hybridfree/eevblog-posts huggingface dataset:
Tektronix 11403 repair, errors G3611 & G3711  - Page 1
Forum section: electronics / repair

author: Satbeginner
author_rank: Regular Contributor
timestamp: July 08, 2017, 11:26:07 am
content: Hi all,I found myself a good looking -but obviously not working- 11304A scope with a 11A52, an 11A72 and a 11T5H plug-in.The physically good looking mainframe powers up, and seems responding to all the buttons and settings, but..... the power-on diagnostics gave several errors on both the mainframe as well as the plug-ins.I removed the plugins, and it seems the type of errors from the plugins are strongly related to the errors on the mainframe.The mainframe errors are in the AD converter, or at least in the read-out of the AD converter.I found there is communication between the big acquisition board and the data-processing board y means of a series of flat cables.When placed on it's left side, the bottom flat cable is the one bringing the data from one board to the other one.On the acquisition board ECL technology is used (dual D-type ECL Flip Flops MC10H131), on the data board these signals are converted into TTL by means of ECL->TTL (MC10125) converters.When I run the AD Converter Voltage tests (+0,8V, 0,0V and -0,8V) the readout is always 0,034V, this could mean the AD converter is dead, or the communication between the AD board and the data board is wrong. (I hope for the latter...)When I remove that particular flat cable, the readout is always 0,1024 V, so that suggest the processing of the data is still working?It is supposed to be a 10bit AD converter, so I think the values will go from -1024 to +1024 ?I found that some of the ECL outputs have wrong levels, so I removed the faulty FlipFlops, and to be sure, I also removed the corresponding ECL-TTL converter.I ordered these parts, so now I have to wait until they arrive, I placed sockets on the boards so it will be easier to replace the chips when they arrive.For now I have some questions:Are there any schematics for this scope floating around somewhere?Are there people with some experience on repairing these scopes that I can share experiences with?Further updates follow when the parts arrive.Un saludo,Satbeginner (Leo)

author: Johnny10
author_rank: Frequent Contributor
timestamp: July 11, 2017, 12:41:08 pm
content: I have an 11402A Unit and 2- DSA602.The 11402 has same issue as yours but I haven't messed with it since it failed.I believe when I first got the unit I ran it with the covers off and per instructions the ADC overheats and goes bad.Did that myself!eBay has a service manual which I would grab if it were me.https://www.ebay.com/i/300868211640?chn=ps&dispItem=1The DSA 602 doesn't have a service manual available which makes it difficult to diagnose and repair.I have repaired the DSA 602 Ram pipeline error.The plugins are probably fine.Failures were listed on self test in 11402 unit but when using the 11000 plug-ins in the DSA 602 all were fine and they all passed Enhanced Accuracy also.Good Luck, Maybe I will pull out the 11402 if you find some success.Actually after writing this reply I bought an 11402 service manual on ebay.
Need to find dual-row 16-pin FCP connector for Fujixerox CM2015FW Mainboard - Page 1
Forum section: electronics / repair

author: DukeOfEarl
author_rank: Newbie
timestamp: July 10, 2017, 04:05:10 am
content: Hello,I hope someone here has a good eye and can tell me what model this FCP connector is and where to source it. It is severely bent off the PCB and while the multimeter tells me the pins still connect through it doesn't seem to work anymore.Searching on Element14 and Mouser I haven't found anything that looks like it matches.The component is marked SJ16 and the board is marked GR001_ESS_EL_MainBoard.See attached picture - thanks in advance!

author: amyk
author_rank: Super Contributor
timestamp: July 10, 2017, 10:42:49 am
content: I see what looks like a logo at the right edge, but it's not clear enough to identify.

author: DukeOfEarl
author_rank: Newbie
timestamp: July 11, 2017, 04:35:59 am
content: I couldn't actually make out what it said myself...
TEKTRONIXS 2430A low voltage PSU problem? - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 12, 2017, 06:54:32 pm
content: Last winter I took it apart after someone here realized one of the channels vertical gain was busted(I think Ch1). I thought it was a setting I had "clicked on" or something, but I knew something was wrong after not being able to turn it back to normal.It's a used ebay TEKTRONIXS 2430A, and I bought it before I'm at the level of a 1-2nd yr EE "course-wise", my 1st DSO. I now also have a mini-osiloscope, a DSO138. And I have yet to use it on this repair.The scope has sat 90% assembled for weeks/months, and I've been using it as a table, and its sitting on its side, like a tower, right now there is mail delveleriy packaging, a drawer of diodes and ICs, ibuprofen, book, box of resistors, rubber armor of DMM, yogurt container from the winter, why did I think I should save that ? Its emptyAnyways when it was all fully taken apart, the 5V rails were 7.3V or so. And using a DMM I never found any problems, and so IDK if that voltage is suppose to be about 7.3V when all the other boards are un hooked. I never checked it with any load, so IDK, its almost back togethger but I never fired her up yet.I've almost put it back together (but can't yet find one cables right place...wow, and I have several schematics)And if I use the working channel to probe the non working 1, what should I NEVER do? IDK ?
Led identify - Page 1
Forum section: electronics / repair

author: Kratto
author_rank: Newbie
timestamp: July 10, 2017, 07:47:54 pm
content: Hello, I'm trying to repair my LED tail lights. I opened the tail lights and desoldered defective leds. Now I need to find same package light diodes. Maybe someone can help me to identify these led's? Vf~2.1V, If~30-50mA.

author: Armadillo
author_rank: Super Contributor
timestamp: July 10, 2017, 08:09:16 pm
content: Try this;https://www.sparkfun.com/products/531
Identify laptop power IC MS4QB - Page 1
Forum section: electronics / repair

author: dominicM
author_rank: Regular Contributor
timestamp: July 09, 2017, 12:19:11 pm
content: I have a laptop with what appears to be a damaged power IC. I would guess that these 2 chips are for 5V and 3.3V so very similar circuits. Second pin from the bottom on the right chip is shorted to ground the same is not true for the chip on the left. The problem is that the markings are either a code or there's simply no info these parts. The chip on the left has "MT4R0" and the one on the right has "MS4QB" (possibly Q could be 0 and B could be 8 ) on it. It's a bit hard to see but I did try several combinations with nothing remotely matching the chip turned up. Is it a code or is it just a custom part with no info? If the latter is there anything else worth trying besides replacing the whole motherboard?

author: amyk
author_rank: Super Contributor
timestamp: July 09, 2017, 10:44:44 pm
content: Going by the style of the component designators I'm going to say it's a Compal board, but I won't know for sure if you don't post the exact laptop model...

author: dominicM
author_rank: Regular Contributor
timestamp: July 10, 2017, 10:17:59 am
content: Laptop is HP 15-p199na and the motherboard is DAY11MBB6Eo REV : E MODEL : Y11A

author: amyk
author_rank: Super Contributor
timestamp: July 10, 2017, 10:52:15 am
content: That would be a Quanta Y11A. Schematic shows SY8208B/SY8208C for 3.3 and 5V respectively.

author: dominicM
author_rank: Regular Contributor
timestamp: July 10, 2017, 12:42:34 pm
content: Quote from: amyk on July 10, 2017, 10:52:15 amNice find! How did you identify the board?

author: dominicM
author_rank: Regular Contributor
timestamp: July 10, 2017, 03:53:21 pm
content: I see the datasheet, after removing the chip it seems it's not the issue as the short remains. There are 4 caps that are shorted and if I connect external 5V to 5V rail, IT8987 ship overheats so it looks that is the fault. Probably not worth fixing this as if I am not mistaken this chip would need to be flashed before it could work.
Help needed: reed relay for Datron DMMs - Page 1
Forum section: electronics / repair

author: doktor pyta
author_rank: Frequent Contributor
timestamp: July 09, 2017, 08:10:37 am
content: I'm trying to find a replacement part for reed relay which is marked Hamlin HE721A5134 or GTI 831A-071E.It has 15V rated coil with 2000ohms resistance, one SPST contact andelectrostatic shield around the reed switch. The shield is connected to pin 9.Package has footprint compatible with DIL14.It is used in AC converter of most of Datron DMMs.Edit:Two active products may meet the specs but it is not confirmed:-Hamlin / Littelfuse type HE721A2420-Gunther / Comus International type 3570-1210-241
mastech hy3005d-3 linear power supply making loud sounds - Page 1
Forum section: electronics / repair

author: jmaja
author_rank: Frequent Contributor
timestamp: July 07, 2017, 09:05:31 pm
content: This PSU has been fine for several years, but today it started making strange noises. I was charging a lead acid battery (12 V 80 Ah) and heard rather loud noise, much louder than the normal relay clicking, but a bit similar sound. The same sound repeated a few times in an hour, sometimes even louder. I disconnected the battery after ten hours and turned the PSU off. It still made the same sound a few times in an hour. I got worried and took the power cord off.What could make such a sound?

author: alm
author_rank: Super Contributor
timestamp: July 07, 2017, 09:24:40 pm
content: A relay with its control circuit oscillating?If you were not using a series protection diode between the power supply and the battery, then any fault could have shorted the battery through the power supply (what is the short-circuit current of that thing?). For example if an overvoltage crowbar circuit tripped. That could easily destroy something.But it could also be something simple like a dried out electrolytic cap that messes up the tap switching.

author: jmaja
author_rank: Frequent Contributor
timestamp: July 08, 2017, 07:25:57 am
content: Note that the sound continued while the PSU was switched off. So it can't be the relay. It only stopped when I pulled the cord off.

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 07:30:39 am
content: Check all electrolytic capacitors. Measure the ESR.

author: Rasz
author_rank: Super Contributor
timestamp: July 08, 2017, 01:18:59 pm
content: something got hot and started cracking while thermally expanding? would crack again when shrinking , for example transformer

author: jmaja
author_rank: Frequent Contributor
timestamp: July 09, 2017, 07:35:35 am
content: Quote from: Rasz on July 08, 2017, 01:18:59 pmProbably, but why. Hasn't made any sounds before although I have been using it at full power (2*5A). I just put the power cord back to see, if it starts making sounds again even while off.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 09, 2017, 08:01:53 am
content: I see 3 possible sources for noise:The two more obvious sources are the fan and relays switching fast. Fast relay switching could be due to a problem with the tap switching and maybe a relay. If it happens the relays might get damaged over time.Another possible problem is a broken diode in the rectifier. In this case the rectifier would work as single puls more and the transformer would see a significant DC current. This would cause large current pulses in the transformer as it would go hup to saturation. Through magnetostriction this can get quite audible - not just the "normal" 100 / 120 Hz hum, but also quite a lot of harmonics. It might be worth checking the diodes / rectifiers.

author: Armadillo
author_rank: Super Contributor
timestamp: July 09, 2017, 08:07:50 am
content: Quote from: jmaja on July 08, 2017, 07:25:57 amlook message
Old, rubberized remote control case has become gooey.  Any fix for this? - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: July 07, 2017, 04:57:24 pm
content: So apparently this soft touch rubbery stuff they used on the cases of old remote controls does not age well. I've got one for a ceiling fan that is just awful - real tacky and unpleasant. Soap and water didn't help at all.Open to any suggestions on how to make this better than it is now... or is there nothing that will improve this? Thanks.

author: Gyro
author_rank: Super Contributor
timestamp: July 07, 2017, 05:24:53 pm
content: Yes, the rubber coating is breaking down (decomposing). Somethink like Talc might help for a short while but your best option is to strip it off completely. It usually comes off with Isopropyl Alcohol (IPA) without damaging the smooth plastic underneath. It will take you a while though.*Edit: * It will get a lot stickier while you're stripping it, you need lots of fresh paper towel or whatever.

author: Pinkus
author_rank: Frequent Contributor
timestamp: July 07, 2017, 05:30:05 pm
content: Quote from: Gyro on July 07, 2017, 05:24:53 pm+1 it is exactly like Gyro says. There is no way to rescue the surface in any way and talk is only fine for a few days but will not last for long.

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: July 08, 2017, 12:07:40 pm
content: I have had this problem with various items, including recently a pair of binoculars. I cannot remember what I used to get rid of the stickiness as I think I tried everything evil in the workshop, but it was some solvent- possibly methylated spirits- and the decomposing layer of the 'rubber' was removed. The stickiness soon returns though. It does not seem to be caused by UV as the binoculars have spent their life in a case from new.I read on another forum a while ago that there is a rubber paint available and this can be applied in several coats with a brush to replace the original coating after it has been removed entirely.BT

author: stj
author_rank: Super Contributor
timestamp: July 08, 2017, 01:59:58 pm
content: i hate this crap,it has failed so-far on:external harddrive case (posted here about it)several satellite remotesmy favourite electric screwdriverthumb sticks on a couple of game padsand an alarm clock.bastards!

author: stj
author_rank: Super Contributor
timestamp: July 08, 2017, 02:57:36 pm
content: meths will discolour a lot of plastics - stick with IPA.
Searching for 1/4 TRS Jack (image included) - Page 1
Forum section: electronics / repair

author: jmibk
author_rank: Regular Contributor
timestamp: July 14, 2017, 06:36:12 pm
content: Hi,I have to repair a audio system, that has a damaged 1/4 Jack. I'm searching for the manufacturer of following parts:Can anyone help me, finding these parts (eg Mouser, Digikey,...)Thank you.

author: cvanc
author_rank: Frequent Contributor
timestamp: July 14, 2017, 06:47:41 pm
content: Is there a logo to be found on the part somewhere? If so please post a photo of it.

author: jmibk
author_rank: Regular Contributor
timestamp: July 14, 2017, 07:37:15 pm
content: There is no information on the part itself.The only thing that helps by identifying the part is that red plastic inlet.

author: nali
author_rank: Frequent Contributor
timestamp: July 14, 2017, 09:05:41 pm
content: There seem to be a few on the Chinese marketplace sites, for examplehttps://tr.aliexpress.com/item/10pcs-1-4-STEREO-PCB-PANEL-MOUNT-HEADPHONE-JACK-free-shipping/924141449.html?spm=a2g10.search0305.4.9.qwfZ1f

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 14, 2017, 10:14:43 pm
content: https://www.amazon.com/uxcell-Audio-6-35mm-Panel-Connectors/dp/B00X77SADC

author: jmibk
author_rank: Regular Contributor
timestamp: July 15, 2017, 01:26:34 pm
content: Okay, thank you for your posts - I will order the parts via aliexpress.
Fluke 289 query - Page 1
Forum section: electronics / repair

author: orbiter
author_rank: Frequent Contributor
timestamp: July 07, 2017, 01:01:10 pm
content: Just got myself a Fluke 289.. It's as brand new but about a year old according to the cal details.My query is regarding the internal watch type battery. Is it a rechargable type batt that charges from the main AA batts? I only ask becasue I'm finding thatif I pull the main AA batts out for just a few seconds, the clock needs ressetting again when it's turned on.Thanks guys

author: mimmus78
author_rank: Unknown
timestamp: July 07, 2017, 01:05:19 pm
content: Yes there is a super cap for this. Old models used to have a super cap that get rusty due to leakage.Maybe your unit is more old than declared, worth checking. You'll find other threads on this subject with more details.Inviato dal mio Nexus 6P utilizzando Tapatalk

author: orbiter
author_rank: Frequent Contributor
timestamp: July 07, 2017, 01:35:59 pm
content: Are you saying that folk are replacing the stock battery with a super-cap?The batt is definately dead reading an unstable 2.4v, assuming it's a 3v one. I just need to know if its a rechargable typebattery or I need to buy a new one?This is the batt in question

author: ElektroQuark
author_rank: Unknown
timestamp: July 07, 2017, 02:07:57 pm
content: It looks like it has been reworked and the original capacitor changed.

author: orbiter
author_rank: Frequent Contributor
timestamp: July 07, 2017, 02:20:49 pm
content: Quote from: EdoNork on July 07, 2017, 02:07:57 pmIt's a battery.. Note the reference designator. Apparently the later 289's used batteries instead of caps.I would just like to know what type of cell it is? If it's a rechargable type cell that's great as it will likely just charge up after a few hours ofhaving the main AA batts installed. Or, if it's a standard type cell I can just make a comfy place for a larger 3v cell to fit in there that will last longer.

author: orbiter
author_rank: Frequent Contributor
timestamp: July 07, 2017, 04:36:05 pm
content: OK so just in case anybody else has this query in future.. The battery that's fitted in the later Fluke 289 isindeed a rechargeable one. 3v Manganese dioxide Lithium. Number ML621.
Sceptre Monitor $3 Re-Cap - Page 1
Forum section: electronics / repair

author: edy
author_rank: Super Contributor
timestamp: July 07, 2017, 03:35:32 pm
content: Hi,I wanted to post my success at repairing a Sceptre Monitor and PC that was dumped on me.The computer and monitor were both messed up. The VGA port on the computer motherboard was loose and jiggling too much, and the monitor was not getting any signal. So needed to diagnose whether it was the computer, monitor, cable or something else.First step... plug the computer into a known good monitor... Didn't work. So I installed a PCI VGA-card so it bypasses the jiggly on-motherboard VGA port, and voila! It worked fine. So one problem solved. Computer works but need to use the PCI VGA board as the motherboard VGA port must have some broken contacts.Second step... the Sceptre monitor (made circa 2006).The monitor was turning on but was seeing no VGA signal, even after plugging into a regular known good computer (or the repaired VGA PCI-card above which was confirmed working on another good monitor). The power light was flicking kind of on/off, sometimes turning red, sometimes blue (to indicate it is getting an image) yet nothing was happening. I do not believe anything showed up on the screen.... not even a warning saying "no input".Opened it up... Pried with a flat-head screwdriver around the edges (held by tabs basically all around the frame). Thankfully I could get to the power supply board easily. Found a bunch of bloated caps (see photo - the ones with red arrow) and replaced them all. Didn't see a need to change anything else at this point.Plugged it in, and it worked! As Dave would say... Winner Winner Chicken Dinner!Next will be to wipe the computer (Windows Vista) and put Ubuntu on it, and I'll have a good machine for the kids or to donate to a nearby school!I noticed these days some monitors are made almost impossible to fix. I had a BenQ only 4-5 years old that died on me and it was impossible to take apart and fix. Everything was glued together or wrapped up in silver foil in layers upon layers with no screws. Horrible! Anyone else finding this is the case?
Something is wrong with this board!!!! - Page 1
Forum section: electronics / repair

author: kgavionics
author_rank: Regular Contributor
timestamp: July 07, 2017, 05:27:44 am
content: Hi guysi'm trying to repair a panasonic Plasma tv model TC-P50G20 which doesn't turn on the power light flashes 4 times.Downloaded the tv manual and they said that's a protection mode due to something wrong with the power board.i removed the back cover, plugged my the tv to take some voltage measurement and when i plugged the AC cable i saw something burning in the SD board.I took the SD board apart and it turned out that a resistor is missing, probably the resistor melted ( see pic1).all seems normal,till i went to the components replacement list: the missing resistor is R423 (22OHM resistor), but i found that the other two resistors R422 and R421 are labled 7R5 like you can see in pic2.7R5 is 7.5 ohm resistor as far as know, but in the part list the value of R422 is 24.9 kohm and R421 is 13.3 Kohmthis tv i got from someone who said that it has never been opened before.i want to know why there's mismatch between the actual board and the part list?Can some one explain to me what's going on?thanks in advance

author: Zucca
author_rank: Unknown
timestamp: July 07, 2017, 08:36:29 am
content: Do you know why those R burned up? Without investigating the purpose of them you can not know if the manual mismatch is reasonable or not. Moreover if you just bilnd replace them there is the risk they will die again.

author: kgavionics
author_rank: Regular Contributor
timestamp: July 07, 2017, 03:12:07 pm
content: Quote from: zucca on July 07, 2017, 08:36:29 amyou're right zucca, after test i found some shorted out mosfet.By the way, i found the picture of an original board on internet ( see picture attached), and it looks that the R423 is not present in the board, so in my case the burn out resistor was R422.The only problem i have now, that between the actual board and manual there's a big mismatch.for instance the burned out resistor is referenced 16402 in the manual, but referenced R422 in the actual board.by the way,i have the right manual and i'm 100% sure about it.
Fluke 8505A Replacement Back Leg (3D-printed) - Page 1
Forum section: electronics / repair

author: pigrew
author_rank: Frequent Contributor
timestamp: June 23, 2017, 09:49:50 pm
content: My Fluke 8505A was delivered with a broken leg.Seeing as I now have a 3D printer, I figured that I should try my hand at drawing a replacement piece. It ended up working quite well.I've uploaded themodel at Thingiverse, in case anyone else needs it. I expect that it'll also work for other Flukes like the 8506A and 8500A.-Nathan

author: OiD
author_rank: Regular Contributor
timestamp: July 07, 2017, 10:54:08 am
content: Thats pretty neat, it looks less brittle that the original!Actually, I wonder if anyone has made the little clip-on feet for the HP scopes that keep going missing and cost an arm and leg to buy...A friend is currently offering me his never used 3D printer for 1/3 the price... problem is its one of those nice fancy ones that cost an arm, a leg and a kidney

author: JLNY
author_rank: Regular Contributor
timestamp: July 07, 2017, 01:54:26 pm
content: Nice work.I definitely second the idea of applying this concept to HP equipment. Not uncommon to get units with missing/cracked back or bottom feet, and even when they are intact they are often so brittle that I wouldn't trust them to hold up a heavy piece of equipment on the back legs.
How to Test Capacitive Touch Screen with Multimeter? - Page 1
Forum section: electronics / repair

author: FPTEC
author_rank: Newbie
timestamp: July 01, 2017, 08:02:43 am
content: Hello,I even found some methods for the resistive, but nothing for the capacitive.Does anyone know of any shape?Thank you.

author: Sceadwian
author_rank: Unknown
timestamp: July 01, 2017, 03:10:03 pm
content: I'm not even sure if you can, they're totally integrated and sealed so there's nothing I know of to even get a hold of to test.

author: OiD
author_rank: Regular Contributor
timestamp: July 07, 2017, 11:13:00 am
content: Other than picking up a capacitive touch PCB with the correct hardware, maybe an LC oscilator and checking for variatons on scope.What do you want to test? If it works? Use it in a project?
Socomec Sicon MODULYS 4500 UPS Repair - Page 1
Forum section: electronics / repair

author: gigabyte091
author_rank: Contributor
timestamp: June 30, 2017, 05:31:47 am
content: Hi Guys,yesterday i picked up an old ups from dumpster. It´s Socomec Sicon MODULYS 4500 VA model. I connected mains and 4 SLA 12V 7.2Ah batteries in series, so input voltage was about 52V DC. Nothing happened. I opened it and checked for burned components and i found nothing. There are 3 1500VA modules, a main board, and one board where is everything connected. Also on that board there are two flyback psu, one is mains powered, and it is working, i can measure 15V on output, and there is another one battery powered, and that one is dead... no output voltage, no voltage on the UC3845... Also voltage regulators on main board are not recieving power... SMTP module is also dead, no input power... I saw only one fuse on board, for the mains powered psu... There is no fuse for battery... I found similar ups, only weaker... have similar board only 2 inputs for modules...Any help is more than welcome.

author: OiD
author_rank: Regular Contributor
timestamp: July 07, 2017, 10:49:14 am
content: Check the batteries, are they dead? can they light up a car light bulb? If they cant then their dead.Check the main input power, follow the PCB, check the input filter all the way to the storage capacitors.Check for blown transistors, fuses to the batteries, control signals...Post pictures to get a better view of the device's PCB.

author: gigabyte091
author_rank: Contributor
timestamp: July 09, 2017, 05:44:03 pm
content: Battery is new, i found out that auxilary power supply is not working, i will upload photos tommorow

author: gigabyte091
author_rank: Contributor
timestamp: July 11, 2017, 04:01:56 am
content: UPS ia fixed, and problem was very simple, one of the switches was dead and i was unable po turn on UPS... UPS is now working, but i want to enable network monitoring, SNMP card is working but in router i can only see UPS MAC address...

author: OiD
author_rank: Regular Contributor
timestamp: July 11, 2017, 05:14:22 pm
content: The simple fixes are the best fixes!Try finding the user manual for the UPS and see if it has a chapter on how to setup the UPS via network. Maybe a default adress or a direct connection to configure it.
Fender 1000 Roc Pro circuit issue - Page 1
Forum section: electronics / repair

author: The Magic Rabbit
author_rank: Regular Contributor
timestamp: July 05, 2017, 09:34:17 pm
content: The guitarist in our band gave me this amp to clean up and see if I could get it going. There's a strange issue where it jumps channels and makes horrible crackling noises, which I've discovered happens when the amp vibrates, and if you tap it. This was initially discovered when the amp seemed to work at low volume but played up when driven, and also when moved.I'm experienced in basic electronic circuits, can solder reasonably well, know my way around basic test equipment, and am sensible enough to give mains electrics the respect it deserves. I don't know much about amplification circuits etc. as most of my experience is with microcontrollers, digital circuits, and LEDs.I systematically worked my way around the board and have identified that R173 (120ohm 10W resistor) seems to be the issue, as just touching it gently and rubbing the top (ceramic part) with the end of a plastic stick causes the amp to go absolutely crazy, jumping channels to and fro etc. quicker than you can blink. This didn't happen when any other components are gently prodded, tapped, or wiggled. I suspect maybe a dry joint, so I removed the board to resolder this joint.Upon removing the board, I noticed some discolouring on the board. The discolouring lines up with what I believe are two 16V 5W zener diodes.Should I be replacing the zener diodes?Is it likely the fault on R173 caused them to overheat, or is this an indication of a separate issue?Should I be replacing R173, and its opposite partner R172, or if resoldering cures it, "job done"?Schematic and photos attached for reference if required.Many thankshttp://cloud.tapatalk.com/s/595d57d54e9ae/Roc_Pro_1000_schematic.pdfSent from my Moto G (4) using Tapatalk

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: July 06, 2017, 06:08:22 am
content: I think this amp is the same as the 1000 Performer. If you need any info I have one on the bench at present, out of its case still after an electronic repair because the case is awaiting new Tolex vinyl covering.BT

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: July 07, 2017, 10:35:43 am
content: I had a look at the 'Performer 1000' PCB in the workshop today- it is more burnt than yours so we must assume that this is normal. This one has had a tough life with an Aussie pub rock band for many years.Maybe replacing the two resistors with the next wattage rating up, and mounting on ceramic beads to lift away from the PCB would be wise. The same with the two zeners.BT

author: Armadillo
author_rank: Super Contributor
timestamp: July 07, 2017, 10:44:37 am
content: Looks like very bad solder joints thus creating heat.I would advise;use a sand paper, sand the black and green solder mask away until you see clean copper areas. Then clean the areas with alcohol. Then you solder the whole pad with solder to add conductive areas and solder mass on the whole areas and made proper joints.
Help choosing a primary cap of a SMPS - Page 1
Forum section: electronics / repair

author: jmibk
author_rank: Regular Contributor
timestamp: July 05, 2017, 01:09:55 pm
content: Hi,i destroyed a main primary cap of a switch mode power supply by drilling through the housing - so i have to replace it.There are two of them (680uF / 200V), they are in series on 230V setting (there is a switch to switch 230V/115V)I need the repair quickly, so do I have to replace it with the same capacity? I have one with 1000uF/200V here.If they need to be the same value, I have two identical 250V/470uF out of another supply. Tue the lower capacity, there will be a power loss on the supply output maybe (that doesn't matter for my application).Thanks for your answers

author: capt bullshot
author_rank: Super Contributor
timestamp: July 05, 2017, 01:37:01 pm
content: They have to be of the same capacity.In many cases you can use the smaller ones as a temporary workaround, sometimes even permanent, especially if you do not load the supply to its full ratings.

author: jmibk
author_rank: Regular Contributor
timestamp: July 06, 2017, 07:54:11 pm
content: Okay, thanks for your answer. I got another power supply from a friend.For my technical understanding:These two caps are in series and they build up a - lets say - capacitive voltage divider. If they are not the same, the voltage across them isn't the same and thats the problem.Capacitance of them equals ripple of the primary dc rail. If the ripple is too big (because current draw of any load on the output) the power supply's protection will switch off causing a not stable output at the end.Are these ideas correct?

author: capt bullshot
author_rank: Super Contributor
timestamp: July 07, 2017, 05:12:29 am
content: Your ideas are correct, I've got some additional information:When connecting two electrolytic caps in series, you'd also want to use the same brand and type, not only same ratings. This is because of the leakage current should be roughly equal then.Add the ripple current issue to the second issue: usually a lower capacity one has a lower ripple current rating leading to premature failure (depending on load condition).
marconi 2386 RF unit - Page 1
Forum section: electronics / repair

author: dummyeng
author_rank: Newbie
timestamp: July 09, 2017, 05:18:10 am
content: HiRecently I got an Marconi that it is separate in two part1- Display 23802- RF Unit 2386First it had overload error that I could solve by service manual Page 33 chapter 5-3 (short TP12 to TP1 on AC2/1)But after I connect rf unit again it shows overload errorI surf on internet all sites that mention on ithttps://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/But I couldn’t find rf unit service manual if anyone had have experienced about this problem I am so glad to hear from you.

author: dummyeng
author_rank: Newbie
timestamp: July 09, 2017, 08:52:42 am
content: i found another thing in psumost of my output voltage are correct 5 or 6 voltage tolerancebut one of them as you see is too different from service manual(-+20)+-34what do u think about this problem
[SOLVED]Burned TI 3.3/5V step-down controller repair - Page 1
Forum section: electronics / repair

author: dominicM
author_rank: Regular Contributor
timestamp: May 24, 2017, 07:16:00 pm
content: So I have a laptop with localised water damage with no signs of life. It draws 5W at the wall. I tracked the issue down totps51225c (datasheet:http://www.ti.com/lit/ds/symlink/tps51225c.pdf). It heats up almost instantly to too-hot-to-touch temp. There are what appears to be burn marks on the right side as pictured. After cleaning with alcohol it seems intact with all pins still soldered. The middle pin on the left is the 3.3V out and opposite side is 5V out. 3.3V out is working but 5V is shorted to ground. I can't see any other reason for it to be shorted than a damaged chip. Have I missed something? I can get a replacement chip no problem but is it likely the problem/only problem? What would a be a sensible next step in this repair and why?

author: Chalcogenide
author_rank: Regular Contributor
timestamp: May 24, 2017, 08:11:48 pm
content: The first suggestion that comes to mind is to remove the chip and check whether or not the short to ground on the 5V rail remains. It could very well be an other component shorted that causes the controller to heat up that fast.

author: dominicM
author_rank: Regular Contributor
timestamp: May 24, 2017, 08:30:29 pm
content: That's a good suggestion, will try tomorrow to de-solder it. Assuming there is no short on the chip itself, what would you try next?

author: flolic
author_rank: Frequent Contributor
timestamp: May 24, 2017, 08:57:50 pm
content: Quote from: dominicM on May 24, 2017, 08:30:29 pmConnect external power supply to 5V rail, set current limiting to 2 to 3A and see what gets hot next.

author: dominicM
author_rank: Regular Contributor
timestamp: July 05, 2017, 08:21:26 pm
content: Thanks for all your suggestions. I only now gotten around to replacing the part, soldering was quite difficult but with some flux paste it wasn't so bad. The chip was the problem, and it all works as expected now, thanks again!

author: Kjelt
author_rank: Super Contributor
timestamp: July 06, 2017, 08:07:49 am
content: I would suggest to add a thermal two way sticker and a tiny heatsink on top of it.

author: dominicM
author_rank: Regular Contributor
timestamp: July 06, 2017, 09:41:08 am
content: It does have a thermal pad which is why it was difficult to solder, is your suggestion due to possibly less than ideal soldering compared to factory?

author: Kjelt
author_rank: Super Contributor
timestamp: July 06, 2017, 11:10:27 am
content: No I was just thinking what the cause of failure was and since nothing else seems to be broken, overtemperature/overcurrent could be a viable cause.On the other hand if it survived for >2 years already it probably is ok as is.

author: dominicM
author_rank: Regular Contributor
timestamp: July 06, 2017, 12:36:23 pm
content: Well it died because of water damage, it had clear burn mark as in the image.

author: Kjelt
author_rank: Super Contributor
timestamp: July 06, 2017, 12:58:51 pm
content: Ah ok sorry overlooked that part of the description.
Sony BVM 2010P PSU Problem - Page 1
Forum section: electronics / repair

author: Gizmo
author_rank: Regular Contributor
timestamp: July 03, 2017, 03:17:50 pm
content: I'd like some thoughts on troubleshooting an old Sony BVM monitor PSU.I bought it in a non-working state, when the power button is pressed the monitor powers up for a split second and then powers itself off. While powered for the brief time, the lights on the control panel at the front appear to behave correctly.I've had a look at the service manual, and the power board is split into GA and GB sections. The GA section is the main power supply and the GB is an over-voltage protection sub-board which shuts down the PSU in the case of voltage issues.The PSU uses two TL494CN chips for voltage control and according to the service manual the capacitor input to the chip which is used to set the oscillator frequency is grounded in case of over-voltage. I've checked, and this pin does appear to be grounded when the power to the monitor is shutdown. This is just tested with a DMM, seeing a small voltage drop to 0 as soon as the power goes.I've recapped the board, but this hasn't made any difference to the symptoms.Next I need to check the voltages with a scope to see if they actually are overshooting a lot, looking just with a DMM, they seem to be ok, but the reading is obviously only for a split second.If anyone has any experience of these monitors or any general advice on PSU troubleshooting, that would be appreciated!

author: Gizmo
author_rank: Regular Contributor
timestamp: July 04, 2017, 10:55:22 am
content: After more digging the LED's on the GB board seem to indicate if there's a problem in either the HIGH-B or LOW-B sections. For my monitor, the HIGH-B LED lights on powering up. Attached is the reverse engineered schematic for the HIGH-B detection section of the circuit.It seems to be a latch formed with Q3 and Q4 with the input to Q4 base being the trigger for the latch. I'm not quite sure when that circuit would trigger the latch, I'm not very good outside of simple digital electronics! I'll do some probing on the input to Q4 and see what's there.I've just probed the 150v rail, and it's coming out at pretty much smack on 150v. There's about a 2-3v overshoot very briefly, then settles down. The base input to Q4 raises to about 700mv with the delay from C1 before it latches and shuts down the PSU. So I'm starting to suspect the top section of this circuit to detect over-voltage is failing.

author: Gizmo
author_rank: Regular Contributor
timestamp: July 06, 2017, 09:19:06 am
content: Aha, I've found the actual schematic of the GB board now.
Repair using an old nail - Page 1
Forum section: electronics / repair

author: TerraHertz
author_rank: Super Contributor
timestamp: July 04, 2017, 09:36:39 pm
content: This was also the first time I could sit in the thing I was fixing, as I was fixing it.The hand controller for an electric lift/reclining chair, had a broken cable strain relief. The chair is pretty crucial for my 87 yo mum. When packing tools to go round and fix it, I expected I'd make a replacement using 3M rubber tape, that I could build into a suitable tapered shape.But that turned out to not be a great idea. The cable is surprisingly stiff. Mostly it needed something to anchor it in the remnant of the existing cable entry. A solid wire tie would have done, but had I thought to bring any? No.So, an improvised cable clamp. One old nail, bent into a circle with what I had, then squeezed to grip the cable tightly. Done.PS. The drill bit I used as a mandrel, is rusty because I'd found it on the ground in the local supermarket parking lot earlier that day. Lucky, since I didn't have anything of suitable size in my toolbag, but the drill was still in my shirt pocket. The perfect size.

author: Vtile
author_rank: Super Contributor
timestamp: July 04, 2017, 09:40:23 pm
content: There is some pride on that work.Nice fix.

author: alm
author_rank: Super Contributor
timestamp: July 05, 2017, 02:44:34 pm
content: Nice creative solution with the available resources. Guess this should be a hit with the steampunk crowd, although for best effect you should have used a brass nail.
STK4141-II pinout? - Page 1
Forum section: electronics / repair

author: orbanp
author_rank: Regular Contributor
timestamp: June 30, 2017, 10:52:45 pm
content: Hello Everyone,I am repairing a JVC RX-150 radio, that uses an STK4141-II hybrid in the final amplifier.The datasheet by Sanyo shows that the chip has 22 pins.The actual chip in the radio, that has the correct part number on it, has only 18 pins!The service manual (same as for the JVC RX-111, available at hifiengine.com) shows an STK4141-II with 18 pins!What gives?Are there different versions of that chip?The Sanyo datasheet shows different versions of the chip (different max supply voltage and rated output power), but all with 22 pins.Thanks, Peter

author: orbanp
author_rank: Regular Contributor
timestamp: July 01, 2017, 11:29:34 am
content: Here are the documents.Peter

author: orbanp
author_rank: Regular Contributor
timestamp: July 05, 2017, 11:55:39 am
content: It looks like that there are indeed two versions of the chip, with the same numbers!Here is the datasheet on the 18-pin chip.The 22-pin version looks like an improved version, it has a current mirror for the input pair, a cascade VAS-stage, and a access to other internal points for bypassing and for tweaking the compensation.Details of such improvements (and others) can be found in Doug Self's essay titled "Distortion In Power Amplifiers" that was available on the net some time ago, and now published in his book on audio amplifiers.It looks like that the newer version of the chip (22-pin) could be used instead of the old one, just by leaving out the outermost two pins on both sides.DISCLAIMER: I have not tried it!Peter
HP 1703A - no x deflection - Page 1
Forum section: electronics / repair

author: qu1j0t3
author_rank: Regular Contributor
timestamp: July 05, 2017, 03:08:36 pm
content: Hello,I have a chance to acquire an HP 1703A "portable" storage scope (with some cosmetic damage to knobs unfortunately). I've checked it out and it achieves a spot but seems to have no X deflection (e.g. horizontal position control has no effect; vertical control and deflection is fine). Can't therefore see a sweep.The schematics and service manual are obtainable. Does anyone have any thoughts or experience with this model or this fault, comments on difficulty of repair, approach, etc? I'm an electronics learner. I do have a 2nd (modern digital storage) scope.Thanks in advance for any comments.

author: alm
author_rank: Super Contributor
timestamp: July 05, 2017, 06:09:55 pm
content: This document by their major competitormight be helpful. Should cover pretty much the same era, so technology should be similar.

author: qu1j0t3
author_rank: Regular Contributor
timestamp: July 06, 2017, 04:15:26 pm
content: Update: The seller believes this is only a timebase problem and using an external timebase will work. I'll test that at a future opportunity.If so, I still plan on investigating the fault.I'm obtaining the manual and schematics on paper for 1703A so if anyone else needs a copy, feel free to contact me. There is a version online but it's very poor quality.
Tek AWG2021 Firmware? - Page 1
Forum section: electronics / repair

author: dretay
author_rank: Contributor
timestamp: July 05, 2017, 02:39:17 am
content: Hello, hopefully someone on the forums will be able to help me - I recently tried dumping the firmware for my Tek AWG2021, but when I reinserted the firmware chips the generator will no longer boot! I'm assuming that I somehow cleared the eepromDoes anyone happen to have a dump somewhere they wouldn't mind sharing?Thanks!

author: timb
author_rank: Super Contributor
timestamp: July 05, 2017, 05:27:34 am
content: You sure you didn't put them in backwards?

author: dretay
author_rank: Contributor
timestamp: July 05, 2017, 07:00:28 am
content: Yah they're definitely installed on the board correctly. I was using a questionable PLCC44 --> DIP40 so its possible pins were incorrectly shorted when I was trying to dump.
Failing Bus Pirate -- Strange Failure Mode - Page 1
Forum section: electronics / repair

author: mdszy
author_rank: Unknown
timestamp: June 30, 2017, 08:28:10 pm
content: So I've had this Bus Pirate V3.6 for quite some time and have recently dug it up from my bin-o-crap to try using it again. However, it isn't working properly.The device fails selftest, here are the errors:Code:~Disconnect any devicesConnect (Vpu to +5V) and (ADC to +3.3V)Space to continueCtrlAUX OKMODE LED OKPULLUP H FAILPULLUP L OKVREG OKADC and supply5V(4.80) OK3.3V(3.32) OKBus highMOSI OKCLK OKMISO OKCS OKBus Hi-Z 0MOSI OKCLK OKMISO OKCS FAILBus Hi-Z 1MOSI FAILCLK FAILMISO FAILCS FAILMODE and VREG LEDs should be on!Any key to exitFound 5 errors.I tried hooking up the device to a logic analyzer and sending some SPI data to the analyzer. It worked, except for the CS pin. I had to disable CS in the analyzer but when I did, it showed the data being transmitted just fine. However, the CS line didn't seem to be working. I measured the voltage on the CS pin with my multimeter and that showed it having a high-level voltage of 3.3V, but a low-level voltage of 2.5V or so.I'm honestly stumped as to what's gone wrong. Like I said, the other SPI pins seemed to be working as the data was transmitted properly, but only the CS pin was failing. Could that *one* IO pin on the MCU have failed somehow?I've attached a schematic of the Bus Pirate if it ends up helping anyone.http://dangerousprototypes.com/docs/images/4/4d/Cct-BusPirate-v3.5.png

author: CJay
author_rank: Super Contributor
timestamp: July 01, 2017, 06:11:22 am
content: It's possible but to me it looks like the 4066 would be a more likely culprit.As it's been in a 'bin' for a while are you sure nothing has been damaged on the board, a resistor cracked or some crud on the board?(and an aside, I *hate* schematics like that which are not much more than a bunch of chip pinouts, the bus pirate is simple enough a device that it could be a 'proper' schematic)

author: mdszy
author_rank: Unknown
timestamp: July 01, 2017, 05:55:49 pm
content: Quote from: CJay on July 01, 2017, 06:11:22 am1. I did check the 4066 and it seems almost like that could be the problem. When I enable/disable pull ups, the input/output of each switch element show an open circuit on my meter.2. I've checked all the resistors according to the schematic and they're all showing their nominal values. The only difference is on two of the three resistor networks, all three resistors measure 8k instead of 10k, and on the third they all measure 10k. I imagine that's not really a problem though.

author: macboy
author_rank: Super Contributor
timestamp: July 05, 2017, 12:43:10 am
content: There's not much to a Bus Pirate. Replace the 4066 first. If that doesn't do it, replace the MCU. You'll need to program the BP bootloader onto it so that it can receive a firmware update, so you'll need a PIC programmer. A Bus Pirate itself can act as a PIC programmer (via PicProg software) but not with the CS line broken.