hybridfree/eevblog-posts huggingface dataset:
high impedance source with low impedance input - Page 1
Forum section: electronics / repair

author: loop123
author_rank: Frequent Contributor
timestamp: March 25, 2024, 04:10:10 am
content: If your amplifier or ADC input is low impedance like 640 Ohm. And your signal source impedance is 200 kOhm with 1 Volt signal, and you put multimeter probe in the input of the amplifier or ADC, will the voltage decrease from 1 Volt or increase? What situation when the input voltage actually increase in value?
High noise floor of Agilent DSO80304B - Page 1
Forum section: electronics / repair

author: Robert_Sky
author_rank: Contributor
timestamp: June 12, 2019, 03:07:45 pm
content: Recently acquired a parts only DSO80304B, It is found the noise floor is much higher than the spec. Some 250MHz clock signal shown in the noise floor measurement when port is open. Attachment is a screen of port1 open and its FFT mag. The FFT show some 250MHz and its harmonic spur.Open the back of scope, the acquisition board does not show obvious bad parts. Indeed someone has try to repair it and failedI guess the high speed clock drive ADC may not be good quality. Then i check the 10Mhz Ref clock out and there is nothing output at the BNC connector of 10MHz. Next step i would like to find why the Ref out is broken. Maybe i will a get a window based 200MHz bandwidth scopeCould anyone offer some hints for debugging?Thanks.

author: Jwalling
author_rank: Unknown
timestamp: June 13, 2019, 09:47:05 am
content: Have you run the calibration, and does it pass?

author: Robert_Sky
author_rank: Contributor
timestamp: June 16, 2019, 12:31:53 am
content: @Jwalling, Thanks for the advice. I have run the calibration. Both vertical and trigger calibration failed.After some near field probe, it is found the clock circuit is not locked to 1000MHz, but around 930MHz. More measurement will be done to the clock circuitThanks.

author: Jwalling
author_rank: Unknown
timestamp: June 16, 2019, 09:54:00 am
content: After a calibration is run, a .txt file is generated in the calibration folder. Open it with wordpad to get more details on the failure(s).

author: Robert_Sky
author_rank: Contributor
timestamp: July 03, 2019, 02:45:18 pm
content: Hi JwallingThanks for the input. After a manual search on the C:\ disk, no calibration file is found. Spent some time debugging the PLL circuit, one of ferrite bead is broken and replace it with a new one. The PLL can lock to 1GHz now, but the noise floor is still same. The noise has nothing to do with the clock.There are not may things can be done for the solder-down BGA.

author: Jwalling
author_rank: Unknown
timestamp: July 03, 2019, 06:25:05 pm
content: It's in a hidden folder. \scope\calWith an explorer window open, put C:\scope\cal into the address bar at the top.Something in these scopes doesn't allow you to show hidden folders persistently. If you change it to show them, it gets changed back.
High output voltage fluctuations for a FAN7554 based PSU - Page 1
Forum section: electronics / repair

author: zyuan
author_rank: Newbie
timestamp: April 24, 2023, 01:45:50 pm
content: Hi,I am attempting to repair a 12V/4A PSU for my Buffalo Linkstation NAS drive. The drive failed to wake up automatically at a scheduled time. I swapped the PSU with a known good one, and the Buffalo NAS worked just fine. The initial test with that PSU under load looked okay with a multimeter, but on the Oscilloscope, it showed very high voltage fluctuation about 2V pp. So, I broke the power brick open to check, and found that the main capacitor was leaking and one of its leg was broken off. Besides that, PCB looked very clean and no burn marks. I replaced all capacitors on that power supply with new ones, and checked the switching MOSFET, voltage regulator (TL431), optocoupler and diode on the output side, everything looks just fine, however, the output voltage fluctuation didn't seem improved.I then realized that this PSU is using the Fairchid PWM chip FAN7554, working under the bust mode. It turns off switching on the primary side when feedback voltage below 0.3V during the light load for saving energy. Such behavior causes the higher voltage fluctuations at no or light load. The circuit diagram of my PSU is almost identical with the example circuit in the Fairchild data sheet, Seehttps://www.alldatasheet.com/datasheet-pdf/pdf/51202/FAIRCHILD/FAN7554.html, except having very beefy filter capacitors, e.g. main capacitor is rated at 100uF/400V and output capacitors are at 1000uF/25V and 470uf/25V.Understood of the limitation on FAN7554, however, the 2Vpp is still too much to me, although The PSU look like having a decent quality. I don't know the original specification of this PSU . But I don't think such voltage fluctuation is good for my NAS drive. I tested all components I can test, even ordered a new FAN7554, nothing helped to improve the voltage fluctuation for this PSU.I would like to know how I can reduce the voltage fluctuation for the FAN7554 based SMPS.Any help and comment are highly appreciated.Thank you in advance!

author: ingalopez
author_rank: Contributor
timestamp: April 25, 2023, 02:33:18 am
content: Hi there!Does the voltage stabilize if you connect aditional load to the PSU? Try some more load, to offset the chip "low power" mode.Check the specs of the FAN 7554. (I guess you already did...), there may be some way to avoid that mode alltogheter.

author: zyuan
author_rank: Newbie
timestamp: May 08, 2023, 11:00:59 am
content: Hi, @ingalopez,Thank you very much. I really appreciate your advise and tips here.You are right that I probably should try to add a resistor between the feedback ping 2 of FAN7554 and phototransistor of the opotocoupler, to bring up the feedback voltage above 0.3V or somewhere near that, to keep the PWM controller ON for the most of time. It may take some time for me to test that, as I need to get a backup PSU first, in case I damage this one.Thank you again.
High pitch noise PS board - Page 1
Forum section: electronics / repair

author: rodrigopires
author_rank: Regular Contributor
timestamp: November 16, 2022, 07:51:57 pm
content: Hello eneryone,I have a Nodor kitchen extractor that is making a humming noise (I mesured around 6.4 to 6.8 kHz) all the time, even when nothing is on so it leads me to believe that its coming from the logics power supply. And the sound gets worse if I turn on the lights...I toucht every component (with a plastic stick) and could not find the source of the sound (also no Change um sound) so no loose cores... Also did nota see any bad caps (aparently).What could bem causing this?Video:https://youtu.be/p3Zme8-ApkQ

author: srb1954
author_rank: Super Contributor
timestamp: November 16, 2022, 09:42:42 pm
content: Quote from: rodrigopires on November 16, 2022, 07:51:57 pmHave you got a scope so you can check for ripple and noise on the power supply outputs? N.B. Check that they are fully isolated from the incoming mains supply first!The PSU control loop might have gone unstable causing it to oscillate at audio frequencies. This could cause some of the magnetic components to produce audible frequencies through magnetostrictive effects. Even the ceramic capacitors can cause noise through piezoelectric effects.

author: edpalmer42
author_rank: Super Contributor
timestamp: November 16, 2022, 10:07:00 pm
content: Take a plastic or rubber tube - size & length don't matter, just make it a convenient length. Put one end on your ear and move the other end over the board. You'll easily find the squealer. Typically, it turns out to be a transformer or inductor.

author: rodrigopires
author_rank: Regular Contributor
timestamp: November 17, 2022, 09:48:20 pm
content: So assuming its a bad control loop, the source of the problem is that 8 dip chip? Might as well change the eletrolitic caps to BE safe.

author: rodrigopires
author_rank: Regular Contributor
timestamp: November 17, 2022, 09:53:24 pm
content: Quote from: edpalmer42 on November 16, 2022, 10:07:00 pmI used a plastic stick to poke every component to try to get a feel for the problem, or change in sound, but was unlucky to find the source... That tube/stethoscope looks like a great idea!
high voltage corrosion damaged PCB ultrasonic cleaning solvent? - Page 1
Forum section: electronics / repair

author: coppercone2
author_rank: Super Contributor
timestamp: August 29, 2019, 06:25:43 am
content: I have a 120V HV battery which has been damaged by water (drip from upstairs cleaning).I thought the charger got damaged, replaced the charger, then found out that the battery is taken apart easily with four screws. The PCBs are not conformally coated... anyway I think what happened is the water got under there and shorted some stuff out and electrolysis corroded the copper into the greenish oxide.It was not charging at all, but I gave it a good cleaning by scrubbing vigorously with a nylon brush while spraying it with contact cleaner.It charges about 1/2 way now. Some of the components might be damaged, but anyway It seems the more I clean it, the further it charges. I was thinking of desoldering the PCBs and cleaning them in a ultrasonic.. but what cleaning agent is good for this kind of cleanup?Can I ultrasonic it in vinegar? It does look suspiciously clean at this point though.

author: coppercone2
author_rank: Super Contributor
timestamp: August 29, 2019, 06:40:48 am
content: and, any idea whatvfy326 ic is? I know its a charge protection chip, but where can I buy a few? The one I have is missing a leg now that I look very closely.

author: PKTKS
author_rank: Super Contributor
timestamp: August 29, 2019, 11:22:21 am
content: In your region (US) it is easy to find a proper solutionSearch for BRANSON chemicals solutions for ultrasonic bathPaul
High voltage device unknown parts. - Page 1
Forum section: electronics / repair

author: quzuwe
author_rank: Newbie
timestamp: February 16, 2020, 01:59:40 pm
content: Hello,I found an old flocking device (?). I guess it was used to create static to have same velvet feeling when applying flocks.I can remember that I had a look at it as a kid and stopped there because of the high voltage.However, now I’m wondering what the components are.I guess (1) is a high voltage transformer to get some kV from mains and (2) is a transformer to get 90kV (there is „90kV“ weakly written on it at the side).But I have no clue that (3) is - maybe an inductor for earth reference or so?. It has mains connected to it and one highly insulated wire going to (2).Additionally, there is a hole in the case where the connector from outside can directly plugged into (2).I’d appreciate any information on the parts and circuitry.Thanks!

author: fcb
author_rank: Super Contributor
timestamp: February 16, 2020, 02:39:15 pm
content: My guess is that once past the interlock (relay PCB at top), mains is fed to the variac (front panel - bottom right). Output from the variac goes to (1) which is probably a step-up transformer, which then feeds high voltage AC to the main transformer (2) where it is turned into EHT - which could then be be switched by (3) - or possibly (3) is a potential divider (for monitoring the EHT).Block (2) is probably a similar design to a TV LOPT (line output transformer), with multiple secondarys connected in series with HV diodes.One other thought. Block 3 could be a high voltage tube/valve. This could be used to shunt regulate the EHT. I've seen similar (but only at a few KV) for regulating focus voltage on high-brightness CRT's.

author: quzuwe
author_rank: Newbie
timestamp: February 17, 2020, 11:36:56 am
content: Thank you @fcb!

author: gbaddeley
author_rank: Regular Contributor
timestamp: February 18, 2020, 08:37:50 pm
content: 90kv doesn’t seem right. The wire insulation and clearance is not enough for 90kv, which can arc a few cm. Maybe 9kv?

author: fcb
author_rank: Super Contributor
timestamp: February 18, 2020, 09:28:02 pm
content: Quote from: gbaddeley on February 18, 2020, 08:37:50 pm50kV cable can be 5mm diameter (https://www.genvolt.com/files/Datasheets/TV%20Cable%20Brochure.pdf)
Highvalue ceramic capacitor replacements (LM5176) - Page 1
Forum section: electronics / repair

author: 24602
author_rank: Contributor
timestamp: April 05, 2024, 05:49:46 am
content: HelloWorking on a device with a LM5176 converter, the output side capacitors need to be replaced.The device has 4x capacitors in parallel on either side of the current shunt (8x total) (schematic screenshot attached)The data sheet calls for 50uf on one side of the current shunt and 360uf on the other (typical schematic attached)Ceramic capacitors at this rating are $10s of dollars each on the main suppliers @ 25V max rating. Output is 16VThe device will work in a buck/boost config as battery and external DC powered approx a couple of amps maxAre these expensive capacitors the best option?

author: inse
author_rank: Super Contributor
timestamp: April 05, 2024, 06:19:44 am
content: The datasheet does not exclusively call for ceramic caps: “a combination of ceramic and bulk capacitors is needed“Polymer electrolytics provide low ESR as well and can be supported by ceramic caps.

author: 24602
author_rank: Contributor
timestamp: April 05, 2024, 07:23:36 am
content: Would you suggest replacing them with one of these?https://au.element14.com/nichicon/ucl1v471mnl1gs/cap-470-f-35v-radial-smd/dp/2309060https://au.element14.com/panasonic/eeefp1v470ap/cap-47-f-35v-radial-smd-reel/dp/2408634or would it be better to use with a lower value ceramic be beneficial for high freq?

author: inse
author_rank: Super Contributor
timestamp: April 05, 2024, 08:16:44 am
content: Low ESR electrolytic supported by some uF ceramics -should- work.A polymer aluminum electrolytic has even lower ESR, possibly you can skip the ceramic.Check design requirements from datasheet and select components accordingly.Allowable ripple current is stated in capacitor datasheets.
Hinge whinge / sanity check, E3631A - Page 1
Forum section: electronics / repair

author: arcitech
author_rank: Regular Contributor
timestamp: July 28, 2022, 02:56:18 am
content: I scored a pair of E3631A power supplies to help along my education on the neo-retro era test instruments, one working and one not, and was excited about how easy the chassis hinge makes the work smoother.But, oh no, did I confuse my numbers? The one I opened has no such hinge. Looked it over an embarrassing number of times. Both are newer Agilent branded and assembled in SEA (one Singapore and one Malaysia, can't tell you which the broken one's from at the moment).Were hinges ditched when moving manufacturing offshore shuffled the COGS deck (materials/complexity vs the average wage hour)? Or am I just hallucinating the various videos I've watched? I've hunted around to no avail.I'm to scared of disappointment to open the working one, especially since the non-working one got even more busted up in transit (even bent the front chassis ears). I've had such shite luck with seller no-fux-given packaging. At least it was the already broken one!

author: IanJ
author_rank: Unknown
timestamp: July 29, 2022, 06:00:17 am
content: Didn't know the 3631A came in an hinged/unhinged variants! The one I repaired was Agilent branded, not sure its exact age though.Beware knackered SMD resistors on the digital board, i had loads fail in my unit. Have heard others say the same.Ian.

author: arcitech
author_rank: Regular Contributor
timestamp: July 29, 2022, 04:10:38 pm
content: Quote from: IanJ on July 29, 2022, 06:00:17 amThanks for the advice. Indeed it looks as if this chassis is entirely comprised of two structures: a transformer brace, and one stamped sheet that's later bent to form the three sides. This is how it comes out of the outer case (the bent front panel 'ears' are from the shipping damage).Based on the SN, if runs are 1-indexed, this _might_ be the first of a run from Singapore's mfg line (or maybe the first of _all_ runs from the island). Still haven't opened my Malaysian one yet...

author: alm
author_rank: Super Contributor
timestamp: July 29, 2022, 07:28:09 pm
content: I don't remember details, but I have seen at least two different frame styles between the 2U high E363x/E364x series. I figured it must have been earlier vs later models, but it's possible they used both styles in the same model.I was dealing with half a dozen of these supplies (different models) at that time, so the details are a bit fuzzy.

author: arcitech
author_rank: Regular Contributor
timestamp: July 29, 2022, 08:33:04 pm
content: The Malay-mfg'd (working) one's got a hinge. Hooraaauuuugh.....
HIOKI 3238  - Page 1
Forum section: electronics / repair

author: hitecelec
author_rank: Regular Contributor
timestamp: July 23, 2019, 12:18:30 pm
content: Hi allI have a hioki DMM 3228 showing inaccuracy in AC voltage ranges. Does any one have the cal procedure or schematicsfor the modelThanks in advanceRegardsAnand
HIOKI 3256-50 shows ERR2 - Page 1
Forum section: electronics / repair

author: abc25339
author_rank: Newbie
timestamp: April 19, 2021, 02:33:24 am
content: Hello every body!I'm a newbieI have an volt-ohm-milli-ammeter, it's HIOKI 3256-50.When I open, it always shows ERR2.Do you know what's happend? Can everyone can guide me to fix it?Thanks!
Hioki 3283 Clamp meter repair help request - Page 1
Forum section: electronics / repair

author: ntj77
author_rank: Newbie
timestamp: November 13, 2020, 02:19:14 pm
content: Hi, I purchased a used non working Hioki 3283 Clamp meter and trying to repair it. Now it is switching ON and measurements are possible except for the "FILTER" option, which is low pass filter especially for measuring VFD. There is no signal at all if I enable "FILTER" key, reading is 0.00.Can someone please help with a schematic of the filter circuit or at least where to look on the PCB?

author: bob91343
author_rank: Super Contributor
timestamp: November 13, 2020, 07:36:16 pm
content: Did you contact the company? They will probably tell you to send it in but it's worth a try.
Hioki 8840 failure / power supply issue - Page 1
Forum section: electronics / repair

author: sqeezer
author_rank: Newbie
timestamp: October 16, 2021, 07:27:54 am
content: I am a proud owner of a Hioki 8840 that is faulty. It starts up quickly to the boot splash screen and then freezes.A quick measurement seems to indicate that the voltages are not properly present. The power supply is arranged in two stages, a switch mode power supply to break mains down to manageable voltages and a secondary DC2DC converter that diversifies into different voltages needed by both digital and analog part. The digital side (+5V) seems to be fine as the instrument boots up nicely. CPU/EPROMs seem happy. I have the hunch that the boot process is failing due to some hybrids not responding as a consequence of missing voltages.The capacitors on the secondary quite convoluted DC2DC converter give me a ballpark of the voltages that should be there but are currently missing. E.g. I figured that a 24V output is not working. This is needed to drive the printer and supplying it externally seems to have no effect on the initial “stuck in boot splash” problem. I see some more candidates for failures, e.g. there is a +9V and a -9V present, but just one -15V, which could be a intentional but I would guess that there should be a +15V.I tried to get support from Hioki. Their support points me to sending the unit in.Is there a service manual for the Hioki 8840 or schematics?Could someone supply the correct voltages/pins on the power connector of the main board?(see white connector in the images with black markings, indicating ground pins)The unplugged connectors are irrelevant to the initial problem (and voltage issues)
Hioki AF-105 needle too low - Page 1
Forum section: electronics / repair

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 25, 2020, 02:29:24 am
content: I got an oldHioki AF-105meter.It turns out that the needle is falling just short of the measured value in all ranges.Adjusting the trimpot gets it a bit closer but not far enough.In theschematicI see a 7.8k resistor an 1k trimmer in series with the coil and a 30k resister in parallel.(along with protection diodes and capacitor)A quick survey shows that all resistors are within spec.So I think that the meter's coil has become less sensitive somehow.What would be the best way to fix this?Replace the 7.8k series resistor with a lower value? (so more current goes through the whole)Or replace the 30k parallel resistor with a higher value? (so more current goes through the coil)

author: tkamiya
author_rank: Super Contributor
timestamp: May 25, 2020, 03:03:20 am
content: How much off are they? They were NEVER known to be accurate. +/-5% error full scale is common. What this means is that say you are in 100V range. You could read 95V or 105V and that'll be within spec. That 5V difference exists all the way to zero. It sounds ridiculous by today's standard, but analog days and in that era, that was pretty common.My "GUESS" is, it has always been the way you see it. My suggestion is not modify it and trying to fix it.I had lots of Hiokis and Sanwas. Those were two of famous/big Japanese multimeter makers. They were all like that. We, in fact, never used those multi-meter to measure anything. We knew what we read were proximate values and treat it as such.

author: floobydust
author_rank: Super Contributor
timestamp: May 25, 2020, 05:27:30 am
content: The meters can be accurate, it's usually parallax error and gravity that makes them seem bad. Ensure the mechanical zero adjust is correctly set.What is typical:Trimpot in parallel to the meter movement (30k resistor) - cal the full-scale meter current i.e. 20uATrimpot in series with the meter movement (500R trimpot) - cal meter coil DC resistance i.e. 15,000 ohmsI would use a DC power supply and series resistor like 100k and go for full scale on the 0.03mA DC range.That is closest to direct access to the meter's coil (it includes internal 30k shunt resistor). Use a DMM in series to measure the loop current. If the meter is out, then the coil 30k (33k in some pics) resistor needs to be adjusted or a clamp diode is leaky, assuming the 30k ohm shunt is accurate.After that, you calibrate the meter's total DC coil resistance, not sure what it is for the AF-105 guessing 15k. That is the 500R trimpot setting the dividers' load resistance including the 7.8k and meter coil... or you can pick a DCV range and calibrate to that full scale- assuming that range's resistors are accurate. If it isn't, then other ranges would be worse for accuracy.
Hioki dmm lcd failing - Page 1
Forum section: electronics / repair

author: najrao
author_rank: Regular Contributor
timestamp: October 31, 2020, 05:36:42 am
content: Would someone wise tell me if this is due to polarizer? I would peel it off and/or replace it, if so. Thanks too.

author: ambrosia heart
author_rank: Regular Contributor
timestamp: October 31, 2020, 08:14:03 am
content: Why/how it occurs I don‘t know. I just know same phenomenon in Sanwa CD800 digital meter after using 13 years. I let it retire.

author: vishaldotgupta
author_rank: Regular Contributor
timestamp: September 16, 2022, 02:34:12 pm
content: you need to change polarizer and may be both.first remove the top one and just look at the lcd through new polarizer.if the spot is visible, you need to replace the bottom one as well
Hioki DSM-8104 repair help - Page 1
Forum section: electronics / repair

author: johnbaker26
author_rank: Contributor
timestamp: August 15, 2025, 01:51:01 am
content: I have two of these DSM-8104 "super megaohmmeters" with error code 009. According to manual is a "power source frequency error" see attached image. One of them starts working once I let it warm up and cycle it on and off. It passes all the tests as well. But after cooking down the problem is right back. I thought maybe the electrolytics so I tested every one with my LC103 which has never let me down. They all test fine. This is testing them out of circuit at their rated voltage. They have 2015 date codes so no surprise. I went over all the solder joints on the connectors hoping it was a bad connection somewhere that expands when warm.Anyone experienced this issue and have any insights or advice on where to go next?

author: johnbaker26
author_rank: Contributor
timestamp: August 16, 2025, 09:19:18 am
content: Well I got one of them working consistently by pushing down gently on the back of the digital board. I reflowed the entire back of the digital board and the problem is the same. Must be a trace? Possibly internal? I had it under the strongest lens under my microscope and no sign of any issues.So I decided for the quick fix using a small rubber donut between the top of the case and the digital board and it works for now. Wish I could figure out what's up with the second one.

author: Sorama
author_rank: Frequent Contributor
timestamp: August 16, 2025, 09:28:14 am
content: Why not using a cooling/freezing spray can so you can individually test components ?After all, you said it starts working after warming op.Soon looking it so have the reverse impact.
Hioki RM3545 Resistance Meter Repair - Page 1
Forum section: electronics / repair

author: Kosmic
author_rank: Super Contributor
timestamp: February 12, 2024, 06:59:39 pm
content: Hello,I have a Hioki RM3545 here that suffered what appear to be an overload on the input. I initially found a blown resistor R3010 (100Ohm?) and it was replaced. Now the instrument seem to work OK on the lower ranges.Unfortunately on the higher ranges it read low. After investigating, 2 more blown resistors were found R341 and R370. I have no idea of their values though.Anybody with a RM3545 could measure R341 and R370 for me ?PS: I already sent an email to Hioki and they answered me it’s not a good idea to do board repairThanks!

author: HighVoltage
author_rank: Super Contributor
timestamp: February 12, 2024, 10:02:15 pm
content: Interesting project, bookmarked.I repaired a Hioki DMM once and they were also not very helpful at all.Hopefully you find someone with such an instrument.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 13, 2024, 01:57:59 am
content: since 1 side of them are connected togetherthis is not an item we see often here, you may wait a long time, i would try to find where the traces goes and see if it could be some range parts

author: Kosmic
author_rank: Super Contributor
timestamp: February 13, 2024, 02:23:33 am
content: Look like it's part of some kind of feedback circuit connected to Sense+ (on the input). The resistors are after some protection diodes and they all goes to an analog switch (DG441).Interestingly if I just remove the diodes (disconnect everything) the instrument is working as expected. I would still like to have that protection circuit in place.

author: gamalot
author_rank: Super Contributor
timestamp: February 24, 2024, 07:46:38 pm
content: I just opened my RM3545 and measured those resistors with a multimeter and LCR. The results are in the attached picture.

author: Kosmic
author_rank: Super Contributor
timestamp: February 25, 2024, 12:33:29 am
content: Quote from: gamalot on February 24, 2024, 07:46:38 pmThank you so much !!

author: Kosmic
author_rank: Super Contributor
timestamp: March 13, 2024, 04:41:25 pm
content: So, I finally got my parts from digikey.The new resistors installed (1k, 499 and 100k). I was able to match the original colorAnd ... now I got a happy RM3545 measuring 1MOhm.Thanks again gamalot for the resistor values
Hirose Df9 31 Pin LCD Display Panel Lead - Page 1
Forum section: electronics / repair

author: G0GCD
author_rank: Newbie
timestamp: April 09, 2023, 05:09:03 pm
content: Had a bit of an accident with an Anritsu MT8801C and damaged the LCD display cable. It's the one with Hirose DF9-31-1V connectors at each end and 31 wires between them - mainboard to display panel.Can anyone point me to a supplier of a replacement?I am awaiting a response from Anritsu UK, and Google has highlight hundreds of places where I can buy a batch of 100, but I only need the one (because I sure won't make that mistake again!).I'm hoping that someone knows of a shop which might have one ex-stock?ThanksJohn G0GCD

author: coromonadalix
author_rank: Super Contributor
timestamp: April 10, 2023, 11:22:15 pm
content: place like thishttps://linkmorecable.com/custom-hirose-df9-31-pin-41-pin-51-pin-vesa-cable-hrs-df9-fpdi-1-cable-assembly.htmlaliexpress ?https://www.alibaba.com/product-detail/OEM-TTL-LVDS-1mm-Hirose-DF9_60753045917.htmllots of answers when you search : Hirose DF9-31-1V
Hitachi 18V lion battery charger relays switching every few seconds. - Page 1
Forum section: electronics / repair

author: pbryd
author_rank: Contributor
timestamp: January 15, 2021, 01:01:09 pm
content: Good afternoon.I'm attempting to repair an Hitachi UC 18v YKSL battery charger.Fault: Charger showed no signs of life.I swapped the blown T3.15A fuse and the chocke (no continuity) and it is now outputting the correct voltages.However, the relay (Panasonic ALDP105) is switching every few seconds.Any help diagnosing the fault would be appreciated.There is a series lamp limiter (40W) on the supply (230V).
Hitachi ED-PJ32 Help With Error - Page 1
Forum section: electronics / repair

author: thedankid
author_rank: Newbie
timestamp: January 04, 2020, 04:01:24 am
content: Hello,Recently I bought a Hitachi ED-PJ32 projector. About 5-7 minutes after start-up, the LAMP and TEMP indicators alternatively blink red. The fan revs up, yet it continues operating. Based off of the service manual (which is attached below), this error occurs when the projector becomes over-cooled (Pg. 27). Yet, it has never been in temperatures under 70oF (21oC) since I've bought it. Based off of what I've read in the service manual, this issue seems to be related to two thermistors. The one hooked up to port E301 is a 10KOhm thermistor (Likely a standard NTC one); the one hooked up to port E302 is a 1KOhm thermistor (in which I have no idea what kind it is) (Pg. 57). The 10KOhm one seems in range, based off of what I've found online using Google. I have no idea about the 1KOhm one. The thermistors in the part list (Pg. 41) seem to be unidentifiable, since custom part names are used. I'm not sure where to go next. I've tried playing around with the 1KOhm thermistor, but it has led me nowhere. The same error occurs. Is there anything I should look at that I'm not noticing within the schematics or repair manual? Are there any tips that can help lead me to the right place?
Hitachi horizontal diff amp fault - Page 1
Forum section: electronics / repair

author: gkmaia
author_rank: Frequent Contributor
timestamp: September 08, 2020, 12:14:13 am
content: I got on a road blocker and not sure where could my problem be.My SWEP OUT & HPOS signal are ok and responding to controls.My current SW3 is ok and sending the character/dot signals through Diff amp 2 when readout is enabled. But it does it by simply stop feeding the signal through TR882.The signal that comes from IC1111-2 does not change so seems SW3 is always on.The X1 signal is ok and responding to controls. 0v OFF and 5.8v ON but it is not switching neither Current SW 1 and 2 on. Therefor I get no signal output on collectors of Tr831 & 832.I've attached a schematic with some measurements. I also toke TR863, 865 and 867 and they are all fine.I did test IC 864 and it seems to have tested ok. But I am not 100% sure about it. I am sure its base is not shorted to ground otherwise my X1 signal would never go 5v.That is what is odd... the base of TR863 goes to 10.7 when X1 is 0v which in theory should get TR863 to conduct as base is 10.7 and emitter is 12. That is more than 0.7v to get it to conduct. And I should be seeing some voltage out of the collector. But nothing... only 0v.So if IC864 was faulty OPEN (not shorted) I should only loose the 10X magnification function. But 1X should work regardless.I am stuck here... i cannot find a reason for collectors of TR863 and 865 to be stuck on 0v... I see no shorts there. there must something that is impeding them to conduct but it is beyond my knowledge.Also tried to play with the blanking input but no luck.
Hitachi Opus 1 (mx-w01) main board extraction - Page 1
Forum section: electronics / repair

author: Quantumplate
author_rank: Regular Contributor
timestamp: May 12, 2023, 10:50:43 am
content: Hi, sounds a bit lame, but struggling to remove the large main board for power supply repair. Any tips welcome! The problem is all the pcb mounted rca connectors at the back. Not happy with the amount of force required so far. Pretty sure i don't know the knack on this one.
Hitachi V-152 Oscilloscope - how to discharge the CRT? - Page 1
Forum section: electronics / repair

author: sad123
author_rank: Newbie
timestamp: October 22, 2021, 12:20:35 pm
content: Hi Everyone,First post.I got an older Hitachi V-152 oscilloscope that needs a few issues sorted.Before I can do this, does anyone have the procedure to discharge the CRTs in these ones? They don't have an anode cap on top like TVs, or a separate connection like a tektronix.Also, does anyone have the service manual for this model (V-152 not V152F).Images of the innards:

author: BrokenYugo
author_rank: Super Contributor
timestamp: October 23, 2021, 02:44:29 am
content: I think this type discharges all the HV automatically, usually the HV supply feeds a divider chain to give the focus and cathode (intensity) voltages, and that naturally bleeds everything down.To be sure, clip a jumper lead from the frame to the shaft of a plastic handle screwdriver and carefully poke at the neck board.EDIT: Also keep in mind the deflection plate amplifiers and their supply run at something like 200 volts and that stuff may hold a charge.

author: sad123
author_rank: Newbie
timestamp: October 23, 2021, 04:11:14 am
content: Thanks. Are the deflection plate amplifiers the four transistors with the heatsinks under the CRT neck with the big capacitors around them?

author: m3vuv
author_rank: Super Contributor
timestamp: October 23, 2021, 07:29:44 am
content: I understand your concerns,many years ago as a kid,think i was 10yrs old at the time,i was playing with an old colour tv we had that had died,it had been unplugged a few mins,not knowing better i decided to take the anode cap off!,bam the thing threw me to the other side of the room,my thoughts at the time was the devil had just pounced on my back,didnt know then a crt acts like a big cap,had a lot of respect for them ever since!!!

author: youngwug
author_rank: Contributor
timestamp: October 23, 2021, 09:40:53 am
content: attach s/m.

author: youngwug
author_rank: Contributor
timestamp: October 23, 2021, 09:59:03 am
content: more 01

author: youngwug
author_rank: Contributor
timestamp: October 23, 2021, 10:02:13 am
content: more 02

author: youngwug
author_rank: Contributor
timestamp: October 23, 2021, 10:04:10 am
content: more 03(end)
Hitachi V-212 broken knob - Page 1
Forum section: electronics / repair

author: nockieboy
author_rank: Super Contributor
timestamp: January 20, 2017, 12:44:20 pm
content: Hi everyone,I recently bought a Hitachi V-212 oscilloscope off eBay, but is has a broken volts/div knob on Channel 2. I'm wondering if it's possible to source a replacement knob for it from somewhere, without buying a whole oscilloscope to strip for one part.Anyone have any ideas?Thanks!

author: int3grate
author_rank: Newbie
timestamp: April 09, 2017, 01:54:53 am
content: I'm not sure if you're still looking for a part, but I bought a broken unit for parts just to fix that same issue. I have another knob if you still need it. The center rod pulls out if you remove a pin, and you can replace that and the plastic knob.

author: nockieboy
author_rank: Super Contributor
timestamp: April 14, 2017, 09:33:41 pm
content: Hi int3grate!Apologies for the delay replying - for some reason I didn't get a notification of your reply to my post.Yes, sounds like an excellent idea. Feel free to message me if you still have the part and let me know how much you want for the item!

author: jpdesroc
author_rank: Newbie
timestamp: October 17, 2024, 06:37:07 pm
content: I'm very late here but saw this old topic about a Hitachi V212 broken volts/div knob you could still have for spare..Do you still have one that could be for sale ?Thanks.
Hitachi V-660 oscilloscope is shrinking the stroke - Page 1
Forum section: electronics / repair

author: Paulo Rato
author_rank: Newbie
timestamp: August 01, 2020, 07:47:58 pm
content: My Hitachi V-660 oscilloscope is showing a defect it is shrinking the line and I need help to fix it, thanks in advance

author: George Edmonds
author_rank: Frequent Contributor
timestamp: August 02, 2020, 01:55:28 am
content: Hi first check the power supplies, but be careful they are switch modeGeorge

author: Paulo Rato
author_rank: Newbie
timestamp: August 02, 2020, 02:38:38 pm
content: already checked friend and everything is fine.

author: SilverSolder
author_rank: Super Contributor
timestamp: August 02, 2020, 04:04:27 pm
content: Have you got the service manual?

author: Paulo Rato
author_rank: Newbie
timestamp: August 02, 2020, 04:32:44 pm
content: https://mega.nz/file/uMt2zQiT#584Mxxu3S8IuSTqq669yHTCyJ-3hfG_2P1ffHZkpDwA

author: madao
author_rank: Frequent Contributor
timestamp: August 02, 2020, 04:35:23 pm
content: and pleas check HV,, probably is HV to much high. (small and bright picture = to much HV )greetingsmatt
Hitachi v352 oscilloscope repair help - Page 1
Forum section: electronics / repair

author: lame_turtle
author_rank: Contributor
timestamp: August 24, 2020, 09:11:13 pm
content: HiI got a v352 a few months ago that I wanted to restore. Channel two was blown, so I replaced the tr101 and everything worked again . I decided I would recalibrate the scope eventually so I recapped it and started using it.After a few days I hadn't turn it on, I fire it up just to see a sinewave on both channels without anything connected on the inputs.I do have a ds1054z if a second oscilloscope is needed.Any idea where to start looking ?Thank youEdit: I used the scope a bit more to understand what's happening.All the controls/functions do work on the scope !The only problem is the scope is only showing a sinewave. Not even a flat line when nothing is connected or the coupling set to gnd. This is happening on both channels.Nothing is obviously burned up inside the scope.

author: shakalnokturn
author_rank: Super Contributor
timestamp: August 25, 2020, 09:19:34 am
content: A good starting point is to check all power supply voltages and ripple.

author: lame_turtle
author_rank: Contributor
timestamp: August 25, 2020, 09:21:47 am
content: Sorry I didn't mention. Psu checks out fine. Tested it and checked for ripple.

author: tunk
author_rank: Super Contributor
timestamp: August 25, 2020, 09:59:46 am
content: What's the frequency and amplitude of the sine wave?

author: lame_turtle
author_rank: Contributor
timestamp: August 25, 2020, 10:51:04 am
content: Found it. Both k30a's where toast. I did have some spares and the scope is back giving a nice flat line when grounded.I'll do a full repair report with photos in the next few days.Thanks
HK 206 PC Speaker Popping Sound - Page 1
Forum section: electronics / repair

author: bobcat2000
author_rank: Regular Contributor
timestamp: March 02, 2021, 01:11:28 am
content: Hi Guys,I have been using a pair of HK 206 speakers for years. No problem no thing. It sounds and works great.I always turn it off by turning the volume dial when I am done listening to the speaker.The other day, the static built-up in my butt was too high. I got a big spark when I touched the volume dial the other day.The speaker still work but every time I turn it on/off, it makes a big pop noise now.I probably ran thousands of volt through the plastic knob to the pot and somewhere to the transistor and to the ground when I touched the knob the other day.May I ask what may be broken inside? It is old so I don't want to crack it open. I will probably break the old plastic housing.It may not have anything look burnt inside anyway since it is still working without any problem.Thanks!https://www.amazon.com/Harman-Kardon-Computer-Speakers-HK206/dp/B00577RM8Y

author: bobcat2000
author_rank: Regular Contributor
timestamp: March 02, 2021, 01:24:45 am
content: Ah! I found this. There is no transistor inside. It has a TDA 1517a amp. So, where does it shorted to make that popping noise? Inside the IC?https://youtu.be/OHz-mC_xyzA

author: fzabkar
author_rank: Super Contributor
timestamp: March 02, 2021, 01:59:14 am
content: https://www.nxp.com/docs/en/data-sheet/TDA1517.pdf"No switch-on/switch-off plop (sic)"

author: bobcat2000
author_rank: Regular Contributor
timestamp: March 02, 2021, 04:56:56 am
content: Thanks.So, I know what goes in to the chip and what goes out from the chip.How do I tell why there is a big pop when I turn on/off the power?The cap discharge too much to the speakers?
HM507 display not refreshing - Page 1
Forum section: electronics / repair

author: shridmaster
author_rank: Contributor
timestamp: November 12, 2020, 03:36:19 pm
content: Hi all,Got a problem on my oscilloscope display, discontinued product so no luck on that front. Scope is the HM507 by Hameg (now Rohde & Schwarz).When the oscilloscope trace drawing cursor reaches all the way to right, instead of clearing the display so it can redraw from the left, it keeps redrawing without clearing. When the trace moves up or down, instead of cleanly moving it leaves a "wipe" effect. This has rendered the scope completely useless.What's odd is that if I click a button, really any button, the display will refresh. Rapidly clicking the trigger button, for example, keeps the display refreshing enough that I can actually see a trace.I've attached pictures of it in use. One is clean trace with no signal, another is a toggled digital signal, and another is a pure sine input. You can see the wipe effect and how by the end all that's left is basically a max and min output.Has anyone seen this before in another digital scope and where I should focus inspection?

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 12, 2020, 04:31:24 pm
content: The HM507 is a combiscope, I guess the problem you have is only in digital mode.Does it operate normally in analog? You say this oscilloscope is totally useless, I do not understand this claim.I searched for schematics for this oscilloscope but could not find them.I believe the schematics of the HM1507 must be quite similar.They are available in the German version of the HM1507 manual.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 12, 2020, 05:10:38 pm
content: Not quite sure I get the problem either...From your description of the issue I thought that the scope was not clearing the previous trace display before drawing the new one, as when Infinite persistance is on.On your last photo (sine wave input?) if the input is stable in frequency I would have expected to see a big fat sine wave displayed showing all the jitter and noise.If your second photo is meant to be a pause, burst of square wave, pause, burst of square wave, pause it looks like the trigger is working but the sampling clock (PLL based?) may be unstable.

author: shridmaster
author_rank: Contributor
timestamp: November 12, 2020, 11:10:58 pm
content: Figured out the problem. The "env" in the screen was the tip. It's in envelope mode.A couple of the knobs and buttons I need to fix this don't quite work, so I think I just have to disassemble and clean this up and I'll have a nice working 50MHz scope! No wonder I swiped it for $40.
HM99AL - Page 1
Forum section: electronics / repair

author: IconicPCB
author_rank: Super Contributor
timestamp: October 14, 2019, 11:38:17 pm
content: Looking for information on above chip.It is a five pin to220 like package and i think it may be a regulator .Also looking for a MOV . The only legible bit of information is a logo which looks like capital letter H or possibly K in inverted font .By inverted i mean letter outline shown, actual letter not printed.Part number on the MOV 2696 5642Any input welcome .

author: IconicPCB
author_rank: Super Contributor
timestamp: October 15, 2019, 08:22:54 pm
content: Nudge!?

author: pbarton
author_rank: Frequent Contributor
timestamp: October 15, 2019, 10:25:54 pm
content: A photo would have helped. Then we could see the manufacturers logo and if it was thro hole or surface mount.The ‘HM99AL’ you quoted could be the “Assembly Location, Wafer Lot, Year, Work Week, Pb-free package” information?Perhaps the second line is the device ID?Probably something like thishttp://wiki.sunfounder.cc/index.php?title=Step-down_DC-DC_Converter_ModuleRegarding the Metal Oxide Varistor, I can’t identify the manufacturer, but that’s not important.For protection choose a component with approx.1.6x higher than the circuit RMS AC voltage,1.2x higher than the circuit DC voltage
HOKI 3005N, metravi RPS-3005 calibration - Page 1
Forum section: electronics / repair

author: MatVer
author_rank: Newbie
timestamp: October 22, 2023, 10:14:35 pm
content: Hello, I recently purchased an equivalent power supply such as the Metravi RPS-3005, HOKI 3005N, Does anyone know how to calibrate these lab power supplies because mine deviates quite a bit from what I set? Kind regards, Mathis
Home made power supply restoration... In memory of my dad - Page 1
Forum section: electronics / repair

author: tchiwam
author_rank: Regular Contributor
timestamp: May 07, 2021, 06:27:41 pm
content: I remember when my dad was building it.By the number of holes in the case, this was repurposed a couple of times since the early 80s.Still works. The TO3 don't have much writing on them so making the schematic of it might be a bit hard.The volt meter is pretty much right on the money...

author: bob91343
author_rank: Super Contributor
timestamp: May 07, 2021, 10:16:51 pm
content: It's a shame to see so much unused space. A bigger transformer, for instance, or more filtering maybe.

author: tchiwam
author_rank: Regular Contributor
timestamp: May 07, 2021, 10:36:19 pm
content: I agree. I know the 2nd hole was for a current limit. So I was thinking to add that part of the circuit.The shunt is just a wire running around the Amp meter...Floating negative would be fun too...Cleaned it a little more and replaced the power cord.The transformer is a Basler something, I need to check the rating.Edit away stupid autocorrect...
Honda CRV Radio Alpine BB717AA, wrong time display - Page 1
Forum section: electronics / repair

author: Aheld
author_rank: Regular Contributor
timestamp: January 15, 2022, 10:33:36 am
content: Hi forum,my Honda CRV Radio, Typ Alpine BB717AA, has a defect in the time generation.After each switching on, it shows a time of "2:00"It seems, that the clock isn't able to synchronize with GPS and also not remembering any time area settings.Upfront of any dismounting activities, I would aks this forum is any body can support with a kind of service manual or schematics of this Alpine BB717AA radio?My current suggestions regarding this issue are (because of the age of this device):- defect battery for memory circuit- defect of real time clock IC- issues of solder connectionsOther ideas are warmly welcome :-)ThanksAxel

author: jceev
author_rank: Newbie
timestamp: January 15, 2022, 01:44:33 pm
content: Possibly due to this recent issue?https://www.theverge.com/2022/1/8/22873403/honda-acuras-y2k22-bug-clocks-reset-2002

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: January 15, 2022, 03:19:11 pm
content: Alpine does not release schematics or service manuals on OEM equipment. Looks like jceev nailed it. you have to wait for Honda to correct it in UK? Maybe because of their laws about release of information.Jeff

author: Aheld
author_rank: Regular Contributor
timestamp: January 16, 2022, 02:45:57 pm
content: Hello jceev and Jeff eelcr,this fits exactly to this issue. Thank you for your replies.I still remember the panic and preparation regarding new year 1999/2000 and nothing was happened.Now for 2021/2022 Microsoft has a big bug in they eMail service and car radios are not able to process this changes?What else in future?Thank you for helping, I'll contact Honda for bug fixing.Br.Axel