hybridfree/eevblog-posts huggingface dataset:
22xx Knob repair; Broken Clips - Page 1
Forum section: electronics / repair

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: November 10, 2023, 07:39:56 pm
content: Hello everyone, I recently acquired a Tektronix 2230 from eBay, and It came with a broken knob. One of the B trigger knob's internal clips had snapped off, and I used cyanoacrylate to fix it. It made a strong bond but it wouldn't fit on the white knob holder.So I added extra force and the knob just shattered. Luckily the knob exterior could be fixed easily, but one clip had disintegrated into a million pieces. The other clip still remains though.Maybe someone that has experience with this problem could give me tips on how to effectively remount the knob securely but still have it removable for future repairs. I don't really want to glue the knob back on.I have always wondered why Tek had to choose this type of knob mounting on 22xx series scopes. Makes it a real pain to service the front panel board for these.

author: colorburst
author_rank: Regular Contributor
timestamp: November 11, 2023, 09:58:36 pm
content: I consider those to be non-removable. Fortunately there are few repairs where it's required. If you do need to remove or install one, use a hair dryer to warm up the plastic. I've been selling those on the auction site and have to emphasize this with every buyer. Never work with them without pre-heating, you will break the clips otherwise. Even with pre-heating, the clips are still likely to break.In your case, I would glue the knob back on with hot melt glue and try not to worry too much about it. If you need to remove it in the future, isopropyl alcohol or careful heat application will help break the bond.

author: DavidKo
author_rank: Frequent Contributor
timestamp: November 14, 2023, 08:31:27 am
content: I have had the 22xx series too and all were removable, but brittle after that time.

author: t1d
author_rank: Super Contributor
timestamp: November 16, 2023, 01:26:55 am
content: Maybe you have a friend, or a local "Makers" group nearby, that has a 3D printer? HTH.
240v UVC lamp - Page 1
Forum section: electronics / repair

author: GadgetBoy
author_rank: Regular Contributor
timestamp: September 24, 2020, 11:16:04 pm
content: So, bought this thing on eBay, seller didn't mention that it was a 240v bulb... Is there an easy way to change the components on this to make it function on 120v?

author: TheMG
author_rank: Frequent Contributor
timestamp: September 25, 2020, 01:56:27 am
content: Add a capacitor and use the bridge rectifier as a voltage doubler like what was commonly done in computer power supplies with the voltage selector switch.

author: GadgetBoy
author_rank: Regular Contributor
timestamp: September 25, 2020, 02:02:11 am
content: I think I know what you mean. Add the cap in the "middle" of the rectifier?

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2020, 02:45:56 am
content: Reconfigure the input as a voltage doubler.The usual configuration is a full wave doubler, it looks like a bridge rectifier except it uses two diodes and two capacitors instead of four diodes.https://electricalacademia.com/electronics/half-wave-full-wave-voltage-doubler-working-circuit-diagram/You might also find that it works fine on 120V perhaps at slightly lower than rated brightness. I have some 240V CFLs from England and I was surprised to find they work fine on 120V although I don't know if that would be detrimental to their lifespan.

author: GadgetBoy
author_rank: Regular Contributor
timestamp: September 25, 2020, 02:50:51 am
content: It does not function on 120 (it's a quartz UVC lamp), so I'm hoping to get it working.From what everyone is saying, it looks like my original plan of putting a single stage WC on the mains input should do the trick.

author: GadgetBoy
author_rank: Regular Contributor
timestamp: September 25, 2020, 07:01:15 pm
content: Found this, which confirms the mental idea I was forming of how to set this up.

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2020, 07:15:28 pm
content: That will work, but it is more complicated than it needs to be. Notice that each of those capacitors is actually in parallel with D3 and D4, so those two diodes can be eliminated and replaced with the capacitors.

author: GadgetBoy
author_rank: Regular Contributor
timestamp: September 25, 2020, 07:31:30 pm
content: Last question, do the caps have to be polarized as indicated in the diagram?

author: Gyro
author_rank: Super Contributor
timestamp: September 25, 2020, 07:42:26 pm
content: No, they don't have to be, it's just a matter of getting a large capacitance in a small space (electrolytics). The polarities shown are the ones youmustuse if they are polarized, to avoid reverse biasing them.
Tektronix 2431L Repair - Page 1
Forum section: electronics / repair

author: PixieDust
author_rank: Frequent Contributor
timestamp: October 08, 2023, 03:43:51 am
content: As per "Reply #52" fromhttps://www.eevblog.com/forum/testgear/blew-up-my-first-oscilloscope!!!/msg5088502/#msg5088502One of my capacitors has died. I have previously, years ago replaced all the RIFAs. Question is, should I go ahead and replace all the remaining capacitors in the whole thing or just replace this one bad one and call it a day?I don't see much consensus on this issue. Some people say replace all the old caps. Others say replace just the ones that are bad.

author: PixieDust
author_rank: Frequent Contributor
timestamp: October 09, 2023, 11:51:15 am
content: I decided to follow the dictum "if it aint broke, don't fix it". Lets see how that goes.

author: PixieDust
author_rank: Frequent Contributor
timestamp: March 03, 2024, 04:53:59 am
content: Well, I finally got around to repairing that capacitor. Repair went really well with the Engineer SS-02 solder sucker. Excellent product.Turned it on, more magic smoke. Another capacitor, just like it on the same board... toast. Time to replace them all I guess. Or save up and get a modern scope.I attached the offending cap that I replaced.Didn't take a photo of the new victim.

author: adinsen
author_rank: Regular Contributor
timestamp: March 03, 2024, 06:30:53 am
content: IMO repair should not exclude getting modern equipment and vice-versa. I prefer the strategy of not fixing things that aint broke, so if capacitors look good, I'd leave them in - except if they're connected to live mains.I still regret not attempting to repair (or at least shelve it for later) my Philips PM3055 when it failed... but my space was (and still is) limited, and analogue scopes take up a lot.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: March 03, 2024, 05:33:44 pm
content: 2400 series DSO's have power supply capacitors that are going bad.All of these scopes I repair first by replaceing all of those.After that, one unit blew that tant cap and damaged the one next to it.I do not remember if I replaced other same value tant's or not but after that no other problems.It was proably damaged from bad filtering from the power supply.Jeff

author: PixieDust
author_rank: Frequent Contributor
timestamp: March 04, 2024, 02:45:02 am
content: Yep, I replaced those caps when I got the scope.
2465B feet - Page 1
Forum section: electronics / repair

author: jonpaul
author_rank: Super Contributor
timestamp: August 23, 2019, 08:49:02 am
content: Hello all: restoring a 2465B TEK scope that is missing the front and rear feet:2 pcs foot bottom front plastic 348-0740-002 pcs foot cabinet cord wrap 348-0729-01Also missing the special TORX - 15 screws.I looked on the Qservice website but these seem out of stock.If anyone has some or is parting out a junker unit, I will appreciate!MANY THANKS!Jon

author: tautech
author_rank: Super Contributor
timestamp: August 23, 2019, 08:58:15 am
content: Try an email to Spherehttps://www.sphere.bc.ca/test/tek-parts/tekparts8.htmlOr see if the guys here can draw up a 3d model so you can get them printed:https://www.eevblog.com/forum/testgear/replacement-knobs-feet-and-fittings-for-test-equipment/

author: jonpaul
author_rank: Super Contributor
timestamp: August 24, 2019, 09:42:12 am
content: Hello all,I did contact Sphere in Canada no response so far.The 3D process can reproduce shapes but the materials are always inferior to the original material, due to the 3D process.Finally a kind TEKer in EU has found them and is sending to me via post.Many thanks for your replies!Bon journee,Jon

author: tggzzz
author_rank: Super Contributor
timestamp: August 24, 2019, 03:24:52 pm
content: Quote from: jonpaul on August 24, 2019, 09:42:12 amThat depends on the original material and the 3d printed material and the process and the shape.Brass is brass, Ti is Ti, unless you are after very specific material properties. If I had to replace feet, I would try one of the nylons.

author: DaJMasta
author_rank: Super Contributor
timestamp: August 24, 2019, 09:06:51 pm
content: Quote from: jonpaul on August 24, 2019, 09:42:12 amNot the case, especially when you're comparing them to the aged original plastics which have become brittle. Not like any stock of Tek analog scope parts is going to be younger than 20 years, even if it's been stored out of the sun. There are certainly weaker parts, materials, and printing configurations that aren't optimized well for strength, but making a part as strong as (or stronger than) the original is entirely possible, especially if you look at PETG, Polycarbonate, or Nylon. I have printed parts in ABS that are more durable than the part they replace and fit the same way and have had good luck building durable replacements for quite a few instruments.As for the original question, have you tried ebay or other second-hand sources? Provided the parts are in decent cosmetic shape, they should be as durable as a stored new old stock part. I'd also replace the screws with non-specialty varieties if it were me, though T15 screws shouldn't be too bad to come by with an online supplier (though no hardware store near me would bother stocking them, so I'd just go with a phillips head of the same size/thread).
2465B need PSU - Page 1
Forum section: electronics / repair

author: jonpaul
author_rank: Super Contributor
timestamp: August 24, 2019, 09:46:41 am
content: Hello all restoring a fine 2465B opt 06, 09.The PSU needs recapping and may have other faults.I would like to have a spare as I have other units.If anyone has a spare PSU that works, I am interested to get one.The units from Sphere, Qservice etc are too costly, a big fraction the value of the 2465B!I have some TM500 and 7000 plugins so perhaps a swap is possible as well.Many thanks!Jon

author: coromonadalix
author_rank: Super Contributor
timestamp: August 24, 2019, 01:55:04 pm
content: pas besoin de repartir un autre sujet, cest mal vuno need to start another thread ..

author: Simon
author_rank: Unknown
timestamp: August 25, 2019, 07:35:23 am
content: Quote from: coromonadalix on August 24, 2019, 01:55:04 pmAnd please keep all posts in English.

author: tautech
author_rank: Super Contributor
timestamp: August 25, 2019, 11:08:19 pm
content: Dunno why jonpaul keeps starting new topics on 2465B rather than benefit from the communities vast knowledge of these scopes and keep all the info in one thread where it can benefit all 2465B owners ? ?https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/

author: jonpaul
author_rank: Super Contributor
timestamp: August 27, 2019, 11:48:45 am
content: Hello Tautech, the 2465 teardown is a very long thread.One must search for a topic.Perhaps the eevblog should consider a separate topic for 2465 TEK scopes or TEK scopes in général rather than just adding to the 2465 teardown, which now expanded to include a lot of repair questions, and other general info beyond a teardown.Just a thoughtAmenitiesJon
2mm heat shrink tubing too big for thin wires inside of USB-C cable - Page 1
Forum section: electronics / repair

author: monster_of_electronics
author_rank: Contributor
timestamp: May 03, 2021, 05:02:36 am
content: I'm trying to shorten a USB-C cable, the wires inside (apart from the power line) are very thin. My smallest heat shrink tubing is like 2mm and it's too big, even after I shrink it. Hot glue and electrical tape seem like they would make a mess. Any ideas for how to better insulate tiny wire solder joints in a spliced cable permanently or is buying 1mm heat shrink tubbing my best option?

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: May 03, 2021, 07:17:49 am
content: You could remove the insulation staggered and use a single heat shrink.o=solder joint. Does this make sense?------o---------------------------o----------------------------o----------------------------o---

author: SeanB
author_rank: Super Contributor
timestamp: May 03, 2021, 08:05:13 am
content: Liquid electrical tape or the cheap alternative, nail varnish. Stagger the joints so that you have a single wire insulation thickness, and then paint the solder, then slip a sleeve over after it is dry, and you have given it a final coat over all the joins.
2n3771 and price is this legit?  - Page 1
Forum section: electronics / repair

author: mkube396
author_rank: Regular Contributor
timestamp: January 10, 2021, 10:40:24 pm
content: I am going for 20 2n3771 for a 20amp PSU 2 36 amp pyramid power supply 4 each and ill have some spars.Mouser is $5.55digikey is $5.52RF parts $3.50all are from ON Semiconductor.has any one ordered from Jameco ? there not going to be Counterfeits like Ebay are they? there listing as $1.95 seems cheep ill order like 30 of them lolJameco is $1.95 for "Major Brands" so I have no clue what they would be sending me there data sheet is for "ON Semiconductor" as long as there not NTE parts or fakes that would be cool...

author: med6753
author_rank: Super Contributor
timestamp: January 11, 2021, 12:26:18 am
content: I've ordered parts from Jameco several times in the past and their stuff is legit. However, I've stopped buying from them because their shipping/handling charges suddenly went outrageous.What's your issue with NTE equivalents/substitutions? I've used them in a pinch with no issues. And I don't think that pyramid power supply would care.

author: mkube396
author_rank: Regular Contributor
timestamp: January 11, 2021, 01:00:09 am
content: i'm running a Kenwood TS-2000 on it so i rather not have the Pass transistors short and blow my radio..so I i would like to run good parts and every one told me to stay away from NTE..

author: bob91343
author_rank: Super Contributor
timestamp: January 11, 2021, 01:40:27 am
content: Perhaps a crowbar circuit is in order.

author: mkube396
author_rank: Regular Contributor
timestamp: January 11, 2021, 01:54:02 am
content: I just rebuilt the crowbar circuit in it so its good...so i guess ill just have to order them and just hope there from ON semiconductor, Motorola, or ST Microelectronics or similar.. i think ill be all right i just though it was crazy cheep. I was more so worried that I was going to get china Fakes i never ordered from them.

author: mkube396
author_rank: Regular Contributor
timestamp: January 18, 2021, 06:55:04 pm
content: ok well they sent me 20 labeled "NJS" New Jersey Semiconductor i guess and 8 of them are from ON Semiconductor
2N6429A equivalent for HP10811 repair - Page 1
Forum section: electronics / repair

author: jpb
author_rank: Super Contributor
timestamp: May 13, 2019, 09:04:01 pm
content: About a year ago I repaired an HP10811 and was doing a final voltage check and managed to blow up Q5 which is a 2N6429A.I replaced it with another NPN in a TO-92 and get a distorted waveform - I then put the repair on hold while I moved house and more recently ordered some approximate equivalents (a multicomp MPSA06) and a BC108.The MPSA06 is a disaster, it has too much gain I think and overloads things so the frequency drops to 1.7MHz!The BC108 is equivalent to the other generic NPN I used and is the right frequency but is distorted.I've just ordered some 2N6429A off ebay but I suspect that they are probably not genuine.Has anyone found a good replacement when repairing a 10811?

author: Daxxin
author_rank: Regular Contributor
timestamp: May 14, 2019, 06:10:49 am
content: Lets try bc414 bc550

author: ArcticGeek
author_rank: Regular Contributor
timestamp: May 14, 2019, 04:14:30 pm
content: The original 2N6429A is a transistor that has very high gain, specified from 500-1300 according to the datasheet. The MPSA06 hfe is between 100-500, so it is quite a bit lower gain than the original. The MPSA18 transistor has high gain like the original part, so I would recommend a MPSA18 - they are readily available from Digikey and Mouser.Good luck!

author: jpb
author_rank: Super Contributor
timestamp: May 14, 2019, 04:51:30 pm
content: Thank you both.The seller of the 2N6429As I bought on ebay cancelled the order today as he didn't have them so it will definitely need to be a substitute.I'll get them from digikey but unfortunately I have to order £33 + VATs worth to get free postage so I may need to collect some other stuff together first (or be extravagant and buy myself some other goodies).I'll buy a selection and see which works best.

author: jpb
author_rank: Super Contributor
timestamp: May 18, 2019, 05:58:01 pm
content: I've made some progress but Q5 doesn't fix the issue.The signal at the base of Q5 is a nice sine wave of the correct amplitude but the output on the collector is a much lower magnitude sine wave (it should be roughly the same magnitude).I'm now suspecting the final stage with Q9. It may be the inductor/capacitors that are part of the stage but all the ones I've checked so far have been ok so I suspect it is Q9 itself but I can't find any info on it.The part number in the manual is :TRANSISTOR NPN PD.600Mw FT6600m142 28480 1554-0833The transistor itself has~61254-0833printed on its face.Does anyone have any info on this or can even tell me which of the many numbers corresponds with the device?

author: jpb
author_rank: Super Contributor
timestamp: May 18, 2019, 06:26:44 pm
content: After removing and testing yet more components, I now think it is the inductor L7 which seems to have gone open circuit.I didn't realise that inductors died like that - I generally suspect capacitors of going bad.Need to order yet more digikey parts - this is getting expensive!
2SB1019 Transistor Replacement - Page 1
Forum section: electronics / repair

author: spongella
author_rank: Contributor
timestamp: April 21, 2020, 09:01:07 pm
content: Hello all, I have just aligned an Icom 28A that was bought used, all is fine except the output on hi is 20W, specs say 25W. Was thinking that the final transistor might be soft so does anyone know a place to buy a single 2SB1019 transistor other than EBay? I prefer a vendor in the US if possible. Thanks and 73's.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 21, 2020, 09:52:43 pm
content: this page could help you i think you meant 2sb1019q17 transistor ?https://vetco.net/products/nte378-pnp-transistor-si-power-driver-power-outputIt list many transistors numbers ... and the equivalent in nte part

author: picburner
author_rank: Frequent Contributor
timestamp: April 22, 2020, 04:33:21 am
content: If you are referring to IC6 it isn't a transistor but a hybrid module, a SC-1019, and you can find ithere

author: coromonadalix
author_rank: Super Contributor
timestamp: April 22, 2020, 06:34:48 am
content: Apparently this one is an equivalent ??https://www.rfparts.com/sav7.htmlandhttps://www.aliexpress.com/i/32329894636.htmlfor a cheaper price ?? maybe a clone or fake ??

author: spongella
author_rank: Contributor
timestamp: April 22, 2020, 09:33:37 am
content: Pardon the typo, yes it is a 2SB1019.Didn't cross my mind that it could also be the power module. Thank you all for the responses, they were very helpful.

author: andy3055
author_rank: Super Contributor
timestamp: April 22, 2020, 09:44:12 pm
content: US supplier:https://www.ebay.com/itm/2SB1019-Original-New-Toshiba-Transistor-B1019-/400388303648?hash=item5d3900ab20
2SC 3133 RD 16 HHF1 - Page 1
Forum section: electronics / repair

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: October 23, 2020, 04:07:35 pm
content: Anyone have any recommendations for the above parts?E bay and Amazon are always suspect, Has anyone ordered these and received good parts? I would be very interested in a good cheap source.2SC 3133 or RD 16 HHF1I am repairing a Kenwood TS 50 and one of the 2SC3133 drivers in the final is blownRF parts is out of stock on the Mosfet no 2SC3133.I realize that I will have to make some changes to the bias to use the Mosfet. I have done this with 520s in a few radios. Works well.These particular transistors however have the emitter connected to the tab and pin 2 and do not use any mica insulation, so using 520s would be a bit difficult.Wally

author: coromonadalix
author_rank: Super Contributor
timestamp: October 23, 2020, 07:00:27 pm
content: They are not mosfets by the wayIf youdo a reverse checkup like this : npn to-220 rf epitaxial transistor some results are showntip41 is not good enough in bandwith2sc2166 seems goodetc... you have to check collector voltages and current, bandwith too

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: October 23, 2020, 08:07:19 pm
content: 2sc2166 does not have the emitter to the tab (fin), it has BCE pinout.2SC3133 has emitter to tab and middle pin and is NPN transistorRD 16 HHF1 is mosfet with source on tab and middle pinPinout is more important since it requires more work in modification of final boardIRF 520 works on specs but does not have source on tab, wrong pinout again.
2SC2937 equivalent - high power/voltage SMPS NPN switcher - Page 1
Forum section: electronics / repair

author: Audiorepair
author_rank: Frequent Contributor
timestamp: April 25, 2023, 09:33:21 am
content: Hi,I'm having no luck finding an equivalent to 2SC2937 for use in an SMPS.Seems Mosfets took over the SMPS job and now nothing out there comes close.Any help appreciated.This is from a Yamaha Rev 1 reverb unit.It is a large PSU construction with a lot of outputs, so really has to be repaired or scrapped - retrofitting a modern one is not really viable.I have included whats available in the service manual - no schematics, but it can clearly be seen these are the mains switching transistors as per usual in an SMPS.(Q101 / Q102)2SC2937 datasheet here:https://datasheetspdf.com/pdf-file/638650/SavantIC/2SC2937/1Cheers.

author: BigBoss
author_rank: Regular Contributor
timestamp: April 25, 2023, 09:58:07 am
content: https://www.mouser.fr/ProductDetail/STMicroelectronics/BU508AW?qs=VJaATVMq%252BXoaBpiIPfuaog%3D%3Dhttps://www.mouser.fr/ProductDetail/STMicroelectronics/BUV48A?qs=JV7lzlMm3yIoXBpWz6h6ag%3D%3D

author: Audiorepair
author_rank: Frequent Contributor
timestamp: April 25, 2023, 10:22:38 am
content: Quote from: BigBoss on April 25, 2023, 09:58:07 amAh, don't know why I didn't find the BUV48A.This is the second time I have tried to find similar transistors, the first time was another old Yamaha SMPS in a keyboard, but lower power.I did find the BU508A but after asking here it was considered unsuitable, as its a video device and some parameters would not work well in SMPS.But yes, the elusive BUV48A seems to be a likely candidate, thanks!
2SC4536 replacement - Page 1
Forum section: electronics / repair

author: mrf245
author_rank: Regular Contributor
timestamp: March 30, 2023, 10:54:51 am
content: Hi allI have a problem with my yaesu FTDX5000 radio. The main RX channel, RF AMP1 transistor, 2SC4536 SOT-89 was fault. The C-E was short.I just searched digikey, mouser and any online shop, they were all stock-out, and 2SC4536 was also discontinued.This transistor is not only a middle-power RF amplifier, but also has special features such as Low Distortion (low IM2 IM3) and large dynamic. Normal RF transistor may not have such features.So does anyone know which one can replace 2SC4536? Thanks!

author: rfengg
author_rank: Regular Contributor
timestamp: March 30, 2023, 06:02:57 pm
content: They are available on Ebay and ships to the US, perhaps you have someone who can order it and ship it to you?https://www.ebay.com/itm/143234690148?hash=item215973ec64:g:i4cAAOSwJYhi1XRR&amdata=enc%3AAQAHAAAA4N60mP7ta8PSulaSqMW%2BIQU42STDYJyt0%2Bjx6TcREZPnEzgBTxK4yaB%2FwIBd1D88%2B1HJI2k2EjRba7YX%2F3Hq6r11cF4Yq%2BA3GqdpgeB2Os0HOP%2Fz%2BfYoz509r9Q13gspNL%2FNY4KKbvu%2BhkICfyl62mZ2HOU2dPeYQzW7yY3mX7DdwGJU%2FDqUayj3xbdA5DEqh8YCqBJvVXE%2Bc4y2MaMJVot4sh%2FL5egHF1p50PIpnQnyCuXIBGTlwhNbbEy5T7jbUn1HfGUD40ZrnePVuLFalxG6rElcAfGquIjytoZ75tTi%7Ctkp%3ABk9SR5LM7rrmYQ
2SC971 replacement - Page 1
Forum section: electronics / repair

author: abhi1981
author_rank: Regular Contributor
timestamp: November 17, 2023, 10:25:24 am
content: Can I replace 2SC971 with BC337?It will be used in the oscillator and main amp of my Akai M-10.DSA1203000-110.pdf(36.53 kB - downloaded 149 times.)

author: quadtech
author_rank: Regular Contributor
timestamp: November 17, 2023, 04:40:10 pm
content: https://www.diyaudio.com/community/threads/akai-x-1810d-bias-oscillator.364477/https://tonbandforum-de.translate.goog/showthread.php?tid=10954&_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=scBc337 looks ok...check the pin out before you replace
3 Digits Seven Segment Voltmeter - Driver Chip - Page 1
Forum section: electronics / repair

author: 2X
author_rank: Frequent Contributor
timestamp: May 22, 2020, 08:18:49 pm
content: Hello,I have the below voltmeter but doesn't measuse (it lights only two segments). The 5V voltage regulator works ok at the back of the PCB. The chip has erased the letters on it and I don't have any part number to check it or replace it. Does anyone knows what is this chip/part number (or it is a microcontroller)?

author: Gyro
author_rank: Super Contributor
timestamp: May 22, 2020, 08:23:15 pm
content: Yes, it's likely to be a programmed microcontroller, using the on-chip ADC.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 23, 2020, 02:54:17 am
content: even if you have the chip, you will need the firmware to program it ?? and a way to connect it to a programmer ?? and thess display are sold pretty cheap nowadays ...

author: 2X
author_rank: Frequent Contributor
timestamp: July 04, 2020, 10:31:52 pm
content: Finally I bought the below from ebay.https://www.ebay.com/itm/0-28-3-Wire-LED-DC-0-100V-Voltmeter-Digital-Display-Voltage-VOLT-METER-12V-24V/173240751862?ssPageName=STRK%3AMEBIDX%3AIT&var=471952596263&_trksid=p2057872.m2749.l2649
3 ply thermal sandwich with copper plate in middle on a Delta-Q 21A charger fail - Page 1
Forum section: electronics / repair

author: Labrat101
author_rank: Unknown
timestamp: December 26, 2021, 05:41:19 pm
content: Hi I had a chargers to repair .Delta-Q 913-3600 . 21Amp @ 36volts. Date 2008 .The Thermal isolation between the power transistors to the main heat sink consisted ofsome what a strange setup . There are 3 layers of insulation that is not like the normal Mylar insulation material but more like coppered heat tape . with a thickness of 0.05mm . The problem is they put a copper sheet between the sheets and over time the the last diode after the transistor arced though the sheet to the copper insert . ( BanG)the copper sheet is connected via 10resistor to the emitters of the 3 power transistors .I can not think of any reason that this scenario has . Over the normal single isolation sheet mylar or similar .I have put up some photo's if some has any idea's why or what this odd array set up has to offer .The other 4 transistors have the same setup with the thermal sandwich . also with the copper plate connected to theEmitters via a smd 10resistor .The whole metal casing is mains grounded .Picture 1 is the 2 plastic sheets they are soft and flexible . and the copper sheet.picture 2 is the placement order without the paste& main heat-sink with another thermal sheet also 0.05mm thick and the locking plate.I want to just replace this setup for a single thermal pad without the copper sandwich .Any idea's for this . or is it a Chinese patent

author: Labrat101
author_rank: Unknown
timestamp: December 26, 2021, 08:36:06 pm
content: Basic I just need to know the reason for this topology . I have never come across this method on heat sinkcooling before . . I don't think its to do with interference or RF emission .So I was hoping that someone else has seen this before and knows the reasons behind this type setup .Thanks

author: Labrat101
author_rank: Unknown
timestamp: December 27, 2021, 07:12:52 am
content: Thanks .The only trouble was when I reassemble I used high grade thermal paste . Not metalized. The sheets they used are only 0.05mm thick.And we use 240v/250v here so the voltages on the primary is around 375v after the large caps totaling 440uf . . The end transistor is a diode from the HV . So there sheet failed. I'm not sure how it ever managed to last as long as it did.What you said sounds probably correct. Built for failures. Some how I will have to find a better solution.If you have any idea on solving this . I am open for ideas.All the other power units I have the heat sinks just one layer and the heatsinks are to neutral/ground .This type of unit is normally fitted inside an electric car . The mobility type .
30-180v power supply only outputs 9v - Page 1
Forum section: electronics / repair

author: Brad808
author_rank: Contributor
timestamp: January 23, 2020, 07:47:38 pm
content: I just got a Sencore ha2500 that was sold as working but unfortunately the power supply section is faulty. When turned on it will only go up to 9vdc. When working properly it is a variable 80 watt power supply from 30vdc-180vdc.https://youtu.be/HaU9DDe1eXUPower supply troubleshooting is far from my strong point so I'd like some guidance if possible.Here are some pics of the supply. I've tested a few diodes and transistors but they are testing fine from what I can see. I'd like a shove in the right direction.There are some test pins around the board and I can see 300v at the 3N100e. It's getting quite hot on the heatsink. Not sure if that is the point of failure.https://imgur.com/a/OGIyDXA

author: Chris56000
author_rank: Frequent Contributor
timestamp: January 24, 2020, 12:18:38 am
content: Hi!I've not found the original instructions for this yet, but here are the circuit diagrams!Chris Williams

author: Brad808
author_rank: Contributor
timestamp: January 24, 2020, 12:30:11 am
content: =-O Whoa thanks! That's going to be insanely helpful. I could barely find a user manual for it I thought a schematic was wishful thinking.

author: Brad808
author_rank: Contributor
timestamp: January 24, 2020, 10:47:39 am
content: I think I might be on the right path now. When I went to measure these diodes/ (fuses?) Inside the heatsink near the transformer they basically crumbled in half. The appear to be input protection on the primary side of the xformer. I'm going to order 2x sa150a, 2x mur1100e to replace all of them on that path and see what I get.[https://i.imgur.com/Lilu4EF.jpg]()
3060 PNY receives power, no signal out - Page 1
Forum section: electronics / repair

author: tekkenboy7
author_rank: Newbie
timestamp: July 04, 2023, 02:35:28 am
content: Hello all,I'm coming over from reddit /u/electronics and I'm in need of some help diagnosing an issue with the gpu that I bought second hand, knowingly broken. Thankfully, the GPU die gets warm and fans receive power. The PCIe slot has no short on the 3.3V and 12V and the 8-pin layout reads normal. Where it gets confusing are the resistors and capacitors down and left of the 8-pin.This picture regarding the red and light blue circles show which larger components are shorting to ground vs not. R22 resistor and the 820uF 3V capacitor below 8-pin is shorting to ground, as well as the R22 resistor closest to the end of the PCIe slot. The 1R0 resistor to the left of the 8-pin is also shorting to ground.Anything else I should be looking at? Any help would be much appreciated and I'll answer any questions.
30v Power supply does not go over 7.9 volts - Page 1
Forum section: electronics / repair

author: jansjobe
author_rank: Newbie
timestamp: June 19, 2024, 08:08:25 pm
content: Hi all!I have a chinese power supply that chokes over 7.9 volts. As i turn the voltage adjust pot further, it shorts and no voltage output. I have removed the diode on the output, but it makes no difference.I have attached the schematic. Can somebody help?

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: June 20, 2024, 06:28:51 am
content: if you search "power supply K305D" you will find loads off post on these units, lots off Chinese makers but all the same unit lots off faults mostly poor soldering and duff diodes

author: jansjobe
author_rank: Newbie
timestamp: June 20, 2024, 01:02:39 pm
content: Well, thanks, but I would like to know how it works and what I should look for. Search for K305 gives only this thread as a hit...

author: xavier60
author_rank: Super Contributor
timestamp: June 20, 2024, 01:57:39 pm
content: It's a complicated design. The wiper pin on the VR pot should adjust smoothly over a range of 0 to 5 volts.Check the voltage on pin 2 of U4. Check the supply pin voltages on U1.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 21, 2024, 01:21:54 am
content: The abrupt nature looks like U4 pin 9 is crowbar-ed by one of, uhh,thingsthat also connected to pin 8.Fuck you whoever drew schematics like that...

author: xavier60
author_rank: Super Contributor
timestamp: June 21, 2024, 01:51:55 am
content: The operation of the control circuitry is mainly based on current signals. The circuitry at the CT is unusually weird.

author: jansjobe
author_rank: Newbie
timestamp: June 21, 2024, 10:17:27 am
content: I suddenly realize that the schematics is not the same as my actual device. Mine says LW-K305D-1, Rev 20191108.There is no D4 at all, and U1 is a TL084 amongst other things. Do anyone have a newer (supposedly) schematics?I do not get 0-5 V on pin 2 of U4, rather 2.19V when VR is at zero. Turning VR pin 2 of U4 rises to 2.35V when output maxes out at 7.8V. Continuing to turn VR makes pin 2 slowly fall again, until it is 1.25V when VR is at maximum.

author: xavier60
author_rank: Super Contributor
timestamp: June 21, 2024, 11:55:03 am
content: Quote from: jansjobe on June 21, 2024, 10:17:27 amNot much can be made of that without seeing the surrounding circuitry. The pot should be tested out of circuit. Look for a large change of resistance across the outer pins while turning it. Do the test in circuit first, while power is off of course.

author: jansjobe
author_rank: Newbie
timestamp: June 21, 2024, 03:08:16 pm
content: I have already tested the VR pot out of circuit, and it works as it should.
3335A Output Level Fault - Page 1
Forum section: electronics / repair

author: veedub565
author_rank: Frequent Contributor
timestamp: December 16, 2022, 06:06:07 pm
content: So my recently acquired HP 3335A seems to have a problem. With output level set to 0dBm I get the following output levels50MHz = -24dBm25MHz = -30dBm10MHz = -38dBm1MHz = -58dBmIf I change the output level from 0dBm to -10dBm, all of those levels drop by exactly 10dB. So I'm templated to say the attenuator is working. If the attenuator was stuck then the output would be down by the same amount regardless of frequency.Any idea's before I start delving into this one ?**EDIT**Just been and tried it again... working perfectly now, weird

author: bsdphk
author_rank: Regular Contributor
timestamp: December 16, 2022, 07:42:12 pm
content: The 3336 uses a special dual thermal converter to level the output, and traditional step attenuator to increase the possible range.If the 3335 is roughly similar design, then that dual thermal converter is your first suspect.Check HPJ or Principles of Operation to find out how it is supposed to work ?

author: veedub565
author_rank: Frequent Contributor
timestamp: December 16, 2022, 08:33:49 pm
content: I had left it plugged in (but not switched on) so maybe it warmed up a bit in between being miles out, and working perfectly.I've got the service manual, I haven't gone through the principles of operation yet, just wondered if it sounded like a common problem, or others had similar issues.It is an old instrument, so maybe just getting a bit temperamental. It's probably very nearly as old as I am, andI'mgetting rather cranky and temperamental these days too

author: veedub565
author_rank: Frequent Contributor
timestamp: December 16, 2022, 08:44:38 pm
content: Just tried it again and it's back to how it was. It's definitely got issues

author: BigBoss
author_rank: Regular Contributor
timestamp: December 17, 2022, 12:29:56 am
content: Seems to me a serial capacitor fault. Because the Output Level Decrement is inverse proportional to the Frequency.A unseen crack of a ceramic cap may be a cause.

author: veedub565
author_rank: Frequent Contributor
timestamp: December 17, 2022, 10:28:11 am
content: I'll have a look around the levelling circuits thenInterestingly I tried it again today and initially it was faulty... and then started working properly again. Knocking it up and down the attenuator range a bit seemed to have an effect. I may write a little GPIB program to hammer it up and down the attenuator range, just in case there's some crud on the contacts to clear off.
34401a 601 error repair - Page 1
Forum section: electronics / repair

author: f14
author_rank: Regular Contributor
timestamp: May 18, 2022, 01:20:54 pm
content: Hi GuysI have agilent 34401a with frontpanel damage. VFD display is broken and I buy a new one(clone ) from aliexpess. after install new VFD . my 34401a have two beep ( the first one is quiter a bit) and VFD display is bright all segments and suck in this. all buttons is not respondI remove the display board and connect the mainboard to PC via GPIB and this mainboard working correctly . (just have one error 601) all functions are goodso I think display board had damage too . I have check LM339M but it normal. seem the MCU 80C51 is dead ?thank you!

author: strawberry
author_rank: Super Contributor
timestamp: May 18, 2022, 04:19:15 pm
content: broken trace or solder

author: f14
author_rank: Regular Contributor
timestamp: May 19, 2022, 12:14:32 pm
content: I realize N80C51BH is dead. so I replace it by AT89S52 with fw found in here . after that display have this message "QTTR022" and when I perform self test it show like second picturewhen I connect the display board with mainboard. I can not access controll via gpib . it freeze . have any idea for this issue ?solved. this fw 88813 is too "new" for my 34401. 88804 working
34401A ACI Fault - Page 1
Forum section: electronics / repair

author: WernerFalken
author_rank: Contributor
timestamp: June 03, 2023, 09:21:36 am
content: Good day! I have THREE 34401As with the exact same overarching fault: ACI doesn't work. Tested 6 digit range w/1mA, 100Hz source.I've tested the following on all three:Self Test: PassACV & DCV @ 5V and 50VDCI @ 1mAFreq @ 100HzResistance @ 100, 1000, 10,000, and 100,000 ohmsFront & Rear Jacks for consistencyChecked R120 & R121 for grinsAll of the above tests had great results... Tried all the different filters for AC... same issue.I also tested the resistance across Lo & I input terminals: about 0.65ohm resistance when in ACI (all three of the 34401A)...0.75ohm on a 34461A in 3A rangeLooking through the schematics and theory of operation, I am not seeing a clear failure mode for this situation - it's not a relay, as all of the other working modes exercise each of them successfullyAll I can think of is that *I* am doing something wrong, but I've checked myself with:34461A reports ACI @ ~1mA (that's what I am giving it)3458A reports ACI @ ~1mAFluke 189 reports ACI @ ~1mAI know I went overkill on validating my source, but really... I have three bad ones, so might as well prove it's not *ME* three times! I mean, how on earth can I end up with three of these things (from different sellers) with the same symptom?Any words of wisdom on this?Thank you!

author: WernerFalken
author_rank: Contributor
timestamp: June 03, 2023, 09:34:17 am
content: Foul language is coming out of my mouth right now.Problem solved. It wasn't *ME*, but it was my equipment. My source, apparently, doesn't like 34401As - not 100% why... maybe the 0.65ohm is a deal breaker.Right before I shut it all down to hit the sack (2:30AM here), I glanced over at my 33522B and thought.... "Hmmmm, I won't really *KNOW* the current level for it w/o doing some math I am not inclined to do right now, but I can see if the 34401As can measure it...."2Vpp @ 100Hz w/HiZ load gives ~14mA on all three 34401As and my 34461A.Problem solved. Never mind. Continue on your way... thank you for listening!Cheers!

author: WernerFalken
author_rank: Contributor
timestamp: June 03, 2023, 09:36:48 am
content: Although... 0.65ohm is nowhere near HiZ... still, problem solved.

author: JohanH
author_rank: Frequent Contributor
timestamp: June 03, 2023, 11:31:40 am
content: 34401A doesn't specify lower than 1% or 10 mA as the minimum current on the 1A AC range (footnote 4 in data sheet).There is an undocumented 10 mA AC range on which you can measure down to 100 µA AC. This can be turned on over the remote interface: DIAG:POKE 25,0,1See the following forum post for further details:https://www.eevblog.com/forum/repair/hp34401a-1ma-calibrator-and-10ma-hidden-range/msg2439456/#msg2439456

author: WernerFalken
author_rank: Contributor
timestamp: June 03, 2023, 04:43:18 pm
content: Those darned footnotes!Thank you!
34401A Beep on/off - Page 1
Forum section: electronics / repair

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: January 10, 2021, 02:54:58 pm
content: Hi!I have 2 34401A multimeters.On both i tried turn off beep function under menu section, but when i turn off beep function and save setting, the beeper beeps despite that if i press any of front panel keys.What i am doing it wrong?Thank you!

author: Hrvoje_CRO
author_rank: Regular Contributor
timestamp: January 10, 2021, 07:41:49 pm
content: Beeper ControlNormally, the multimeter will emit a tone whenever certain conditionsare met from the front panel. For example, the multimeter will beepwhen a stable reading is captured in reading hold. You may want todisable the front-panel beeper for certain applications.When you disable the beeper, the multimeter will not emit a tone when:1) a new minimum or maximum is found in a min–max test.2) a stable reading is captured in reading hold.3) a limit is exceeded in a limit test.4) a forward-biased diode is measured in the diode test function.Disabling the beeper has no effect on the tone generated when:1) an error is generated.2) the continuity threshold is exceeded.3) you turn off the front-panel menu.Turning off the beeper does not disable the key click generated whenyou press a front-panel key.The beeper state is stored in non-volatile memory, and does notchange when power has been off or after a remote interface reset.The beeper is enabled when the multimeter is shipped from the factoryI've found this above."Turning off the beeper does not disable the key click generated whenyou press a front-panel key." So i assume that everything is ok with my 34401A's?Thank you!
34401A DMM freezes in AC mode - Page 1
Forum section: electronics / repair

author: Nevada
author_rank: Contributor
timestamp: December 10, 2023, 09:59:06 am
content: I have a 34401A with a very strange behaviour: when I switch it to AC mode (either in voltage & current or frequency counter), the display freezing after some minutes. If I push any button then it continues measuring, but freezes again after a while. Some similar loop later, the meter freezes completeley (although it shows the shift button press, but I guess it's only a front-panel feedback - so the main processor stop working). It passes on self test.Do you have any suggestion?

author: wn1fju
author_rank: Frequent Contributor
timestamp: December 10, 2023, 01:44:35 pm
content: I can't help you with your particular problem, but it seems like these 34401A's have a mind of their own. For instance, I can leave my unit set to DC volts for an hour only to come back and see that it has switched itself to AC volts. I thoroughly inspected/cleaned the front panel board, I even put a scope across the Vcc rail for an hour to see if there was a power glitch. Everything checked out fine. It remains a mystery.

author: Swake
author_rank: Frequent Contributor
timestamp: December 12, 2023, 04:18:51 pm
content: Spooky stuff here :-DThe shift indicator is indeed managed by the local display controller

author: Nevada
author_rank: Contributor
timestamp: December 13, 2023, 07:56:52 am
content: As far as I can see, the AC measurement made by an AC-DC converter (AD637), and is processed by the DC section. So the question, what is the difference between the AC and DC measurements?

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 13, 2023, 08:17:29 am
content: Quote from: Nevada on December 10, 2023, 09:59:06 amHello,please engage TEST command first. That should already come up with an error code, related to this AC malfunction, see service manual, chapter 6, Self Test Procedures.My first guess is, that the shift registers, which provide the steering signals for the AC circuit, might have a problem.See AC Circuit Schematic, sheet 4/8, U309, U311.But let me know first, what the outcome of the TEST is.Frank

author: Nevada
author_rank: Contributor
timestamp: December 13, 2023, 08:20:43 am
content: Unfortunately (?) there is no any error after a Self Test.
Agilent34401A  Error 625, need help. - Page 1
Forum section: electronics / repair

author: 晓看风云
author_rank: Contributor
timestamp: June 28, 2025, 02:32:47 pm
content: I have an Agilent 34401A that shows an error during startup. The error code is 625, which seems to be related to GPIB or port issues. When disassembling, I first checked the circuit near U700 and found black substances around the power rail 7805. Based on experience, this indicates it has suffered high temperatures.Additionally, upon careful observation, there are slight burn marks on the circuit board wires of the GPIB port, likely caused by static electricity or other factors at the GPIB interface.When scanning with a thermal imager during startup, the temperature of U700 rises rapidly to 70°C or even higher.I suspect U700 has failed and need help confirming what can replace U700 and whether firmware programming is required.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 28, 2025, 05:42:05 pm
content: you may need to check all tantalum caps too, some may short and create problemssome 34401a mcu fw are found here and on the websearch here some have been put there :https://www.ko4bb.com/getsimple/index.php?id=manualsput34401ain the search field