hybridfree/eevblog-posts huggingface dataset:
Keithly 191 Repair - Page 1
Forum section: electronics / repair

author: at2marty
author_rank: Regular Contributor
timestamp: April 10, 2014, 12:04:43 am
content: A little while back I scored what I think is a decent Ebay auction. I got a Keithly 191 multimeter along with a Keithly 175 multimeter for around $50 US including shipping. I briefly checked them out when I received them, and they both seemed to "work" correctly. They had a few cosmetic defects, which I don't really care about. I was more interested in getting a couple of bench meters to mess around with. The 191 is a nice meter with pretty high precision, and best of all, it's kind of "old school".I finally got around to messing with the 191 a bit. I noticed that even though it has 6.5 digit accuracy, the least significant 2 digits would never settle down. They constantly would change readings, I also noticed that sometimes when I powered it on, I would just get a "-1. " reading that would just flash, and would not go away no matter which buttons I pressed. If I power cycled it once or twice, eventually it would start to "work".The troubleshooting part of my mind went to work, and I went back to the fundamentals. CHECK POWER!I downloaded the manual for it and began testing power from both a cold power-on and a warm power-on. The operating voltages are +5VDC, +15VDC and -15VDC. I noted that the -15VDC was out of spec and the +5VDC was right at the limit. I also noted that during a cold power on the -15VDC was essentially "not there".Visual inspection revealed that a filter capacitor for the 5V regulator (electrolytic 100000uF 10V) was showing just a slight bulge. The others looked fine. I don't have an ESR meter but on a hunch I decided to replace all of the electrolytics in the power section.When I removed the old capacitors, I found that the one on the -15V regulator had been oozing crap out of the bottom. It took some time to clean the mess up, but I was able to solder in new capacitors.After replacing the caps, I went through as much of the calibration that I could with the equipment that I have. All digits are now steady and if I apply 190mV on the 200mV setting I get a reading of 190.001. If I apply 1.9V on the 2V setting I get a reading of 1.90001. If I apply 190V I get a reading of 190.000 on the 200V setting.For calibration I used an old Eico resistance decade box (un-calibrated) and my Fluke 3330B voltage standard (un-calibrated). However, the readings that I get are consistent with the other meters that I have. I really don't care or don't need accuracy down to the nanoVolt range.I'll post some photos when I get the chance to do so. I really have a love for the "old school" equipment.
Trimmer pot repair and selection - Page 1
Forum section: electronics / repair

author: chipwitch
author_rank: Frequent Contributor
timestamp: April 08, 2014, 02:43:15 pm
content: I have a blown current probe pcb. The coil (not a hall effect probe) is intact but the trimmers blew. One is completely unidentifiable. The other has the following marks: 82MR50 9534F. My guess is this is a 50 ohm pot due to reading 0 to 44 ohms and then infinite for about 10 degrees of rotation. The "MR50" seems to suggest the same. It's a single turn pot. I can repair the pcb, but I need to determine the pots' size.The second one is more difficult. It sustained significant damage and basically disintegrated. Both pots are parallel to respective power resistors. The 50 ohm pot is parallel to a 2 ohm resistor. The other is parallel to a 200 ohm resistor. These are obviously used to limit current from the clamp's coils, one resistor/pot pair for each of the two scales. I realize I could put just about any pot in their place and that as long as the pot is larger than its respective resistor, the total resistance value will be anywhere from half the resistor value up to the value of the resistor, asymptotically.I am new to electronics, and through analyzing this simple circuit, I learned a couple things. One, don't burn up your current probe. But, aside from that, this arrangement of pot/resistor is rather elegant in that the resistor is carrying the brunt of the current and the trimmer is simply fine tuning it. Plus, using this arrangement means you could get very high precision resistance values by using a resistor and a much higher value of pot. Beautiful!So, with a very high value pot one gets high precision, but not much change in Rtotal. As one decreases the value in trimmer pot, down to the value of the parallel resistor, one increases the change in Rtotalat the expense of precision. Another way of saying it is, precision is directly proportional and Radjustisinverselyproportional to Rdeltabetween resistor and pot. Of course, current capacity of the pot will trump too low value of pot .My question is this: is there some rule of thumb resistor/pot ratio that is often used for general selection of trimmer that is a compromise between precision and R adjust range (pot power limits aside)? I'm inclined to use a 5k pot for the 200 ohm resistor in keeping with the ration of the 2 ohm resistor. I'm sure that's fine, but I'm still curious if there is general rule of thumb.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 09, 2014, 03:02:32 am
content: The main resistor plus high value trimmer is the classic way to do it, and almost any precision can be achieved. The only rule of thumb is Ohm's Law, and I find it handiest to make a spreadsheet. You start with the resistance limits you need (or voltages if working with dividers or similar) and then choose parts to match the desired window. You can also include power in the sheet so you know if the parts are going to go up in smoke!
Leader LS1020 Oscilloscope Repair - Page 1
Forum section: electronics / repair

author: TheRuler8510
author_rank: Regular Contributor
timestamp: April 08, 2014, 03:33:48 am
content: I picked up a Leader LS1020 Oscilloscope amazingly cheap, $20. It is a cute little scope in pristine excellent condition, except there is no vertical deflection. It sweeps fine, so I guess the inputs are blown--both channels.Anyone have any advice how to attack it? The only schematics I can find on-line are of the power supplies, so I am going in blind.Thanks for any advice!

author: tautech
author_rank: Super Contributor
timestamp: April 08, 2014, 06:05:09 am
content: Just offer a simple but distinct waveform (square-wave, even probe cal output) to one input and follow the signal path with another scope. It is possible one fault has affected both channels.

author: TheRuler8510
author_rank: Regular Contributor
timestamp: April 08, 2014, 11:12:43 pm
content: Quote from: tautech on April 08, 2014, 06:05:09 amGood answer...thanks!
Hameg HM203-6 Repair Question - Page 1
Forum section: electronics / repair

author: SubSonic
author_rank: Newbie
timestamp: April 04, 2014, 07:00:52 pm
content: Hi everyone!Just got time to troubleshoot my Hameg HM203-6 which i got from ebay.CH2 was working CH1 not.I found the culprit. It's resistor R152 (6R81) which sits on the -12V rail (marked in attached photo and schematic).Look like it's blown as it don't look ok.EDIT: The faulty resitor reads around 0.725 kOhmsAs it seems quite difficult to take the scope apart to get to the bottom side of the frontend board to desolder the resistor and put a new one in i thought about just bodge a 6R81 across the old one. Will this be ok or will the old one have any effects during operation?Also what do you guys thinks this resistor is doing? some kind of current limiter?-Markus

author: edavid
author_rank: Super Contributor
timestamp: April 04, 2014, 07:50:01 pm
content: The resistor probably blew up because something else is shorted, perhaps C120. You are going to have to find out what.

author: SubSonic
author_rank: Newbie
timestamp: April 04, 2014, 08:12:18 pm
content: Thanks for the hint. Just checked and the rail after the resistor is indeed shorted to ground.I would highly appreciate any hints on how to take the HM203 apart.

author: Bored@Work
author_rank: Super Contributor
timestamp: April 04, 2014, 08:39:03 pm
content: Quote from: SubSonic on April 04, 2014, 08:12:18 pmAsk Hameg for the service manual. If the service manual doesn't contain that information ask Hameg for the details.
Farnell PSU repair - Page 1
Forum section: electronics / repair

author: Flump
author_rank: Frequent Contributor
timestamp: April 02, 2014, 05:41:18 pm
content: I bought a Farnell 30/2 PSU which is faulty from a silent key saleI have not fired it up yet to see what problems it has but i did noticeall all the buttons on the front have issues like not locking in etc.So first thing is I need to track down some new switches then I cango from there.Does anyone know where to go for switches like these ? I cant find anyon ebay.I need2 which are 6 pin1 which is 18 pinthe pins stick out top and bottom of the switches as shown

author: Christopher
author_rank: Frequent Contributor
timestamp: April 02, 2014, 05:47:47 pm
content: We have loads of these at work. Nice supplies, but they are all dodgy, broken meters, dodgy buttons the list goes on...There was a schematic somewhere... Try these guys:http://www.advanceproductservices.co.uk/

author: lowimpedance
author_rank: Super Contributor
timestamp: April 02, 2014, 10:38:33 pm
content: Any chance a simple clean and lubrication will restore proper function ?. I have had some success doing just that, (usually dried and gummy grease in the mechanical latch area).Its interesting to note just how many products have used these types of switches, and yet seem to be hard to source!!.
Current clamps repair - Page 1
Forum section: electronics / repair

author: Simon123
author_rank: Regular Contributor
timestamp: March 23, 2014, 07:24:35 pm
content: Hello!I found this piece broken in my current clamps.What is it?Looks like, bond wires went to thing in the middle.

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2014, 07:29:14 pm
content: It was a hall sensor chip, bare silicon that gives a very small differential voltage output that varies according to the magnetic field through the face of the chip. Generally does the DC current sensing side, with a wound call that does the AC field side. Sadly if you do not have a chip wire bonder it is not repairable. Not likely to be easily available as a spare part either. Might come as the complete meter or the complete clamp assembly.

author: Simon123
author_rank: Regular Contributor
timestamp: March 23, 2014, 07:34:36 pm
content: Its iskra meter, i bought it cheap on flea market.At least voltage and resistance measurment is working.Could i just use hall sensor from fan?Or modify it to measure AC only?

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2014, 07:44:25 pm
content: Hall sensor from fan generally has some conditioning electronics inside. Look at older FDD drive motors, you might find one that has 4 wire hall sensor chips to sense motor drive. A small square black block ( there will be 3 of them connected in parallel on 2 wires and 2 leading to the motor drive chip) under the stator on old 5 1/4 inch drives, and then you can place this on a small board in place of the sensor. May not be accurate any more but probably will work somewhat. Post pics of the main board and the rest of the meter.

author: Simon123
author_rank: Regular Contributor
timestamp: March 23, 2014, 07:57:51 pm
content: https://plus.google.com/photos/yourphotos?pid=5994075362018111826&oid=1055825818130393523953 picturesIts pretty old-1988(the same brand as Digimer 10.It had sticker, that it was last calibrated on 2009, but i cant see any new trimmer glue, so they proably just tested it.It uses intersil 7106 lcd multimeter driver.

author: Simon123
author_rank: Regular Contributor
timestamp: March 27, 2014, 02:43:39 pm
content: I tried this sensor, but it doesnt work properly.Current gets close to 5A in 200A position, but A adjust doesnt work and it doesnt measure current.
repair: garrison pedestal fan - Page 1
Forum section: electronics / repair

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 22, 2014, 03:18:03 pm
content: HiDon't know if repair stories are OK here, but I figured it can't hurt to post it.Problem: Garrison 16" pedestal fan stops working. (model #043-5641-2)Symptom: When power button is pressed, the numeral "1" lights up briefly and a forlorn beep is heard then it shuts down. Fuse is not blown.Cause: There is a fairly large single-sided PCB in there. You need to replace the electrolytic caps labelled EC1-EC5.It's simple to take apart but kind of unwieldy, remove the fan assembly to make it easier to work on the PCB.ValuesEC1 4.7uF 400VEC2 10uF 25VEC3 470uF 16VEC4 220uF 16VEC5 220uF 16VI guess the caps are not very high quality, sometimes just flexing the PCB makes the fan work again. Replacing these caps solved the issue.Protect the plastic base from solder blobs...Problem: Fan is haunted, moves even when "off".Cause: Bad solder joints. Really huge blobby cold joints, short to the base/gate of whatever is driving the oscillation motors.Inspect board for any other questionable joints and redo.Note that there is a brake on this fan, a touch sensor activates a reversing relay causing the motor to stop and grunt ... it's normal.One less thing in the landfill, I guess. It's really a shame, it's otherwise OK as far as low-end consumer electronics go, why cheap out on the caps?? Oh well.

author: SeanB
author_rank: Super Contributor
timestamp: May 23, 2014, 01:36:16 am
content: Just remember as well to strip the fan housing and apply a drop of motor oil to the front and back bushing of the motor. This will help it run better. If you are feeling brave do the same with a thin screwdriver blade to the pivot and the pivot drive as well. While you are inside the covers clean the dust out as well.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 23, 2014, 07:14:44 pm
content: Quote from: SeanB on May 23, 2014, 01:36:16 amThe fan wasn't even old enough to get a good cake of dust on the blades! The lube was still fine.As for the pivot drive, it's two of them and they seemed fine.I have had no luck lubrifying fan bearings, no matter what I use it seems to cook itself into lacquer. Even the special "high temperature" bearing oil I purchased for my brushless motors.I have a 20 year old 6 inch desk fan that I periodically take apart, clean out the shaft and bearings and put on bearing oil which lasts a few weeks.IIRC, sleeve bearings use a special bronze alloy that's supposed to be lubrified for life, and adding oil doesn't really help except to reduce squeaking.If I get a chance I'll try MoS2 or graphite powder next.
yamaha amplifier repair (equivalent for 10gl2cz47) - Page 1
Forum section: electronics / repair

author: paulhm81
author_rank: Regular Contributor
timestamp: March 27, 2014, 06:34:18 am
content: hiI need some help repairing a yamaha mixer/amplifier. I attached the schematic for the power supply. The unit was powered from a crappy generator at an outdoor party and when the fuse blew of course they used a shunt. The problem is this diode - 10gl2cz47. I can't find it anywhere. It's in the upper right corner of the schematic. I found the following parts blown also - q817(2sk2842) , r872,873,874,875 so i presume ic803 is fried also. If anyone has a bit of time to take a look i'd appreciate it. I attached the datasheet for the diode. Please tell me a replacement for this diode.Thank you!

author: miguelvp
author_rank: Super Contributor
timestamp: March 27, 2014, 06:50:44 am
content: http://www.chip1stop.com/web/USA/en/dispDetail.do?partId=TOSH-0040235&utm_medium=cpc&utm_campaign=aggregator&utm_source=fc&utm_term=TOSH-0040235&cid=fc_TOSH-0040235They have over 3,000 at $3.35 each, I think it's the right part but double check.

author: Shock
author_rank: Super Contributor
timestamp: March 27, 2014, 07:06:07 am
content: Ebay.com 3 hits.

author: miguelvp
author_rank: Super Contributor
timestamp: March 27, 2014, 07:10:07 am
content: Also check the 20dl2c and 20fl2c from Toshiba for the 200 and 300 VRRM rating, couldn't find the 400 one equivalent.Edit, duh, the 400 one is 20gl2cEdit again: link to the 20gl2c from findchipshttp://www.findchips.com/search/20gl2cdatasheet:http://download.siliconexpert.com/pdfs/2012/2/12/6/52/45/133/tos_/manual/20gl2c41a_en_wm_20081227.pdfbut the link on my previous post will give you the original one.

author: paulhm81
author_rank: Regular Contributor
timestamp: March 27, 2014, 07:26:26 am
content: thanks miguelvp - i will look it up. The first link was 80$ shipping. That's the first reason for searching an equivalent so i can buy it in europe, maybe even a local dealer. I'll look at that 20gl2c. I didn't know what to choose because of that Ultra Fast Reverse-Recovery Time : trr=35ns (Max.) I found one diode in a local dealer that was rated 1200 Vrpm but the recovery time was 40 ns and i don't understand if that's an issue. The datasheet is attached.

author: miguelvp
author_rank: Super Contributor
timestamp: March 27, 2014, 07:33:10 am
content: $80 shipping??? do the ebay thing like shock mentioned, will take a month from china but way cheaperhttp://www.ebay.com/sch/i.html?_nkw=10gl2czNo hits on the 20gl2c, btw the 20gl2c is the same company as the 10 one so, ebay it if you must.

author: paulhm81
author_rank: Regular Contributor
timestamp: March 27, 2014, 08:16:04 am
content: got 2 of them on ebay I searched ebay.de before posting here but for some reason i didn't get any hits. That's strange. Anyway, thanks for your replies and i hope i wil get it fixed. It'a about time i looked at it because it's been sitting on a shelf for 2 years. I didn't have a schematic and the fried resistors were smd and i had no idea what values they had. Found the service manual onhttp://www.eserviceinfo.com/few days ago.
APC UPS Repair Project - Overvoltage on battery - Page 1
Forum section: electronics / repair

author: CallumA
author_rank: Newbie
timestamp: March 15, 2014, 08:16:44 pm
content: Hi!I acquired an APC SUA1000RMi2U from eBay for a very low price in hope that the only issue would be a dead capacitor (which was leaking electrolyte on the board).I took out the board, removed the capacitor, cleaned the electrolyte, put in a new capacitor to no avail (looks to just be a filtering cap for the battery).The UPS will work fine on battery if I connect "simple" things such as an incandescent light bulb (40W) however if I connect a computer LCD it will immediately over volt and shut down (with over voltage indicated on the front panel LEDs). Same result with even an LED light bulb (only 6W, died). This happens with the devices on their own or with the 40W incandescent.I recorded a video of the UPS working just on battery with the incandescent bulb and then I plug the LCD in to the back:My next guess would be to replace all the MOSFETs but since they're all screwed to a heatsink (some sandwiched between two heatsinks) which are in turn soldered on to the board I thought I would check that this could be the issue and if not, does anyone have an idea what it could be?Thanks in advance!Callum

author: johansen
author_rank: Super Contributor
timestamp: March 16, 2014, 12:05:42 am
content: i have a 1400va of the same.if it was that large 40 volt capacitor next to the H bridge that leaked out, that doesn't surprise me but the fact that it still works means the fault lies downstream in the output voltage sensing network.i'm not familiar with these things so i can't comment further.

author: CallumA
author_rank: Newbie
timestamp: March 16, 2014, 01:35:59 pm
content: Quote from: johansen on March 16, 2014, 12:05:42 amYep, that's the one.The voltage sensing network? Is that supposed to provide feedback to keep the voltage constant? The output does definitely over volt (you can see as the light flashes brighter when a device is plugged in) momentarily.Thanks

author: EEVPiobee
author_rank: Contributor
timestamp: March 17, 2014, 02:46:38 pm
content: And I'm pretty sure you checked for the obvious: "Is the battery is still good" right?(Just saying, I personally do these kind of stupid mistakes myself)

author: CallumA
author_rank: Newbie
timestamp: March 19, 2014, 10:56:44 am
content: Hm, I thought I replied to this before. Obviously not.My multimeter doesn't update very frequently however I didn't see the voltage fall below 24v whilst reproducing the issue (the pack is supposed to be 24v).
E3631A repair, what's this schematic symbol? - Page 1
Forum section: electronics / repair

author: sportq
author_rank: Regular Contributor
timestamp: March 31, 2014, 02:29:28 pm
content: I've got a partially broken Agilent E3631A that doesn't read the actual voltage and current back when the output is switched on, all three channels work just fine though. I'm looking in the ADC section which is quite understandable, even for me, and I found these symbols on the schematic. See designators E2 and E3 on the attachment.I'll probablymyself when someone replies but what are they?.Pete

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: March 31, 2014, 02:44:29 pm
content: Ferrite beads

author: cyr
author_rank: Frequent Contributor
timestamp: March 31, 2014, 02:46:24 pm
content: Beaten by a few secondYep, ferrites. I don't think I've ever seen the symbol except on HP schematics, doesn't seem to be that well standardized.

author: sportq
author_rank: Regular Contributor
timestamp: March 31, 2014, 03:56:51 pm
content: Ah, makes sense. I'm not near the instrument right now but I'll check it later and report back.Pete

author: sportq
author_rank: Regular Contributor
timestamp: April 01, 2014, 08:59:29 am
content: I checked it out. It's as you say a ferrite but it looks weird, it's surface mounted with no tracks connected to the pads at either end with the trace flowing under it. I'll post a picture later if anyone's interested.Pete
HP 33120a (Attempted) Repair - Page 1
Forum section: electronics / repair

author: jastervoid
author_rank: Newbie
timestamp: March 16, 2014, 03:55:19 am
content: I've got a sick HP 33120a function gen that I could use some help repairing. I get a 2 beep error code on startup and nothing on the display. According to the service guide (linked in below) the beeps indicate the main processor cannot communicate with the front panel processor.I went ahead and checked all the power rails and they all check out ok. There's also a -13v supply using a 7805 (U1102 on the schematic) from the -18v rail. I had to desolder the VFD from the front panel pcb to access all the smd goodness underneath including the regulator.So of course the output of the 7805 measures 3.6v instead of the expected 5v. The input voltage is only 5.2v. There's a string of 4 resistors (R1103-R1106) that are used to limit current through the 7805. Curiously they are marked as 10 ohms in the schematic but are all 75 ohms on the board.I lifted the output leg of the 7805 and the voltage jumps to 5v as expected; so the regulator seems ok. Something is drawing too much current off that -13v rail.Simple Ohm's law math tells me that maximum current through the regulator in this circuit is about 36ma. Measuring current on the output of the regulator shows 44ma, almost 10ma extra. This is where I get stuck and could use some help. How do I go about isolating the component that is drawing the extra current?33120a Service Guide

author: free_electron
author_rank: Super Contributor
timestamp: March 16, 2014, 03:59:07 am
content: check the tntalum caps on the frontpanel.if that doesnt work the lm339 that does the level shifting

author: dc101
author_rank: Regular Contributor
timestamp: March 16, 2014, 05:49:02 pm
content: You might try connecting to the serial port and seeing if you can read the specific error code. Hopefully that will help you at least determine if it's the display, the keyboard or both. U1101 also uses the -13 v rail. Have you checked around that at all?

author: dc101
author_rank: Regular Contributor
timestamp: March 16, 2014, 05:50:19 pm
content: I'm assuming of course that you have already checked the front panel ribbon cable and it is ok?
Repairability of Tektronix 24xx - Page 1
Forum section: electronics / repair

author: echen1024
author_rank: Super Contributor
timestamp: March 12, 2014, 01:14:16 am
content: I am and always have been getting interested in purchasing one of these scopes for parts or not working, but have always wondered about the repairability. I see that the scopes use many custom Tek parts, and the error 04 is NVRAM. I was wondering, given any broken 2400, what are the odds one can repair it with someone who is very skilled in analog systems.

author: PaulAm
author_rank: Frequent Contributor
timestamp: March 12, 2014, 01:34:31 am
content: People repair these all of the time. The NVRAM error is probably a bad battery in the Dallas NVRAM chips. Pop the chip, read the contents, program a new chip and install.Performing a full cal is a bit involved though. Get a service manual and read through it and make sure you have the required equipment, or its functional equivalent, before starting.Repair difficulty is going to depend on the model, the 2400 series has DSO and analog models.Best course: buy a second parts unit of the same model. Either you'll be able to salvage the parts to get the first one fixed or it will become a second project.Check through the yahoo tekscopes archives. There are known problems that show up: Dallas NVRAMs, the power supply, shorted tantalums, fried u800 chips, flaky eproms, etc. A couple hours reading will give you a good taste of what you're letting yourself in for.

author: echen1024
author_rank: Super Contributor
timestamp: March 12, 2014, 02:26:26 am
content: Quote from: PaulAm on March 12, 2014, 01:34:31 amI understand that error 04 is related to NVRAM.

author: David Hess
author_rank: Super Contributor
timestamp: March 12, 2014, 02:42:55 am
content: On the analog models calibration is more difficult than NVRAM replacement so if the calibration data is already lost, that is a problem. In comparison, the calibration is relatively easy on the digital models so when I lost the NVRAM contents changing mine, it was not a large setback.

author: echen1024
author_rank: Super Contributor
timestamp: March 12, 2014, 03:04:42 am
content: Worst thing is is a lack of reasonably priced ones. I'm talking about the Analogs, which are what I'm interested in.
Repairing a Kindle Keyboard keyboard - Page 1
Forum section: electronics / repair

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: March 05, 2014, 11:26:02 pm
content: I took it apart and it uses those film switches for each key. It turns out the menu key is the key that's not working. Is there any way to fix this kind of keyboard?I'm not sure what the official description is for this keyboard type.The Kindle Keyboard is one of the earlier versions.

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2014, 11:28:53 pm
content: I don't really know, but depending on where you are, I can probably send you the keyboard from my dead Kindle..

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: March 05, 2014, 11:57:47 pm
content: Quote from: Monkeh on March 05, 2014, 11:28:53 pmI may take you up on it but I do really want to know if this keyboard is fixable. Are you saying it's not possible?Do you know what the real name is for this thin button that's used for the keyboard?

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2014, 11:58:27 pm
content: Quote from: GiskardReventlov on March 05, 2014, 11:57:47 pmI have no idea if it's possible or not, I've never looked into it.

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: March 06, 2014, 12:36:03 am
content: Quote from: Monkeh on March 05, 2014, 11:58:27 pmOk, the keyboard looks so simple but there's nothing that looks obviously broken.

author: Shock
author_rank: Super Contributor
timestamp: March 09, 2014, 07:42:10 am
content: http://en.wikipedia.org/wiki/Keyboard_technology
Repair/re-solder of SMD Micro USB Port - Page 1
Forum section: electronics / repair

author: Mad Professor
author_rank: Regular Contributor
timestamp: February 25, 2014, 07:37:46 pm
content: Good day all.I am looking at doing a small repair on a hisense sero 7 pro tablet computer.The fault in question in the micro usb/charger port.By striping the unit down it seems that the smd micro usb/charger port is not damaged, but due to alot of use it seems that the usb port has been flexing and has caused dry solder joints.So my question what is the best or easiest way of doing this repair, as far as I can see it's just a case of re-soldering the dry joints.What tool(s) would be best suited for this kind of repair?Thanks for your time.

author: lapm
author_rank: Frequent Contributor
timestamp: February 25, 2014, 07:45:58 pm
content: if its just bad solder joints, you could try to re-heat them whit soldering iron or hot air...If you use soldering iron use small tip and good light, magnification if bossible... I have replaced one broken micro usb connector on external hd container. Was not fun...

author: ablacon64
author_rank: Frequent Contributor
timestamp: February 25, 2014, 08:10:26 pm
content: Best approach it to remove the conector, clean and tin the pads AND the conector's leads, and then soldering it back in place. That way you avoid mixing different solder alloys and eliminates corrosion.Not an easy task, since it's very small, but you should use the soldering iron. Don't recomend hot air since you'll ve reusing the conector and the plastic may melt.Also, before connecting the power cable, double check for shorts.

author: DL8RI
author_rank: Regular Contributor
timestamp: February 25, 2014, 08:16:42 pm
content: Hi,had it two times (one was a Smartphone, one a Headset), just use a soldering-station.And fix the stupid thing with 2-Component-Epoxy after this

author: Mad Professor
author_rank: Regular Contributor
timestamp: February 26, 2014, 03:24:07 pm
content: Thanks for your replies.I do have a Atten 858D+ hot air station, But I have never used it yet, and never done hot air rework before.I have been looking on RS web site at the micro usb ports.The one fitted to the hisense sero 7 pro tablet computer, looking very much like aHirose ZX62D-B-5P8orHirose ZX62D-B-5PA8.As I have not done hot rework before, can anyone give me some tips of what sort of temperature, etc.Thanks again for your time.

author: G7PSK
author_rank: Super Contributor
timestamp: February 26, 2014, 03:32:36 pm
content: If you are going to remove the old on first it would be just as well to fit a new one as they are cheap enough, in fact it would be wise to get several units and practice soldering on one first. Use the iron with a small bit and plenty of extra flux as well. If you go for just re-flowing the solder also use plenty of flux otherwise you will end up with dry joints again.
Flex cable repair, how to rejoin a broken flexible ribbon cable - Page 1
Forum section: electronics / repair

author: Comeinhandy
author_rank: Newbie
timestamp: February 26, 2014, 10:33:41 am
content: Hi, I have been stuck on repairing my broken flex cable in my camcorder for ages, but yesterday managed to rejoin the 4 broken wires in a flex cable. I also made a video as I seem to see quite a few people with the same problem and thought that this might help:Flex cable / ribbon cable repair video on youtubehttp://youtu.be/FzqIoq8LEEcOr just search for comeinhandynow on youtube if you don't like linksCheers. Jon
Help Repair - Metcal/Oki MFR 1110  - Page 1
Forum section: electronics / repair

author: Woznick
author_rank: Newbie
timestamp: February 25, 2014, 09:13:06 pm
content: Hi All,I picked up a Metcal/Oki MFR 1110 Soldering Station and Iron which is faulty, and would appreciate any help to get this up and running.The fault is that the unit when turned on will pulse both LEDs for a brief moment before then turning off until the mains is reset. Having pulled it apart all looks in tact with no damaged/blown parts inside. I've deduced that the protection circuit in the first switch mode stage (FS7MO680) is kicking in which is why it initially powers up, but then the protection kicks in and locks up until the mains is reset.The 5v & 12v regulators are working fine and I believe the issue lies with the protection circuit around the main PWM (MC34023) which links back to the 1st switchmode IC (FS7MO680) causing that to shut down. I've replaced the main Mosfet to no avail, interestingly removing the mosfet enables the unit to stay powered up with both LEDs lit, so it suggests that there is an issue with the protection / current monitoring after the main mosfet IC. Removing the front facing PCB (which looks to have the protection/ shutdown circuit) enables the unit to stay powered on which is no surprise as the protection circuit is removed.Does anyone have any ideas on how to fix the unit ? ideally I'm seeking schematic/repair manuals for the unit ?Thanks in advance

author: zapta
author_rank: Super Contributor
timestamp: February 26, 2014, 12:30:16 am
content: This is a very long shot but maybe it's similar enough to the MX500 such that the MX500 schematic will help?The MX500 has a disable signals that is connected to a few over collector protection signals such that each one of them can disable the power. The trick is to find which protection signal caused the shutoff.
repair dim CRO trace - Page 1
Forum section: electronics / repair

author: djacobow
author_rank: Super Contributor
timestamp: February 21, 2014, 10:07:17 pm
content: I have an old 20 MHz Goldstar CRO (OS9020-G) that I actually bought new in high school. I used it through college, but hadn't taken it out of storage until EEvblog got me back into electronics.It seems to work just fine except for the trace is very dim, even with the brightness turned up all the way.Anyone have some hints on where to look first to fix this guy up? I don't have schematics, sadly.I'd like to get it going again because, if nothing else, it works much better for lissajous patterns than does my Rigol DSO.

author: Andy Watson
author_rank: Super Contributor
timestamp: February 21, 2014, 10:37:57 pm
content: Is this info useful:http://www.eserviceinfo.com/downloadsm/43481/LG%20Goldstar_9020.htmlLooks like the same beast!Edit: Oh hum! I thought I'd linked to the "home page" for that model, but it appears to be a direct link for the download. You'll be wanting the other two parts:http://www.eserviceinfo.com/downloadsm/43482/LG%20Goldstar_9020.htmlhttp://www.eserviceinfo.com/downloadsm/43483/LG%20Goldstar_9020.htmlOr go to the eserviceinfo home page and search for the model number.

author: JOERGG
author_rank: Contributor
timestamp: February 21, 2014, 10:41:52 pm
content: Or here, Google is your friendhttp://www2.produktinfo.conrad.de/datenblaetter/125000-149999/130079-sp-01-en-Oszilloskop_OS5020.pdf

author: djacobow
author_rank: Super Contributor
timestamp: February 21, 2014, 10:42:27 pm
content: Andy, that's it!
Power Designs 6050A Repair - Page 1
Forum section: electronics / repair

author: idpromnut
author_rank: Unknown
timestamp: February 17, 2014, 05:09:33 pm
content: Hi! I will update this post as I get along with pictures and schematics (if needed), but I wanted to throw out a request for help; I am in the process of repairing a PDI 6050A, whose symptoms were negative output, current limit lamp flashing, very small voltage when the voltage is turned all the way to 60V. I will list a more detail later, but suffice to say that there was a blown internal fuse (on what seems to be on the isolated side of the mains transformer) on the input to the unit, which I replaced. This solved the flashing current limit lamp, but I am still getting a negative voltage on the output.I have verified that all the transistors and diodes seem to be functional, and have checked that none of the big caps are shorted (I haven't checked all of them yet). I also checked the voltage and current control pots: these seemed a little out, but even when shorted or removed, there was no obvious change on the behaviour.I am at the point where I need to trace out the circuit, and I wanted to ask if anyone has the schematics for this unit. If not, I will begin reverse engineering the board tonight.EDIT: robrenz, I saw your post about this; did the manual(s) you bought contain schematics? For the 6050A? Thanks!EDIT: just called manuals plus, and they confirmed that there are schematics for the 6050A, so ORDERED!Cheers!Chris

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2014, 07:21:23 pm
content: Schematic has many test voltage points and has a table of test point voltages when set for 7V, 15V, 25V, and 60V. The manual I got from manuals plus was an original PD not a copy.

author: idpromnut
author_rank: Unknown
timestamp: February 17, 2014, 07:51:03 pm
content: Nuts, I forgot to ask them if it was a copy or an original, but at this point I'd be happy with a naked schematic
Parts help required please (Mastech MS5205 Repair) - Page 1
Forum section: electronics / repair

author: orbiter
author_rank: Frequent Contributor
timestamp: February 15, 2014, 03:36:42 pm
content: Hi All,Could some of you guys help me with some parts numbers please as I'm getting rather stuck. I've tried looking on Farnell, Mouser etc for replacement OR equivalents AND on the following websites but I'm not having much luck with the SMD markings..http://www.s-manuals.com/smdhttp://www.marsport.org.uk/smd/mainframe.htmI'm trying to repair a reasonably new'ish Mastech MS5205 Insulation Tester which I've shorted out by accident. It initially blew a couple of SMD transistors Q20 and it's adjacent transistor (it also vaporized the track beneath the transistor which I have repaired temporarily for now)The main issue is part numbers though. I could just buy a new unit for about £90 but I thought having a go at a repair on this would be more beneficial to me not being an EE in the diagnostics dept, especially as I don't have schematic either soIf anyone does have a schematic that would be greatAnyway the parts I'd like to know replacement numbers for if necessary are listed below, as I have most others. I don't mind at all spending £30+ odd quid on bits if needed as I love repairing SMD stuff down to 0402 (depending on accessibility.) I've posted a pic of the board in the hope of some help with replacements/equivalents.8525 (u3)8512 (u2)ED0J2YJ3Y80M (or maybe upside down W08)C2NJYA7W16 (the number 16 is written sideways on the transistor after the A7W)Also how do I identify Diode D1 ?Many Thanks for any assistance guys.

author: MrAureliusR
author_rank: Unknown
timestamp: February 15, 2014, 06:04:40 pm
content: A lot of those small SOT-23 packages use codes that don't represent the actual part number at all. Most cases you need to know the manufacturer, and often they'll have a reverse code lookup tool. Without knowing the manufacturer for those parts... man. It'll be near to impossible to figure out that way.One solution would be to get a transistor tester, figure out what kind of transistor they are. If you have a schematic, then take a look at each one. Schematics also sometimes list exact part numbers. Also, try and find the BOM (bill of materials) as this will explicitly state the part number used for U1, D4, etc etc.Good luck!

author: orbiter
author_rank: Frequent Contributor
timestamp: February 15, 2014, 09:07:58 pm
content: Understood mate..As mentioned, I've not got a schematic for the Mastech MS5205 so I'm out of luck there. I do have a PEAK Atlas DCA Pro component analyser but trying to find similar spec parts would IMHO still be a huge PITA, even with the details the tester spits out.If anyone does know any more details on detecting the required parts no's here please do chime in?Thank you
Who makes great troubleshooting flowcharts and repair manuals? - Page 1
Forum section: electronics / repair

author: Tectonic
author_rank: Contributor
timestamp: February 07, 2014, 08:52:29 pm
content: In your experience, who makes the best repair manuals and troubleshooting flowcharts? What makes them better than the rest?I've been tasked to write troubleshooting and repair instructions. I wouldn't mind looking at a few great examples for inspiration.cheers!

author: G0HZU
author_rank: Super Contributor
timestamp: February 07, 2014, 09:05:42 pm
content: The faultfinding flowcharts in the Advantest TR4172 spectrum analyser service manual take some beating for thoroughnessThere's nearly 90 different (cross referencing) flowcharts to navigate along if the analyser develops a fault. It also has various test routines in its program memory that can be accessed using special combinations of front panel key presses and it can self test its own synthesised LO and give a frequency readout for each LO on the CRT display when in faultfinding mode. These keypress routines are given in the flowcharts as you progress through them. At the end of each branch of the complex flowcharts there is usually a component identified as the faulty part.I've never seen anything else like it and it puts HP/Agilent to shame but then this TR4172 analyser cost a lot more money and is far better built and far more capable than the equivalent flagship HP spectrum analyser from the 1980s. Awesome engineering from Japan

author: Tectonic
author_rank: Contributor
timestamp: February 08, 2014, 05:28:28 pm
content: I've had a look at the manual for the TR4172 and it is quite impressive. What about their more modern equipment, did they improve in the last 32 years?
Triplett 630 Analog Meter Calibration/Repair/Adjustment - Page 1
Forum section: electronics / repair

author: proschuno
author_rank: Contributor
timestamp: March 16, 2014, 12:53:22 pm
content: So I just obtained a free Triplett 630A multimeter from a guy, and after testing and measuring it it works quite well, especially on the 1.2 mA DC range, it's spot on. However, it tends to be a little off, usually by 3-4%, on the voltage and any currents above 12mA Dc range.Also, what read 120V AC on two flukes read 100V on the triplett, so I doubt it'll work accurately on high voltages ( which I frequently work with playing with vacuum tubes). The original manual says that it can be precise as 1.5% on all ranges (is this true, or just 'hype'?)EDIT:Measuring the internal resistors, many of them have fallen out of spec, they are .5% resistors. I'm supposing this is what's leading to inaccuracies, however all the resistors for the mA range have fallen out of spec, yet they are accurate for the most part (as stated the 1.2 mA range is spot on).So could there also be something wrong with the dial itself?

author: Napalm2002
author_rank: Regular Contributor
timestamp: March 16, 2014, 04:06:25 pm
content: i also am curious. anyone?

author: echen1024
author_rank: Super Contributor
timestamp: March 17, 2014, 03:02:07 am
content: Quote from: proschuno on March 16, 2014, 12:53:22 pmI would swap out the resistors first, and then try again. Also might try some Deoxit on the switches.

author: Vgkid
author_rank: Super Contributor
timestamp: March 17, 2014, 03:55:06 am
content: Here is the manualhttp://www.triplett.com/wp-content/uploads/2012/11/84-668.pdfWhatranges is it ogg on, andWhat ranges is it off on, and how well is it on resistances?
Hitach V-1150 repair help needed - Page 1
Forum section: electronics / repair

author: phil
author_rank: Regular Contributor
timestamp: February 05, 2014, 11:04:40 pm
content: Hello,I recently scored a hitachi V-1150 on ebay. It arrived today and did even work for about 3 minutesThe focus went crazy in that time, drifting all over the place. No way to get the trace focused for more than a few seconds.After a few minutes the trace vanished and was never seen again. Tracefinder does not help, XY mode does not help either. I checked all voltages mentioned in the service manual. They are spot on. Also, the horizontal and vertical deflection seems to work as far as I can tell by looking at the plate's waveforms.HV is there, too. I could discharge the tube via 10mm air gap. However, I lack the equipment to measure this voltage directly.There is no response on the screen when I switch the unit off. But there is a short, wide beam on the screen when I switch the unit on while the cathode is still hot. This lasts about 0.5s or so.I *think* that the problem is either with the Z blanking or with the focus voltage. Has anyone had a similar problem with an analog scope?Got any hints for me?- Phil

author: phil
author_rank: Regular Contributor
timestamp: February 06, 2014, 09:50:15 pm
content: Well, I checked theservice manualagain and I think I found the problem.Page 199 shows the Z-axis amp.TR1746 and TR1747 control the Z blanking. TR1747 is dead and TR1746 behaves stragely and seems to be damaged. I will try to source these two transistors and see if that fixes my problems. Blanking occures when R1747 is pulled low.Disconnecting the blanking circuit (lifting R1747) from the HV output stage restores the beam as expected. Of course, the use of the scope without is severely limited due to the beam not blanking on return.However, this does not really explain the fuzzy focus. While the focus behaves normal when the blanking stage is disconnected, the question remains why it failed in the first place.Maybe some voltage drop on the supply lines due to the dying transistors?Phil
Site for Asking Home Appliance (Microwave Oven) Repair Questions? - Page 1
Forum section: electronics / repair

author: fuzzoli
author_rank: Regular Contributor
timestamp: January 26, 2014, 07:53:30 pm
content: Hello world!sci.electronics.repair has gone down hill since the "good 'ol days". There are 9 junk posts for every good one. So my question is: Where do we go these days to ask repair-type questions? I have a microwave oven acting like its fried itself. I have a feeling I'm on the right track, but would like some community input.At the risk of being off-topic, but to satisfy the curious, here's what's going on: The MO seems fine when idle -- the clock is good, and all the buttons work. Once you try to cook something, everything goes dim and / or slow -- the display, the interior light, the fan motors, etc. So there's not much that would effect the low-voltage stuff (uC, display, etc), as well as dim the bulbs and slow down the motor other than the mains voltage. I have a GCFI testers plugged into the 2nd outlet of the electrical box. The interesting part here is the tester shows all wiring as good (two lights on), but as soon as I plug the MO into the other outlet, *both* lights of the tester goes out! A meter across the 120v AC Mains shows 60 volts at this point too. There is no open neutral as far as I can tell, no significant load being placed on the mains, and other high current devices work fine in the same outlet. Obviously at the lower voltage, the MO struggles to run, if at all.The only thing I see which might be a problem is maybe a bad cap or something else on the "Noise Filter" board. For reference, the MO is a Frigidaire / Electrolux GLMV169 (I have the service manual).So does anyone know a good place to post?Thanks!-FrankHolland, PAUSA

author: Tinkerer
author_rank: Frequent Contributor
timestamp: January 27, 2014, 12:04:17 am
content: While not an expert, a voltage drop etc seems characteristic of a partial short somewhere.

author: SeanB
author_rank: Super Contributor
timestamp: January 27, 2014, 04:55:16 am
content: If the mains voltage is dropping have you tried another outlet in the house? If the wiring was done with the push in terminals in the socket then they can go high resistance and have the 60V drop. I would replace the socket outlet as a first fix, and screw the wiring to the terminals rather than using the push in holder.

author: richard.cs
author_rank: Super Contributor
timestamp: January 27, 2014, 09:58:57 am
content: It's definately sounding like a wiring fault rather than anything to do with the microwave, the low voltage is probably just more noticable with a microwave that with other large loads.

author: KJDS
author_rank: Super Contributor
timestamp: January 27, 2014, 10:50:56 am
content: What happens when you plug a kettle into that socket?
Transformer Repair - Page 1
Forum section: electronics / repair

author: nadona
author_rank: Regular Contributor
timestamp: January 25, 2014, 06:41:02 am
content: I just found out that my buster 2303's TR2 7 volt secondary is openedIs there any place who can fix (rewind) this?Never mind. I decided to add separate 7V transformer next to the original.