hybridfree/eevblog-posts huggingface dataset:
Lite Brite LED clock - Page 1
Forum section: electronics / projects

author: meanpc
author_rank: Contributor
timestamp: August 13, 2012, 09:02:17 am
content: First post! Been watching/listening to EEVblog and Amphour for about 6 months now. Not an engineer, but I am proud of my latest project:http://www.instructables.com/id/Lite-Brite-LED-clock/
Device / Package identification (Diode / Rectifier) - Page 1
Forum section: electronics / repair

author: mani9876
author_rank: Newbie
timestamp: August 02, 2025, 09:14:32 am
content: Hello!I need some help identifying a device / package.It must be some kind of diode, or rectifier. It's integrated in a Webcam, which is powered via PoE. It sits between the RJ45 Connector and the PoE SMPS.I've already googled some hours, but I am not able to find a device with that footprint, maybe anyone knows it.Thank you!

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: August 02, 2025, 09:56:29 am
content: Hi,what is the size?Picture of the top please.Good luck

author: mani9876
author_rank: Newbie
timestamp: August 02, 2025, 10:55:15 am
content: Hi!Here is the picture of the top, not perfect, because it's burned.The size is exactly 3mm x 3mmAnd I've made some measurements, it's definitely a bridge rectifier, two of the pins are internally connected together.

author: mani9876
author_rank: Newbie
timestamp: August 05, 2025, 06:17:14 am
content: Finally, after more hours of googling, I've found it :-).https://www.diodes.com/assets/Datasheets/SBR05M100BLP.pdfThanks!

author: Kean
author_rank: Unknown
timestamp: August 05, 2025, 02:21:08 pm
content: Well done finding that.I did a search for DFN3030 parts but I didn't come across anything close to matching so I didn't reply. I was expecting a higher current/power part based on the pads.
Field weakening and motor noise - Page 1
Forum section: electronics / projects

author: jeroen74
author_rank: Frequent Contributor
timestamp: March 26, 2014, 01:17:05 pm
content: I have a PMSM that's controlled with Field Oriented Control. One of the nice things with FOC is that you can use field weakening by setting a negative current on the D-axis that opposes the magnetic flux from the permanent magnets to make it go faster than nominal speed.But... I noticed, the more field weakening the noisier the motor gets; it's virtually silent upto its nominal speed of 3000 rpm, but field weakening makes it sound like shit. The closest description of the sound would be it sounds like an active mechanical torque limiter on an electric screwdriver. It's really loud then.Is this normal? It's basically Microchip's appnote AN1078 modified to run with an encoder for position measurement instead of sensorless that runs on a custom board. And something I inherited...The motor is an Siboni S040-2B-352, and according to the datasheet it should be able to spin at 5000rpm safely.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 26, 2014, 02:29:08 pm
content: Maybe boost speed by stepping up the supply voltage?

author: jeroen74
author_rank: Frequent Contributor
timestamp: March 26, 2014, 02:54:51 pm
content: Unfortunately that's not possible, the 48V supply voltage is fixed. It's an existing machine design where a few dozen of these motordrive boards are used inI'm researching whether field weakening is a viable technique.I just read Microchip AN1017 and I quote (emphasis added by me):QuoteSo I guess it's normal... though this is the only document so far I found that mentions acoustic noise.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 26, 2014, 03:55:48 pm
content: It seems to be normal for field weakening. From my experience with a few variable speed fan motors, they run pretty smoothly up to about 70% or so of their rated speed, then the noise and power usage start going up quickly.If possible, it might help to change the motors from Y to delta.
RIGOL/ DG3101A has no output power - Page 1
Forum section: electronics / repair

author: azemati
author_rank: Contributor
timestamp: February 06, 2023, 07:56:45 am
content: Hi everyoneIn the Function generator DG-3101A,Unfortunately, the output power has decreased 100 timesAccording to the picture of the IC whose number was deleted, I changed it and put LM7121 in its place, but it still does not workCan someone give me a schematic of the amplitude part of this function generator?Thank you for guiding me

author: michael_song
author_rank: Newbie
timestamp: June 20, 2025, 02:07:23 pm
content: THS3095
Tps-l2 walkman chewing tapes - Page 1
Forum section: electronics / repair

author: diggitt
author_rank: Newbie
timestamp: February 17, 2025, 11:11:35 am
content: Hi, I’ve got a tps-l2 and I have replaced all of the rubber parts. Every time I try to play a tape it spits it out right next to the pinch roller. I’m not sure what could be causing this? Thank you

author: coromonadalix
author_rank: Super Contributor
timestamp: February 17, 2025, 12:14:51 pm
content: you have clutch in all tape cassette, it could be it, you have tension tapes or you feel the tension with your fingers

author: benj38
author_rank: Frequent Contributor
timestamp: February 17, 2025, 09:38:11 pm
content: Quote from: diggitt on February 17, 2025, 11:11:35 amIf it eats the tape it means that the take-up reel is not moving or is not strong enough to spool the tape.Look to see if the take-up real is moving when in "play" without a cassette, and if it is, whether it is strong enough. Feel with your fingers if it is very easy to stop it form turning or not. Compare to the other real when in rewind (ignore the speed difference, focus on the power it takes to stop the real). Better yet, try to compare to another working player if you have one.
Replacing DDR3 memory chips - Page 1
Forum section: electronics / repair

author: ealex
author_rank: Frequent Contributor
timestamp: November 22, 2024, 06:06:46 pm
content: HelloI'm trying to fix an asus ux31e ultrabook that shows a lot of RAM errors.The fault happens exactly after the 2GB mark, and then the faulting addresses follow a base-2 pattern.By the looks of it either one or more of the DRAM chips have broken solder balls, or at leas one of them is faulty.Worst case - the CPU itself has a bad solder joint, and that's way out of my expertise and available tools.I assume it's a mechanical problem because the keyboard is very unresponsive and requires quite a lot of pressure to register any key press.I've got it for free, so worst case I still get a very nice LCD for witch I can find external driver board, a good SSD and some LiPo cells.The plan is to first try and reflow all 8 of the ram chips: apply some good flux and re-melt the solder.If that fails I might try getting a new set of RAM chips - or maybe I can try it "rossman style" and rebuild the balls with leaded solder and a lot of flux.I can play with it as long as I don't damage the board.The motherboard uses 8 Elpida EDJ4216BASE-DJ-F chips:https://www.alldatasheet.com/datasheet-pdf/view/458060/ELPIDA/EDJ4216BASE-DJ-F.htmlThose are no longer available at mouser / farnell (only on aliexpress and at a high price).I think the closest ones are AS4C256M16D3C-12BCN available at mouser:https://ro.mouser.com/datasheet/2/12/AllianceMemory_4G_DDR3_AS4C256M16D3C_May2020_Rev1_-2301319.pdfThe main difference seems to be the DQUx / DQLx pins placement - all other signals seems to match.Are there any other parameters I should be aware of ? the replacement chip seems faster than the original one : DDR3-1666 versus DDR3-1333(I think I should add an extra layer of aluminium foil on the side with the cpu / chipset to protect it as much as possible)Thanks,Alexandru
R&S SMU 200A Power Supply schematic? - Page 1
Forum section: electronics / repair

author: Crambone
author_rank: Frequent Contributor
timestamp: February 16, 2024, 08:08:55 pm
content: Guys I have a power supply issue trying to identify a fried component.LAMBDA Vega 450Product Code V403NBLattached a photoThe component in question attaches to the negative leg of C14 radial electrolytic 10uf 63v.I tried to identify while on board but no visible markings under a microscope. I removed it and it just shows an open no readings at all.Any help would be appreciated.

author: sprit
author_rank: Regular Contributor
timestamp: October 26, 2024, 06:30:56 pm
content: Hi Crambon, wish you have a nice day.As for your problem, I can tell you it is the resistor. The value is 4R7. Hope this helps.Sincerely, Jing Feng

author: Harry_22
author_rank: Frequent Contributor
timestamp: October 27, 2024, 11:48:35 am
content: Hi!Don't switch it on!I will help you as soon as I land.

author: Harry_22
author_rank: Frequent Contributor
timestamp: October 27, 2024, 08:21:26 pm
content: Hi again!Due to the fact that R&S equipment still contains these units, I do not have the right to provide an online repair guide.I'll write to you in a personal message.The rest of you please forgive me.
Help Identifying SMD Diodes on a Yaskawa SGD7S Stepper Driver PCB - Page 1
Forum section: electronics / repair

author: Zer00
author_rank: Newbie
timestamp: May 08, 2024, 12:28:28 am
content: Hello, I am currently attempting to repair a Yaskawa SGD7S-5R5A00A002 stepper driver that ended up receiving 100 extra AC Volts on the input (ouch). Besides a couple of MOVs being blown, some passive components on the board were also a goner. I also tested some diodes and they were suspicious at best, so I'd prefer to replace them.The issue is, I have completely failed to identify most of them. Any help in this department would be greatly appreciated. The diode markings are as follows:D101:E3 W67D102:U 68 03 ?(Not sure if it's a zero or a D)D103:T68Thanks in advance!

author: fzabkar
author_rank: Super Contributor
timestamp: May 08, 2024, 02:30:18 am
content: T68 = SMTPA68http://markingcodes.com/search/c/t68
Philips TL-S tubes - Page 1
Forum section: electronics / repair

author: mocha
author_rank: Newbie
timestamp: April 11, 2024, 06:39:56 am
content: Hey all,Anyone here have any old school knowledge about ballast-free florescent lamps? Specifically I'm talking about this lamp which was still on the market up until about 15 years ago.https://www.assets.lighting.philips.com/is/content/PhilipsLighting/comf2571-pss-globalWe still use this lamp on an old rail vehicle in a 600 VDC series circuit with dropping resistors. Someone told me that in the old days the tribal knowledge was to occasionally switch the polarity of these bulbs or else the mercury would migrate and they stop working. I need to try this on some of the 'bad' bulbs that we have.We'll probably start looking at low voltage LED strips as a replacement. Anyone know anything else about these old style tubes?

author: SeanB
author_rank: Super Contributor
timestamp: April 11, 2024, 07:51:27 am
content: They have that external starter strip, which basically enables the beginning of glow discharge without high voltage to start, or a preheat. You can emulate it with a strip of copper tape down the outside, but it only works on the T12 tubes, not the T8 or smaller ones. Yes flipping the lamp around helps even out the stripping of the cathode from being run as an anode, and being bombarded by the electrons, and at the cathode end being bombarded by the mercury ions.Replacing with LED tubes is probably the only way, using 2 in series on the 600VDC rail, and using 230VAC tubes, which you will need to order from the EU, or direct from Osram China. Leave the ballast resistor in place, it will help with keeping the spikes out of the lamps, and will limit current if a lamp fails. You will need to place a 1A fuse in series with the 2 lamps for safety as well, but it all can still fit in the original gear trays and not need much work, other than replacing the R18s sockets with regular lamp sockets. That will allow you to do the rework in sections.

author: mocha
author_rank: Newbie
timestamp: April 12, 2024, 05:34:28 am
content: Sounds like you have a lot of experience with florescent tubes! I guess this was the old school knowledge that's been mostly lost along the way because even the people in rail don't know much about this stuff anymore. In our case I think we will convert the circuit to low voltage 36VDC LED strips with a minimal controller, it's also desirable to get the 600VDC out of the passenger compartment. Thanks.
Removing pull-tab from Tektronix TM500 series plug-ins - Page 1
Forum section: electronics / repair

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: February 09, 2024, 05:27:35 am
content: Hi, I am restoring an old FG501 TM500 series counter/timer. I wanted to remove the front panel sheet metal faceplate, however, I still have one last step, remove the pull tab.This appears to be easier said than done though as it looks like there was maybe a tab? Or the plastic was welded on.Does anyone know how to remove these?Thanks.

author: srb1954
author_rank: Super Contributor
timestamp: February 09, 2024, 08:42:39 am
content: Quote from: BlownUpCapacitor on February 09, 2024, 05:27:35 amWith TM500 instruments these pull-tabs are usually broken off so hardly anyone ever has a need to remove one.Looking at the very few of my TM500 units that still have intact pull-tabs it looks like the back of the tab is locked into a keyed section of the moving latch behind the panel. Maybe you can lever the end of the tab out of the keyed section. I haven't tried it on my units for fear of breaking the fragile tab.It looks like there were several variations of the design of this locking mechanism over the product life of the TM500 series so you may have to investigate further which version you have.

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: February 09, 2024, 08:27:47 pm
content: I've tried drilling into that keyed section, but it doesn't appear to be coming out.I might snip it off and glue it back on if it doesn't come out.

author: alm
author_rank: Super Contributor
timestamp: February 09, 2024, 10:08:01 pm
content: Quote from: srb1954 on February 09, 2024, 08:42:39 amYou must be unlucky. I think I've had one plugin with a missing pull-tab in about a dozen TM500 plugins.Quote from: BlownUpCapacitor on February 09, 2024, 05:27:35 amTry searching the TekScopes groups.io group. I remember there being at least 4 different versions. Looks like this is the older version as discussed inthis thread(and others I'm sure). The ones I'm familiar with had the pull tab friction fit into a cavity likehere.

author: fmashockie
author_rank: Frequent Contributor
timestamp: February 10, 2024, 02:25:14 am
content: Quote from: alm on February 09, 2024, 10:08:01 pmYea these are very different than the ones on my CG5011 I'm working on repairing. They are very easy to remove - just pull forward from the side and lift up. I second Tekscopes groups.io - someone there will definitely know!
Capacitor + diode identification help (pics) - solved - Page 1
Forum section: electronics / repair

author: Nexxen
author_rank: Regular Contributor
timestamp: September 16, 2023, 04:32:19 pm
content: Edit: I added a component to avoid creating a new topic. I feel like I'm spammingIt's a diode. No markings (see pic) it's the white one, bigger than others.Looks like a germanium diode and from another source it has two (2) black stripes.Ok, looks like a 1N34A.Yet again, I have two caps with AE1 marking but I can't figure out what they are.Values show as 26-28pF but no Vloss nor ESR readings. I can get a reading every 10 times and it varies.No idea if it is correct because it's a kind of cap I don't know of.As I have to order new ones I'd rather be safe asking.Thanks.P.s. I tried many online SMD id sites but I couldn't find anything. I'm talking 30+ minutes.Edit2: AE1 could be the manufacturer's id code. On the board are others and have different markings. Probably impossible to track.

author: fzabkar
author_rank: Super Contributor
timestamp: September 16, 2023, 06:47:51 pm
content: Could they be precision capacitors? Mica???What is the application?

author: Nexxen
author_rank: Regular Contributor
timestamp: September 16, 2023, 07:17:36 pm
content: On an old motherboard.https://www.eevblog.com/forum/repair/desoldering-help-big-160-leg-ic/Frack on a stick ( Dr Reid- Scrubs), it connects to the Xstal oscillator (32KHz). So ~26pF sounds good, the caps probably corroded to the pads that are in...Reading you made me check and realize it was there all along. Guess doin' stuff while tired ain't the best course of action...Any cap will then do, unless notEdit: yes, probably a 27pF, being readings 26 and 28 I'll go with the average.
Testing Varactor Diode for HP 8640B - Page 1
Forum section: electronics / repair

author: _rushin_or_draggin_
author_rank: Regular Contributor
timestamp: November 19, 2024, 02:58:11 am
content: Hey all,I am currently troubleshooting a phase lock issue on my HP 8640B. I have gone through service sheet 4 where step 12 led me to service sheet 7. Reading through 7 it says a low varactor anode voltage at A7TP2 could mean a bad varactor assembly or a bad PLL filter. I have checked all the voltages around the PLL filter and they seem okay for the most part. I decided to check the anode voltage and it is around -0.9V when it should be -13.6 to -16V.Checking service sheet 5 it says the resistance from varactor anode to ground should be 61.9k. When I check it I get nothing at all, full open. I am already expecting the worst and have started looking at replacement oscillator cavities. Looking at the schematic though, is it possible that the inductors on the buffer amp and filter between the varactor diodes could be blown? It's a long shot but it's currently next on my list of things to check.I know it says to not take the cavities apart, but does anyone have any experience with it? Or maybe any knowledge on why I would be getting an open between the varactor anode and ground? I have attached a screenshot of the schematic. Thanks!

author: Dave Wise
author_rank: Regular Contributor
timestamp: November 23, 2024, 01:17:50 am
content: My own 8640B came to me with an open metal-film resistor on the FM board. There was no sign of violence, the resistor was simply dead. You may have the same type of failure.HTH,Dave Wise
HP 8563E repair - Page 1
Forum section: electronics / repair

author: EE4all
author_rank: Regular Contributor
timestamp: December 21, 2022, 08:52:06 pm
content: I am working on a 8563e that shows error 334 LO AMPL. The YTO is fine, and I can show signals on the trace, but they appear low, especially in the low band. Checking the LO distribution amplifier calibration, I can't even adjust the voltage into the specified negative range. Likely a bad amp, or the drive control for it.

author: EE4all
author_rank: Regular Contributor
timestamp: December 21, 2022, 11:08:02 pm
content: Ok, CLIPs and service manual in hand. I will follow the diagnostic procedures and report back.

author: EE4all
author_rank: Regular Contributor
timestamp: December 27, 2022, 04:45:18 am
content: Just to close this off, the YTO was working, but output was far too low for the amp to work properly without throwing errors. I replaced the YTO with a strong one, and the LO error went away.

author: Tony_G
author_rank: Super Contributor
timestamp: December 27, 2022, 05:22:35 am
content: Just out of interest, did you get a YTO from another 8563E (or one that was a spare part) or did you use a different YTO and work it to fit?I have an 8563E that works fine but just interested in what you did to repair.TonyG

author: EE4all
author_rank: Regular Contributor
timestamp: December 27, 2022, 05:38:46 am
content: I got the YTO from another 8563E that I got for parts. The original YTO was completely dead, and I ordered a replacement refurbished one off of ebay. That is why in my first post I assumed the YTO was ok, as all the errors except the LO AMPL one went away after making the adjustments for the new YTO. I would later figure out that although it worked, the output being under 0 dBm was far too low. A few days later another very old and broken 8563E that I bought showed up, and it had a strong YTO! I was able to use it to fix the first 8563E. The refurbished YTO is going back to California.

author: EE4all
author_rank: Regular Contributor
timestamp: December 27, 2022, 04:40:27 pm
content: Here is how I was measuring the YTO output power level, as I didn't have an analyzer that would cover such a high frequency. I didn't bother dialing in the offset to the power meter (for the attenuators). There are 40 dB worth there, as that sensor has a maximum input of -20. Setting span to 0, and then measuring it, the highest point was here, with -4 dB.
Audio Run Capacitor/Spark Arrest Cap. replacement help - Page 1
Forum section: electronics / repair

author: WhatsICC
author_rank: Contributor
timestamp: May 05, 2023, 04:26:05 am
content: I’ve got an Audio Reflex MR-110 Turntable. It’s an OEM of the JVC VL-5. Exactly identical except for the film cap used. A Rubycon .047uf M 1500WV oil NP cap. The JVC variant seems to use a regular “orange drop” poly film cap. Same capacitance .047uf as the JVC service manual calls for, however no voltage rating given in the manual.I have a .047uf 630v poly cap. Could anyone give insight if this would be sufficient enough to replace with the existing .047u 1500wv capacitor as this seems way overspec? I have read this has been done before, andhttps://www.justradios.com/captips.htmlstates this under Non-Electrolytic Caps.The table is a direct AC motor and this is the only cap; I am assuming it is a run cap.

author: floobydust
author_rank: Super Contributor
timestamp: May 05, 2023, 04:54:46 am
content: It's not a run cap, too low in value. It's most likely just to suppress arcing across the motor's on/off switch. I replaced similar one in my Thorens.For a modern replacement I use 275VAC X2 film cap. It is subject to mains transients when the TT is off, hence the high voltage rating. But if it fails short circuit no fire hazard or anything, because it's in series with the motor (when the switch is off).So I would say your 630V part is fine, if it fits.

author: WhatsICC
author_rank: Contributor
timestamp: May 05, 2023, 05:32:17 am
content: Thank you for the affirmation! I appreciate it.I'll install the new cap and start spinning. I should have looked for an X2 or Y capacitor for safety but overlooked them.I was wondering why the original 1500v capacitor was so high, I overlooked the transient spikes from the mains.Thanks again for the insight!
HP LaserJet series - need a schematics of PSU - Page 1
Forum section: electronics / repair

author: Jurek_p
author_rank: Newbie
timestamp: August 21, 2022, 09:11:29 pm
content: Hello,Please help me with the schematics of the power supply unit. The model numer is RG-2500, but I can't find it anywhere...This power supply is included in the following printers: HP LaserJet 4 / 4M (C2001A / C2021A), HP LaserJet 4 Plus / 4M Plus (C2037A / C2039A), HP LaserJet 5 / 5M /5N (C3916A/C3917A/ C3952A).https://usermanual.wiki/Hp/HpPrinterC2001AUsersManual549338.731490769.pdfThanks a lot.

author: tooki
author_rank: Super Contributor
timestamp: August 22, 2022, 07:46:36 am
content: Check that part number more carefully.But the chances of finding a schematic are very, very low. It’s unlikely they were ever published, since the power supply is intended to be replaced as a module.I’d open it and begin doing the typical troubleshooting for a power supply of that age. It’d be unsurprising to find dead electrolytics in something from that era.

author: Jurek_p
author_rank: Newbie
timestamp: August 22, 2022, 08:04:33 am
content: Thanks a lot for your answer. The PSU is working fine. I just got this one from recycling and want to use it in a project which needs a +/- 12 VDC supply. This PSU supplies 24VDC and couple of 5VDC outputs. My idea is to modify a 24V output as +/- 12VDC outputs. I'm not sure if it would be as easy as worth doing it. Just as experiment. Without schematics I won't be able to do it, I think.It would be nice to have about 1.5A from both 12VDC outputs for my purpose.I have measure the current from 24 VDC output with 10 Ohms load and it's about 2.46A. I think it's a lot for this unit. It's 56W and I don't think it's meant to be pushed that hard. But I don't know... this is probably 50W PSU?

author: wasedadoc
author_rank: Super Contributor
timestamp: August 22, 2022, 12:53:04 pm
content: Even if you get the schematic I think you have little chance of modifying it to give +/- 12 Volts at anything near 1 Amp. The transformer in a switched mode power supply is a key part of the design.For low very currents you could make a virtual ground at the middle of the existing 24 Volt output using a couple of low value, high wattage resistors. For higher currents you would need additional active circuitry and power transistors. Think about it. If you are taking 1.5 Amps from the +12 side but close to nothing from the -12 side, the overall 24 Volt output is still giving 1.5 Amps. That "extra" 12 Volts and 1.5 Amps has to go somewhere as 18 Watts of heat.I suggest you just go on ebay and buy a couple of those modules like in the attached photos. The 12 Volt 2 Amp one is £5 delivered in the UK. Less then US$15 for two?
SR630 schematic wanted - Page 1
Forum section: electronics / repair

author: Oldguy
author_rank: Newbie
timestamp: December 20, 2021, 02:32:27 pm
content: I am looking for a schematic for Stanford Research Systems SR630 a 16 Channel Thermocouple Reader.I am in the process of repairing one. I have the manual with a complete parts list but it does not have a schematic. So... If you have the schematic it would be really helpful to get a copy. Thanks.
Brymen 235 - Page 1
Forum section: electronics / repair

author: Wazoo23
author_rank: Newbie
timestamp: October 29, 2022, 12:33:23 am
content: Hi,I bought one of the EEVblog BM235 multimeters a few years back as a hobbyist and was really happy with the quality. But last year it started getting stuck in a boot loop when i try to use diode mode. It will light up the whole display then say diod in a endless loop. I can still however still switch to capacitance by pressing select. I was wondering if anyone has a ideas. That or even a pinout for the main IC, i have had 0 luck trying to search it.Thanks
3-terminal gas discharge tubes - Page 1
Forum section: electronics / projects

author: gardner
author_rank: Regular Contributor
timestamp: May 26, 2014, 07:16:05 pm
content: Are there any good design guides out there for using GDTs? In particular, I want to understand the use of 3-terminal ones . The specs show nominal strike voltages for the tube, but it's not clear whether this is between any pair of electrodes, or if the strike voltage varies depending on which electrodes are in play. I *think* that the three terminal devices are designed to protect a signal pair by crowbarring either one or both to earth/ground, and you'd typically run the two outside electrodes to your signal paths and the centre electrode to your ground/earth -- but that's mostly a guess. I also *suppose* that striking an arc between any two electrodes will effectively allow all three current paths simultaneously -- once the tube's full of plasma, the whole thing will conduct any which way. Is that one of the design objectives for the three-terminal tubes, or do I have that wrong?

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: May 27, 2014, 03:50:40 am
content: Your concept of the operation of the GDT is correct as far as I have ever seen them used in transient suppression ie combined common and differential mode.Many moons ago I installed and maintained telemetry and instumentation equipment in an area of the UK that was notorious for lightning discharges. All of the underground and overhead cables- for data, telephone and 0-10mA or 4-20mA loops were protected at either end by arrestors using, at the simplest, a 3-terminal GDT, two 63mA fuses (?) and a pair of 75 volt zeners. We also used self resetting arrestors which eliminated the fuses but still used GDTs as the main shunt to ground. Bear in mind that they are not instantaneous.Regards, BT

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 27, 2014, 04:06:05 am
content: Yes, the GDTs are made in both 2-terminal and 3-terminal varieties. This shows a belt-and-suspenders circuit that uses both...From:http://electronicdesign.com/components/gas-discharge-tubes-help-protect-vdsl-equipment-and-xdsl-splitters

author: gardner
author_rank: Regular Contributor
timestamp: May 27, 2014, 05:02:47 am
content: Thanks. After a bit more rummaging around, I found this:http://www.littelfuse.com/~/media/Electronics_Technical/Datasheets/Gas_Discharge_Tubes/Littelfuse_GDT_SL1021AB_SL1024AB_PMT8_Datasheet.pdfIt kinda answers my questions:"The three electrode configurationis used in applications where simultaneous crowbaraction of two signal lines is required."And there's a diagram showing the tip and ring go on the outer electrodes and the earth in the centre. So I guess that's me sorted.There's a timing diagram that shows the On-State voltage reached after 800ns -- I think a TVS diode would turn on in a few ps and a MOV in under 10ns -- so, yeah, not super fast.
Keithley 2100 - DSP pin assignment/interconnection - Page 1
Forum section: electronics / repair

author: Arca
author_rank: Newbie
timestamp: March 03, 2021, 05:52:39 pm
content: Hello all,I got a "broken" Keithley 2100.It had error +599 that I solved by replacing the 1000uF capacitors. Now it looks to run fine, Self Test is OK.I have a question about the DSP. It seems that there is some "bridges" between pins on the ones I have.Is it normal ? Could you show me picture of your DSP to compare ?Thx

author: picburner
author_rank: Frequent Contributor
timestamp: March 03, 2021, 06:32:18 pm
content: pins 14 and 15 are both VSS, so there is no problem, for the others I don't know.

author: picburner
author_rank: Frequent Contributor
timestamp: March 04, 2021, 01:40:06 pm
content: This pic is taken fromhere, the instrument is one of the Keithley 2100 clones.With a little imagination, since the pic is poorly defined, it would seem that the pins are short-circuited here too.

author: Arca
author_rank: Newbie
timestamp: March 04, 2021, 05:43:14 pm
content: Hello,Thanks a lot for your answer !So yes you are right, it seems that it's normal.I admit that I was a little bit stressed because my soldering iron fell inside... 😅So thank you again !

author: arturmariojr
author_rank: Contributor
timestamp: August 04, 2021, 03:19:02 pm
content: For Keithley Service Manual, it is the same as Array M3500A. Here you are the service manual.Best wishes!Artur
Help IDing some graphics card components - Page 1
Forum section: electronics / repair

author: edavi
author_rank: Contributor
timestamp: February 22, 2021, 10:01:44 pm
content: I'm fairly new to finding the right replacement components when it comes to the unmarked capacitors/resistors on a PCB, which looks like what are missing on this card. The card in question is a Gigabyte GTX 1080 TT (it's their weird blower edition card). This card was given to me since it was 'dead' and I'd like to bring it back to life (considering the only issue is these components that got ripped off). Will I most likely have to eyeball it for replacing? I've attached a picture of my card and a reference new one from newegg's website. From what I see, the big two pads to the left, LB10 and LB9 are ripped off, C1064, C1079, and C1078 are ripped off as well. Also, I have an LCR meter to check other values of components on the board.
ONsemi/Fairchild FSFR1700XC datasheet? - Page 1
Forum section: electronics / repair

author: shakalnokturn
author_rank: Super Contributor
timestamp: September 13, 2020, 11:03:06 pm
content: This is in a Samsung UE46F5000 TV as the main supply control.ASWO states the FSFR1700XSL as a replacement for the obsolete FSFR1700XC.I have actually replaced it with a FSFR1700US because that's what I had around and it does the job.I would have preferred to compare figures before doing the replacement, somehow the FSFR1700XC datasheet doesn't seem to exist.Anyone know why or have it?

author: pepona
author_rank: Contributor
timestamp: September 14, 2020, 02:29:28 am
content: Google FSFR1800, there is a lot of info.https://ar.mouser.com/datasheet/2/308/FSFR1800HS-D-1810025.pdfhttp://dalincom.ru/datasheet/FSFR1800.pdfWe used the 1800 to replace the 1700 and it works perfect.I hope it was useful to you.RegardsMarcos

author: shakalnokturn
author_rank: Super Contributor
timestamp: September 14, 2020, 09:38:39 am
content: Thanks, good to know the FSFR1800 works too, I have plenty of data sheets even for FSFR1700 with different suffixes I'm really after the datasheet for the FSFR1700XC mainly to check RDSON and power limit.
Help identifying receiver ic - Page 1
Forum section: electronics / repair

author: Texx
author_rank: Newbie
timestamp: May 18, 2020, 08:49:06 am
content: Hello!I would like to repair RC car (Maisto brand). Receiver IC seems drwaing excessive power and can not connect to remote anymore. Unfortunately IC doesnt have markings. It is soic 16 working on 3.3V dc working on 2.4Ghz. U2 on board. Could you give some hints?

author: telectric
author_rank: Contributor
timestamp: May 18, 2020, 09:07:13 am
content: Hi,It looks like a conformal coating has been applied. This sometimes is opaque enough to obscure the chip markings. I'd take some isopropyl alcohol (90% or greater) and see if the CC will come off. You might get lucky.Regards, Tracy

author: RoGeorge
author_rank: Super Contributor
timestamp: May 18, 2020, 09:22:01 am
content: Some toys manufacturers use their own custom ICs, chances are they won't sell replacement ICs.Look on the car, or on the remote, (maybe in the user manual, too) for a label with the FCC-ID code. Search online for that code number, and you might find the schematic diagram on the FCC-ID website. Not all toys has an FCC-ID.

author: Texx
author_rank: Newbie
timestamp: May 18, 2020, 09:28:24 am
content: I can try to clean, but as it looks the same style in remote, they have done it on purpose. Anyway if it is custome part than I give up. I had an idea that that is something pupular than can be bought on LSCShttps://www.youtube.com/embed/Gy-k7pGKnHk

author: fzabkar
author_rank: Super Contributor
timestamp: July 03, 2020, 11:03:36 pm
content: Tell us the markings on the other ICs. I have studied numerous RC circuits. Maybe something will jog my memory.This is the FCC ID search URL:https://apps.fcc.gov/oetcf/eas/reports/GenericSearch.cfm

author: Texx
author_rank: Newbie
timestamp: July 05, 2020, 10:19:24 pm
content: Thank you for support but I don't have that board at me anymore. Only that picture above!
Cap question - Page 1
Forum section: electronics / repair

author: dropkick
author_rank: Contributor
timestamp: April 01, 2020, 05:10:18 am
content: Is C11 (the one that's split open!) a tantalum? Does it matter if a tantalum or regular electrolytic is used for replacement? This looks to be part of the IR sensor or a data line on a old stereo.EDIT : Cancel that... looks like a supercap? 0.047F

author: keymaster
author_rank: Regular Contributor
timestamp: April 01, 2020, 07:51:24 am
content: More like a super cap ,it looks to me. (https://eu.mouser.com/ProductDetail/KEMET/FME0H473ZF?qs=sGAEpiMZZMsCu9HefNWqpqdI4%252BbldnBQ1YyRdOJK%2FBLJ9vTZGQJtww==)
Tektronix 11403 - Error G3731 on Digitalizer Board - Page 1
Forum section: electronics / repair

author: scroky
author_rank: Contributor
timestamp: November 18, 2019, 05:31:57 pm
content: Hi,after a few months of non-use the my wonderful main frame Tek 11403 complains about replacing the lithium battery of the CPU board when it is turned back on. I will replace the two lithium batteries on the mainfraime, but continuing the diagnosis, now i will complain about the error G3731 in the DIGITALIZER / POINT ACQUISITION / AD Voltage section with a variable measurement -0.864 ...- 0.851V while the correct interval is -0.750 .. .-0.850V.Furthermore the enanched accuracy is no longer available: ENANCHED ACCURACY FAILED: MAINFRAME: MAIN TIME INTERPOLATOR. PLUGIN NA. TRIGGER NA.It seems a problem that cannot be easily solved since the manual does not provide indications on errors and on chip level repair, but only on board level reapir.Does anyone have any experience with this?ThanksAlessandro
Issue with voltage divider for DC bus voltage sensing - Page 1
Forum section: electronics / repair

author: XaviPacheco
author_rank: Regular Contributor
timestamp: September 30, 2019, 01:02:10 pm
content: In the picture below, you can see a string of 10 resistors used for DC bus voltage sensing. I think that the blue resistors (the original ones) are 400k/1W. The colors are: yellow, black, black, orange. One of the resistors got open, and I replaced it with the one you see different in the string, the one in the red circle. It's a 390k/1W resistor. The equipment worked well for a couple of hours, then the resistor in the white circle got open.Do you think the new resistor could have affected the string so that a new resistor got damaged? Well, indeed we have a variation of 10k in the array with the addition of a 390k, which leads to increase the current. I did not find the 400k resistors in the market in that package (MELF). What would you recommend?

author: duak
author_rank: Super Contributor
timestamp: September 30, 2019, 06:40:39 pm
content: Is the unit a motor drive or induction heater?What I think is that the first two resistors in the divider chain are subjected to larger AC voltages than the following resistors. I suspect the replacement resistor failed because it may not be capable of the same AC+DC voltage as the others.If you look at the circuit board you will see a wide trace on the the other side that may be capacitively coupling to the connections between the resistors. If this is correct, the other chain is actually under more stress.I would do the following:1. if you cannot find an exact or better part, then replace the bad resistor with one from the other end of the string, that is, the lower voltage end.2. put the part or parts you can find in the now empty spot. I would also put a 10K resistor in series with the 390K to better match the 400K. You may have to do this to both resistor strings to ensure they are identical.3. clean the resistors and circuit board to ensure there is no conductive contamination.
led string in parallel - Page 1
Forum section: electronics / repair

author: pcmad
author_rank: Regular Contributor
timestamp: December 23, 2019, 11:24:47 pm
content: string of led in parallel 20 in the array led are taking more power than normal and are flickringtesting on multi meter in diode mode show leakagefeeling the led i feel no heatany tips to find the faulty one with out taking them apartthank you

author: German_EE
author_rank: Super Contributor
timestamp: December 24, 2019, 09:56:57 am
content: Attach your diode array to a 400mA current limited power supply. SLOWLY increase the current and see which diodes light first, these will be the devices drawing the most current at full brightness.Running twenty diodes in parallel without matching them first is not a good idea as (as you have found out) some will take more current than others. You need to either a) match the diodes before you solder or b) change your design so that you have a current limiting resistor for each diode.

author: pcmad
author_rank: Regular Contributor
timestamp: December 25, 2019, 10:05:13 pm
content: thank you found it as you stated also the 20 string led i did not make its came pre made
LG43UF680V TV - Page 1
Forum section: electronics / repair

author: mountpleasure
author_rank: Newbie
timestamp: August 29, 2019, 07:29:50 pm
content: Hi my LG43UF68V TV has sound only and a snowy static picture, from all inputs. Help please

author: Rasz
author_rank: Super Contributor
timestamp: August 30, 2019, 07:20:04 pm
content: what about OSD?

author: mountpleasure
author_rank: Newbie
timestamp: August 30, 2019, 08:22:53 pm
content: OSD is white static fuzz
Repair of an Hp1345a Display. - Page 1
Forum section: electronics / repair

author: Simon Spiers
author_rank: Regular Contributor
timestamp: April 24, 2019, 04:56:44 pm
content: Is there anyone who could point me in the right direction with thus fault on a HP 1345a display. It was working originally and the sth display intensity started flashing, which I first thought was an HV flashover.I squirted a few Ics on the A1 board u15,16 and 25 and this is what happened!Am i looking at a stroke generator fault or Vector fault? I am close to giving up with this bloody thing!

author: pbarton
author_rank: Frequent Contributor
timestamp: April 24, 2019, 08:38:36 pm
content: Warning: I have no experience of the HP1345A/3562A, however your display reminds me of the Digital Equipment Corp (DEC) GT40 vector display, on which I spent many hours landing the lunar module (a.k.a. moonlander).Your photo appears to me that your are missing some ‘Z’ blanking as there are far too many lines visible (Z appears to be permanently stuck ‘ON’).The ‘Intensity Control’ U25 appears to be a good place to start. Is the O/P on U25 switching or is it stuck?Furthermore, you mention "intensity started flashing" which could also indicate a problem with the Z circuit.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: April 24, 2019, 09:01:15 pm
content: Another options is to replace it with an LCD:http://www.simmconnlabs.com/

author: Simon Spiers
author_rank: Regular Contributor
timestamp: April 24, 2019, 09:02:32 pm
content: Thanks for your rely. I have been probing around and found one op amp is dragging the -15 V rail down and is shorting the output of its associated DAC (u16 & u18). So it looks live to op amp has failed. I'm hoping the intensity control chip is good as it is not available from anywhere I can find.

author: Simon Spiers
author_rank: Regular Contributor
timestamp: April 24, 2019, 09:04:52 pm
content: I~ have considered replacing with a LCD display. But as the 3562a is far from reliable, i can't justify the expense.

author: duak
author_rank: Super Contributor
timestamp: April 25, 2019, 09:16:49 pm
content: I would check for bad tantalum caps - here's one experience:https://whatever.sdfa3.org/tag/hp1345a.htmlI'd then check the Z-axis drive stuff on schematic 5 (figure 8-14). The cathode and first grid of the CRT are 2500 V below circuit common so you have to be careful with probing. I'd expect Q4-Q6 or something around around them to be shorted or open.Cheers,
Trio CS1352 oscilloscope trigger/blanking board photo needed - Page 1
Forum section: electronics / repair

author: gkmaia
author_rank: Frequent Contributor
timestamp: April 20, 2019, 04:53:00 am
content: It may be a very long shot. But is there any one with a Trio CS 1352 who could send me a photo of the trigger/blanking board both sides? My board has some weird jumpers that do not match the schematic and I need to check and not sure if those are factory revision or previous owner fiddling around.

author: TsungaM
author_rank: Newbie
timestamp: April 24, 2019, 08:35:34 pm
content: I have one my bench rigt now...This is my first post on this forum, let's see if I manage to attach the pictures... (and that it's the right board).Do you, by the way, have a schematic, because I have not. I'm thinking of modifying mine into some cool x/y-display.

author: gkmaia
author_rank: Frequent Contributor
timestamp: April 24, 2019, 10:01:15 pm
content: WOW! That is super helpful. I have the schematics. Please send me yuo email on a private message and I will email that to you.Thanks!!!!

author: TsungaM
author_rank: Newbie
timestamp: April 25, 2019, 10:31:59 am
content: Great! If you need any other pictures or more detailed I can give it a try. I'll send you a pm with my email.
Removing Tektronix 2246 Mainboard - Page 1
Forum section: electronics / repair

author: atw58
author_rank: Newbie
timestamp: April 23, 2019, 04:14:00 pm
content: I am fairly certain the Ch A triggering U421 28 pin DIP is faulty and getting a replacement part from Qservice. I removed all the mainboard screws, freed the power supply pins and took out the crt but something near the front is holding the pcb. After some fruitless searches for 2246 and 2465 front panel/mainboard teardowns, I'm hoping for some advice. Removed all the knobs at the front and thought the front bezel might come off easily but this is not the case.

author: med6753
author_rank: Super Contributor
timestamp: April 23, 2019, 04:36:06 pm
content: If the 2246 is similar to the 2465 or 2430 look at the top of the front bezel. Is there a plastic strip running across the top? If yes, carefully pry it up. There will be 3 or 4 screws underneath it. Should also be screws on the underside. Once removed front bezel should come off. And chances are you will find out why the board can't be removed because there will be screws attaching it to the front frame.Hope this helps...not familiar with the 2246.

author: atw58
author_rank: Newbie
timestamp: April 23, 2019, 04:40:35 pm
content: When in doubt read the service manual last. Turns out the front potentiometer and switch boards must be removed to reveal the last screw that holds the mainboard.Thanks for the suggestion.

author: Testtech
author_rank: Regular Contributor
timestamp: April 24, 2019, 10:57:54 pm
content: Why remove the board? Cut the legs off, heat and remove the pins, resolder from the component side.The 2246 board is a PITA to remove, and not necessary...
HP 8591C  spectrum analyzer Repair ... - Page 1
Forum section: electronics / repair

author: barry@tnt
author_rank: Newbie
timestamp: April 24, 2019, 08:12:40 pm
content: ..hello every one ...im in need of any assistance on the repair of the hp8591C spectrum analyzer , as the history of this unit ithas been parked up most of its time before heavy use by its previous users , came in for a monitior/screen beingdefective , the unit remained scraped an parked up for some years before a new screen was bought for it , at the timewhen the screen was changed and the unit was first powered up some of the boards top side started to smoke , later found outthat their are some 22uf 25v tantilum capacitors that burnt an shorted on the boards , The analog interface board had a resistor an cap burnt ....And their was another small board with just the caps shorted out ...... I have been thou all the boards for more damage but have not seen any thing else to cause a problem , so far the unit powers up with the grid on screen , software version is displayed, and i can adj the frequency span interms of numbers with the dial , but their is no noise floor , an when connected for self calibration it runs the mode but the test fails i think the calibration output is not working an so is the spectrum for the noise floor ....(power supply voltages all test ok except for one which was the 15v+ ... was droping to 13.8 an 12.6 at different times)i did injected an outside 15v source but did notting to bring up the functionality of the noise floor on the spectrum ! ...not sure if its a software problem or hardware ! ....Any assistance in troubleshooting this unit will be greatly appreciated as i would really love to get this up an running for mypersonal use !