hybridfree/eevblog-posts huggingface dataset:
Rechargeable Vacuum  - Page 1
Forum section: electronics / repair

author: vidarr
author_rank: Frequent Contributor
timestamp: January 03, 2019, 02:20:24 pm
content: The batteries of this vacuum are dead. I hard wired the plug so I can run it on 12vdc wall-wart and it works fine enough. It seems maybe a bit fast, but I don't know because I only ever heard it running off the dying batteries (was not able to plug in and run while charging). I am wondering though, should I put a capacitor and resistor into the circuit? Right now, it is just the dc motor. There are no markings on the motor and I cannot find any datasheet from Black & Decker. If I should do this, how would I calculate this? Or maybe some standard, generic practice?Thanks.

author: soldar
author_rank: Super Contributor
timestamp: January 03, 2019, 02:27:13 pm
content: Unless the motor overheats I would say it is fine.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 03, 2019, 03:12:48 pm
content: One could check the old battery and get the voltage from there. With a different technology one may not be able to get exactly the same voltage though, but at least close.
YIHUA 305D Cannot adjust current - Page 1
Forum section: electronics / repair

author: thecuban12
author_rank: Newbie
timestamp: January 07, 2019, 01:00:29 am
content: I recently acquired a broken Yihua 305d that was stuck at 50v output. I replaced the transistor that is known to cause that issue and the voltage side is working perfect. Now the issue I'm facing is that the current side cannot be adjusted. it will stay at zero unless a load is applied and even then it won't let you adjust it. I was hoping someone could point me in the right direction. Thank you!

author: montarbo
author_rank: Contributor
timestamp: January 07, 2019, 07:41:28 am
content: Its normal that the current meter stays at 0 unless you connect a load to it, no load=no current. If the load is stuck and cant be adjusted even with load attached then the try looking at bad solder joints in the front panel board, check for leaky caps on main board and so on. Report.

author: Armadillo
author_rank: Super Contributor
timestamp: January 07, 2019, 09:56:01 am
content: The Current Adjustment is actually Current LIMIT Adjustment, so its adjust the limit of the current. You can imagine a water pipe with 2 water tap/valves. One valve is adjusted by the landlord to half Open, the other valve is adjusted by the Tenant. So when the tenant fully open the valve, only half of the flowrate can be achieved. But if tenant adjust to lower than half, the water flow rate can varies between 0 to half. Got the idea? So depending on the load you put, the current can be less then or equal to the current limit set but no more.To test your power supply.1.0 Turn Current Adjustment and Voltage Adjustment Knobs to FULLY ANTICLOCKWISE - 0 limit2.0 Hook a Ampere Meter Connected to measure 10A max onto the +ve and -ve output3.0 Turn On - Observe the Current read 0 ampere.4.0 Then slowly rotate voltage knob so that 1V ~ 2V showed up.5.0 Then slowly rotate the current, SLOWLY rotate the current knob up and observe the Ampere Meter reads the current and tally with the power supply readout.6.0 If you can adjust up to say 1A or the current limit of your PS, then consider the PS is OK.If any abnormalities, then turn-off the power supply immediately and inform us back.

author: thecuban12
author_rank: Newbie
timestamp: January 08, 2019, 02:53:16 am
content: Thank y'all for the help. I think it is working properly I just haven't used it in years and forgot how one workedat least for what I need it to do.!
Philips airfloss transistor identification - Page 1
Forum section: electronics / repair

author: f114
author_rank: Newbie
timestamp: June 09, 2018, 07:48:53 pm
content: Could someone help me identify this transistor that had the encapsulation broken?. It is not possible to see the transistor code as per the attached images.This pcb board belongs to philips airfloss. With the breaking of this transistor the mechanism of firing of the jet of air and water is not working, I believe that this transistor is the responsible that drive of the small electric motor in the top.

author: HummingBird
author_rank: Contributor
timestamp: January 02, 2019, 10:46:30 pm
content: Hi, do you still need the information? I have nearly the same problem but maybe access to a second airfloss - or did you find out which type it is?EDIT: Checked the 2nd one, thats it - smoking little bastard: DMG6968U-7 Mosfet N-ch 20V 6.5A SOT-23Question is - why did it blew up? Hmpf.Regards, Klaus.
dsn-vc288 firmware - Page 1
Forum section: electronics / repair

author: montarbo
author_rank: Contributor
timestamp: December 30, 2018, 03:41:07 pm
content: Hello,I got one of these Chinese volt-ammeters (dsn-vc288) with a blown 3.3 volt regulators, that in turn killed the STM8S103F3. I already have the parts at hand and attempting to fix though the whole thing is cheap at ebay. Any chance or anyone help getting the code/ firmware for the STM8??BR

author: hamiltont
author_rank: Contributor
timestamp: January 02, 2019, 05:21:09 pm
content: Haven't tried to dump the OEM firmware, but I have come across an open-source alternative firmware -https://github.com/cocus/vc288-alt-fw/

author: hamiltont
author_rank: Contributor
timestamp: January 02, 2019, 05:24:26 pm
content: Also, a channel "Upcycle Electronics" has reverse engineered the specs, which may be useful if as you try to fix it -https://github.com/Upcycle-Electronics/DSN-VC288Keep us posted, I would love to see more English info on repairing these chips - they are low cost but often arrive with issues

author: montarbo
author_rank: Contributor
timestamp: January 02, 2019, 10:28:51 pm
content: The chip is fried so it's being replaced. STM8 are quite easy to program.I know about provided github's, but thanks. The alternative firmware have a bunch of TODOs so its no something to start with and not fully fledged as of author's statement.
Help identify component (capacitor?) - Page 1
Forum section: electronics / repair

author: ductileironbagpiper
author_rank: Newbie
timestamp: January 02, 2019, 12:06:05 pm
content: I am repairing a 1960s-era IBM Executary 214 dictation machine. For some reason the DC motor is running backward. In the picture below you will see a component broken in half attached to the motor. I would appreciate any help identifying the type and size of the component. It looks like a ceramic capacitor, but I can't interpret the markings. Thank you!

author: djQUAN
author_rank: Frequent Contributor
timestamp: January 02, 2019, 12:14:30 pm
content: Looks like a 0.1uF ceramic capacitor. It is just accross the terminals to suppress noise in a brushed DC motor.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 02, 2019, 12:30:57 pm
content: yeah an 0.1uf say 1kv for the spikes ??

author: djQUAN
author_rank: Frequent Contributor
timestamp: January 02, 2019, 12:51:18 pm
content: 50V is fine, it filters the ripple from the motor current, I have seen many on old tape decks.
TV Repair - Choosing a MOSFET replacement - generic - Page 1
Forum section: electronics / repair

author: anonymic
author_rank: Newbie
timestamp: December 31, 2018, 09:19:40 pm
content: I'm in the process of repairing a TV and believe the failure is down to one positively nuked MOSFET on the main board. It's an expensive board but I know the part number of the MOSFET. The problem is that it's only available in 3000 off quantity. I'm okay with replacing the part with an exact equivalent because apparently a firmware update to the board resolves the problem once it is repaired.I've googled how to choose MOSFET's but I'm met with terminology and equations I just don't understand, use cases I can't identify, and in this application, a solution I don't understand. Searching here I mostly find users looking to solve specific problems for their circuit. Here the circuit exists but is merely missing a known component.So my part number is ZXMP3F30FH P-Channel MOSFET in a SOT-23 package for what it's worth. One reference I found said it's okay to replace it with a BCW72LTIG or SBCW72LTIG bipolar transistor. I'm not really interested in asking if that's appropriate because a yes or no really doesn't help me learn anything. If anyone would like to expand on the whens and whys of replacing a MOSFET with a standard transistor, I'm certainly interested however.My main question is, if I'm looking at a datasheet and I need something that isn't going to self destruct when I power the unit on, what parameters are most important to me to look for? Should I be looking for higher or lower values for those particular parameters?

author: Armadillo
author_rank: Super Contributor
timestamp: December 31, 2018, 09:51:14 pm
content: Replacement part recommended is TSM2307CXContinuous breakdown Voltage and Currents, those listed as "Absolute Maximum Ratings" at the top of every datasheet.You would have to read up about mosfet, I am afraid.

author: anonymic
author_rank: Newbie
timestamp: December 31, 2018, 10:18:38 pm
content: Thanks for the part number.My first go-around was with Digi-key's parameter search, which netted me the exact part and nothing else. Perhaps I should have selected a range from the datasheet value to something somewhat higher and that would have given me a range of solutions that would work. My concern was that if a particular parameter was too far from the datasheet value it would throw something else out of the acceptable range.

author: fzabkar
author_rank: Super Contributor
timestamp: December 31, 2018, 10:43:48 pm
content: How about this one? It has better RDSon and Id specs ...https://au.mouser.com/ProductDetail/Diodes-Incorporated/DMP3056L-7?qs=sGAEpiMZZMshyDBzk1%2fWi0dsXOGve85x57LCxQMsytBvvrEFpdn1rw%3d%3dhttps://au.mouser.com/datasheet/2/115/DMP3056L-526286.pdf

author: anonymic
author_rank: Newbie
timestamp: January 03, 2019, 02:46:29 am
content: Thanks fzabkar, I've already ordered the part recommended by Armadillo. TBH, the part wasn't the target, the reasoning was.
Keithley 2010 hangs on boot - Page 1
Forum section: electronics / repair

author: unprintable
author_rank: Newbie
timestamp: January 01, 2019, 08:17:07 pm
content: Hi there!I have an offer for an Keithley 2010 which hangs on boot - you only see the display initializing with all segments active but no further sign of life.What might be the problem here?Should i give it a try or might that be lost money...?Did someone had a similar problem and could tell what the cause of this malfunction has been?I know that this problem could probably be caused by many things...Thanks in advance!Regards,Alex
Unusual uneven brush wear in blender motor (Optimum 9400) - Page 1
Forum section: electronics / repair

author: fzabkar
author_rank: Super Contributor
timestamp: January 01, 2019, 07:29:42 am
content: Some time ago a friend asked me to help him troubleshoot a commercial grade blender, model Optimum 9400. The symptom was that the blender's motor either wouldn't start, or it would start intermittently. It turned out that the armature circuit was open. The stator was OK.When my friend removed the brush holders, he found this:https://web.archive.org/web/20230522151510/www.users.on.net/~fzabkar/Blender/worn_brush.jpgThe short brush wasn't stuck -- it really had worn down that low. We couldn't find any reason for the dissimilar wear. All we were able to determine from the owner was that the unit had previously been returned to the supplier for service after it had failed a routine insulation test (why?). New brushes restored the unit to fully working condition, with no hint of arcing or vibration.BOM for semis:PIC16F1503, Microchip, 8-bit uC, 14-pin, 2.3V - 5.5V, 16MHz:http://ww1.microchip.com/downloads/en/DeviceDoc/41607A.pdf26T12BI, NELL Semiconductor, 25A, 1200V TRIAC, TO-3P:http://nellsemi.com/nell-cht/certi/9c3e7f1f6191ff20c800af7842994fff.pdfMOC3023, Fairchild, optocoupler, 400V Phototriac Driver Output:http://www.ti.com/lit/ds/symlink/moc3022.pdfPT-1540P, Mallory Sonalert Products Inc, buzzer, 4kHz, 5Vpp, 1.5mA:https://www.state-elec.com/store/PDF/PT-1540P.pdfHT7044A-1, Holtek, TinyPower Voltage Detector, 4.4V:http://www.sycelectronica.com.ar/semiconductores/HT7044A.pdfInternal photos:"a comparison of the parts that make up the blender":https://www.froothie.com.au/Documents/Optimumv.sLowerQualityBlenders_20may2014.pdfhttps://www.froothie.com.au/optimum-vs-lower-quality-blendersUser Manual:http://www.froothie.si/Documents/Optimum%209400%20User%20Manual%20RO.pdf(Romanian)https://www.medirando.com/images/medirando/media/Optimum_9400_UserManual.pdf(German)My CCD scans of the control PCB:https://web.archive.org/web/20230522151507/http://www.users.on.net/~fzabkar/Blender/Blender_PCB_bot_resize.JPGhttps://web.archive.org/web/20230522151504/http://www.users.on.net/~fzabkar/Blender/Blender_PCB_top3_resize.JPGhttps://web.archive.org/web/20230522151511/http://www.users.on.net/~fzabkar/Blender/Blender_PCB_top2_resize.JPG

author: Armadillo
author_rank: Super Contributor
timestamp: January 01, 2019, 08:02:44 am
content: High Load, High Current, Positive Brush has been shown to wear faster by embrittlement process of the graphite.

author: fzabkar
author_rank: Super Contributor
timestamp: January 01, 2019, 07:56:05 pm
content: Quote from: Armadillo on January 01, 2019, 08:02:44 amIt's an AC commutator motor.
yihua 936 iron ceramic element falling apart - Page 1
Forum section: electronics / repair

author: McGoober
author_rank: Newbie
timestamp: January 01, 2019, 07:13:41 am
content: i was changing out the tip one day and noticed the ceramic of some sort inside the element is cracked. i flipped it upside down like an idiot and dumped bits of the coke all over the floor. its pretty much contaminated from not cleaning the floorthe element assembly is a metal tube 5mm in diameter packed with ceramic, the temperature sensor i think in center. i really dont want to spend another week or two to get a replacement, what are my choices? could i sacrifice a ceramic bowl, crush into sand and pack it into the element?

author: Armadillo
author_rank: Super Contributor
timestamp: January 01, 2019, 07:51:55 am
content: The element will be enclosed by your solder bit. The whole piece of soldering iron plus new handle is cheap.There is no other choice except to buy a new one.Imagination leads to learning experience which is good.But heat transfer is essential and centrality of the element, expansion and keeping in shape are factors which will deny your desired result.Save and enjoy the time while waiting would be the best advice for you.

author: beanflying
author_rank: Super Contributor
timestamp: January 01, 2019, 07:58:46 am
content: Be a little careful buying elements for these or Aoyue, Hanba etc. They vary from model to model so check feedback and reviews as to suitability. One of my Stations (secondhand buy) came with the wrong elements fitted to the iron and I suspect is why it was sold by it's former ownerYes they do crack or burnout occasionally so buy two when you sort out the correct model and a supplier they are cheap and no use to not have one on the shelf.Non Repairable BTW.
Hameg 507 service manual Help.. - Page 1
Forum section: electronics / repair

author: yaban
author_rank: Newbie
timestamp: December 26, 2018, 04:22:51 pm
content: Hameg 507 service schematic manual Help..component test device is broken down from high voltage need help smd resistor burnt service diagram where to buyI can find

author: coromonadalix
author_rank: Super Contributor
timestamp: December 26, 2018, 05:04:44 pm
content: Maybe ask Hameg directly, maybe they could provide you some infos or manual / schematics ?? if you dont try you'll never know ?

author: Calambres
author_rank: Frequent Contributor
timestamp: December 26, 2018, 07:41:17 pm
content: I have that manual. Drop me a PM and I'll send it to you. Just allow me a couple of days for the answer.

author: Calambres
author_rank: Frequent Contributor
timestamp: December 31, 2018, 11:56:30 am
content: OOOOPPPSSS!!!!Sorry, I misread the file name in my database. The file I have is for the Hameg 203-7.Sorry for the confusion!
LCD hissing repair - Page 1
Forum section: electronics / repair

author: Kralik
author_rank: Newbie
timestamp: December 28, 2018, 11:07:01 am
content: Hi,I started using my old (4:3 ratio)Fujitsu Siemens lcd as my secondary monitor. it runs perfecly, but the hissing sound drives me crazy. The monitor is pretty old so i dont know if some of the caps are damaged or they dried out (it might me) or the sound is making the CCFL tube. The sound starts right after i turn the lcd on, even before the image comes on, but i guess the CCFL tubes must be already on. I read that the tubes start making noise when they are set on low brightness (bcs PWM) but after i turn the brightness down, it starts making different noise(without effect on the first one)Do you know whats causing the sound? or is it just common problem with older models?Thanks very much,kralik

author: coppercone2
author_rank: Super Contributor
timestamp: December 28, 2018, 11:15:33 am
content: i had a shitty TV that would be unusable at low brightnesses because of noise

author: Kralik
author_rank: Newbie
timestamp: December 28, 2018, 11:18:21 am
content: yeah, but even on high brightness the noise is the same and it drives me crazy, only if i turn down the brightness the second noise starts... can there be something to repair or its just a deal with old models of monitors?thanks

author: Dacke
author_rank: Regular Contributor
timestamp: December 30, 2018, 03:35:07 pm
content: I've worked on and repaired more TVs and monitors than I can count and the few times I've heard hissing it's almost always been a bad CCFL that's arcing within the tube or there is a bad connection with one of the CCFL sockets and it is arcing there or onto the metal lcd frame. If you have good hearing and are in a quiet place, you can put your ears up to differrent parts of the monitor and usually pinpoint what area it's coming from. You may also smell ozone there. The area where it is occurring will generally look black/burnt or even rusted (ozone accelerates corrosion).

author: Armadillo
author_rank: Super Contributor
timestamp: December 30, 2018, 03:46:00 pm
content: Since it's old;The first step would be;Open up and blow all the dust away with compressed air.that's the first step, before even delving into electronics.
Brymen BM235 strange EF-detection failure - Page 1
Forum section: electronics / repair

author: jogri
author_rank: Frequent Contributor
timestamp: December 26, 2018, 11:25:57 pm
content: Today i discovered a rather strange problem with my 235:When i turn on EF-detection and hit/slap the top of the meter lightly (where the antenna sits), it "detects" a EF-field, showing bars and beeping. Funnily, this corresponds with the high/low setting: If it is in "high" mode, all four bars show up, together with the beep. However, if i switch to low sensitivity, i get only 2-3 bars and a beep. It just beeps a few times and then shuts up until i hit it again. I have not yet tested if it still detects EF-fields, since every time i held it against a wall, it beeped. Did anyone encounter the same problem and knows how to fix it? Not that i would need that function more than once a year, but it sure is a nice thing to have.(Did i treat my multimeter that bad that now it starts crying every time something bumps into it? Yeez, i should tell it to buck up...)

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: December 26, 2018, 11:48:36 pm
content: Well what about known sources such as live wires, a socket does it fail at all or does it make repeatable tests, eg same distance vs sensibility. Try also with extension cords. Do you have an NCV pen?Some of them are very sensitive devices and can pick some electrostatic charges.. eg rubbing in a dry towell or cotton t-shirt,[Edit sorry for my poor english :S ]

author: jogri
author_rank: Frequent Contributor
timestamp: December 30, 2018, 11:00:21 am
content: It does still detect ef-fields, the lowest i could find that it detected was a laptop power supply at standby (.35W). I think the circuit is still fine, but since it is now shock sensitive i can't use it to run it across a wall...
Minghe B3606 - higher input voltage - Page 1
Forum section: electronics / repair

author: asymcon
author_rank: Contributor
timestamp: December 18, 2018, 08:37:56 pm
content: Hi,I had a little accident with my B3606 today, I plugged 48VDC into its input, forgetting to look at the specs, which only list 40VDC. Almost inaudible pop later, and now I see input voltage on the output, impossible to set.Looking over the board, nothing seems to be visibly burned. Any kind of assistance on what component might need replacing would be appreciated.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 18, 2018, 09:18:54 pm
content: Thread :https://www.eevblog.com/forum/reviews/b3603-dcdc-buck-converter-mini-review-and-how-the-set-key-could-be-fatal/75/Schematic :https://www.eevblog.com/forum/reviews/b3603-dcdc-buck-converter-mini-review-and-how-the-set-key-could-be-fatal/?action=dlattach;attach=137507;imageMaybe 1 or 2 regulators have failed on the + line

author: asymcon
author_rank: Contributor
timestamp: December 18, 2018, 09:40:10 pm
content: Just to be sure, this is B3606 not 3603

author: coromonadalix
author_rank: Super Contributor
timestamp: December 18, 2018, 11:33:15 pm
content: Sorry i should have wrote maybe there is some ressemblance in the input stage ??

author: asymcon
author_rank: Contributor
timestamp: December 19, 2018, 09:51:20 am
content: This is how the PCB looks like. D4 was obviously blown, so I replaced it. I assume you mean these two components?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 19, 2018, 10:32:59 am
content: thoses are lm272 op ampsooooooooooooh found this:https://github.com/UsrnameTaken/B3606Check the docs folder you have B3606.pdf you have the schematic, hit the downloadUS1 and US2 are the main regulators circuitry, maybe one of them is kaput ? or power diodes need to be checked too ?You have an small blog about the 3303 with some upgrades, need translation (russian).https://mysku.ru/blog/aliexpress/33406.htmlgood luck

author: asymcon
author_rank: Contributor
timestamp: December 20, 2018, 08:25:27 am
content: D4 terminals are shorted, even if the SS14 is lifted, so my totally illiterate guess would be that XL4016 is dead because Vin = SW.Hopefully anyone with more proficiency in reading schematic can confirm this.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 21, 2018, 12:12:11 am
content: ss14 should protect against reverse voltages

author: limces00
author_rank: Newbie
timestamp: December 30, 2018, 10:10:54 am
content: Hi. I did the same mistake and after that the output voltage become the same as input voltage. So by trying I discovered that the LM2596 was damaged. I replaced the LM2596 by a LM2596HVS and added a resistor before the imput of the XL1509. Now my B3603 accept till 55-60 volts input and regulate till 40 volts output.
LED or NEON - Page 1
Forum section: electronics / repair

author: innkeeper
author_rank: Unknown
timestamp: December 29, 2018, 03:23:14 pm
content: i'm about to replace an almost dead 120v ac neon panel light (power indicator). I'm sure you have all seen it ... neon bulbs start flickering and eventually dyeing.On paper neon panel lights have a similar lifespan as LED panel lights, though i am not sure that holds in practical applications.if it were you, and you were going to replace a neon panel light, would you replace it with a neon or led and why.

author: JackJones
author_rank: Regular Contributor
timestamp: December 29, 2018, 03:29:35 pm
content: There is a certain charm in neon that can't be replaced with leds. They are pretty robust as well, and you can extend the lifespan quite a bit by underdriving them.Edit: The life expectancy is apparently to the power of 3-4, so a drop of 10% in current gives about 50% more lifetime. Given it's just an indicator it doesn't need to be super bright so lowering the current is always a good option. They are also low power consumption and cheap as well.

author: james_s
author_rank: Super Contributor
timestamp: December 29, 2018, 11:17:57 pm
content: I'd just replace it with neon, they're cheap, readily available, will last a long time, and it's a drop-in replacement.

author: IanB
author_rank: Super Contributor
timestamp: December 29, 2018, 11:29:57 pm
content: Quote from: innkeeper on December 29, 2018, 03:23:14 pmI've experimented with both. On balance, it seems neon lamps look better as they emit light in all directions and therefore appear larger and brighter. LEDs generate a tiny spot of light which is then directed by some kind of lens or diffuser. Once you put them behind a cover they can look a bit feeble.So my choice would be to replace like with like. As someone else said you can lower the current a little by increasing the value of the dropper resistor and this should increase the lifespan.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 29, 2018, 11:49:08 pm
content: This is way off topic, but back in the day, at my old work, we made up some Mains distribution panels(Small ones that go at the base of a standard full size 19" rack).Someone stuffed up the ordering, & we got 125v neon indicators (encased in a plastic rectangle), instead of 250v ones.We then had the boring job of fitting the correct value component & disposing of the incorrect ones.There was a waste basket near where we were working, so being lads, we, instead of walking over to the basket, tried to get them in from where we sat.One hit the concrete hard & weirdly, gave a brief flash of light.We then spent some time trying to make them flash from impact, which worked every time with those that hadn't already hit the floor, but those that had already flashed wouldn't repeat it.I always meant to research why this happened, but never got around to itAnybody else seen this phenomenon?
Keithley 2015 Won't Save Calibration  - Page 1
Forum section: electronics / repair

author: oddiohead44
author_rank: Newbie
timestamp: December 29, 2018, 05:55:28 pm
content: Hi everyone! I am wondering if somebody can help me with this issue.I had to replace some components in one of my 2015 meters and I had to do a partial calibration. DCV, R and DCI. After I have finished all of those test spot on against my 34401 which I know is within spec. I choose Y to save and everything seems fine until I turn the power off and when I turn it back on it reverts back to where it was before I calibrated it.Any thoughts?
HAMEG 205-2 repair - Page 1
Forum section: electronics / repair

author: LorenzoDaniele
author_rank: Newbie
timestamp: December 28, 2018, 08:34:56 pm
content: Hi,I just started repair of HAMEG 205-2 CRO from Ebay ( listed as not working ) and noticed all power devices on the edge of the "XY" board, supposed to be dissipating in the back chassis plate were all "flapping in the breeze" i.e. no more screws washers ecc. . Looking at some photos and videos I saw how those parts are fixed. Particularly I'd like to ask if somebody knows what are those very thick white insulators (with plastic screws ) that fix the final Y amplifier transistors BF458 and if they are easy to get or to replace. I suppose the original design did not choose ordinary mica or conductive silicone foil due to their very low thickness and resulting parasitic capacitance from collector ( back of the TO126 package ) to ground that would be very bad in this point ( i.e. shunting the deflection plates to ground ). In fact those white spacers look almost 1 cm. thick , but they must be also a good thermal conductor !!?? I also decided to replace the BF458s ( T2105-T2106 ) but they are marked as "selected" on the schematics. I am not sure if to do matching selection on Vbe or on Beta. Any ideas ? Thanks !
Stanford Research Systems SR650 - Page 1
Forum section: electronics / repair

author: Magiciaen
author_rank: Contributor
timestamp: December 28, 2018, 11:29:10 am
content: Hi all,Earlier this year I scored a broken Stanford Research Systems SR650 bandpass filter for $100 shipped. I rebuilt the whole thing, a blown tantalum cap had caused a cascade failure in the instrument. I need two of these for my experiments, so still on the lookout for one more.I cleaned the switches during the repair, and although the unit works great, the switch contacts bounce like crazy. I don't have a schematic of the instrument, but I do have one of the SR560, which is fairly similar in design. There is no hardware debouncing of the switches at all, and so I assume it's done in software. The switches are organised as rows and columns for demultiplexing, and the columns are tied to a NOR gate which signals an interrupt on the Z80 microprocessor if any switch is pressed.My SR650 seems to be quite an early one, serial number 3036. If there is any software debouncing at all, it doesn't seem to be very good. I was thinking of modifying the hardware to add a physical debouncing circuit to the column lines before they reach the NOR gate, but thought I'd ask here if anyone knows if there was a firmware update, or even better, if anyone has the firmware from a recently produced unit. My hope being it was a firmware issue they eventually fixed. The new SR650 I used in my lab at university definitely didn't have this problem, but I no longer have access to it.
JFET U3114 - Page 1
Forum section: electronics / repair

author: xantia_99
author_rank: Contributor
timestamp: December 28, 2018, 09:22:52 am
content: HiKnowledge about Jfet U3114, let me know. I can not find data for it. I have to find a equivalent. Today I will test it in my Heathkit IT-3121 but I doubt it will give anything. I guess it is an early Teledyne component but I am not sure.
hameg hm507 schematic  - Page 1
Forum section: electronics / repair

author: yaban
author_rank: Newbie
timestamp: December 27, 2018, 08:13:04 pm
content: hameg hm507 schematic help...HM507 Analog digital scope I have a component test function is subjected to excessive voltage is broken I need a hm507 schema to repair I need your help.

author: madao
author_rank: Frequent Contributor
timestamp: December 28, 2018, 06:05:07 am
content: HiYou can trying asking by hameg about schematic.Hameg and Rohde& Schwarz is very helpful and give always schematic, if he had it. (of coruse obsolete devices only)https://www.rohde-schwarz.com/us/contact_63733.html?change_c=trueregardsmatt
12V Inverter Repair - Page 1
Forum section: electronics / repair

author: jheatac
author_rank: Regular Contributor
timestamp: December 28, 2018, 02:49:38 am
content: Hello,I have a question for those of you who are smarter than I am... And when it comes to electronics, that doesn't take much! I am learning though.I am working on 12VDC to 120VAC inverter... About 3kw. Cheap Chinese, I'm sure.It was in protected mode when I got it. Found the quad op-amp responsible for protection, then the circuit tripping the fault.I thought I had it figured out down to a bad thermistor used for overheat. The thermistor is over a hole in the board, on the cold air side of the board... Seems like you would want it on the discharge air side, but anyways.I have figured out that if the resistance is less than 657 ohms, it will pull the circuit down and trip the op-amp allowing the inverter to function. The resistance of the thermistor at about 60F is about 140k... A far cry from what it takes to trip the circuit.Now here is my real question..Can a PTC thermistor fail and act like a NTC?The thermistor out of circuit is about 140k at 60F... If I hold it in my fingers it will drop to about 112k... breathe hot air on it and I can get it down to about 85k... It seems relatively responsive. This would be a NTC, correct?To fit the circuit, it would need to be PTC because an overheat condition would be greater that 657ohm.Should I assume the thermistor is fine and troubleshoot what is forcing the other side of the op-amp high?The inverter was functional after satisfying the protection mode... that is until I was playing with the bench transformer and overvoltaged the damned thing... Now I have mosfets out of it and have bigger issues...
Repairing balance control on a Nikko NR-750 Receiver - Page 1
Forum section: electronics / repair

author: thevenetian
author_rank: Newbie
timestamp: January 02, 2019, 03:31:21 am
content: Got this receiver from craigslist for $20 untested and figured I'd take the risk. Got it home and it seems to be working, except that the knob for the balance is loose so when you turn it, its not actually turning the unit inside.Removed the top of the unit and can see that the screw that holds the plastic knob to the shaft is missing.Looking for assistance on where I could find that size of screw, or how to even measure it so I can go online and hunt it down. Perhaps there is a set of a certain sized screws I can get and assume it will be included.See photos.

author: fzabkar
author_rank: Super Contributor
timestamp: January 02, 2019, 07:48:16 am
content: If it helps, it's called a "grub screw".

author: drknob
author_rank: Contributor
timestamp: January 02, 2019, 02:38:49 pm
content: https://www.amazon.com/Hilitchi-260pcs-Socket-Assortment-Plastic/dp/B014OMFU1I/ref=sr_1_6?ie=UTF8&qid=1546439821&sr=8-6&keywords=grub+screw

author: coromonadalix
author_rank: Super Contributor
timestamp: January 02, 2019, 06:58:17 pm
content: Or called "set screws", flat screw driver, or hex screw with some allen keysNot sure of the dimensions, we use at my job metric m2 or m2.5 screws in similar shafts / knobs ...
What sort of circuit can I use to replace the C520D/AD2020/CA3162 - Page 1
Forum section: electronics / repair

author: SK_Caterpilar_SK
author_rank: Regular Contributor
timestamp: December 10, 2018, 09:40:55 pm
content: Hello. I have an old universal voltmeter manufactured in Czechoslovakia "TESLA DV10" based on the good old C520D and 74141 BCD top decimal nixie driver. Unfortunately either the C520D or 74141 is damaged. The multiplexing transistors and all diodes have been replaced so it should be working like new. But the numbers show on the nixies its not suposted to. Ill get a picture if necessary but the point is. Can I replace the CD520 with some circuit because I cant get any modern equivalent for it. If even possible to create a circuit for it. I found I can replace the 74141 with regular BCD to decimal decoders and creating the high voltage output stages separately.Im attaching a schematic just in case someone spots a thing or two .Thanks in advance.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 10, 2018, 11:04:32 pm
content: Normally the ca3161 comes with the ca3162 to do, for an example an multimeterThe 3162 is the converter to bcd outputs and the 3161 is the bcd decoder to displayYou can find tons of projects around themex:http://blog.novaeletronica.com.br/en/voltimetro-digital-usando-ca3161-e-ca3162/Compare this to your meter circuit pinouts, the c520d could be an ca3162

author: SK_Caterpilar_SK
author_rank: Regular Contributor
timestamp: December 26, 2018, 04:30:29 pm
content: Yes it is. I found many other names for this tipe of AD converter.. In fact this circuit is a really old one and very common. the C520D is the german copy of the american AD2020. This circuit is also known as the CA3161 and as NTE2054 which is the most recent (probably still in manufacturing) one of this exact same AD converter that is pin compatible..HOWEVER.. Still seems to be unobtanium. I would not care at this point if there would be a replacement thats not pin compatible. I would simply make an adapter PCB for it.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 26, 2018, 05:02:34 pm
content: The ca3161 and ca3162 should be easy to source ?? or not ?? i have them at home sitting duck, doing nothing for a long time ?Nte is an equivalent often sold higher priced, in the past they where also kown as Ecg parts, i think Nte bought Ecg ??Maybe they are now unobtaniumi dont know lollI'ts been a long time since i've played with theses, they where socketed, never soldered, the project was cancelled.

author: frantisek
author_rank: Regular Contributor
timestamp: December 26, 2018, 07:16:26 pm
content: Caterpilar PM.
Keithley 2001 "No Comm Link" - Page 1
Forum section: electronics / repair

author: C0nr
author_rank: Newbie
timestamp: December 25, 2018, 06:12:33 pm
content: Hello there, I have here a Keithley 2001 witch show powered on just „no comm link“. I replaced all the old capacitors, erased and reflashed the EPROMS but the problem is still alive.With the help of the service manual form xdevs.com I checked the voltages of the power supply and recognize a strange behaviour at U103. Pin 2 should have 8 volts but I measure about 1.2 volts.Should I replace U103(LM317T)?Also, on the measure points the -/+ 8 VF are not there. At the beginning +8VF is about 7.5 v and -8 is about -5.5v. The longer the DMM is powered on, the voltages change. After 10 minutes it is about at -2,4V and +11V. I tried to understand this behaviour with the schematic but I have no idea where to look exactly or what it could be.I also discovered a spot which looked like an arc to me. R303 is one resistor before the TLPs. If it was an arc could that crack the TLP U311? I measured the diod of the TLP U311 (Pin 1 and 2) which looks normal compared to the other optocouplers.TiN wrote in thishttps://www.eevblog.com/forum/repair/keithley-2001-meter-went-for-cal-working-arrived-dead/post what potentially could cause that comm error.QuoteI checked the cable between the boards witch seems ok. ADC board is also not lose.Can someone tell me how I can check the other compontents?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 25, 2018, 07:26:22 pm
content: Seems an arc to me, be sure to toroughly clean the board, and measure the components, the resistor and the TLPDid you measure voltages over 300vdc ?? there was talk over Keysight meters who had component (s) who could not stand the full meter specs 1kv at the input ...If the voltages drop, is there any anormal regulator (s) dissipation after your 10 minutes ?? do you have an flir or any electronic thermometer ??You may have something who consumate more current and may affect another voltage Ex: if you have some virtual ground, or symetrical supply (ies) ...Is the pcb was "unseated" ??https://www.eevblog.com/forum/repair/keithley-2001-meter-went-for-cal-working-arrived-dead/And finally if you use the comm port, is it isolated ?? Normally you use usb and or serial isolation between pc and usb related equipment, i always do.Service manuals and repairs and firmwares dumps : i'm on my cell phone can't see it for the moment.https://xdevs.com/fix/kei2001/#internal

author: TiN
author_rank: Super Contributor
timestamp: December 26, 2018, 03:03:39 pm
content: Well, you gotta repair power supply and replace all capacitors on both analog and digital boards. That is your number one job BEFORE turning on anything with this 2001's units. Once you have that done, then you can worry about digital issues. Old TLP optos may go bad too, I had to replace few before. Cable between boards may also "look" ok but actually missing connections on connection points, because it's just crappy crimp flat cable.
Philips / Fluke PM5138 - Page 1
Forum section: electronics / repair

author: Devilsea2001
author_rank: Newbie
timestamp: December 25, 2018, 09:55:48 pm
content: Hi guys,My name is Jo, from London UK.Unfortunately my baby PM5138 doesn't work anymore, it power up , display ad it h and dial are ok, I can change any parameter but no it out on the front BNC at all, only noise .If I change mode selecting PCK and changing the symmetry, I get a.perfect 1K square wave on the output.AlI checked the psu and all the output voltage are ok, clean and stable.Do someone have experience on this lovely unit, any help is very welcome.Thanks for your time.Happy new yearGiuseppe
Tektronix PS-2217 (119-5549) problem - Page 1
Forum section: electronics / repair

author: Fiveten
author_rank: Newbie
timestamp: December 24, 2018, 10:42:13 pm
content: Hello all,I have a TDS460A power supply that doesn’t seem to be working. It is not the common one that you find in the forums. It is not like the similar LeCroy power supply that is similar to the common tek PS. The problem I am having is that with the scope assembled there is no standby power and I am getting a clicking sound from the PS. With the PS out of the Scope I am getting low fluctuatiing voltages. On the + 5v side I am getting 1-2.3v on the -15 I’m getting -13v, + 15 I get 12-14.6v and -6.3v I’m getting -6.13v. Someone has worked on it before and all of the electrolytic caps have been replaced. What would anyone recommend checking next? Does anyone know where I might get a schematic or any test info on this PS?Thank you.

author: Fiveten
author_rank: Newbie
timestamp: December 25, 2018, 01:25:21 am
content: Just some more info:It uses the UC3844N chip and I have checked the diodes in circuit.I have done all my tests on bench with PS out of the scope.I have tried testing with a single load on the +5v output. Would I need to load each voltage output to properly test?
Voltage Drop when console is powered on. - Page 1
Forum section: electronics / repair

author: bhopki14
author_rank: Newbie
timestamp: December 27, 2018, 01:35:27 am
content: Hello,I am repairing a vintage gaming console, Atari Jaguar to be specific. I have recently replaced the U38 Power Regulator (SOIC-16W package "Step-Up / Down / Inverting Switching Regulator" ), the smd can be found here.https://console5.com/store/mc34163dw-soic-16w-package-step-up-down-inverting-switching-regulator.htmlIt appears to be soldered well and in working order. When I test with the multimeter, I see the required 9.5v when the power adapter is plugged in AND the console is powered off. However, when the console is powered on voltage drops to 5.5v.Normally I would think that something is shorting out, bad ground, bad solder, but the power adapter itself drops to 5.5v. Not just the components on the board. So I tested the power adapter on my second Atari Jaguar, and everything works fine. So I don't believe that the power adapter is the problem.Do anybody have any idea what I could check/test out next? I'm at a lost.Below is a link to a view of the motherboard.https://upload.wikimedia.org/wikipedia/commons/thumb/3/33/Atari-Jaguar-Motherboard-Flat.jpg/1471px-Atari-Jaguar-Motherboard-Flat.jpg

author: Inverted18650
author_rank: Frequent Contributor
timestamp: December 27, 2018, 02:08:49 am
content: Hey mate, you will need to provide more info. What "power regulator" did you replace? Is it a "wall wart" or did you desolder and replace a voltage regulator IC, or power transistor? I do not work with Atari systems but a power rail, is a power rail, is a power rail. If the voltage "collapses" under load you could have a bad regulator or its under powered.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 27, 2018, 05:47:43 am
content: Your power supply probably can't provide enough current to meet the needs of the system. This can certainly be caused by bad parts or shorts, but it also could be as the previous poster mentioned and you've just swapped to one that isn't up to the task.How much was the original adapter rated for, and how much is the current one rated for?

author: james_s
author_rank: Super Contributor
timestamp: December 27, 2018, 05:51:08 am
content: He says the power adapter works fine on one Jaguar and not on the other, so clearly the console that is causing the voltage to sag has a fault that is causing it to draw too much current.

author: Armadillo
author_rank: Super Contributor
timestamp: December 27, 2018, 05:59:31 am
content: Well, you got 2 of the same atari, just compare point to point ohms to ground, between the good one and the bad one starting from the adapter socket inwards.That way, you can trace and locate point of low resistance or bad component.

author: james_s
author_rank: Super Contributor
timestamp: December 27, 2018, 07:19:17 pm
content: Did you test the diode that goes with it? Also when a buck regulator fails the output frequently rises to the input voltage so it's not unlikely that every IC powered by that regulator has been fried.
Sneaky Cable Wire Problems - Page 1
Forum section: electronics / repair

author: t1d
author_rank: Super Contributor
timestamp: December 23, 2018, 11:47:02 am
content: A while back, I was having cable problems. The tec discovered that inside the old coax wire terminals, the internal plastic insulator had shrunk and some cross over to the wire shield had developed. He replaced all the terminals and the issue was resolved. I thought a shrinking plastic insulator was odd.Now, I had new problems. The tec found that the plastic insulator within the outdoor transitional coupling, between the pole supply cable and the internal house feed, had split, longitudinally. He replaced the coupling and the issue was resolved, again.In both of these situations, the causes and solutions were verified with their electronic meters. I saw the readouts, myself, and proper service was restored. Both were related to the plastic insulator, which I suspect are both made of the same type of nylon.Maybe there was some cross over leakage? Maybe there was some added capacitance? In either case, the problems seem to be rather minor. I am wondering if they were of greater importance, because modem speeds have become so fast; for me, 65Mbps...I'm sharing for two reasons... Because I find the problems sneaky and hard to find (non-electronic-equipment.) And, I find it interesting, on an electronic level.

author: Armadillo
author_rank: Super Contributor
timestamp: December 23, 2018, 12:27:29 pm
content: I suppose, must be a known common fault, prior case studied failure of the material [uv, chlorine attack etc], regularly serviced by the tec.This could be similar to a case before, a known brand of electrolytic capacitor would leak because of wrong dielectric material was used.If that is RF, I think SWR meter with prior experience, would have been an easy cake for the tec.

author: Gregg
author_rank: Super Contributor
timestamp: December 24, 2018, 03:23:36 am
content: A TDR (time domain reflectometer) will show the distance to an anomaly and all the tech needs to do is follow the wire and if a connector is found at the approximate distance, it would certainly be the easiest place to start looking for a problem.

author: cdev
author_rank: Super Contributor
timestamp: December 24, 2018, 03:34:55 am
content: Depending on the dielectric, coax connectors and dielectric material may be relatively resistant to or fairly susceptible to degradation due to compression or sharp bending. Different rules apply for different grades of coax.They have different kinds of connectors now that are less susceptible to signals degradation.Yes, speed upgrades are more demanding of coax cable runs.A TDR is the best way to find a short or open or serious problem with coax but they are an expensive piece of gear that most people cant afford.

author: Armadillo
author_rank: Super Contributor
timestamp: December 24, 2018, 05:15:36 am
content: For that expenses, better use a FDR, basically a auto SWR meter.