hybridfree/eevblog-posts huggingface dataset:
NAD 515Bee CD player - Page 1
Forum section: electronics / repair

author: JDelectrician
author_rank: Newbie
timestamp: March 14, 2025, 11:40:03 am
content: Hello everyone, I've been lurking around this forum for a long time and now I have a problem of my own.I have an old CD NAD c515bee player that will no longer power on into its standby state (no standby light when plugged in). I found the 5v standby voltage present throughout the circuit, and at the supply pins on the microcontroller. I found that when I momentarily increase the voltage to the mcu, the standby light comes on and i can see the standby outputs present from the MCU. Everything works normally until the next power removal, and I need to do the little bump again.Do you think there is a problem in the MCU, or can it be in the power section? The 5v reading is solid on the multimeter, but could one of those other things be failing and I can't see the flicker without a scope?I feel like if the MCU is working once it is on, it is unlikely to have just one bad pin that needs a bit of a kick.Thanks in advance for any help.

author: benj38
author_rank: Frequent Contributor
timestamp: March 14, 2025, 03:36:01 pm
content: Did you check the AC ripple on the different supply rails?

author: JDelectrician
author_rank: Newbie
timestamp: March 14, 2025, 05:39:50 pm
content: Thanks - no not yet. I need to get to an oscilloscope. I am going to swap in some other 5vdc sources and see if it changes.

author: ME
author_rank: Frequent Contributor
timestamp: March 14, 2025, 07:09:57 pm
content: Set your mulimeter to ac volts and measure the supply,that will test for ripple as far as i know?.

author: benj38
author_rank: Frequent Contributor
timestamp: March 14, 2025, 07:16:06 pm
content: Quote from: ME on March 14, 2025, 07:09:57 pmFor this basic diagnosis purpose, yes it will. I would investigate anything above say 50mV

author: JDelectrician
author_rank: Newbie
timestamp: March 14, 2025, 09:05:52 pm
content: Much appreciated. I am going to try with multimeter.

author: Stringwinder
author_rank: Contributor
timestamp: March 14, 2025, 10:41:39 pm
content: My wild idea is that something is missing a reset at power on.Or the reset line(s)/circuits are not free to do their job.Page 29 in the service manual suggests a check of 5V on pin 5 of BN63.Follow the reset signals like CN62 pin 6 ST+5V to IC62 pin 2 and other connections.The output goes to RESET on IC61 and could stop it from starting in the first place.IC62 = H5VT28C low voltage detector.
Nad c325 - noise on one channel - Page 1
Forum section: electronics / repair

author: martinho1974
author_rank: Newbie
timestamp: May 27, 2023, 09:47:29 pm
content: Nad c325 - noise on one channelI ask for your help to try to find out the cause of this problem.Intermittent popcorn-like noise on the left channel.It is more evident if I leave the amplifier unplugged for several days.The noise tends to decrease if you leave it running for a long time, after 2 or 3 hours, it decreases considerably but does not disappear.The noise is also audible through the headphones.It is independent of the source and volume of the sound.Curiously in standby the noise persists in the headphones but not in the speakers.?there is also a hum on both channels under the same conditions as the noisethe pre amplifier part does not suffer from this problem, I connected it to another amplifier and there is no noise.

author: shakalnokturn
author_rank: Super Contributor
timestamp: May 27, 2023, 11:07:01 pm
content: I repaired a NAD C315BEE recently if the C325 is anything similar this may be of some use.NAD have as far as I know always suffered from weak solders, these Lead-free designs are no exception the C315 needed a lot of reflowing. This could be the cause of your "popcorn".In the C315 the main power supply filter capacitors where rated for 50V while fed with 45V, very low margin! One of them had bulged and lost enough capacity to cause hum.

author: martinho1974
author_rank: Newbie
timestamp: May 30, 2023, 10:02:25 pm
content: Correct me if I'm wrong.If the problem is only in1 channel, and if it decreases as the temperature increases, this limits the area to look for, on the left amplifier part, and on bad joints or faulty transistorshttps://youtube.com/shorts/jYwfrlkJ6T8?feature=share3

author: David_AVD
author_rank: Super Contributor
timestamp: May 30, 2023, 10:49:25 pm
content: Get yourself a can of freeze spray and see if you can narrow down the issue to a specific component. A transistor will be the likely cause for this noise.

author: martinho1974
author_rank: Newbie
timestamp: May 31, 2023, 04:40:25 pm
content: It's been on for 24 consecutive hours and the noise has practically disappeared.From experience, if i unplug it for another 24 hours, the noise returns to the cpoint of going into protection mode.Is this the expected behavior of failed transistors?

author: David_AVD
author_rank: Super Contributor
timestamp: May 31, 2023, 10:11:46 pm
content: Transistors can fail in all sorts of weird ways. It's hard to know if they are definitely the issue in your case.If you don't have freeze spray (yet), may try heating the bad channel with a heat gun on low (or a hair dryer) to see if that makes the noise go away faster.
NAD D3020 v2 Amplifier Protection Mode - Page 1
Forum section: electronics / repair

author: raso
author_rank: Newbie
timestamp: April 27, 2021, 06:33:28 pm
content: I picked up on eBay a spares/repair NAD D3020 v2 amplifier for $70. It will turn on and then flashes red and turn off. I couldn't find the service manual for V2 but another post here did have it for V1 (https://www.eevblog.com/forum/repair/help-repair-a-d-class-amplifier-nad-d3020-v1/). They seem to be very similar with the main difference with the V2 having a Phono Input - which is why I want it. Service manual says red light means "Check Protection Circuit".The Amplifier is an OEM UcD102 (https://www.hypex.nl/product/ucd102-oem/52) unit from Hypex which the spec sheet says has DC-Error Detection on the output. I found a test point on the main board (DCERR) and it does go high on startup. Disconnecting the amplifier completely does allow the unit to power up and even the headphones work (separate amplifier) - so not a complete loss if I just use it as an Headphone amp with Phono.After some probing around it looks like 2 of the Main MOSFETs on the UcD102 are blown (short between source and drain). Sure enough when I check the output terminal for that channel there is -28DC volts on it. Good thing I didn't hook up any speakers to it.While I wait for the replacement MOSFETs to arrive should I keep looking for other problems? Not sure why they would have blown, could be heat I guess since the unit is very compact with no active cooling (just a thermal cutout on the amp heatsink)P.S. For future generations trying to dissemble this amplifier.Remove the two screws on the back, then peel off the label plate - its glued on!!. You can then remove the four outer screws, 2 for each side panel. Then you can pull off the side panel with the NAD logo - careful there are plastic clips (bottom seam, top inner, front inner) . You should be able to slide out the amp now and flip it over. The other side panel is attached to the top/front with screws you don't need to remove it since you can disconnect the wires going to the display/controls/antenna.To get to the amp board remove the 3 screws on the main board and the screw between the optical and coax digital input on the back. The main board is connected to the lower board with a very tall standoff. Gently pull the board back (to clear the digital coax jack) and up being careful with the standoff.As they say "You are in like Flynn"
NAD S300 Amp Question - Page 1
Forum section: electronics / repair

author: uslrs
author_rank: Contributor
timestamp: January 23, 2025, 11:23:12 am
content: Hi All, I've been doing some repair work on a NAD S300 amplifier and am struggling to understand the function of the plus and minus drive lines with respect to the operation of the gain stage and power amp - J315/J321 on the gain stage and J515/J521 on the power amp.I'd really appreciate a basic explanation of how the circuit functions in relation to these signals and how they relate to/influence the input signal. Many thanks.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 23, 2025, 01:10:25 pm
content: on one page you have the power amplifier section, drives lines are just a name to the driver section of the second pagethere was not enough place to put all the schematic, drive line could be called pre-driver section etc ...the "output" line is returned to the op amp TL074, who provide output feedback to the pre-driver section, and another op amp section for the error detection ...q501 is your Bias transistor, it should be placed on the heatsink ? or at least be in contact with

author: uslrs
author_rank: Contributor
timestamp: January 23, 2025, 02:46:22 pm
content: Thanks coromonadalix, the gain stage is on the main board with the power amp separate, hence the connector identification. This pair is duplicated for the other (right) channel. I think I understand your point to mean these 'drive signals' are simply interconnections between the main and power amp boards and the title 'drive' is simply an identifier. That makes more sense now although I'd like to understand the circuit operation better before the complimentary driver pairs (Q507/509, Q511/513, Q515/517, Q519/521). Am I right in thinking the primary purpose of the op-amps is to reduce inherent noise (i.e. to improve THD)?
NAD T513 power supply load ! - Page 1
Forum section: electronics / repair

author: guizmo1967
author_rank: Regular Contributor
timestamp: September 26, 2024, 04:38:44 am
content: Hello,I tried to repair a NAD T513 DVD/CD player that was showing "no disk error". Replacing the laser unit did not solved the problem.I noticed that the LA6560 Five-Channel Driver was getting really hot but did not bother to replaced it so I gave the unit to a recycle center.I kept the power supply for learning purpose but it is not working once removed from the player, I think it's because there is no load !There is only one connector (15 pins)1 VF+2 VF-3 -27VA4 5.2VA5 PWR_CTL6 D.GND7 5V8 12V9 A.GND10 3.3V(1.8V)11 3.3V12 3.3V_M13 D.GND14 8V15 M.GNDMy questions are:Do every power rail needs a load ? If so, which one and what king of load, just a resistor ?What would you do to make it work outside the player ?Thank you !

author: wasedadoc
author_rank: Super Contributor
timestamp: September 27, 2024, 12:14:07 am
content: I would try loading at least the supply that is monitored in the feedback loop. Finding a schematic is probably the easiest way of determining that.

author: guizmo1967
author_rank: Regular Contributor
timestamp: September 27, 2024, 05:34:13 am
content: Here is the schematic of the power supply !

author: guizmo1967
author_rank: Regular Contributor
timestamp: September 28, 2024, 12:50:07 am
content: Remember, this power supply was working fine when plugged in that DVD player ! I don't have that DVD player anymore, I just kept the SMPS.I get voltage on the first 4 pins only and it is fluctuating, not stable that's why I think it needs a load.Do I put a resistor between pin 1 and 2This is my readings:Pin 1: -15V (not stable)Pin 2: -22V (not stable)Pin 3: -27V (not stable)Pin 4: +4.98V (not stable)On the schematic, pin 3 and 4 are marked VA ??
NAD T743 - Page 1
Forum section: electronics / repair

author: huhu
author_rank: Newbie
timestamp: April 25, 2025, 07:14:31 am
content: Hello electronics engineer, I'm looking for the following IC from a NAD T743 receiver. I've already contacted NAD directly, but unfortunately, no help, no answer, just useless information.See picture

author: coromonadalix
author_rank: Super Contributor
timestamp: April 25, 2025, 03:52:40 pm
content: from ai : The ALI M6759 is an 8-bit microcontroller from Acer Labs. It is compatible with the 8032/8052 instruction set and includes MTP Flash ROM for firmware updates. It also features three 16-bit timer/counter registers. While the search results mention a 44-pin QFP package, it's unclear if PLCC44 (Pin Grid Land Chip) is a standard packaging option for this microcontroller. More information would be needed to confirm if PLCC44 is available for the M6759.genuines or fakes ?https://www.aliexpress.com/i/1005002098120556.htmlhttps://www.ebay.com/itm/286457765954https://www.aliexpress.com/item/1005003198810592.html... and you may or will need a programmer and the fw file to put in it ??

author: thm_w
author_rank: Super Contributor
timestamp: April 25, 2025, 10:21:28 pm
content: How do you know that you need this part?

author: huhu
author_rank: Newbie
timestamp: April 26, 2025, 05:48:51 am
content: High, I ran a test (heated the IC), and after that the IC stopped working. After cooling down, it worked again. I tried to read the contents, but unfortunately, it wasn't possible.

author: Sorama
author_rank: Frequent Contributor
timestamp: April 26, 2025, 06:02:21 am
content: Quote from: huhu on April 26, 2025, 05:48:51 amAre you sure it’s not a bad contact?Have you lifted the ic out its socket and visually inspected it, including the socket?

author: picburner
author_rank: Frequent Contributor
timestamp: April 26, 2025, 06:25:04 am
content: If the fault really lies in the micro, as a last resort, you could try to read the firmware contained in the M6759 withthis device(you will have to use a PLCC-44 to DIP-40 adapter) provided that it is full compatible with the 8051 and there are no active protections.Of course you will have to keep the M6759 "cool" for the entire duration of the operation.

author: huhu
author_rank: Newbie
timestamp: April 26, 2025, 06:55:36 am
content: Hello, I tried to read the contents of the IC, but it has a protection, unfortunately it is not a contact error, because after the read attempt the error occurred again.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 26, 2025, 12:41:54 pm
content: well the chip is read protected ? you will need another NAD T743 for parts ....

author: peterkos2
author_rank: Contributor
timestamp: September 08, 2025, 07:39:55 am
content: Hello. I am also looking for this microcontroller ALI M6759 for the NAD T 753 receiver. Did you manage to solve it? Thanks for the answer
NAD310 Repair, BUK555-60B Alt, IRL540N? - Page 1
Forum section: electronics / repair

author: TaylorD93
author_rank: Regular Contributor
timestamp: March 26, 2023, 07:18:34 pm
content: Hi Everyone,I recently picked up a NAD310 Amplifier from ebay, it was spares repair and after finding the service manual online i set about fault finding. Luckily the circuit is really easy to fault find and i traced the issue to the Output stage, bit of an odd layout (to me anyway) where the "high" side of the Class AB output is a MOSFET while the "low" side is a BJT Device.Anyway, the MOSFET has failed, it is a BUK555-60B, this seems to be discontinued now, so other than a Used device or a possible counterfeit device, id rather find a modern replacement i can buy from a reputable seller in the UK.Im not so great with MOSFET Datasheets, alot of figures im not sure of the significance of, but i am looking at the IRL540N as an alternative, similar Vgs of 1-2VDC and Power rating. Also a similar minimum TransconductanceThe IRL540N does have a higher VDS rating (100V instead of 60V) and a slightly higher RDS at 0.11 Max, but as its in a Linear/Amplifier output stage, i would presume that the RDS is not so critical as it is not being used in a switching circuit. the 540N does also have a slightly higher Input capacitance, but again as its a Audio amp, does 2200pF (IRL540N) vs 1450pF (BUK555-60B) really matter?Could these changes cause oscillation of the amplifier? or is it worth just trying it out anyway?I have a 8 Ohm resistive load i can test the amp with first before actually running it with a set of speakers, but i rather avoid any further damage to the amp because of my component selection.Any thoughts or guidance would be greatly appreciatedThank you, Taylor

author: David_AVD
author_rank: Super Contributor
timestamp: March 27, 2023, 02:31:56 am
content: You can buy the correct part here:https://www.utsource.net/sch/buk555-60b.htmlI've used them a few times and not had any issues.
NAHP ( not another hantek post) - Page 1
Forum section: electronics / repair

author: iyahdub
author_rank: Newbie
timestamp: September 19, 2019, 10:46:18 pm
content: hi, everyone.As I know some o you have dissected the dso5072 , I would like some advice.After an atrocious experience with banggood delivery ( they didn't even know who had my parcel), and after some private detective work I managed to get my scope delivered. But, despite fully functional, it has a "dead" vertical line on LCD ( stays on a purple-ish colour once turned on).Will this be just a connector problem , or should I just live with it?My issue is that it will be a minus if I ever intend to sell the scope in order to upgrade it, eventually... ( I shall post a picture once I get home).Thanks in advance .
NAME OF CHIP Q4 - Page 1
Forum section: electronics / repair

author: fabr
author_rank: Newbie
timestamp: January 15, 2025, 07:07:16 pm
content: This is the board of a vacuum cleaner. It does not give voltage to the motor, I need to change the Q4 chip but I can't see the complete code. Does anyone have any idea what chip it might be?

author: coromonadalix
author_rank: Super Contributor
timestamp: January 15, 2025, 07:19:41 pm
content: can you clean it better ?

author: wraper
author_rank: Unknown
timestamp: January 15, 2025, 07:34:09 pm
content: Seems to be IRFH5301, but could be IRFH5300-IRFH5304, IRFH5306-7 too. Last digit is mostly destroyed but looks like it could be 1 based on the first photo, second last looks like 0 but it's partially destroyed too.

author: Gyro
author_rank: Super Contributor
timestamp: January 15, 2025, 07:35:18 pm
content: If that's a 5007 on the top row (3rd photo), it could be an IRFH5007. It depends too much on the photo angle - it could almost be two different parts in the 2nd and 3rd, you're much better looking at it close up with a magnifier and reporting back what is readable.

author: fabr
author_rank: Newbie
timestamp: January 15, 2025, 08:06:58 pm
content: Sorry for the poor quality of the photos and thanks for the replies. I'm looking at it right now and what I get to see is "53?". I will look at some data sheets because I think it is "5301" as some said. I will keep reading the suggestions and thanks for the help
Name that component: 6x6mm, marked "100", meausres <0.2 ohm - Page 1
Forum section: electronics / repair

author: mcovington
author_rank: Regular Contributor
timestamp: November 14, 2022, 02:26:08 am
content: Not exactly a repair question, but could have been; if this belongs in a different forum, please advise.From a defunct Wi-Fi router I salvaged a number of surface-mount parts, each rather large (maybe 6 or 7 mm square), gray ceramic, labeled "100". I thought they might be power resistors, but they measure less than 0.2 ohm. I haven't checked inductance. Are they inductors? The SM equivalent of ferrite beads? Or what?

author: fzabkar
author_rank: Super Contributor
timestamp: November 14, 2022, 02:35:30 am
content: Probably 10uH inductors (10 x 10^0). If they connect to an output pin on an adjacent IC, then they are probably part of a switchmode converter.

author: TheMG
author_rank: Frequent Contributor
timestamp: November 14, 2022, 05:02:09 pm
content: A picture is worth a thousand words.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 14, 2022, 05:12:55 pm
content: Can't understand why people keep doing this.Make it a question, not a puzzle.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 14, 2022, 09:53:40 pm
content: That's coil. Probably 10uH.

author: mcovington
author_rank: Regular Contributor
timestamp: November 15, 2022, 12:58:10 am
content: Thanks. The large size does suggest an inductor.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 15, 2022, 02:06:52 am
content: I guess you're seeking a short?Often it'll be one of those ceramic capacitors, but there're hundreds, so better inject some current and find the one heating up.
Name that fuse! - Page 1
Forum section: electronics / repair

author: Factotum
author_rank: Contributor
timestamp: December 07, 2023, 01:44:30 am
content: Currently repairing a HDBaseT unit (HDMI over Cat6) which has been damaged by a sparkie "helping out".Have four of these fuses as part of the PoH (their version of power over the data cable) circuit.I know they are Littelfuse (in the 4532 / 1812 package) but after reading multiple data sheets can't see them following regular manufacturer markings.It's also not clear if they are fuses or PPTC units.Any thoughts?Thanks!

author: fzabkar
author_rank: Super Contributor
timestamp: December 07, 2023, 02:01:29 am
content: PTC polymer, quick blow, 1.1A, 24V, POLY-FUSE, Resettable PTC.https://www.tme.com/au/en/details/1812l110_24dr/smd-polymer-fuses/littelfuse/https://www.tme.com/Document/bf4e37aecf6e0d1a558d90b8c5d5e616/1812L020PR.pdf(datasheet)

author: Factotum
author_rank: Contributor
timestamp: December 07, 2023, 02:32:06 am
content: Quick answer .I understand that the one you have linked is a 24v unit verses the 16 from the photo…Thanks again!

author: Factotum
author_rank: Contributor
timestamp: December 07, 2023, 02:35:47 am
content: Bonus points - I’ve just pulled the board out of the chassis to keep testing and prepping and found more damage on the underside. Marked DT I’m guessing they are transient diodes of some sort perhaps.My google skills are poor today

author: fmashockie
author_rank: Frequent Contributor
timestamp: December 07, 2023, 03:18:21 am
content: Seems like it could be a SMF15A. Uni-directional TVS diode 15V, 200W.https://www.mouser.com/ProductDetail/Littelfuse/SMF15A?qs=zMpzAB%2FftDfu7OqK5zgklA%3D%3DThere are a bunch of smd marking code search engines. But hotenda.com tends be on point for future reference.

author: Factotum
author_rank: Contributor
timestamp: December 19, 2023, 04:53:55 am
content: Close but no cigar on that second set of diodes.After a part removal the board is clearly marked for polarity so figuring directional TVS or Schottky. Package is a gull wing about 44 x 35 mm so close to a SMB DO-215AA.Hotenda got me this :https://www.hotenda.com/marking-code/search/part/SMBG15CA.htmlWhich seems to meet most of the criteria...
Name that part - Page 1
Forum section: electronics / repair

author: jheatac
author_rank: Regular Contributor
timestamp: August 03, 2024, 08:49:39 pm
content: Can someone tell me what these are?I removed them frome something I scrapped but I don't remember what. At first glance they look luke a light bulb but there is no filament. I also know there was no need for light at their location on the board.Marked 102 and 08EThanks

author: fzabkar
author_rank: Super Contributor
timestamp: August 03, 2024, 09:17:20 pm
content: Neon NE-2 lamp.https://www.google.com/search?newwindow=1&q=neon+%22ne-2%22&udm=2

author: Andy Watson
author_rank: Super Contributor
timestamp: August 04, 2024, 12:02:55 am
content: They look very well made for "lamps". Also, ...Quote from: jheatac on August 03, 2024, 08:49:39 pmI think they are most likely some form of gas-discharge (possibly neon) voltage stabliser/supressor.

author: jheatac
author_rank: Regular Contributor
timestamp: August 04, 2024, 12:51:23 am
content: I don't remember 100%, but I am thinking they are off the power supply board for a relatively newer (1080 era) sony projection TV.I really don't think they were for an indicator because they were in the middle of other components just sitting on the board.Neon bulbs need a driver/ballast to get them started, don't they?

author: rhodges
author_rank: Frequent Contributor
timestamp: August 04, 2024, 01:02:41 am
content: Quote from: jheatac on August 04, 2024, 12:51:23 amNo. Neon will conduct at 90 volts if I remember right. I think older fluorescent starters had neon elements and also some thermal contacts. If you are old enough, you will remember the two flashes of a fluorescent lamp before it was on.
nanoVNA - Page 1
Forum section: electronics / repair

author: bob91343
author_rank: Super Contributor
timestamp: May 12, 2022, 03:50:12 pm
content: I have two units. They both worked perfectly and sat on charge for a couple of years with occasional use.I unplugged them and put them on the work bench. Now they are both in trouble and I don't know how to fix them.One does not respond to the power switch. The battery is fine.The other powers up normally but within a few seconds shuts itself off. Every time.Help please.

author: metrologist
author_rank: Super Contributor
timestamp: May 12, 2022, 07:56:12 pm
content: How do you know the batteries are good?

author: bob91343
author_rank: Super Contributor
timestamp: May 12, 2022, 10:25:30 pm
content: I measured the voltages.

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 13, 2022, 08:15:25 am
content: Not good enough.. some dead batteries show good voltage on open load.. once on load, voltage goes down like free fall.. you need to verify its mah capacity using a capable charger..or make one yourself.. using a dso and a resistor can do that as well..

author: bob91343
author_rank: Super Contributor
timestamp: May 14, 2022, 12:31:43 am
content: Apparently there is an intermittent. One of the units now seems to operate normally.
National (Technics) Panasonic finals.. - Page 1
Forum section: electronics / repair

author: PKTKS
author_rank: Super Contributor
timestamp: November 29, 2019, 09:49:07 am
content: Well not for sure the place to post such sad news.But for sure affects all people related with electronics andrepair parts in the last 4/5 decades,What once was (perhaps) 50% market of silicon partsin audio/video gear... National/Panasonic (and Technics)and probably several cloned others.. reached final dayhttps://www.techpowerup.com/261612/panasonic-exits-silicon-manufacturing-businessWondering what the future of the National/Panasonic parts may bePaul
National Matsushita Panasonic VP-2941A Miliohm meter manuals request - Page 1
Forum section: electronics / repair

author: rvalente
author_rank: Frequent Contributor
timestamp: August 28, 2015, 03:15:33 pm
content: Mates,would some one have the National/Matsushita/Panasonic VP-2941A miliohm meter service manual (or even userguide)?Got this unit few years ago, but came with no probes (as always, people always loose the damn probes.... it's 4 wire). Managed to find the pins but I wish I had more information.Greetings, Renan

author: rvalente
author_rank: Frequent Contributor
timestamp: January 27, 2017, 04:43:39 pm
content: Hello,anyone?

author: rvalente
author_rank: Frequent Contributor
timestamp: May 30, 2021, 12:30:30 pm
content: Searched again after a few yeard and found japanese manuals, its better than nothing.https://3d-yd.com/detail/?ID=1005
National NV-M3 Panasonic Vintage VHS Camera shutdowns after some seconds - Page 1
Forum section: electronics / repair

author: APOPAP
author_rank: Newbie
timestamp: August 25, 2025, 12:28:47 pm
content: Hello everyone,Just found an old Panasonic National NV-M3 VHS Camera without the original charger but with a special bag with a led, switch and fuse that is designed for a lead-acid 12v 6Ah battery. It has two cables coming off the bag that leads to the camera terminals (Only + and - ). Pretty sturdy design I think.I tried connecting it to a Computer PSU (12.7v) but I get battery error and keeps turning off after some seconds. Sometimes the tape mechanism opens, but a tape is currently stuck there. I tried using a 13.5v power supply. Now, there is no battery error, but I get a lense error "WHITE, LIGHT" and turns off after some seconds. Is there a protection mechanism for the tape? I want to try every possible solution before I try replacing the caps. Also, I dont think it is a capacitor problem because it drops that error. Any help will be greatly appreciated.Thanks!

author: CaptDon
author_rank: Super Contributor
timestamp: August 25, 2025, 01:45:35 pm
content: Is there a slide switch along the top of the camera near the handle? It slides forward and backward. On the models that had that switch in one position it had to have a tape in place and ready to go, either for recording or playback through the viewfinder. If no tape was in place OR the mechanism was jammed the camera would indeed shut itself off!! In the other position the camera could be used as a normal NTSC or PAL format camera taking the composite video feed from the jacks on the mating power supply or over the shoulder battery bag. If you don't have the 'mode' switch you will need to get the mechanism working. The loader motor needs to be able to cycle one mechanical switch and I believe one or two optical sensors. Usually there is a carriage closed sensor and two end of tape sensors which must be satisfied for the unit to remain energized.

author: APOPAP
author_rank: Newbie
timestamp: August 25, 2025, 03:36:16 pm
content: Quote from: CaptDon on August 25, 2025, 01:45:35 pmThanks for the reply! Unfortunately I cant see any button other than the eject on top of the unit.Before the unit turns off, there is a picture in the EVF ViewFinder, if this plays a role.So, it may be the tape mechanism that has a problem, like the old belts or something? Thanks
National Oscilloscope VP-5220A 20MHz analog oscilloscope repair - no picture - Page 1
Forum section: electronics / repair

author: NeoRecasata
author_rank: Newbie
timestamp: June 27, 2020, 03:29:24 am
content: Hello! I have this scope that was stored in a hot area of my house. It was working well before storage but after some years, it seems to have no picture/ display on the CRT screen but the power led and screen lighting is working.I tried googling the service manual for this scope but I couldn't find it.I've tried to work on repairing this scope before, here's what I have done that time:1. Removed the main power connector from the AC mains step down transformer and measured all voltages.it has 3 windings measuring 46v AC, 89v AC, and 18v AC (center tapped).2. Isolated the power board (removing all 5 jumpers to other boards).3. Measured voltages silkscreened where J1 is connected (J1 connects the H amp board)it measures +15v DC on the +12 volt rail, other silkscreened voltages measured fine, +B1 is 115v DC, +B2 is 250v DC.-- I have seen a small trace jump on the CRT screen of the scope when I switched the power on (while disconnecting 5 jumpers to other boards), in other words, a dot goes down from the center and then disappears.Those were the things I have done before I gave upI have no knowledge about repairing analog devices ie. oscilloscopes, but I have tinkered with CRT displays before, knowing the risks of working with CRT screens.I think heat caused this, probably the electrolytic caps must have dried.Here are the photos of the scope with descriptions:It includes some pictures of the boards and where I measured voltages.https://imgur.com/a/AIW3MDK
National RQ 501S reel-to-reel - Page 1
Forum section: electronics / repair

author: abhi1981
author_rank: Regular Contributor
timestamp: December 18, 2022, 05:55:25 pm
content: Hello,The motor of my National RQ 501S reel to reel player, is occasionally making a squealing sound.So, I opened it and found that it was a rather complicated design. There seems to be no way to oil the rear bushing.There's an ELNA 4uf 10wv bipolar capacitor, which is showing almost 4 times its value.Should it be replaced with the exact same value cap??

author: abhi1981
author_rank: Regular Contributor
timestamp: December 19, 2022, 10:47:27 am
content: Joined the negatives of two 10uf 16v capacitors back to back to make one non-polarized cap. The final size was exactly the same as original. Glued them and covered them with heat-shrink tubing.Oiled the bearing using a fine needle of a 2.5ml syringe.

author: amyk
author_rank: Super Contributor
timestamp: December 19, 2022, 11:07:08 pm
content: Electrolytic capacitors showing as higher than their marked value usually means they're either leaky or have been idle long enough that they need to be reformed slowly before applying full voltage.

author: abhi1981
author_rank: Regular Contributor
timestamp: December 20, 2022, 04:11:43 am
content: It's a 50+ years old capacitor. Wouldn't it be better to change it??I can try reforming as an experiment.
Nava [Roland TR-909 replica] Hi-hat and Ride/Crash trigger problem - Page 1
Forum section: electronics / repair

author: belzrebuth
author_rank: Frequent Contributor
timestamp: December 07, 2019, 12:50:35 pm
content: Hi all,I've got a problem with a Nava that was built from someone else.The hi-hats and the ride and crash are slowly rising to full volume when first triggered by the sequencer.When they reach full volume they respond normally.The only thing these sounds share is that they're samples triggered from an eprom and that they have identical trigger circuits and very similar analog paths from the eprom to the output.Hi-hats are reaching full volume faster than the ride and crash but their behavior is similar.Schematics are here for all the sounds:https://www.dsl-man.de/display/DSO/Nava+TR-909+Clone?preview=/17236005/17301561/Nava_v1.0l_Schematics.pdf#NavaTR-909Clone-Schematics:A circuit explanation is here:http://www.network-909.de/hihatand.htmSo far the only clue I've got is that when I try to measure voltage (essentially putting a very big resistor parallel to the resistor which goes to gnd (say r491 on the hi-hat circuit) the sound completely stops.Things I've tried:Replaced the NAND chips and the 4013 ff.Replaced the 100pF capacitor.Replaced the actual EPROM on one of these sounds (don't know why just did it in case it did something)Replaced IC51 (M5218) and C132Checked q70 on the crash circuit in case it's a fake or malfunctioning..swapped it with the handclap one; clap works fine so q70 is good.Also replaced the shift register responsible for propagating the trigger pulse from the MCU to the corresponding circuits..Still nothing..I'm unsure on how to proceed..Any ideas would be much appreciated as this is troubling me for quite some time.

author: SMdude
author_rank: Frequent Contributor
timestamp: December 07, 2019, 09:41:44 pm
content: R491 is holding the reset line low, so if the voltmeter causes the reset line to be in its reset state, then it probably won't put out any sound.For the volume problem you are having, what if you warm up areas of the board and also use some freeze spray. Doing this should help you to quickly identify the area causing you grief.I think q84 or q52 or the signal that comes from Accent_HH(I would look at the Accent_HH signal first) or C547 in the DAC multiplexer cct or the 4051 ic111, perhaps has a few channels with poor on resistance vs temp stability. That would also explain the problems you have with the other circuits too. By looking at the voltage of Accent_HH you should be able to tell if the problem is before or after there. It seems that line controls volume and is a quite nifty VCA circuit.Cheers
Navman 8120 chart plotter - Page 1
Forum section: electronics / repair

author: mrpelikan
author_rank: Newbie
timestamp: June 12, 2021, 03:17:50 am
content: First forum post, so bear with me. Against my normal judgement on not getting involved in consumer electronics, I've been talked into repairing a boatie relative's Navman 8120 chart plotter. It turns out the issue is a dead inverter for cold cathode backlight. An LED upgrade is available from a vendor in the US but we need to decide whether to spend that many dollars on an older device.That aside, on lifting out the LCD screen to withdraw the cold cathode I must have slightly lifted the protective glass front from the LCD screen.Between the glass & LCD screen is a viscous (water-clear?) filler. This is probably to exclude the marine environment from LCD panel.The filler has retreated away slightly from inner edges of LCD panel on 3 sides plus a couple of small bubbles under the glass. Due to the dead CCFL I haven't powered up the plotter yet but assume the bubbles and retreated filler will affect/distort the image.Anyone know what this filler compound might be? Better yet, what could be used to fill the voids?
NCI Weigh-Tronix 2520-2 Shipping Scale bricked - lost calibration? - Page 1
Forum section: electronics / repair

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: April 26, 2025, 12:32:16 am
content: I have a 1980s vintage NCI Weigh-Tronix 2520-2 200lb shipping scale, originally owned by Fedex. Very heavy, with a separate VFD display unit on a cable and RS232 interface. I used it a couple decades for weighing my eBay sales. One day the power switch fell apart. I purchased a new switch and soldered it in. When I power on, it displays the usual "------" (middle segment on all digits), but it's supposed to reset to 0.000 after a few seconds, and it doesn't do that, nor does it register weight. I suspect I may have accidentally shorted the battery and erased or corrupted the calibration. It's effectively bricked now. I can't find any documentation anywhere on the scale.There are 3 switches on the PCB:S1 (CAL SEQ) – momentary pushbuttonS2 (STORE) – momentary pushbuttonS3 – 4-position DIP switch labeled:I/O ENABLEMODETESTFUNCTION(All DIP switches are OFF by default.)Only the TEST switch seems to do anything. When I turn on TEST and press CAL SEQ, the display cycles through:CAL 0CAL 100CAL 200StorEIt stops at "StorE" until I press the STORE button, which exits the sequence.I tried going through a full calibration by applying weight to it (just with my hands as I don't have any reference weights), then pressing STORE at each stage. But afterward, the display just shows random values fluctuating rapidly between -999.999 and 999.999. Turning off TEST just returns to the frozen "------".I can read the ROM, and I suppose I could run it through an EF6803 disassembler, but I think understanding 6803 ML is beyond my skillset.Does anyone have experience with this model or know how to recover it? Or is it end of the road for this once trusty scale?I'm honestly quite surprised the BR2325 battery lasted as long as it did, it has to be over 35 years old or so.

author: CapLeaker
author_rank: Regular Contributor
timestamp: April 26, 2025, 01:45:28 am
content: Check that battery. If that is at 3.0V, it’s just about dead and needs replacing.All the basic programming is on the (EE)PROM with the sticker on top. I ‘d do a backup of that. The calibration gets lost if the battery dies. I think it needs calibration and you need to figure out how to get it into calibration mode. Maybe call Weigh Tronics and ask them how that is done or get a user / service manual.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: April 26, 2025, 01:04:24 pm
content: Hello GnatGoSplat,I have no knowledge about the scale you own.However, I suggest you redo the calibration process with weights that approximate as close as possible the awaited values.I would say that a ballpark of ± 1 lb could be a decent starting point. Use jerrycans filled with water to mimic the calibration weights.
Neatest way to repair broken vias? - Page 1
Forum section: electronics / repair

author: cesare
author_rank: Contributor
timestamp: October 28, 2022, 11:28:02 am
content: I recently picked up a Fluke PM3394B which was refusing to display any traces, or trigger on any input, but at least the digital side of things looked to be ok.Turns out the the analog board had various vias which had become disconnected, and a couple of broken traces, and fixing these had lead to a functioning oscilloscope - result!The dodgy vias are very small diameter, and may be laser cut (not sure, but it's a mid 90s Philips design, so whatever they were using at the time). To sort these, i've traced the missing signals to other places where the vias were working, and used connections between these points to resolve the missing signals. It's not the neatest, but it's working. Here's a shot of the board with it's extra wiring:If the vias were larger, i'd have pushed a wire through and remade the connection that way. Given these are too small, and the dodgy ones are blocked, is there a better technique? Will drilling out the holes (assuming I can track down a thin enough drill bit) work, or will I just in reality end up doing more damage, and I should stop at this point as it's working?BTW, the failure seems to be caused by thermal cycling. This scope had two extra daughter cards for TV and external sync options, and the trace and via failures were under these boards, so i'm speculating that extra heat or lower airflow from these boards has caused thermal issues over time with the board.

author: Psi
author_rank: Super Contributor
timestamp: October 28, 2022, 11:48:24 am
content: Looks good to me as is.You could put a little PCB glue or UV cure solder mask on top of the wires to anchor them down a little.But really, it's not something that moves around and might experience vibrations, so I wouldn't bother

author: cesare
author_rank: Contributor
timestamp: October 28, 2022, 05:00:25 pm
content: Ok, i'll try some glue. Just wanted to make sure I wasn't missing some obvious technique!

author: coppercone2
author_rank: Super Contributor
timestamp: October 28, 2022, 05:18:28 pm
content: copperset via, out of stock because of pandemic (someone was making a replica for sale).
NEATO XV-11 robot vacuum Battery Issue 0002 error [FIXED] - Page 1
Forum section: electronics / repair

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: June 11, 2018, 02:38:21 am
content: Had an intermittent, the permanent, battery fault issue on my Neato XV-11 (now about 6 years old). Symptoms were blank screen and no boot-up - solid amber LED lights around the red Start button when docked to the charger. Buttons unresponsive. Removing and reinstalling batteries ineffective, as were suggested Reset attempts using Start + other buttons. Batteries were newish and load-tested fine. Tried suggested web solution of plugging USB link into computer. No joy initially but it did boot when also docked to power station - that's when LED came on and Battery Issue 0002 showed up. Stripped it down - turned out to have a few problems - bad solder joints on a 100uF 25V electrolytic cap, one leaky 100uF 35V cap and a bad solder joint on a power connector to the main board. Easy fix and working fine now. Presumably joints failed over time from frequent bumping into objects. Thought this might be useful to others who encounter this quite common battery fail message.Worth noting that the various plastic posts into which the multidinous cover screws are fitted do become fragile and crack over time. Have managed to patch a couple using RapidFix - uses methacrylate adhesive and fine powder to weld/strengthen plastic. Pays to be gentle with them. Plenty of online videos about how to strip these units down.

author: antohagg
author_rank: Newbie
timestamp: May 09, 2021, 01:36:02 pm
content: Do you remember which caps you changed.Did change the c10 a while ago to solve the boot issue, but now i get battery error all the time.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 10, 2021, 12:59:56 am
content: Sorry. Don’t recall. But I don’t think there’s a great many in there IIRC. I had chronic hard-to-resolve NiMH battery problems with mine until I switched to third party Li batteries configured to fit battery compartment. Since then completely trouble free. Strongly recommend switching over.
NEC MultiSync UN462VA white stripe exactly in the middle of the screen - Page 1
Forum section: electronics / repair

author: Laughwvst
author_rank: Contributor
timestamp: September 09, 2022, 10:14:34 am
content: Hi. Got my hands on this new out of the box MultiSync UN462VA whit that kind of white/black line going through the middle of the screen as shown in the attachment.The manufacturer just sent us a new monitor and did not want the old one back, so now this is left to me to thinker with. I was wondering before I open the monitor and take a look, somebody here might have a hunch where to start looking the fault, or is the panel itself just faulty. The display cost over 2000 €, so I am willing to put a little money towards it if it is worth repairing.See the video to see how the line is acting. It sort of slowly and dimly becomes whiter when something should appear into the same area. Then the same happens also backwards.https://youtube.com/shorts/g7YhCLWGl7wThanks guys.- Ben
NEC uPD6258 serial EEPROM datasheet - Page 1
Forum section: electronics / repair

author: Gyorgy Albert
author_rank: Contributor
timestamp: November 22, 2024, 01:35:14 pm
content: Hi forum members,I am looking desperately for the datasheet of an older 3 wire serial EEPROM made by NEC, uPD6258. It is a SOP8 3 wire device (similar to the Microwire interface) with 8 kbit capacity. Maybe I am lucky, and someone can help with the complete datasheet. It is in a pre-2K generation measurement instrument, and holds the calibration coefficients, which I would like to backup. All what I found are two lines in the 1995 NEC Semiconductor Selection Guide (including the uPD6257, the smaller 4kbit brother).Thanks in advance,Gyorgy (George)

author: coromonadalix
author_rank: Super Contributor
timestamp: November 22, 2024, 03:47:18 pm
content: some references here but programming wise ?you have to check in many programmers their supported devices listhttps://www.eevblog.com/forum/beginners/substitute-for-d6254-808e-eeprom/msg248913/#msg248913attached a Renesas doc with some interfacing