hybridfree/eevblog-posts huggingface dataset:
Need an alternative for this MOSFET - Page 1
Forum section: electronics / repair

author: onlyprinzp
author_rank: Newbie
timestamp: November 10, 2017, 06:18:28 pm
content: Hello,I have a macbook logicboard 820-2850-A which was not turning on. Managed to find the part which was the problem.The part in schematic:Q7535CSD58857Q5MLP5X6-LFPAK-Q5Want to replace the faulty MOSFET with a working one, dont have any of this home, so I would like to know is there an alternative MOSFET for this?Thank you!

author: SaabFAN
author_rank: Frequent Contributor
timestamp: November 10, 2017, 07:46:56 pm
content: Basically any MOSFET in the same package should work. You just need to know if it is P-Channel or N-Channel.Btw. check if it is really a MOSFET. If it is near the Charging-Connector, it could also be an ESD-Protection Array. They are supposed to fail open, but often enough they fail short, taking out traces, connectors or just suck away enough power so the Laptop doesn't turn on.If the computer turns on with the component desoldered, it was most certainly a ESD-Diode.

author: onlyprinzp
author_rank: Newbie
timestamp: November 11, 2017, 12:17:48 pm
content: Hello,thanks for your reply. I am sure it is this mosfet cause it got very hot extremely fast. When I desoldered it, the laptop started booting and so on, just now it wont finish the boot cause I think this part is missing. I know that it is an N-Channel MOSFET, just I dont know with with other mosfet i could change it. I cannot find a datasheet on the one i need.

author: up8051
author_rank: Frequent Contributor
timestamp: November 11, 2017, 03:14:55 pm
content: https://www.elvikom.pl/szukam-zamiennika-tranzystora-csd58857q5-t40368.html
HP E4421B error 513 - Page 1
Forum section: electronics / repair

author: Ej
author_rank: Newbie
timestamp: September 29, 2017, 08:32:38 am
content: Hi guys,I'm new here, sorry to bother y'all.....found a E4421B 3 GHz gESG series generator working ok, but it has one flaw: error 513, Het. VCO unlock....nevertheless everything seems to work. Something is wrong with the 1 GHz PLL. Anyone seen this and knows which part should be replaced?Thanks, Eric

author: Ej
author_rank: Newbie
timestamp: October 31, 2017, 09:45:30 am
content: Solved it by swapping the defective plugin with one from eBay. Not the best way but now I see no more annoying errors

author: Samogon
author_rank: Frequent Contributor
timestamp: October 31, 2017, 04:25:38 pm
content: 513 oven is cold, usually it disapears in few minutes.

author: Ej
author_rank: Newbie
timestamp: November 08, 2017, 10:12:10 pm
content: Your comment is not correct, oven cold is error 514, 1 GHz reference oscillator unlocked is 513.

author: Samogon
author_rank: Frequent Contributor
timestamp: November 09, 2017, 06:56:35 am
content: Oopsy, my bad

author: Ej
author_rank: Newbie
timestamp: November 11, 2017, 03:13:02 pm
content: What forced me to solve it this brute force by forking out $$$ is the fact HP doesn't publish any real schematics, that's the real bad!The reference 10 MHz oscillator to which the 1 GHz PLL is locked on this newer board is smaller then on my original plugin.
Original or used part for repair HP 66332a / AG 6632B  - Page 1
Forum section: electronics / repair

author: OP27
author_rank: Newbie
timestamp: November 14, 2017, 04:57:32 pm
content: Hi all,I am currently repair the device HP66332A.The my device has a broken front cover. (transparent display cover, VFD it is OK)Where i can buy parts? I need the whole front cover.I found the part number (service manual agilent): "5063-3426" Front Panel Assy, Std unit.Nowhere can not find this partThe part can also be used. Thank you for any help.
CMU200 low TX modulation. - Page 1
Forum section: electronics / repair

author: g4wyz6
author_rank: Newbie
timestamp: March 17, 2017, 04:40:05 pm
content: HelloI've just brought one a CCU200 and found that the TX analogue modulation is very low, if I set the CMU200 for 28.3kHz FM deviation monitoring using a Marconi 2505 Modulation Meter the deviation is only 5kHz noisy but the modulation frequency is correct. If I switch the modulation of and look at the carrier its clean.This CCU does not have the CCU-B41 audio generator option, but I believe the analog modulation is derived in the Digital board?Is the deviation low?As I maybe chasing my tail.Any help would be appreciatedMike

author: g4wyz6
author_rank: Newbie
timestamp: March 17, 2017, 10:16:48 pm
content: Well I've discovered the CMU200 had more self-tests then I thought - used the scroll key!Narrowed the fault down to the CMU-B21, MC68K module.Mike

author: g4wyz6
author_rank: Newbie
timestamp: April 28, 2017, 02:32:17 pm
content: The MC68K module (DSP) the data was reloaded and even tried the previous firmware.Eventually thought this maybe the wrong branch, it turns out the fault was on the A7 'ADC MODULE1, DDC MODULE1, TXDSP MODULE1, AUC MODULE1 in the DIGITAL BOARD'.The fine dust had turned into a dark grey glu as the previous owner had kept it in a cupboard for a number of years, but there was surface corrosion on the cover shells, more like a damp garage.FM deviation is now OK, but low level deviation i.e. 5kHz is 6kHz (20% one of specification), tried re-calibration but no effect. Does anyone have any info on this module please.73'sMike G4WYZ

author: RF_fanatic
author_rank: Regular Contributor
timestamp: November 10, 2017, 10:09:45 pm
content: The root cause is most likely a defective: 1100.2500.02 board (add on board in the Dig unit, the board with the large heat conductive tape)If the deviation or signal waveforms are distorted than the cause for the problem is in 90% this boardYou can easy test this by :Setting the generator at for instance 1200 MhzSet the analyzer at 1200MhzSet span to 1MhzAnd than modulate in various modes. DSB, SSB, AM, FM (and select deviation) FM Stereo (if K14 installed)It must show the typical waveform responses, often the SSB and DSB are distorted, for instance a DSB response in a SSB mode. Or too low deviationSometimes it can also be detected during calibration if it fails to use the full 500khz
Replaced the display in my 34401A - Page 1
Forum section: electronics / repair

author: woody
author_rank: Frequent Contributor
timestamp: November 10, 2017, 05:53:18 pm
content: Happy to report that I managed to replace the display in my Agilent 34401A. The old display showed signs of having been used on 5 digits for the best part of its life, the new display is bright and evenly lit (although that is hard to show on a photo)It took me an hour, most of which was spend in taking the front off and taping kapton to the legs of the new display. The threads on this forum about similar repairs helped a lot. Thanks guys!The experience I got from repairing slot machines in a previous life paid back today. A solder sucker is like a bicycle, once you learn how to use one you never forget it
Help identify this IC - Page 1
Forum section: electronics / repair

author: OmegaHyperion
author_rank: Contributor
timestamp: November 06, 2017, 11:02:03 pm
content: Well, im repairing yet another thing, and this time its a scale. Its giving me error codes that point to the ADC or some preamp in the thermal compensation system being shot, but i dont have a thermal camera to check the chips. I have traced the PTC to this chip, but im having difficulties finding a data sheet, let alone a place to buy it, so i cant replace it. (i checked the PTC, it works, since i dont have a part number i cant check the exact value, but it did reliably change resistance proportional to temperature)I was hoping someone here could help identify and or help me find the data sheet to this chip, and thus help this old scale work once more.

author: Cyberdragon
author_rank: Super Contributor
timestamp: November 07, 2017, 12:10:10 am
content: It's a 3562 TKS2 chip apparently. Found it from alot of Chinese sellers ranging from US$0.10 to $5.00. However, there appears to be no information, not even the function of the chip. They don't even have any real photos of the chip, just stock chip photos, and all the datasheet links are broken or "available on request".Oh, and all of the product descriptions are random words and numbers in the catagories that make no sense at all. They really don't want anyone knowing what this chip is.

author: amyk
author_rank: Super Contributor
timestamp: November 07, 2017, 04:15:52 am
content: Manufacturer is European Silicon Structures (or European Siliconstructures, depending on which webpage you read...), acquired by Atmel a long time ago. Maybe if you trace the pinout it might correspond to a current part.

author: Chris56000
author_rank: Frequent Contributor
timestamp: November 08, 2017, 10:11:51 pm
content: Hi!I've seen this idea of a T- filter circuit between pins 9 & 10 of a chip, which the small picture you've posted clearly shows, before, but I can't remember for the life of me where I saw it!Can you tell us what the board is from? I'm sure that there's some sort of TV IF, PLL or gain block IC that has this filter going between 9 and 10 in exsistence that's more widely known!Chris Williams

author: OmegaHyperion
author_rank: Contributor
timestamp: November 09, 2017, 12:21:34 pm
content: The board is from a Sartorius BP310S Precision Scale.Its showing error codes that show problems with the temperature compensation circuit. I checked its PTC, so my guess would be that this chip is the problem.
HP 53131 Option 030 BG7TBL 8Gb Clone Brd - Repair - Page 1
Forum section: electronics / repair

author: B1nary
author_rank: Contributor
timestamp: November 08, 2017, 06:45:57 pm
content: I am new at this but I'm going to try to repair this board - to learn something if nothing else.The 8Ghz board was used once. The next time I needed to use it. It was dead. Some things I've noticed - it is not very sensitive and requires a pretty good signal to trigger (at least -10dBm). I used a LCR meter to measure the components in circuit and an RF probe to try to trace the RF Signal generator test signal from the SMA connector through to various components but I don’t have a schematic and the seller off eBay refused to provide any information on this board that would help. I am probably doing something wrong but I don't have enough knowledge to know what it is. I will list the readings I got in hope someone will have the patience to help me through this. I’ve set the RF Gen to 0dBm, 500MHz and connected it to the SMA input of the option board. As noted, I bought an RF Probe (a suggestion from a user on the board) and would like to know a few steps and reading I should expect using the probe. The HMC362S-8G chip has 5V on pins 1, 3, and 4. The pin-out says this is right. Pin 5 is the input from the SMA connector. Using the RF Probe and with an input of of 0dBm I get a 30mV reading on pin 5. I get 3.2mV on pin 1, 3.2mV on pin 3 and 4.3 mV on pin 7.Based on these reading can someone tell me if the chip is good or bad. At least I'll have a place to start. I am brand new at this and should I post this in the beginners form?Any suggestions will be greatly appreciated.For what it is worth I sent a request to Analogue Devices asking if they could tell me how to determine of the Divider chip was good or not;Here is the answer I got from "Ron"."Here is a link to the Datasheet for the HMC362. We can not offer any additional support at this time".BTW - the link was to the wrong data sheet :-(Lesson, don't ask a manufacturer for help.(Edit) I uploaded the HMC362 chip info. I hope this will make it easier for anyone who might offer a suggestion or twoC10-101.7pF, C15-.73K, C7-18.9uF, C8-18.9uF, C12-18.9uF, C21-18.9uF, C22-18.9uF, C5-18.9uF, C11-3.8nF, C17-3.6nF, C4-18.8uF, C6-18.8uF, R3-299R,R2-17.8R, C18-91.4nF, L3-0.2R, C3-18.8uF, L1-0.2R, C2-18.8uF, C20-18.8uF, R15-0.01R, R12-74.5R R4-74.2R, C19-18.8uF, C9-10.1uF, C1-10.1uFFinal Edit - in case anyone else has a problem with this boardAfter lots of testing (because I am new at this it took me a lot longer than someone with experience), I concluded the HMC362 S8 (4x) divider chip was bad. I replaced it and found the sensitivity of the board was vastly improved. As received I was lucky to get -10dBm to -15dBm for sensitivity. After the chip was replaced it is consistently -22dBm to -23dBM from 100MHz to 4.4GHz (highest my RF Gen will go)
Looking for old Rare Clevite Transistors for my PS - Page 1
Forum section: electronics / repair

author: JMdoubleE
author_rank: Newbie
timestamp: November 08, 2017, 03:19:45 am
content: Hey guysI have an old "Power Designs Inc" power supply that finally kicked the bucket. I am attempting to re-cap it when I realized the two main transistors are BAD!I am asking here because most websites I have seen only have one of the two that I am looking for!I need1x 2N257 transistor....TO-3 style1x 1356 aka 2N1356....TO-3 styleI believe both of these were made by CleviteIf anyone has a lead on em, I will gladly pay for your troubles as well as some shipping!If not...I guess this one is going into the dumpster!Thanks Guys...JOE

author: amyk
author_rank: Super Contributor
timestamp: November 08, 2017, 03:25:44 am
content: You should be able to find a compatible if not identical replacement.

author: texaspyro
author_rank: Super Contributor
timestamp: November 08, 2017, 06:00:16 am
content: Quote from: JMdoubleE on November 08, 2017, 03:19:45 amIf you dumpster it... members of the Cult of the Worshipers of Power Designs will hunt you down and hurt you!Power Designs supplies are holy relics filled with great mojo and are not to be blasphemed or trifled with. You should say 1000 Hail Teslas and beg forgiveness for even thinking of doing that.

author: Armadillo
author_rank: Super Contributor
timestamp: November 08, 2017, 08:27:17 am
content: http://www.talonix.com/shop/item.aspx?itemid=2685

author: floobydust
author_rank: Super Contributor
timestamp: November 08, 2017, 10:49:02 am
content: 2N257PNP Germanium 40V 3A TO-3,substitutes hereStronger Germanium parts:2N2065A40V 5ANTE 12145V 10A
No Display and no Output on ATTEN ATF20b - Page 1
Forum section: electronics / repair

author: weedhopper
author_rank: Newbie
timestamp: September 01, 2017, 08:26:08 pm
content: HelloWhen I start my ATTEN ATF20b, first, nothing appair.After short Time, right Keyboard is flashing and turning off.Nothing more, no Output.Question : is it Atten Repair Center in France ?Any Help will be welcomedThank you in advanceJP

author: weedhopper
author_rank: Newbie
timestamp: November 07, 2017, 08:54:19 pm
content: THANK YOU FOR YOUR HELP !!!!!!!!!!!!!!!!!!!!!!!
Tektronix LA probe P6860 - Mechanical Fastener Question - Page 1
Forum section: electronics / repair

author: rfdes
author_rank: Regular Contributor
timestamp: November 07, 2017, 10:30:16 pm
content: Regarding the nut bars used with the P6860 probes and the adapters, does anyone happen know the screw size/pitch of the lock down fasteners?I only have one nut-bar and one of the holes is stripped. I was thinking of buying some steel 'key-stock' and drilling/tapping a set of holes. I might even try filling the stripped hole with JB Weld epoxy and retapping. I figure I have nothing to lose.

author: lukier
author_rank: Unknown
timestamp: November 07, 2017, 10:57:23 pm
content: I don't know what's inside the nutbar, but for the PCB mounted probe scenario I bought the #2-56 PCB inserts (see Digikey 36-4871CT-ND) and they seem to work fine.

author: rfdes
author_rank: Regular Contributor
timestamp: November 08, 2017, 12:44:42 am
content: Thanks... that's all I need to know!
Weller DSX-80 desoldering iron repair - Page 1
Forum section: electronics / repair

author: Velund
author_rank: Regular Contributor
timestamp: November 07, 2017, 11:53:39 pm
content: Hello everyone.Just found that DSX-80 desoldering iron, that I use with my WMD-3 station, started to demonstrate wrong behavoir. Once I put it back to stand, temperature on a WMD-3 display changed with three dashes, and looks like it starting to cool. I tried to straighten wire where it come to a handle, and temp. reappeared on display immediately. Turned it off prompltly, and now thinking how to repair it, because it is needed often in thru hole rework.If it is broken wire near entry to handle - it is possible to shorten cable little bit to fix it, or new cable necessary anyway?

author: stj
author_rank: Super Contributor
timestamp: November 08, 2017, 02:23:02 am
content: this is a common problem, you can shorten the cable, or buy a new length.if you are in Europe, Rapid sells replacement cable for irons.
tti tg315 service manual? - Page 1
Forum section: electronics / repair

author: vixo
author_rank: Regular Contributor
timestamp: November 06, 2017, 06:00:03 pm
content: I picked up a cheap, new TTI TG315 on ebay. Unfortunately the DC offset isn't calibrated properly which is annoying.. looking inside there are a fair few trim pots but nothing on the pcb is labelled. Does anyone have a service manual or could give me any tips on finding one? I don't want to start twiddling pots randomly...

author: glarsson
author_rank: Frequent Contributor
timestamp: November 06, 2017, 06:16:15 pm
content: Have you tried the obvious option; ask TTI? They are usually very nice and will send what they have available.

author: vixo
author_rank: Regular Contributor
timestamp: November 06, 2017, 06:32:54 pm
content: I have sent them a message at aimtti.us. No reply yet - thought i'd ask on here in the meantime

author: bd139
author_rank: Super Contributor
timestamp: November 06, 2017, 06:53:47 pm
content: Compare with the TG200 series manual. I think they have the same or very similar boards in them. Just a different case and counter arrangement. The design has been around forever.DC cal on these usually calls for a DMM 4.5 digit or better, connect it across two pins in the DC summing amp and adjust the trimmer until there is a null reading. If you can find the summing amp and pot you can do this without the service manual. Basically you’re trimming the offset of the op amp.

author: vixo
author_rank: Regular Contributor
timestamp: November 06, 2017, 07:08:57 pm
content: thanks! good shout on the TG200 series manual. I'll have a look and a rummage..
PM3285A Oscilliscope repair - Page 1
Forum section: electronics / repair

author: toolnuts
author_rank: Contributor
timestamp: November 07, 2017, 07:53:09 pm
content: Hi All,I am trying to repair a Philips O'scope and I can't find the right part.On the back of the mains plug-in there was soldered a filter of some kind. It was solderedon the back of the combo filter/plug-in for the power chord.I have the repair manual but it dose not have the filter in the BOM.The nomenclature on the filter is DVE 565-1 LD2 250V-SHAny help would be appreciated.Thank you,Paul

author: toolnuts
author_rank: Contributor
timestamp: November 07, 2017, 08:35:46 pm
content: Ha,It turn out that it was just a capacitor - so I have it handled.Thanks anyway,Paul
Sorensen / Xantrex XHR 600-1.7 repair - Page 1
Forum section: electronics / repair

author: komradebob
author_rank: Contributor
timestamp: November 05, 2017, 10:07:44 pm
content: So I have a Sorensen / Xantrex 600V power supply that just blinks it's display LEDs at me when it gets powered up. Seems like it might be the low voltage switching supply not starting up correctly, but I've heard these are prone to failing in this manner due to 'current sense resistor' being burned out.Of course, the schematics are unobtainium.Before I go poking about in the guys of a 600VDC supply, I thought I might ask if anyone has any experience fixing them.Thanks!Bob

author: coromonadalix
author_rank: Super Contributor
timestamp: November 06, 2017, 01:49:01 am
content: Does it have the correct main ac input voltages settingshad the same problem with one wrongly configured ...

author: Seekonk
author_rank: Super Contributor
timestamp: November 06, 2017, 04:25:55 pm
content: Agree with above. This can also happen when there is a problem with the self powering secondary winding that powers the control inverter. The initial power up of the inverter chip is through a high ohm resistor that charges a cap. This can not supply enough power to keep it running. That is when the secondary winding supplies power. If that doesn't happen, it just keeps cycling on and off.
High voltage power supply repair for cash - Page 1
Forum section: electronics / repair

author: ankurb
author_rank: Contributor
timestamp: November 05, 2017, 03:53:50 pm
content: High voltage power supply potential fixing?If anyone is in the Los Angeles area and wants to help I can offer some money out of pocket. Honestly, don't want to kill myself trying to bite off more than I can chew trying to fix it.Below are some pics.Thanks!

author: IRFP460
author_rank: Contributor
timestamp: November 05, 2017, 09:37:19 pm
content: I'm pretty sure that's not a high voltage power supply but just the controls for one.It's missing a transformer and all the other high voltage parts, i'd assume they're connected via that 8-pin connector on the back.

author: ankurb
author_rank: Contributor
timestamp: November 06, 2017, 01:36:45 am
content: Hmmm not sure. Thanks. I'll ask around but I know it is an older style with vacuum tubes so older stuff.

author: cdev
author_rank: Super Contributor
timestamp: November 06, 2017, 01:48:18 am
content: Thats what I was thinking too. You have a control panel for a supply there.Also, be aware that very high voltage is quite dangerous.Note the very bright indicator light, lock, etc.

author: ankurb
author_rank: Contributor
timestamp: November 06, 2017, 03:06:46 am
content: Thanks for the info.Looks like I'll stick to my previous setup with flyback.

author: IRFP460
author_rank: Contributor
timestamp: November 06, 2017, 09:25:12 am
content: Quote from: ankurb on November 06, 2017, 01:36:45 amThat's true, it's an older model, but even with the magic of tubes you can't create high voltage without a transformer or something similar

author: voltz
author_rank: Frequent Contributor
timestamp: November 06, 2017, 10:11:55 am
content: A bit of searching came up with this:Field Emission Corp High Voltage Supply Model 3145Have to agree, it looks like a controller for a larger system. The main give-away is there are no high voltage terminals to be seen anyway other than a multi pin cable connector. The unit probably connects to a main generator unit which then does all the high voltage stuff.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 06, 2017, 11:07:15 am
content: What kind of tube is in the third down pic?IMG_1480

author: ankurb
author_rank: Contributor
timestamp: November 06, 2017, 01:44:47 pm
content: The tube is labeled Amperite 115N010T delay relay.
Electroluminsecent display in Hocking Phasec 2200 Eddy current instrument - Page 1
Forum section: electronics / repair

author: Jwalling
author_rank: Unknown
timestamp: November 05, 2017, 04:13:23 pm
content: My first guess that is this is screen burn, but it's much more apparent on the right-hand side of the display. I would expect it to be more uniform. I've pretty much no experience with these - is it repairable or does it need to be replaced?Haven't pulled it apart yet to get a part #.

author: Jwalling
author_rank: Unknown
timestamp: November 05, 2017, 05:48:14 pm
content: Digging further to see what else needs doing, I found a battery. But not just any battery!I removed the white powder (leaking of course). OK, I can understand a two cell stacked battery, but these are obviously different capacities. I think they are Ni-Cad.Is this custom made? Never seen anything like this...May have to use an external pack with two cells as clearance to the next board up is very tight.

author: Armadillo
author_rank: Super Contributor
timestamp: November 05, 2017, 05:58:29 pm
content: From the dimension, looks like a CR2020 + CR2040. Funny combination of different mAH. Got to be self made, judging from the poor soldering of the tap.In which case, might as well be CR2020 + CR2020 of same mAH and save 2mm height.

author: Jwalling
author_rank: Unknown
timestamp: November 06, 2017, 09:44:37 am
content: Quote from: Armadillo on November 05, 2017, 05:58:29 pmI think that they're Ni-Cad, not lithium.

author: Armadillo
author_rank: Super Contributor
timestamp: November 06, 2017, 10:11:55 am
content: Quote from: Jwalling on November 06, 2017, 09:44:37 amOh yes, you are right. This odd looking shape is in-fact NiCad battery, thanks.
BK Precision 1685B Constant Current Faulty - Page 1
Forum section: electronics / repair

author: peterrash
author_rank: Contributor
timestamp: November 03, 2017, 09:17:43 pm
content: (Note: mechanical engineer, never repaired a power supply before, please forgive any ignorance)Has anyone attempted repair of the BK Precision 1685B Switching Power Supply? Or even better, got access to a schematic or service manual?I picked one up for cheap on eBay, and its got the following symptoms:Current shown on the display is always 180mA above the actual current (even when open circuit)Constant current mode doesn't activate even if the current is above the set limit (eg. set at 1A, increase voltage, current goes above 1A)Once current gets high enough above the set limit (about 100-200mA or so above the setpoint) the supply kicks into overload protection modeI initially thought that something in the ammeter circuitry was faulty, but its interesting that the OLP still seems to work properly.[edit: 180mA, not 18mA]

author: peterrash
author_rank: Contributor
timestamp: November 06, 2017, 03:42:14 am
content: I've disassembled and inspected the supply, nothing seems amiss. I also performed some more testing, and found that the overload protection always activates at 125mA above the current setpoint, even though the constant-current mode doesn't activate. This seems to indicate that the setpoint adjustment and current sensing are working, but for some reason the supply doesn't try to activate constant current mode and doesn't report the correct current.I also noticed that if I set the current limit to zero, the constant current mode does come on, but the readout still shows 180mA.Any ideas greatly appreciated...
HP 8648C with low output - Page 1
Forum section: electronics / repair

author: mmaseda
author_rank: Contributor
timestamp: November 05, 2017, 02:44:59 pm
content: I have a HP 8648C signal generator with option 1EA (high output). At 100 MHz I can only get 14 dbm out. Manual says I should get out around 20 dbm. Power also seems to be low at other frequencies. I’ve already checked the attenuator and RPP modules and they appear to be fine. Any idea where I should check next?
Nordmende LCD-TV - defective SMPS (JSK4180-024/A/B) primary capacitor blowing up - Page 1
Forum section: electronics / repair

author: freccia
author_rank: Newbie
timestamp: November 04, 2017, 05:35:50 pm
content: Hi all,I have a fault in the power supply of a Normende lcd tv. At switch on the led turns from red to blue. The lcd switches on and the display shows no signal on screen. After around 20seconds, the capacitor in the primary, 120 microfarads 450volts becomes very hot and steam comes out of it. I changed this capacitor 2 times, but the same happens every time. On standby(red led), smoke is not seen from this capacitor.Any ideas about how to tackle this problem? Any help would be appreciated. Thanks

author: Armadillo
author_rank: Super Contributor
timestamp: November 04, 2017, 05:58:09 pm
content: Your power factor controller circuit is defective.You can temporary remove D2 from the circuit, put in a new capacitor 150uF/450V 105C and use your TV.But of course proper way is to repair the PFC.

author: Armadillo
author_rank: Super Contributor
timestamp: November 04, 2017, 06:19:55 pm
content: Quote from: Armadillo on November 04, 2017, 05:58:09 pmAfter you have confirmed defective PFC and if you want to repair your TV fully [must have PFC, can't live without it];Measure one by one each of the resistors R25, R37, R38, R39 are correct values, if so then change the PFC controller L6562.EDIT: I LOG IN AGAIN TO REMIND YOU TODISCHARGE THE CAPACITORBEFORE WORKING ON IT.

author: freccia
author_rank: Newbie
timestamp: November 05, 2017, 05:32:49 am
content: Thanks a lot for the info. Will check the resistors and maybe the ic as well.Sorry for the trouble, my fault, assumed that the circuit diagram was the one I was looking for but I got this circuit diagram from this web site and it says Nordmende N3202lb, but it does not match my power supply, it has different component numbers. on the power supply I have STA208tv rev B02. Does anyone have this circuit diagram please. Or at least the chassis number for this model please? Thanks

author: Armadillo
author_rank: Super Contributor
timestamp: November 05, 2017, 06:40:50 am
content: Quote from: freccia on November 05, 2017, 05:32:49 amHard to find for this schematic. The board is just single sided. I think you would have to trace to the PFC controller without the schematic.

author: freccia
author_rank: Newbie
timestamp: November 05, 2017, 06:45:27 am
content: I think I found that diode you were talking about. I think it is the one attached to the heat sink, connected to the fet. Will try to remove that and see what happens.
Brymen vs Scope measurement discrepancy - Page 1
Forum section: electronics / repair

author: Crossphased
author_rank: Regular Contributor
timestamp: November 04, 2017, 08:25:59 pm
content: Hi,I was setting up a recently acquired audio amplifier, to characterize the amplifier, when I ran into a measurement discrepancy between my BM521 and my Tek 2465A. I'm using a brand new Siglent 2042X function generator to provide the waveform. The function generator is supposed to maintain the selected peak to peak voltage across different loads. That is, I believe the FG is able to modify its output impedance to maintain the selected VPP.I started with 1VPP selected on the SG2042X, @ 1khz. The Brymen measure this to be .356 V but cant pick up the frequency:https://farm5.staticflickr.com/4464/24316879128_bd4e9a3b52.jpgI am aware we are comparing peak to peak voltage to RMS, but 1 VPP computes to .707 VRMS, not .356 VRMS. (curiously a division by two)If the peak to peak voltage is raised to 2, the Brymen measures .711 VRMS and is able to pick up the frequency:https://farm5.staticflickr.com/4532/37459341474_2a1c887b7c.jpg.711 VRMS measured, the value should be 1.414 VRMS for a peak to peak voltage of 2. Again, this is a factor of 2 error (.711 vs 1.414)When VPP is raised to 3, BM521 measures 1.064 VRMS:https://farm5.staticflickr.com/4469/24316879438_1385a92402.jpg1.064 VRMS measured, the value should be 2.12 VRMS for 3 VPP. And again there is a factor of 2 discrepancy.At this point I was baffled and hooked up the FG to my Tek2465 scope to see what was going on. I am using 10X probes, so the the display on the scope should be multiplied by 10. Sure enough, at 3 VPP selected on the FG I measure ~3 VPP out (3.12 V using cursors):https://farm5.staticflickr.com/4461/24316879008_c9f0f29132.jpgAt this point I'm not sure if I'm making a silly logical error, or there is something amiss with the Brymen. I know I'm using a frequency of 1Khz but the same result was witnessed for 100 hz, 200hz, etc. Does anybody have any idea what's going on?P.S. - having trouble embedding these images if anybody has a tip let me know

author: barry14
author_rank: Regular Contributor
timestamp: November 04, 2017, 09:12:44 pm
content: There is nothing wrong with either the DMM or the scope. You are using the wrong factor to convert volts peak-to-peak to volts RMS. For a sine wave, you need to divide the volts peak-to-peak by 2.828. That is, 3 volts p-p is equal to 1.06 volts RMS (again only for a sine wave).

author: Crossphased
author_rank: Regular Contributor
timestamp: November 04, 2017, 09:41:46 pm
content: Hey Barry,Thanks, I was being a bonehead lol. After your reply I realized my mistake.The voltage for a single peak (upper half of sine wave) = 1.414*VRMSThe Peak to Peak is obviously double this.Thanks for being sharp!
Hantek DSO-5202B No signal and no buttons - Page 1
Forum section: electronics / repair

author: Rogerm
author_rank: Newbie
timestamp: November 13, 2017, 12:57:27 pm
content: Hello:I have a DSO-5202b SN 22*** HW1.01 and the buttons do not work and the signal does not appear on the screen.The source voltages are fine, reprogram the nand flash backup and it remains the same.Do you have any idea what it can be?Thank you.
Tagarno and the Stereo Microscopic - Page 1
Forum section: electronics / repair

author: ebclr
author_rank: Super Contributor
timestamp: November 02, 2017, 05:08:05 am
content: I already have a nice Stereo Microscope, But I'm teased by the Tagarno due to David videos, But this thing in on 3k range.Do Tagarno will improve my SMD working compared to a stereo microscope, I feel that I will lose the stereo deep of field,DO Tagarno Is an inspection only thing?What is the point to invest 3K in something that can be done with 600 USD AmScope / camera set.I'm trying to justify myself and buy the Tagarno, But I'm afraid to buy a tank to kill one antAny thoughts?

author: Psi
author_rank: Super Contributor
timestamp: November 02, 2017, 05:28:29 am
content: I wouldnt get a targarno for one person use. They are great when multiple people need to see things at once. But a stereo microscope is way better for doing actual work.

author: RoGeorge
author_rank: Super Contributor
timestamp: November 02, 2017, 09:18:56 am
content: I would never change my $50-100 stereo optical microscope for a Tagarno, or for any other USB camera with a stand, even if the Tagarno would be for free. No way!Stereo vision and depth perception is crucial for working.Then, no time lag is gold (refresh rate is irrelevant, time lag is the real killer when viewing through a live webcam - it can give you sea-sick and induce puking to some persons, not kidding here).

author: Armadillo
author_rank: Super Contributor
timestamp: November 02, 2017, 09:37:33 am
content: Let's put it. You were "astounded" when you leapt into stereo, so why not if you have the money to realm into another world. There is no reason to strain yourself when you have the money to spend.Let's say from F15 to F22. Be the one.Can't bring the money when you are out, you know what I mean.

author: jmelson
author_rank: Super Contributor
timestamp: November 02, 2017, 05:28:48 pm
content: Quote from: ebclr on November 02, 2017, 05:08:05 amI have not used any digital microscope for SMT assembly. So, take my comments with that in mind. But, there are so MANY artifacts that a digital camera / display will insert, that unless you NEED this capability (for demos, documenting, etc.) then I think a good stereo zoom microscope can't be beat. There is no lag or motion blurring when you move things, there is no color distortion, your eyes + good optics are WAY better than xxx pixels/line, and so on. I've been using old stereo zoom microscopes both at home and work for 10+ years, and find them very comfortable. You **MUST** have the table at an optimum height for YOUR body, so you don't crane your neck to see the eyepieces. This is probably the MOST important part of the setup. You can get an office chair with a height adjustment to make the final +/- couple inches adjustment for optimum comfort.I routinely do soldering of chips down to 0.4mm lead pitch, try THAT with a visor magnifier!Jon
Dolce Gusto Piccolo - change water temperature setup - Page 1
Forum section: electronics / repair

author: Roland_W
author_rank: Contributor
timestamp: November 03, 2017, 08:52:56 pm
content: Hi All,I bought the Dolce Gusto Piccolo. After a time, I found that the temperature of the water is not hot enough to proper extract the coffee.After searching internet I found that the right temperature is from 92 to 96 C. But my coffee machine have only 80.I made some researches about Dolce Gusto Piccolo, and I found youtube video, about how the machine look inside :Schematic from the youtube link : 20170111_175537.jpgI measure the little temperature sensor is a NTC element - 10 k Ohm. By adding the series resistor 820 Ohm, I change the PID goal temperature to the 93 C.Adding the resistor DSC_0656.JPG - to setup right temperature, by try and change.See the running machine after changes :https://youtu.be/KdGcTu1xn_YThe little coffee machine work for now perfect
Old ADE Capacitor Marking V- - Page 1
Forum section: electronics / repair

author: Dipski
author_rank: Contributor
timestamp: November 02, 2017, 01:50:17 pm
content: Hi folks, I've got a power supply to repair (board dated 1987) - its 240V cap is an old ADE marked as 100uF 385 V- and having not seen a capacitor marked as V- I just thought I'd check if the minus symbol had any particular meaning.

author: glarsson
author_rank: Frequent Contributor
timestamp: November 02, 2017, 01:55:08 pm
content: It's not a minus sign. It is a straight line indicating DC.

author: Dipski
author_rank: Contributor
timestamp: November 02, 2017, 01:59:13 pm
content: Thanks Glarsson, I suspected so but given it didn't have dashes under the line and seeing it for the first time I thought I'd double check - thanks mate.
AIM LDO (Low Distortion Oscillator) 501 - Page 1
Forum section: electronics / repair

author: tattus123
author_rank: Newbie
timestamp: November 01, 2017, 03:55:32 pm
content: Does anyone have a schematic or manual for this beast?It's a microprocessor controlled audio oscillator but unfortunately has an intermittent problem with the range control buttons locking up.The attached jpeg is form the October 1985 advert in Studio Sound magazine.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 01, 2017, 04:14:53 pm
content: Even without a manual, may first suspects would be old caps in the supply and maybe oxidized contacts of switches and relays. For the contacts it may be enough to do a little exercise by switching them several time. Sockets might be a problem to.Such old computer parts might also get close to EPROM data retention time.
Tiny/low profile linear pot for front panel  - Page 1
Forum section: electronics / repair

author: calin
author_rank: Regular Contributor
timestamp: November 01, 2017, 03:48:13 pm
content: Recently I got an old 10Mhz Leader 300 oscilloscope from Craigslist for like 20$ .. one old crusty thing for sure but for my kiddie to use on his RC stuff outside in dirt is good enough.Of course it was not working and the knobs for trigger and Y position were literally stuck frozen. I had to literally snap the darn things off to be able to disassemble the front panel and clean it so the original-s are gone .. shaft broken)I bodged 3 temporary 20K pots and got the scope back to life but I want to get it back to "pretty" stage only problem is I cannot find anywhere 20K pots that are this small. Well the size is standard 9mm straight PCB mount pots but the profile/height is just 3.5 mm (close to that) and shaft is just 4 mm D. I attached couple of pictures - they seem to be made by Alpha Taiwan but meh cant't find anything that "thin".Does anyone have any idea of a source/replacement for this small pots?The closest I found are all 9mm, something like thishttp://www.taydaelectronics.com/20k-ohm-linear-taper-potentiometer-round-knurled-plastic-shaft-pcb-9mm.htmland I also found some Bourns PTV09 series that are also very similar. I don't mind the shaft being to big, a bit of Dremel and polish can solve that problem.. but the thickness has to be under 4-5mm so they fit between the front panel PCB and front panel.
HP 3478A "dead" battery and high range Ohms - Page 1
Forum section: electronics / repair

author: ChrisHoldt
author_rank: Newbie
timestamp: November 01, 2017, 02:41:40 pm
content: Hello everyone!For better or worse I made and won a "lowball" offer on an HP 3478A. ($90 not including postage to the UK)The seller had the following in the description: "rejected at a local calibration facility for dead internal battery and high range Ohms"As I do too often I buy these things without doing enough research.Having read about the battery I really hope it isn't completely dead and I can replace it before it loses calibration. Thankfully I've found a lot of info about this process!The high range Ohms is what particularly worries me... I am waiting to hear from the seller about any other information from the calibration but I assume they found an issue reading high range resistance. What is the best way to go about figuring out exactly where the issue lies.Last thing, I just want to check I'm not missing anything for the US to UK power conversion.Install the correct powerline fuse: 125ma 250v slow burn.Change the switches on the back to 240v 50hzOpen her up and change the internal transformer switch as detailed in the service manual.Now I just need to wait for it to arrive in a few weeks!Thanks!
Odd Apple iPod Classic battery problem - Page 1
Forum section: electronics / repair

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: November 01, 2017, 07:21:48 am
content: I have a couple of iPod Classics - one bought original in which I've replaced the motherboard and clickwheel and the 2nd bought as a replacement in case the other dies. Both have new batteries PAB-616-0183 3.7V 700mAh. Both have the same issue - work perfectly if I ensure the battery doesn't run completely flat (or at least to it's low V cut-off protection voltage) but if let either go flat the iPod shows a failed battery logo when I plug it into power again. I can recover them fine with a few hours at 100mA or so and 4.2V on power supply. Can't understand why they won't recover after the protection circuit kicks in.When the original first died, I ordered a replacement from China and had this problem. Assumed it was bad manufacture issue. Replaced the batteries for both units recently with Oz-sourced units (which look like the same manufactured items with a sticker over them) and they behave the same way. There are no problems with charge capacity on the new units - they'll run for hours and recharge fine if not flat. When I stripped and tested the control circuit on the problem China-sourced battery, I couldn't find any fault with it. So I'm completely foxed. Seems unlikely both iPods have developed the same charge system fault and am wondering whether perhaps there's some mismatch in the control circuit where the iPod voltage detection system is looking for a voltage different from the low V shut-off in the battery's control board and signalling a battery failure erroneously?Wonder if anyone's encountered this problem and found a cure. It's mainly nuisance value having to extract the battery repeatedly and trickle charge it for start-up. A permanent fix would be nice if anyone knows of one.
FLUKE 5100B up to 19.999V ac and dc only. please help. - Page 1
Forum section: electronics / repair

author: clexzzz
author_rank: Newbie
timestamp: November 02, 2017, 09:10:37 am
content: Hi good day,i have some question about fluke 5100B. So far we can only use it up to 19.999V ac and V dc. When we try it 20V and up and press OPT, the display says OL. Can you please help us. Thank you. Sorry for my english.

author: Benta
author_rank: Super Contributor
timestamp: November 02, 2017, 11:34:08 am
content: Please do not cross post. It does not improve your chances of an answer.

author: Simon
author_rank: Unknown
timestamp: November 02, 2017, 06:44:32 pm
content: If you post triplicate posts again you will be banned!
GWInstek PSP-603 repair - Page 1
Forum section: electronics / repair

author: crispus
author_rank: Regular Contributor
timestamp: October 30, 2017, 12:04:40 am
content: I am the happy owner ofthispower supply. It arrived on October 6th.Hereis a short review andheresome similar schematics.I knew that had a short, so I started to look after it. Didn't take too long to found out that the main switching transistors (V9/V10) are in dead short. Changed them temporarily with other 2 from a PC PSU.Connect the power supply from a transformer (~75Vac)using the "debug cable" - up to 3 light bulbs in series with the load:and seemed to work (above the multimeter you can barely see that the light bulb is starting to glow)There were some issues with Farnell, made another order to TME and two weeks later I got the replacement transistors from TME. I replaced them with BUV48A.While playing with the 'now working' power supply I considered that the problem is fixed and thedebug cableis no longer needed.It was so wrong.I was testing the short protection when the hell broke loose and nearly fell off my chair. Something was terribly wrong.Now, the painful part.Changed the transistors again after one week when Farnell finally shipped the order, the control was working butno output.I started with TL494 which had no Vref. Pull it out, solder a socket (good choice), put a good one in place. But stillno output.Followed the output of TL494 and seemed OK. After the control transformer (T2) R29/R32 are burned (open circuit). The transistors were pretty determined not go alone.Changed them too, butno output.Pull the TL494 out, measure with the multimeter R & C, allseemsto be fine. Noticed though that the frequency is kind of odd:I made on a breadboard a test circuit with TL494, similar values: ~37 Khz, but in the PSP is almost 10 times higher. Hmmm. The absolute max frequency in the datasheet is 300 Khz.Accidentally I touch the capacitor on the breadboard and suddenly the frequency goes beyond 300Khz. Fix it, 37 KHz again. Take the again the capacitor out, it goes above 300 KHz.It seems like a déjà vu.Measure again the capacitor, this time with my LCR meter (thanksiloveelectronics). The capacity is right, but the other parameters not nearly what a capacitor should look like.Go again to the donor PSU, and replace the culprit.And now, IDO have the output.Many thanks toealexwho guided me through this journey.
Repair: Rohde & Schwarz FSEA 20/30 - Page 1
Forum section: electronics / repair

author: Bicurico
author_rank: Super Contributor
timestamp: October 29, 2017, 03:55:03 pm
content: Hello,My next repair project will be a Rohde & Schwarz FSEA 20/30.I will receive it within the next weeks, presumbably, and it has a known fault:STEST aborted: RF-Modul RF-Converter, state 18(see attached picture)It is a device from a friend and he got it like this amongst other stuff. If I can repair it, that would be awesome, if not, no loss anyway.My plan, once I receive the device, is:1) Test it, get to know the installed options and firmware.2) Clean it externally3) Clean it internally: disassembling it, cleaning all contacts, re-assembling itI hope/wish that step 3 could actually lead to a positive result and the device starts working again.If not, what are my options? The RF Module is probably the most complicated component and I have not seen any replacement parts on eBay.What are your suggestions?Regards,VitorPS: Also posted here -https://www.eevblog.com/forum/testgear/rohde-schwarz-fsae-30/msg1335536/#msg1335536

author: Kilo Tango
author_rank: Regular Contributor
timestamp: October 29, 2017, 08:23:10 pm
content: Hi,Best of luck with the analyser. It might be a bit more involved than just clean contacts but you might be lucky.The service manual is available on ko4bb's website, it is not bad,there are a selection of self test functions that you can start that may help you.Ken
Sharetree Type 450 Signal Generator - Page 1
Forum section: electronics / repair

author: Specmaster
author_rank: Super Contributor
timestamp: October 29, 2017, 01:41:16 pm
content: I did ask about this a few months ago and nobody seemed to have heard of this make at all so were unable to give me any information. However with new people joining all the time I thought that I'd give it another shot as I'd really like to get this working it is nice and compact, covers the bands of interest for domestic radios which is perfect for my requirements if only I could get it repaired.It was built in Britain by Sharetree Ltd, in Stroud, Gloucestershire.Is this bringing back any distant memories? Are you able to throw any light on this at all please, seems a shame to have it sitting there gathering dust or going to landfill.EDIT:It was made the Parametron Division of Sharetree Ltd and it seems that Parametron is unique and special oscillator so I'm guessing that maybe this company was active in that field years ago and that this generator possibly uses that type of oscillator?