has EHT,the hairs on your forearm will be attracted to the TV screen & stand up.The reason for the short wait is that at switch on the initial transient,even with a faulty line output circuit is often sufficient to cause a brief appearance of EHT.

author: C_Munns
author_rank: Newbie
timestamp: July 29, 2014, 06:13:12 am
content: Looks like we have functioning EHT
KEPCO BOP 36-12M Bipolar power supply /Need Help in trouble shooting - Page 1
Forum section: electronics / repair

author: mash
author_rank: Newbie
timestamp: August 01, 2014, 07:36:39 am
content: Hello Everyone,I am using a Bipolar power supply (KEPCO BOP 36-12M) from last 6 years. Actually it was a part of test setup, in which this power supply was configured/interfaced to a computer & always operated remotely with some measuring software.Every time we simply start the test from software in computer & just switch on the main circuit breaker of this power supply. That's it, automatically as per the program in software, power supply will vary the output from 0V to -30V to +30V to 0V. Then we get the results in software.But, recently we got a problem with this KEPCO BOP 36-12M power supply. If we switch on the main breaker, Immediately voltmeter needle going to maximum& full out put voltage coming continuously (without any command from software). I have attached some pics below.Also, all the manual controls of the power supply are not responding & in remote software, it was showing power supply not ready.So, some settings were changed or some thing else.Is any one know about this type of issues. Please help.

author: mash
author_rank: Newbie
timestamp: August 01, 2014, 07:59:41 am
content: To verify the Kepco 36-12m individually, I have removed the Kepco 36-12m from test rack by removing all the rare connections.Then by giving only input power connection, switched on the front breaker. Again same thing. The volt meter showing maximum voltage immediately. Manual controlls are not working.How to get it to normal condition??? Please Help.

author: tautech
author_rank: Super Contributor
timestamp: August 01, 2014, 08:24:40 am
content: Sounds like a failure to regulate, that could result from a number of causes.Failure of the series pass transistors is a possibility.Getting a schematic is your first task.They are available:http://www.kepcopower.com/bopbuy2.htm#manBut at $75 ouch.This one has block diagrams that may be helpful, but a schematic is what you need.http://sites.fas.harvard.edu/~phys191r/Bench_Notes/E2/bopfull.pdf

author: SeanB
author_rank: Super Contributor
timestamp: August 02, 2014, 07:14:37 pm
content: Most likely pass transistors or drivers are short circuit. Less likely is dry joints on the wiring so the base of the driver is open circuit, where the leakage will drive it to full.
Small Knobs For Graphic Equalizer - Page 1
Forum section: electronics / repair

author: German_EE
author_rank: Super Contributor
timestamp: July 26, 2014, 09:48:00 pm
content: I have a graphic equalizer on my bench that I've just repaired. Electrically everything is now OK but the knobs are missing from some of the sliders, and this is where the fun starts.The sliders are 15mm apart and each knob is 6mm x 8mm with a snug fit on the 4mm shaft. Lots of people sell slider knobs but they are all TOO BIG, the average being 25mm x 16mm, and the only ones I can find are these:http://www.rapidonline.com/mechanical-fastenings-fixings/cliff-cs11-push-button-slider-knobs-539017Does anybody know of a source ofsmallslider knobs, rectangular in shape, that can fit a 4mm shaft? Normally I'd head to the manufacturer's website but they went out of business years ago so this is not an option. So far I've tried RS Components, Digikey, Mouser, Futurlec, Rapid and Radio Shack.

author: Psi
author_rank: Super Contributor
timestamp: July 26, 2014, 11:18:20 pm
content: Maybe have a look in the digikey/mouser section for tack buttons accessories etc.You can buy small plastic caps for tack buttons that maybe the size your after.You might have to manually drill the inner hole a little bigger, but that wont be noticeable in the finished result.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 27, 2014, 03:39:55 am
content: http://www.ebay.com/itm/Vintage-EQUALIZER-MIXER-10-pcs-Black-SLIDER-KNOB-clean-good-cond-/271556088253?pt=Vintage_Electronics_R2&hash=item3f3a0111bdMeh, won't ship outside the US, but it's a start.I just searched for slider knob, maybe you can just replace all the knobs ?

author: German_EE
author_rank: Super Contributor
timestamp: July 27, 2014, 10:00:43 am
content: Yeah, well, he only has ten of them and I'll need 32 if I am going to replace the full set, plus he only wants to ship within the USA (so why advertise on a global shopping website). There are lots of knobs on Ebay but most of them seem to be for the full size sliders and are 25mm long and 11mm wide, too big.One suggestion I received off-board was to approach the local Maker Lab and get 32 knobs 3D printed, that might be a viable option as they might be able to do all 32 of them in one pass.
LeCroy 9414 Gain/Convergence Error - Page 1
Forum section: electronics / repair

author: davorin
author_rank: Unknown
timestamp: July 26, 2014, 07:17:23 pm
content: Good evening...Just acquired a broken 9414 DSO which shows after self calibration following error when showing the error log:Code:Ch1 Ch2 Ch3 Ch43000 1000 0 0For the 0.1V range...Interesting is the fact, that when showing the DAC constants the values of dac0 - dac3 for Ch2 are constantly changing...Applying a square wave signal shows it correctly for Ch1, Ch3 and Ch4, but Ch2 is non-visible, e.g. to high offset, even when choosing GND for Ch2.Something easy to fix with readjustments?

author: davorin
author_rank: Unknown
timestamp: July 27, 2014, 04:10:24 pm
content: This is weird...after my Fluke 606A/AN has repaired himself....Just tried out my new F82357 adapter under Linux to see how it works and if it is possible to make screen dumps not only from traces but also from menues...Reading through the 9400 remote programming manual I saw that it also support calibration via GPIB...and it returned "0" both for *CAL? and *TST?...Now with a quick test all channels are working nicely...and no more errors as it can be seen on the screen dumps...
Home calibration of HP 3456A - Page 1
Forum section: electronics / repair

author: resistor
author_rank: Regular Contributor
timestamp: July 25, 2014, 06:09:11 am
content: Hi all,I got a deal on a "broken" HP 3456A on eBay that ended up only having a dead capacitor in the power supply. Now that I have this spiffy piece of equipment, I'm concern that it probably need to be recalibrated (power rails may have shifted slightly with the new cap, etc). But my cursory research seems to indicate that getting it professionally calibrated is both out of my budget, and overkill for my hobbyist needs.So, the question: is it plausible to calibrate this device at home? At least to a reasonable level?

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 25, 2014, 07:57:47 am
content: No chance.(This has been discussed several times here, already).For a proper calibration, you need a calibrated reference for each cardinal point and for all modes, i.e. 100mV, 1V, 10V, 100V, 1kV DC and AC, 100 Ohm, 1k, 10k, 100k.. and so forth.That means, you would need an expensive calibrator, which itself has to be calibrated.Those pseudo solutions, buying those cheap 5V or 10V cheap reference PCBs, plus one resistor plus one current source may calibrate one or a few ranges and modes, but that has nothing to do with real 'calibration' of the instrument..Frank
Analog discovery broken micro USB port - Page 1
Forum section: electronics / repair

author: R_G_B_
author_rank: Frequent Contributor
timestamp: July 24, 2014, 09:48:10 pm
content: Can anyone help the Analogue discovery board USB port is not solders on the board on my board at least. I only discovers this when I tried to insert a cable into the miro USB slot and the port dislodged bits self.I tried to resolder it to the board. With no sucess also the micro USB port only has two pins for the differential data. I would like to get this problem fix please if anyone can help. I upload the pcb image.

author: thm_w
author_rank: Super Contributor
timestamp: July 24, 2014, 10:18:23 pm
content: I can't tell from your photo but it looks like the data traces are torn and side ground pads are ok. You will have to resolder it and run some thin jumper wire from each pin to the component the signal needs to connect to. This can be quite difficult without the appropriate equipment (small soldering iron tip, good flux, magnifying glass, etc.)Or ask manufacturer for an RMA.

author: R_G_B_
author_rank: Frequent Contributor
timestamp: July 25, 2014, 07:27:02 am
content: Looks like I'm going to have to send it back. Hope its still in warranty.
Please Help - Alesis MEQ230 graphic eq - Page 1
Forum section: electronics / repair

author: swampwasp
author_rank: Newbie
timestamp: July 23, 2014, 04:36:37 pm
content: Greetings everyone! Im a total newbie here my first postId really appreciate some help as i have tried everything i know (very little)..http://www.alesis.com/meq230(mines form 1989 i think!)i have no idea what happened to it, it doesnt turn on. didint get a charger with it.i takes 9v AC so i modded an ac/dc adapter, made sure i got 9vAC out of it and tried that..no response.opened it up and took everything apart, no damaged/blackened parts or pads. the caps look OK - completely fresh (looking), flat tops. (Fed it 9vAC when disassembled and tested the power jack, Its OK and powering the board and components etc.not sure what to do next! any idead what might need fixing??i dont own an oscilloscope, just a crappy multimeter but might get access to one.Cheers!

author: paulhm81
author_rank: Regular Contributor
timestamp: July 23, 2014, 06:03:32 pm
content: hellofirst thing I would check is the output of the two voltage regulators. The 7912 should output -12v and the 7812 should output +12v. The output pin on both of them is pin 3. Next I would check the relay. Do you hear a click when you turn it on?

author: Anks
author_rank: Frequent Contributor
timestamp: July 24, 2014, 11:35:51 am
content: Ive fixed loads of Alesis gear over the years and normally when it wont turn on its because the previous owner lost the PSU and tried one that was so incorrect it took out the voltage regulators. Some Alesis is very fussy about the voltage and as such can be a paint to find a universal PSU to work as well as it being run from AC. Also check the diodes as these tend to go as well.The reasoning a Alesis tech gave me for the AC was based on common mode rejection due to everything in a rack normally being balanced. That being said most things in a outboard rack normally take the 240 or 120 from the wall and deal with dropping and isolation inside the unit. A more feasible reason would of been the need for a positive and negative supply like that used for mixers.Other things that Ive seen but this is normally on the Quadaverb Miniverb units and off the top of my head cant remember the MEQ230 is that there is normally two big dropper resistors that tend to get hot and go open.Ill have a better look at the pics and see if anything jumps out at me.
Venom Dual 2-10 Amp Lipo Charger? - Page 1
Forum section: electronics / repair

author: Technoman
author_rank: Newbie
timestamp: July 22, 2014, 02:16:13 am
content: Hey folks! This is my first post here and I don't know if any of your are familiar with Lipo chargers for Remote Control Helicopters but it shouldn't matter I don't suppose.The problem I'm having is this.... I plugged in a 4 cell Lipo battery to port 2 of my Venom Dual 2-10 Amp charger yesterday and I heard a tiny pop. Since then the charger gives a broken connection error message.I've taken the case apart to look inside to see if there was something obviously wrong with the charger but found nothing.Where do I go from here?There are some fairly large capacitors on each port and I wonder if the one on port 2 might have failed.Or maybe I should look elsewhere?I've fixed a few things on circuit boards long as someone can point me in the right direction or if there is something obviously burned out. I don't know a lot about tracking down an issue when none is apparent.Any help would be greatly appreciated.

author: Flump
author_rank: Frequent Contributor
timestamp: July 22, 2014, 02:44:34 am
content: some good internal pictures of both sides of the circuit board would help

author: Technoman
author_rank: Newbie
timestamp: July 22, 2014, 09:17:38 am
content: Here are some pics. Let me know if another angle is needed. Thanks.

author: Technoman
author_rank: Newbie
timestamp: July 23, 2014, 02:30:32 am
content: Now both ports in the charger are dead. I plugged a battery in this evening and heard a tiny pop just like port 2 did and now I get a broken connection error message on port 1 as well.I think I may have some blown mosfets. I took the heat sink off this evening and I can see two areas of the board that have gotten pretty hot. There in the same place on each port. Each spot has a cluster of 4 MOSFETS.Can I test those in the board? I'm getting a reading on some of them after opening the gate but not all of them. I can't get my pics to load now. I'll try again later.If you look at the 2nd pic on the back of the board there are 2 dark areas. The mosfets are on the other side of the board in those dark areas.

author: Technoman
author_rank: Newbie
timestamp: July 23, 2014, 09:51:36 am
content: Here are the pics with the heat sink off. You can see the two dark areas surrounding the Mosfets.Both sidesRight SideLeft side

author: amyk
author_rank: Super Contributor
timestamp: July 23, 2014, 12:05:30 pm
content: I don't see any images...

author: Refrigerator
author_rank: Super Contributor
timestamp: July 23, 2014, 01:45:45 pm
content: No pics, mate. Better get em up quickly, i want to see those boards.

author: Technoman
author_rank: Newbie
timestamp: July 23, 2014, 11:13:47 pm
content: Can I upload the pics here are do I have to have them uploaded elswhere?I can see them here, I guess they are blocked somehow?
Laptop audio jack replaced but sound comes out of speakers when jack inserted - Page 1
Forum section: electronics / repair

author: istimat
author_rank: Newbie
timestamp: July 23, 2014, 06:54:19 am
content: Hi! So I replaced an audio jack in a laptop and it appears as if the replacement jack has a normally open instead of normally closed contact (or the other way around because I didn't think to check before replacing it.) and now the built in speakers only work when there is a jack inserted. Is there a possibility that there are NC and NO switched audio jacks? Or did I do something else wrong?Another thing then: I could see on mouser for example that there is a jack with an "exclude leg" so is there such a thing as an include leg?

author: istimat
author_rank: Newbie
timestamp: July 23, 2014, 10:28:04 am
content: It has the internal switch but I'm guessing it's not NC but NO or the other way around.

author: amyk
author_rank: Super Contributor
timestamp: July 23, 2014, 11:26:57 am
content: Find the schematic and check what it is.
hp 54645A  ROM - Page 1
Forum section: electronics / repair

author: warmaq
author_rank: Newbie
timestamp: July 24, 2014, 03:39:05 pm
content: I'm looking for firmware hp 54645A. I need name/type 2 chip DIP32 and hex.Regards

author: NickAmes
author_rank: Contributor
timestamp: July 26, 2014, 04:00:39 am
content: I took a firmware image of my HP 54645Dbefore I sold it. I'm not sure if it's correct, as the reader was very jury-rigged. Maybe it will be useful to you. The EPROM part numbers were AM27C040-150DC.
HP 6200B - Page 1
Forum section: electronics / repair

author: v1t0r
author_rank: Contributor
timestamp: July 22, 2014, 07:14:28 pm
content: Hi.I'm trying to find a more common substitute for 1n5059, to repair my HP 6200B power supply.Does anyone know an ideal replacement?Thanks

author: grumpydoc
author_rank: Super Contributor
timestamp: July 22, 2014, 07:32:41 pm
content: http://uk.farnell.com/nte-electronics/nte580/standard-diode-3a-600v-axial/dp/4525966?Ntt=1n5059&whydiditmatch=rel_default&matchedProduct=1n5059
(Solved) Problem charging Samsung Note 10.1 GT N8013 , trouble shooting ideas? - Page 1
Forum section: electronics / repair

author: Rick Law
author_rank: Super Contributor
timestamp: July 21, 2014, 03:00:41 am
content: (Edit: Solved!)I need some trouble shooting suggestions on a Samsung Note 10.1 GT N8013 tablet. My kid got an "open box" new machine off eBay, all is well except it charges very slow.I made a USB breakout to see what is going on. The break out is clean USB male (into the charger) straight connection to USB female which in-turn connects to the Samsung USB cable into the machine. On the V+, I connect male to female via a 0.1ohm shunt to measure current. The other three lines are pain straight connection from male to female. The USB female than connects to the regular Samsung USB cable into the machine.Using the supplied Samsung charger (5v, 2A), it is taking in 85mA. The charger looks new and unused.Tried three different regulated wall-wart and connect that to my USB break out (which then connects to the Samsung USB cable to the tablet), it takes in 84-85mA.Tried an adjustable CC/CV board, it takes in 84-85mA.Connected it to a PC (powered down but this PC continues to provide USB power), again, 84-85mA.Unless it is meter over-shoot, I see that right at the start, it takes in more current for fractions of a second then drop to 85mA. If I "pulse it" a bit by quick connect/disconnect (by fiddling with the gator clip on the shunt to break/reconnect the power), it took in 200-300mA but the X over the icon said it is not charging while my shunt is telling me over 200mA is going through the shunt (varies on different tries, once it took in 400mA-ish).At this time, since different 5V supply were tried, I think the charger is ok but the fault is either the cable or the tablet.I am thinking IF I can get a new cable locally, I can try that and see if any it makes a difference. If it is not available locally, I don't have enough time to mail order one since if I must return the machine, I must act within a week or so.Any ideas on other things to test?Thanks...RickEDIT: I was able to locate a store locally (I had my concern if I can find one). Turns out to be the USB cable. The Samsung cable it came with doesn't work. Using the Samsung 2A charger and after market cable, it is charging at 1.7Amp instead of 84mA.On a side note, when using non-Samsung charger like a plain wall-wart, shorting the D+/D- doesn't work. D+ and D- both measures 1.2V during charge. On a quick test, tie them together at 1.2volt does not seem to trigger charge either. Perhaps I will experiment more with that.

author: urbis
author_rank: Unknown
timestamp: July 21, 2014, 03:49:09 pm
content: Hi Rick,Some tablets require the two data lines to be shorted to charge at "high speed".Does this have the original Samsung cable and charger with it?Just a thought...

author: urbis
author_rank: Unknown
timestamp: July 21, 2014, 03:50:01 pm
content: Just noticed this isn't Micro USB - ignore me.
Arcade Machine Switchmode PSU Troubleshooting - Page 1
Forum section: electronics / repair

author: Womble76
author_rank: Newbie
timestamp: July 21, 2014, 05:47:43 am
content: Long term EEV blog viewer but first time poster here, my hobby is mainly arcade PCB repair which I have been doing for about 5 years now. Unfortunately my test bench arcade PSU let the magic smoke out recently, and vaporised its fuse. The fuse didn't just blow, it was totally destroyed, just the end-caps remain and glass dust.I was hoping to fix it as it is one of the older ones and seems much better built than the flimsy modern ones available.Ignore the resistor lead that looks like its bent onto the power transistor, that's a leg I lifted during troubleshooting and the angle of the photo is deceptive.What is bugging me is the sheer amount that seems to be wrong with it, half the bridge rectifier diodes are short circuit, which is what I assume blew the fuse, and there is a lump blown out of the surge suppressor resistor, which I guess occurred before the fuse opened.So far so good, but a number of other resistors throughout the unit are also totally short circuited, without a mark on them, from a couple of quarter watt ones, up to some of the 1 watt ones. Am measuring these out of circuit (one leg lifted) by the way.The only build issue seems to be cracked joints on a single decoupling electrolytic on the output of a 7805 but I doubt that had anything to do with the cascading failure due to where it is located. All other electrolytics seem fine based on their ESR anyway.My question is actually whether anyone more familiar with switch mode PSUs has come across failures like this? It seems unlikely that so many resistors would go totally short circuit without any physical signs of trauma. None of the transistors or voltage regulators appear to be shorted so am also curious as to what was the first failure that set off what looks like a chain reaction.Any advice would be appreciated, beyond the obvious "bin it", which is a conclusion I am almost at anyway.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 21, 2014, 06:24:49 am
content: Lightning?If the transistor dies, lots of things can go. Assume it goes three-way-short, and you'll see transients in the 100s of V on the base terminal.Neat, it's a HOT. 500Vceo, 1500Vcbo, 5A, 2MHz. Guessing a self-excited (blocking) oscillator. Not sure what the white block is, maybe more brains in there. Probably not much on the board otherwise, anyway, so on the upside, not much to replace; downside, replace ~everything.Tim
Circuit Breaker for Paper Shredder - Page 1
Forum section: electronics / repair

author: DomesticHacks
author_rank: Regular Contributor
timestamp: July 23, 2014, 05:51:48 pm
content: I have an old paper shredder where the cap went bad and while replacing the old one i noticed, that the circuit breaker lost it's button.Not a problem, I replace it, but the amp value was written on the lost button.Its an older version of this one:http://www.e-t-a.de/produkte/schutzschalter_sicherungsautomaten/thermische_schutzschalter/p/2-5700/Since I have not that much experience with bigger machines running on mains voltage I have no idea which amp value to choose.I attached an image of the specification plate and my questions are:- What value for the circuit breaker should I choose?- And just out of curiosity: What is the relation between the 0.3kW and the 3A ? Since this isn't just W = V * A

author: SeanB
author_rank: Super Contributor
timestamp: July 23, 2014, 06:32:26 pm
content: 3A breaker will do. The 3A and the power of 0.3kW is because the motor is mostly inductive and has a lagging power factor. It will draw an apparent power of around 600VA, and a real power of around 300W. The breaker will likely be a thermal breaker, as these will handle the switch on surge of the motor fine but will trip in a few seconds if the motor is stalled.

author: DomesticHacks
author_rank: Regular Contributor
timestamp: August 04, 2014, 09:40:59 pm
content: Thanks, I ordered the 3A one.
Quick fix: Fluke 115 DMM - Page 1
Forum section: electronics / repair

author: gel_banana
author_rank: Newbie
timestamp: July 18, 2014, 08:15:52 am
content: Hi guys, This is my first post here. Though I shared my quick repair job that I've done last night. I received a non working Fluke 115 DMM from my dad's acquaintance. I though it was just a dead battery. But turns out the battery has leaked out and corroded the contact tabs.So I thought I'd tried replacing it with a 9v battery cap. I've got lucky that the battery fits in snugly.Works like brand new. Just have to take note of the wires being pinched down.

author: saturation
author_rank: Super Contributor
timestamp: July 18, 2014, 05:27:28 pm
content: Good job. I rarely see 9V batteries leak so this is first for me seeing that corroded terminal.

author: darko31
author_rank: Regular Contributor
timestamp: July 18, 2014, 06:55:39 pm
content: +1 Nice job. Now use quality alkaline batteries, it's a nice Fluke.

author: GreyWoolfe
author_rank: Unknown
timestamp: July 18, 2014, 09:18:06 pm
content: , good job. I agree with darko, don't use crappy batteries. Name brands only and your meter will serve you well.

author: sfiber
author_rank: Regular Contributor
timestamp: July 19, 2014, 12:08:52 pm
content: I use gp alkaline on ut61e and after 1 year it still work properly.Please be nice to GP O0.what a wonderful input protection fuse there.

author: gel_banana
author_rank: Newbie
timestamp: July 20, 2014, 02:18:09 am
content: Thanks guys. But I've stopped using alkaline batts for a while now. Now I've mostly stocked up on GP dry cell. They are fairly cheap about a dollar each.
elenco xp800 - Page 1
Forum section: electronics / repair

author: ijchan223
author_rank: Contributor
timestamp: July 19, 2014, 08:25:11 am
content: hi guys , i acquired a elenco xp800 from a repair shop when they shut down . The power supply is missing the DC output cap (c6). According the the Manual i have it calls for 77000-123000 uf however it doesn't list the voltage. what is the minimum voltage cap i need? Logic says 30v is the min i need to run, however because caps aren't cheap i would like to confirm that i don't need something larger.http://www.manualslib.com/manual/235996/Elenco-Electronics-Xp-800.html?page=7#manual

author: mij59
author_rank: Frequent Contributor
timestamp: July 19, 2014, 08:52:04 am
content: Hi,Are planning to use the 10A rated output current ?If the output is 0-28 Vdc you'll need at least 35V caps.

author: ijchan223
author_rank: Contributor
timestamp: July 19, 2014, 04:55:02 pm
content: Yes i am planning to use all the existing circuitry. Thank you very much, i knew i would screw the minimum value I needed.I would have tried to crammed a 60v cap in there to be safe, but the only reason i didn't do so because they are huge and expensive.

author: mij59
author_rank: Frequent Contributor
timestamp: July 19, 2014, 05:23:22 pm
content: Quote from: ijchan223 on July 19, 2014, 04:55:02 pm100000uF 50V at Digi-key 565-3323-ND about 25 Euro ex VAT and shipping.100000uF 35V at Digi-key 565-3314-ND about 18 Euro ex VAT and shipping.Just do a parametric search of what you need.

author: ijchan223
author_rank: Contributor
timestamp: July 19, 2014, 08:58:33 pm
content: Thanks for part suggestion, I found one locally that will work. I just need to make some new brackets to hold it into the housing and i would be in business. The original brackets are tiny, like 2 inch wide at best, not sure what type of magic cap they used back in the day but i have a feeling it was way smaller than what is in the manual
Metcal MX5000 repair - Page 1
Forum section: electronics / repair

author: oliver602
author_rank: Regular Contributor
timestamp: February 04, 2014, 09:17:01 pm
content: Just payed over the odds for a broken Metcal MX5000 (silly me). Powers up, detects whether or not a handpiece is connected with tip, but doesn't warm up. Just shows 'Ready'. Looked inside and someone has replaced a LM2576 which made fire judging by the adjacent burn marks on the inside of the enclosure.Anybody got storys, tips or advice? Or a proper manual would be very handy(I see a calibration menu)? My google skills really don't seam up to the task. I've only been able to find a very basic manual. I can't even find teardown photos to compare.Oliver

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 04, 2014, 09:18:21 pm
content: I think the circuitry isn't too different to the 500, for which there is a schematic available.

author: quarros
author_rank: Regular Contributor
timestamp: February 04, 2014, 09:22:56 pm
content: Here is a link to the schematic:http://www.mikrocontroller.net/attachment/193474/MX-500P-11.pdf

author: Metcalman
author_rank: Newbie
timestamp: April 28, 2014, 09:45:05 pm
content: Contact Technical Support 714 799 9910, it may still be under the 5 year warranty.

author: oliver602
author_rank: Regular Contributor
timestamp: July 19, 2014, 03:59:06 pm
content: Thanks for the info.Maybe someone else will have luck fixing it or of interest to someone experimenting with DIY Metcal supplys. I've listed it on ebay UKhttp://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=251593198053. My electronics knowledge is too primitive. I haven't changed any components, evidence someone else tried before me.2 boards in this MX5000, main power supply (24V and 48V out if I remember) shows good voltages on a DMM. Second board with MCU and display shows damage around a switching regulator. The MX5000 was showing steady 13.56Mhz on the selected hand piece output with iron attached till the switching regulater literally exploded like a gun shot. Output was unstable after that. Photos on ebay listing.Thanks
HP 5326B Voltmeter Assembly Repair - Page 1
Forum section: electronics / repair

author: merox
author_rank: Regular Contributor
timestamp: July 18, 2014, 05:08:02 pm
content: Hi folks,i've got an old HP 5326B frequency counter laying around in my cellar which I bought a few years ago on ebay.The frequency-counting part works perfectly fine, but unfortunately the voltmeter assembly is broken. This assembly is used show the trigger level and it also turns the device into an 4,5-Digit voltmeter. The assembly consists out half a dozend ECL-chips, which are next to unobtainable by todays measures.To repair this assembly I need one MC1014P (Dual R-S Flip-Flop - Positive Clock) and one MC1033P (Dual R-S Flip-Flop - Single Rail, Negative Clock). Can anybody give me a hint how I could possibly replace those chips? I've been looking around on eBay for quite some time, the MC1033P is available for about 12 bucks (excl. shipping to germany), but the MC1033P seems to be completely unobtainable.So my questions are:Does anybody have those chips laying around, willing to sell them to me for a small amount of money + shipping?Does anybody know about some russian equvalent chips?Does anybody of you have experience in recreating these chips?(I hope my english isn't too bad, i normally only talk to people from china and india)
BK 1535 Oscilloscope Repair - Page 1
Forum section: electronics / repair

author: mzinicola
author_rank: Newbie
timestamp: July 17, 2014, 03:10:52 pm
content: Does anyone have the schematics for the BK Precision 1535 O'scope that they can send me? My scope has a focus problem and I would like to repair it. Thanks.

author: tautech
author_rank: Super Contributor
timestamp: July 17, 2014, 08:04:50 pm
content: Google search found it:http://elektrotanya.com/bk-precision_1535a_2x5mv_35mhz_delayed_oscilloscope_sm.pdf/download.html