hybridfree/eevblog-posts huggingface dataset:
B. P. Precision 2121 Oscilloscope Smoking Capacitors- need help repairing - Page 1
Forum section: electronics / repair

author: jkbk1969
author_rank: Newbie
timestamp: February 19, 2019, 02:13:04 pm
content: Hi, I work in a Technical college and this week alone I had 5 bk precision Oscilloscope pop and blow smoke and 2 power supplies do the same. I have been able to repair the PS but the scopes have been more challenging. The students said they turned them on and they popped then started to smoke.I found that one or two of the capacitors in the Power supply section. So I changed the two capacitors (C902-C903) I get power, and the freq. display lights up, but it doesn't read and the CRT does not display anything.I was wondering if anyone else has had this problem.Thanks Jackie

author: Chris56000
author_rank: Frequent Contributor
timestamp: February 21, 2019, 10:45:33 am
content: Hi!Can you provide a link to the rest of the schematic/manual please?I can help you go thro' this and fix it if I have the rest of the bookwork – from the snippet you provided it's possible C902/C903 failed off their own bat but there's not enough on that extract to help fault find the rest of your scope!Chris Williams

author: SilverSolder
author_rank: Super Contributor
timestamp: February 21, 2019, 03:27:03 pm
content: Wow, so many things breaking at the same time? Do you have a problem with the mains voltage being too high or spiking?Or are the students plugging 110V equipment into 220V? lol

author: jkbk1969
author_rank: Newbie
timestamp: February 21, 2019, 04:22:19 pm
content: This class has been special, we just have a lot more students, but I'm thinking they are just old. I tried to upload the manual but it it not working right now. I can not find the bk precision manual. But the Elenco has all the same boards in it. I looked. The elenco only needed some adjustment.https://www.manualslib.com/manual/235958/Elenco-Electronics-S-1325.html

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 22, 2019, 02:34:31 am
content: How old are these CRT scopes, and how long have they not been used?It seems that you dusted of some long unused equipment for a big class...A known failure of (high voltage) electrolytics is if they are stored for a long time the oxide gets damaged (Disolves in electrolyte? Converted back to aluminimum?) As a result the capacitors start leaking a lot of current when voltage is reapplied.Old Electrolytics can often be regenerated by slowly increasing the voltage, limiting the input current, and checking the do not get to hot in the process. When they are able to withstand the full rectified mains voltage again you should keep them charged for a few hours or days to strengthen the oxide layer.There is plenty of literature about gegenerating old Elco's.
TDS3054 Synchronization trigger repair - Page 1
Forum section: electronics / repair

author: Aldan
author_rank: Newbie
timestamp: February 21, 2019, 07:22:27 pm
content: Hello to all!Who knows, please tell me how to repair the synchronization trigger of the TDS-3052?Where is this synchronization trigger, which signals is controlled.It keeps synchronization only near the maximum amplitude of the signal (sine or rectangle).Only 5-10% of the maximum.I changed to new chips: MM9577-ACE; MM9595-VUW; MM9576-VJG and even from despair C8600DCZP33C1 and so on trifles.Everything remained unchanged, that is, there are no new faults, except this one.Respectfully,Aldan

author: ArcticGeek
author_rank: Regular Contributor
timestamp: February 21, 2019, 08:22:43 pm
content: Unfortunately there are no schematics for these scopes that have been released to the public, so it's difficult to know where to look.I am curious though - where did you obtain the replacement parts for the unit you were trying to repair? Did you buy the parts new?
Repair Fluke 77 series I -> U1 really dead? - Page 1
Forum section: electronics / repair

author: ElecSeb
author_rank: Regular Contributor
timestamp: February 21, 2019, 08:54:03 am
content: It has been a while and this DMM has been on my desk ever since (collecting dust)...Now the time has come to pick the device back up and hopefully revive it, but I have a gut feeling U1 is really dead...I have cleaned the PCB and replaced 2 broken C, furthermore I have placed back the C mentioned in this topic of mine:https://www.eevblog.com/forum/repair/repair-fluke-77-i-starnge-c-not-in-schematics!/But after rebuild the DMM is still dead. So started to measure and according to the SM:Put the UUT function switch in the VDC position -> DoneUsing a DVM, check +VDD (TP-1) or the positive battery post for 3.1V dc +-.1V ->TP-1 (red probe) with P15 (U1) = 0.03VUsing a DVM, check +VDD (TP-1) or the positive battery post for 3.1V dc +-.1V ->+bat & -bat = 9VUsing a DVM, check +VDD (TP-1) or the positive battery post for 3.1V dc +-.1V ->TP-1 (red probe) with -bat = 9VDo i read the SM manual wrong or is the U1 just terminated/defect. Do I have some other options to test?Read on an other topic, on eevblog, about 2 minuted 400 degrees heating on U1 (reflow internal bonds)? Could this be a solution?

author: ModemHead
author_rank: Frequent Contributor
timestamp: February 21, 2019, 01:48:50 pm
content: If U1P8 (Vdd, TP1) is at 9V battery voltage with respect to U1P48 (Vss), then U1P15 (analog ground) should be 3.1V below Vdd. U1 has an internal rail-splitter to create a bipolar supply this way. So if it's not happening, there isn't much else to blame.Try making the measurements with sharp probes right on the chip. There could be some value in reflowing the (external) leads on U1 in case there's a dry/cracked joint, which is definitely not unheard of with U1 on the 7x meters.No experience with trying to reflow internal bond wires, but I do vaguely recall someone talking about that here.

author: ElecSeb
author_rank: Regular Contributor
timestamp: February 21, 2019, 02:08:40 pm
content: Quote from: ModemHead on February 21, 2019, 01:48:50 pmI already soldered the chip with additional new solder (to test), no result.Might reflow this weekend just to test. If it is not doing a thing, then sold as parts.
TDS 420 serial issues. - Page 1
Forum section: electronics / repair

author: marshkillz
author_rank: Newbie
timestamp: February 16, 2019, 12:38:54 am
content: I got a TDS 420 from someone on craigslist who sold it to me dirt cheap (10$) with some other test equipment with the complaint that it wouldn't turn on.After doing some troubleshooting and adjusting voltages I got the thing working, but with no trace, which turned out to be the DSP card which cost 60 for a new one.Which leads me to this point, Ive been trying to enable options that were lost via the serial debug port on the CPU card but I cant get anything but garbage back.Below is an example of what It returns while booting.fb d4 ca 94 b4 af 2f 3a 0a ca 4a ca f5 3a 9a 55 ûÔÊ”´¯/:.ÊJÊõ:šUda d4 9a 6a f4 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b ÚÔšjô...........1b 1b 1b 1b 1b 1b fb fb d4 ca 94 b4 af 2f fa 54 ......ûûÔÊ”´¯/úT74 b5 ea 8a da f5 ba ba 55 ca 74 f4 1b 1b 1b 1b tµêŠÚõººUÊtô....1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b fb fb d4 .............ûûÔca 94 b4 af 2f fa 54 74 b5 ea 8a ea 9d 3a 6a 8d Ê”´¯/úTtµêŠê:jba ca f4 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b ºÊô.............1b 1b 1b 1b fb fb d4 ca 94 b4 af 2f fa 54 54 d5 ....ûûÔÊ”´¯/úTTÕ6d 0a 2a 3a b5 da ba b5 ea 8a fa 1b 1b 1b 1b 1b m.*:µÚºµêŠú.....1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b fb fb d4 ca 94 ...........ûûÔÊ”b4 af 2f ea 3a 3a b5 da ba d5 9a ea aa 74 ba 94 ´¯/ê::µÚºÕšêªtº”a5 fa 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b ¥ú..............1b 1b fb fb d4 ca 94 b4 af ef 53 f4 34 85 da ca ..ûûÔÊ”´¯ïSô4…ÚÊaa ba da 55 ca fa 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b ªºÚUÊú..........1b 1b 1b 1b 1b 1b 1b 1b 1b fb fb d4 ca 94 b4 af .........ûûÔÊ”´¯ef 53 f4 34 f6 2c e9 d7 56 ab 2a ba 55 ca 74 f4 ïSô4ö,é×V«*ºUÊtôAny ideas why the serial port would be messed up like this?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 16, 2019, 03:24:51 am
content: Look up the TDS 420 and similar Tek scopes of that vintage for electrolytic surface mount capacitor failures. There may be circuits failing because of that.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 16, 2019, 03:30:32 am
content: Some starting points:http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=243742https://forum.tek.com/viewtopic.php?t=136193https://www.eevblog.com/forum/repair/textronix-tds-420-repair/

author: charlyd
author_rank: Frequent Contributor
timestamp: February 17, 2019, 11:20:43 am
content: create a console adapter and run the debug boot to see what is really happening. and yes can be lots of CAPS.. and tracks & pads.

author: marshkillz
author_rank: Newbie
timestamp: February 19, 2019, 01:32:05 pm
content: I already went through replacing all the caps when I originally had the DSP fault which ended up not fixing the original issue.The message I posted as an example is what shows up on the serial debug terminal when booting. The scope seems to work perfectly fine except that it doesn't seem to be communicating correctly over the serial debug port.
What package is this? - Korg MS-20 Mini repair - Page 1
Forum section: electronics / repair

author: krivx
author_rank: Frequent Contributor
timestamp: February 18, 2019, 04:04:57 pm
content: I am looking at a Korg MS-20 mini synthesizer power board that has some issues.IC1 appears to be a 3.3 linear regulator, it has 9V (input power) on one pin and 3.5V on another. 3.5V looks a little high to me, it's powering 3.3V logic. I think this part may have had it's maximum input voltage exceeded.Forgive the blurry photo, I just had a phone at hand. Does anyone recognize the package of IC? It looks like a sot-23-6 but has 5 normal "gull-wing" legs and one additional wide leg attached to ground. I would like to replace this.The markings are "GO3 6DB". The second character may be an O or a 0 (zero), I'm not sure.

author: krivx
author_rank: Frequent Contributor
timestamp: February 18, 2019, 04:15:47 pm
content: Further staring at google images results tells me this could be a Sot-89-5:

author: fzabkar
author_rank: Super Contributor
timestamp: February 18, 2019, 08:22:44 pm
content: http://www.smdmark.com/en-US/search/code?id=G03R1154H036B, Ricoh, 3.6V fixed, 150mA regulator, SOT-89-5, marking G03+6xx:http://www.mouser.com/ds/2/792/r1154h-e-844161.pdf

author: krivx
author_rank: Frequent Contributor
timestamp: February 19, 2019, 08:26:05 am
content: Quote from: fzabkar on February 18, 2019, 08:22:44 pmThis look right, thank youSurpisingly it looks like 3.59V is correct.I double-checked the microcontroller used (H8S/2210C) and it will run at 3 - 3.6V. So this doesn't seem to be an issue.
Help needed to repair the Telequipment D54 Oscilloscope - Page 1
Forum section: electronics / repair

author: GranpasScopes
author_rank: Newbie
timestamp: February 18, 2019, 08:47:17 pm
content: Hello! I was hoping to get some direction about getting two scopes my grandpa had back in working condition:1. Telequipment D54 Oscilloscope (like the one here)2. Tektronix 2215I would like to get started with the Telequipment D54. Here is what I see after I turn it on:i. With both channels turned off, there's a green dot on the screen slightly offset to the bottonm of the center of the grid. I can move this around with the top left adjustment but I don't know which adjustment to make it move up or downii. When I turn on either channel, the clear dot turns into a hazy column around the center of the grid as if there's a lot of noise on the input, but nothing's connected. I connected a lead to either channel and touched the lead to the 'test' hole but nothing changediii. Each channel has a AC/DC/GND switch. Should putting this to GND force the scope to display a flat trace on the display at 0 offset?How do I go about testing whether the Telequipment D54 is in working condition and what to fix if not?I am reasonably comfortable with digital electronics and basic passive and active components.If needed, I can upload pictures for ii
Keithley 2010 possible problems, error codes and schematic - Page 1
Forum section: electronics / repair

author: charlyd
author_rank: Frequent Contributor
timestamp: February 04, 2019, 08:22:17 pm
content: hello i bought a keithley 2010 and i am looking for info to fully test and know what possible problems i have to cover to get the unit fully operational.I found a Schematic from a Keithley 2000 and was wandering if there is something like a schematic for the Keithley 2010 model. I found the service manual with partlist and board layout but no schematic.can somebody help me out with more info please..

author: coromonadalix
author_rank: Super Contributor
timestamp: February 04, 2019, 09:45:10 pm
content: I think someone here or on the web did a partial reverse schematic (s)I never saw a full model 2010 schematic

author: coromonadalix
author_rank: Super Contributor
timestamp: February 06, 2019, 09:49:44 pm
content: From this thread :https://www.eevblog.com/forum/repair/keithley-2010-low-noise-multimeter-noisy/https://doc.xdevs.com/docs/Keithley/2010/2010_reversed_partial_sch_and_fw.zip

author: charlyd
author_rank: Frequent Contributor
timestamp: February 17, 2019, 11:30:13 am
content: does anybody know? is this K2010 DMM ( and maybe other Keithley in the series ) Always that nervous in reading out?

author: Echo88
author_rank: Frequent Contributor
timestamp: February 17, 2019, 08:16:00 pm
content: What do you mean with "nervous in reading out"?

author: charlyd
author_rank: Frequent Contributor
timestamp: February 17, 2019, 10:31:11 pm
content: the steps is in MED so i would assume even to the right 4 digit you can read a number but-> NO the right 4 digits are so fast that they show every segment so like 8888...

author: picburner
author_rank: Frequent Contributor
timestamp: February 18, 2019, 10:28:09 am
content: The instrument, like many others in this category, on the lower ranges (100mV - 10V) has an input impedance >10Gohms.If you leave the inputs connected to nothing it is normal that the last digits move continuously, the instrument captures any disturbance.If you try to connect it to a stable source you will see that the reading will be equally stable.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 18, 2019, 05:16:34 pm
content: The meters can choose different speeds. So the user can choose between slow accurate readings and fast, but more noisy readings. This can go up to a point of some 1000 updates per seconds and thus to fast for the eye. In some instruments the setting can survive a power down.The preferred speed for manual readings is more like 1-5 updates per second ( e.g. 10-50 PLC mode). Than the reading should be reasonable stable on most ranges. The lowest voltage range may still show a little more noise.
Vintage Allen Bradley resistor ID - Page 1
Forum section: electronics / repair

author: DaJMasta
author_rank: Super Contributor
timestamp: February 16, 2019, 09:14:40 pm
content: Figured repair forum was good because it's an old part, but I have a package of these resistors and I have no idea what the code means. Pretty sure they're the mil spec style 1/2W Allen Bradley resistors.They're 5 band, Orange, White, Gold, Gold, Yellow.... and I've seen somewhere that the last yellow band means they're "high reliability", but that would suggest 3.9 Ohms, 5% tolerance, if I'm reading the code right.... and they all seem to measure 4.30-4.35 Ohms.Any ideas?

author: Stray Electron
author_rank: Super Contributor
timestamp: February 17, 2019, 01:28:33 am
content: I still have a couple of sealed packs of AB carbon comp resistors and I poked through the package material (in other words they still haven't been opened) and measured them with a calibrated HP 3468A 4 wire meter and the resistance value is well out of spec. I have a heap of ex-MIL circuit boards so I went and checked the value of about 15 of the old AB carbon comp yellow band resistors on them andallof them are out of spec. AB resistors don't seem to hold up well with age.

author: DaJMasta
author_rank: Super Contributor
timestamp: February 17, 2019, 01:45:07 am
content: Haha, so they probably are 3.9 ohm resistors! Funny so many seem to insist on using them in older hardware... I guess they have the look but if that yellow stripe really means "High reliability", I would not touch a standard one with 10 foot pole.

author: Dacke
author_rank: Regular Contributor
timestamp: February 17, 2019, 02:34:32 am
content: Carbon comp resistors tend to drift over time, usually increasing in value. The higher the resistance value, the more they drift. I have quite a bit still in my inventory, and probably 70% of them have drifted upwards by 10-15%, and the brand doesn't really matter. Allen Bradley, Ohmite, IRC, they all do it. But yeah, the only time I see them used anymore is for repairs/restorations to keep something "original".

author: Stray Electron
author_rank: Super Contributor
timestamp: February 17, 2019, 05:24:53 pm
content: Quote from: DaJMasta on February 17, 2019, 01:45:07 amHigh wattage and certain value SB carbon Comp resistors are worth a LOT of money to people that repair old military electronics. The problem for them is that they can't change the component type without reproving the new assembly meets ALL of the original specs including vibration, hot and cold cycling, etc. Pretty much an impossible task once the assembly and test line has been shutdown. I've seen some of the obsolete component sellers sell high wattage AB resisters for over $100 each. That's actual sales not "asking prices" on E-Greed. The repair contractors don't mind paying that because (1) it's still cheaper than spending time looking for another cheaper part, (2) the bill gets passed on to .GOV anyway. AudioPhools have also been known to pay obscene amounts of money for components that they insist "sound" better. Other than that, I don't know why anyone would want to use these old parts.
An object lesson in design flaws... - Page 1
Forum section: electronics / repair

author: kc7gr-15
author_rank: Contributor
timestamp: February 17, 2019, 08:40:14 am
content: Recent scrounging efforts netted me a nice wireless (DECT) VoIP phone, specifically a Snom M9 for cheap. I soon found out why. Subsequent testing revealed a lack of ability to transmit on the Ethernet side.Thinking the transceiver chip might have gone bad, and/or might be replaceable, I popped open the base unit -- and, after a brief inspection, found myself having to retrieve my jaw from the floor.It seems, rather than using a standard Ethernet connector with a built-in shield, Snom went the cheap route with a basic RJ45 receptacle and a strip of copper adhesive tape pasted across its backside. The adhesive on the back of the lower part of the tape had lost its tack, allowing the edge of the (very conductive) tape strip to peel back and (drumroll) short out several contacts on the Ethernet pulse transformer -- which was mounted directly behind the jack.The fix consisted of trimming off some of the tape, and putting everything back together.So, in essence, someone ended up dumping a perfectly decent $200 cordless phone on the surplus market because a manufacturer didn't think things through in both component placement and type of component to use. I know it's not the first time, and it certainly won't be the last, but... a loose strip of tape? Seriously?!

author: OwO
author_rank: Super Contributor
timestamp: February 17, 2019, 10:12:30 am
content: Planned obsolescence.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 17, 2019, 10:29:20 am
content: Sometimes design flaws happen - usually not be full intention but in an attempt to save a few cents.Rather similar to the case described I remember the EMI shield in the Commodore C64 was made out of cardboard covered with aluminum foil. Over time and with chaining humidity the composite bends and could short out the supply at one corner. A piece of insulating tape fixed it.It's quite common to see products fail quite often at a similar spot. If this usually only happens after the warranty period such design flaws / weaknesses may not get fixed with a high priority - especially not for products (like the phone) that are only produced for a short time anyway.
Compaq Presario 425 CRT screen not working. - Page 1
Forum section: electronics / repair

author: UncleAwesome
author_rank: Newbie
timestamp: February 17, 2019, 10:28:22 am
content: Hi.I have a 2 videos about this but I will provide a short explanation.This is a pc and a monitor in one machine that broke during shipping.vga signal from the pc is ok. I tested the continuity on the cable from the pc output, to back of the crt, and it's fine.The screen gets voltage, I can hear the static.When I turn of the monitor I get a flash on the screen.There is a faint glow on the back of the tube.Video 1:Video 2:If anyone have any suggestions that would be great.
Unknown IC on Toshiba HDD PCB - Page 1
Forum section: electronics / repair

author: fzabkar
author_rank: Super Contributor
timestamp: February 16, 2019, 11:50:22 pm
content: Can anyone recognise the chip at locations IC12 and IC13 on this Toshiba HDD PCB?https://st.overclockers.ru/images/lab/2018/12/04/1/106_toshiba-10tb-pcb_big.jpgThe chip is an op amp or instrumentation amp (perhaps a dual amp). It amplifies and buffers the output of the piezo shock sensors at MT1 and MT2.I don't need this information for a repair, but I'd like to add this chip to my database.http://www.hddoracle.com/viewtopic.php?f=100&t=1577Thanks.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 17, 2019, 12:57:50 am
content: Would you have a photo where markings can be read better?

author: fzabkar
author_rank: Super Contributor
timestamp: February 17, 2019, 02:11:36 am
content: Sorry, I work mostly from other people's photos. :-)AFAICT, the markings are ...93A331832HS29604I presume that "1832" is a YYWW (year/week) date code. Other Toshiba PCBs use amps made by Rohm, but there is nothing on Rohm's web site that matches the above markings.

author: amyk
author_rank: Super Contributor
timestamp: February 17, 2019, 03:50:29 am
content: It is probably a custom marking.
BGA / LGA / Reballing / Chip replacement - Page 1
Forum section: electronics / repair

author: charlyd
author_rank: Frequent Contributor
timestamp: February 11, 2019, 10:39:35 pm
content: hello i am looking for someone who want to replace some big boys for me...1x LGA1151 CPU socket - on a motherboard / (bought with socket destroyed)1x ATI Video chip (need to be replaced on a laptop motherboard.) i have the chip.1x Acer 9650M GS video card ( need reballing )who has the equipment to help me out for a reasonable price….please let me know by sending me a PM.greetz charly

author: Rasz
author_rank: Super Contributor
timestamp: February 12, 2019, 10:28:45 pm
content: Quote from: charlyd on February 11, 2019, 10:39:35 pmno, needs new gpu, gpus not available, garbage

author: charlyd
author_rank: Frequent Contributor
timestamp: February 16, 2019, 11:28:03 pm
content: for the acer card already tried and worked for few weeks..so need reballing

author: KaneTW
author_rank: Frequent Contributor
timestamp: February 16, 2019, 11:36:18 pm
content: Reballing won't help. The issue is with the silicone<->substrate bond.

author: flolic
author_rank: Frequent Contributor
timestamp: February 17, 2019, 12:06:32 am
content: Reballing is in 90% cases waste of time. I have more than enough experience to confirm that.
Benq 2200w LCD monitor (intermittent issues) - Page 1
Forum section: electronics / repair

author: 13hm13
author_rank: Frequent Contributor
timestamp: February 16, 2019, 09:49:16 pm
content: I recently got this monitor (manuf. 2008) from a dumpster.Upon plugging in, it worked (on initial inspection) ... but all is not well ...The screen intermittently flickers (moves) a bit horizontally. Also, the monitor seems to have problems with signal lock (screen blanks momentarily, with message of 'D-Sub' or 'DVI') I have it plugged via std. VGA.More importantly, the front-panel buttons (including PWR) often do not work. Only way to shut off is to pull the AC cord.Even more important, after plugging in (from OFF period of more than 1 hr), it is very hard to restart (pwr on) monitor.Looking/checking inside, I de-solderedallthe electro caps (none of which were bulging) and ck'd with ESR meter. All check okay, but I replaced a few that were just barely high ESR (only very slightly so). (Note: I only have one of those cheap (but effective) $10 ESR meters).All the solder joints seem to be okay, and the monitor does stabilize a bit after being continuously on for a few hrs. While on, the image quality is just fine.Any ideas as to the culprit?Thx in advance!

author: Whales
author_rank: Super Contributor
timestamp: February 16, 2019, 10:18:09 pm
content: Thoughts:Bad buttons + signal lock instability: dirt & corrosion.Signal lock instability: unstable power supply (caps?) or bad cable.VGA signal is being fed in I presume?yes

author: 13hm13
author_rank: Frequent Contributor
timestamp: February 16, 2019, 10:37:06 pm
content: Quote from: Whales on February 16, 2019, 10:18:09 pmALL buttons are un-reactive.Buttons are hermetically sealed type.PSU caps check okay (please see OP).Yes, VGA signal ... but problems is much morebasic.... failing to pwr up (should do so regardless of input -- including the "Benq" logo splash screen).

author: Whales
author_rank: Super Contributor
timestamp: February 16, 2019, 10:44:14 pm
content: "hermetically sealed type" ? Can you share a picture?Failing to power up: I have had some monitors that refuse to show anything at all, including branding, until you supply a valid signal.
Philips 3226 oscilloscope vertical position starts low, then rises - Page 1
Forum section: electronics / repair

author: jpwolfe31
author_rank: Contributor
timestamp: February 19, 2019, 09:34:18 pm
content: I have an older scope that works fine, but the vertical position when powered on is so low that you can only see the very tops of the waveforms. After 5 to 10 minutes, you can see the entire waveform. After 15 minutes the waveform is centered and the scope works normally. Any experts that know where the best place to start on this problem would be.I have the service manual but have never worked on a scope before.

author: cowasaki
author_rank: Frequent Contributor
timestamp: February 19, 2019, 09:51:31 pm
content: I'm not an expert with old scopes at all but have you dropped, moved or banged it? Have you taken it apart to have a look if the fault is obvious? The vertical deflection is faulty whilst cold but as it warms the deflection starts to work. This sounds like a dodgy connection. Is the board on the end of the tube loose? Connected properly? I had a similar issue with an old scope and pulling the board off the back and pushing it back on fixed the issue.I'm sure someone with far more knowledge of these old scopes will be along shortly.......

author: nsrmagazin
author_rank: Regular Contributor
timestamp: February 20, 2019, 01:49:33 pm
content: I am not an expert also, I hope we find such a person with knowledge of old scopes. At some point the voltage or current should be rising. What is responsible for the axis? How is it powered. The display seems to be ok, so something back in the line is causing the problems. Can you take some readings?

author: Chris56000
author_rank: Frequent Contributor
timestamp: February 20, 2019, 07:32:33 pm
content: Hi!The PM3226 is a straightforward 2 channel 15 MHz basic oscilloscope with no frills or complicated bells and whistles!Begin by referring to the circuit diagram for Unit 1, which contains the two vertical amplifiers. My recommendation to start with is to replace the four or five small 68uF electrolytics on this PCB – two of them, C269 and C309 provide emitter decoupling for the long–tail pair immediately before the final Y amplifier transistors, and leakage here will cause the operating points of the transistors to vary at random, resulting in their collector currents varying!Because the transistors forming the Y amplifier are direct–coupled, any random variations in operating currents will cause the voltage–drops across the various load and feed resistors to vary and with this, the potentials at the Y plates of the CRT, resulting in unwanted vertical movements of or inability to centralise the trace, which is the symptom the OP is experiencing!If replacements of the 68uF electrolytics on Unit 1 don't resolve your fault, there could be thermally defective transistors on the Unit 1 Y amplifier, and the best method of tracing this is to use a can of freezer–spray sold for this purpose!Chris Williams
OWON SDS8302 repair help needed - Page 1
Forum section: electronics / repair

author: Tester3000
author_rank: Newbie
timestamp: February 16, 2019, 11:27:04 am
content: Hello guys, I have a OWON SDS8302 Oscilloscope with a weird issue and I was wondering if somebody can help me troubleshoot the fault. The scope turns on normally, makes some relay clicks on initial startup screen then boots into the main scope screen but for some reason none of the controls respond. There is no trace signal and the screen seems to be frozen or locked up. I took a look inside and found nothing obvious, all power rails seem ok, and the main board looks clean under the microscope. I decided to do a firmware update thinking it may resolve the issue as OWON has released a firmware update for this model. I was able to connect the scope to my PC and install the USB drivers normally but when I run the patch software and click start to do a firmware update, for some reason it says "unable to read SN, make sure USB is connected". The weird thing is that the USB drivers install normally but it still doesn't communicate with the scope. I even tried the PC software to see if it would make a USB connection, it doesn't. I was wondering if it would be a good idea to do the firmware update using the JTAG header on the mainboard, if so, will someone please help me with the hardware and program needed to dump and rewrite the S3C2416+K9F1G08 NAND Flash. I do have a backup of the firmware which I downloaded from OWON. I know the NAND Flash may be security locked but there is a file called Public.key in the Patch installation folder which I believe is for unlocking the flash but I'm not sure. I want to do a firmware update to know if the issue is hardware related or not .. Any help will be greatly appreciated! Paul
Datasheet for NEC D9318GB - Page 1
Forum section: electronics / repair

author: wholder
author_rank: Regular Contributor
timestamp: February 15, 2019, 09:07:08 pm
content: I'm trying to reverse engineer an optical spectrometer made in the early 90s that uses this IC (see attached image for more details), but I'm coming up empty. If anyone has an old NEC databook that might contain information on this chip, I appreciate a scan, or photo of the info. Thanks in advance for any/all help.Wayne

author: oPossum
author_rank: Super Contributor
timestamp: February 15, 2019, 09:24:17 pm
content: https://datasheet.datasheetarchive.com/originals/scans/Scans-054/DSAIH000101776.pdf

author: wholder
author_rank: Regular Contributor
timestamp: February 15, 2019, 09:26:42 pm
content: Thank you soooo much! I had just about given up hope. This info will really help a lot.Wayne
Oscilloscope Tektronix 2230 Power failure  (Hiccup) - Page 1
Forum section: electronics / repair

author: ramijosefer
author_rank: Newbie
timestamp: February 15, 2019, 12:13:32 pm
content: Good afternoon.I would like to repair a Tektronix 2230 oscilloscope, which has the following fault:When you connect it, try to turn it on and off and then try again to turn it on and off, and so on. I think that for this purpose they call it the "Hipo".I have disconnected all the sources of output, in case I could have a short circuit in any of them. But it remains the same with the Hiccup effect.I have some knowledge of electronics and would like to repair it.I would need help from someone who has had the same problem, or who knows, I would be very grateful.Greetings.

author: David Hess
author_rank: Super Contributor
timestamp: February 15, 2019, 02:25:37 pm
content: These are pretty old instruments so chances are the aluminum electrolytic capacitors in the switching power supply have dried up and need to be replaced. The blinking power light is caused by the switching power supply continuously restarting.
Tek 465: a trace is blurry in some conditions - Page 1
Forum section: electronics / repair

author: gabriele
author_rank: Contributor
timestamp: February 13, 2019, 10:42:06 pm
content: Hello all,I recently brought an analog oscilloscope, a Tetronix 465, the problem is that the trace in the channel one is blurry when the timebase is set from 2ms/div to 0.2ms/div. I suspect some contact issues because sometimes pressing on the timebase knob cause that the trace to became normal.I never dissasembled an oscilloscope, despite my suspect, i need help to know what could be the problem and how could i can solve it. I attach some pictures of the issue, in the first two photos the trace on top is CH1.Sorry for my english if it is not good, it is not my native language.Thanks in advance.EDITPulling the switch to limit the bandwidth to 20MHz hide the problem completely.

author: JohnPen
author_rank: Regular Contributor
timestamp: February 14, 2019, 09:34:54 am
content: First thought is to buy a switch cleaner aerosol spray. With the scope off spray the switch contacts while cycling the switch over it's full range. Similarly do the rest of the scope's switches while you have the case open. Let the cleaner evaporate and then try the scope to see if the problem is fixed.

author: tggzzz
author_rank: Super Contributor
timestamp: February 14, 2019, 02:37:56 pm
content: Quote from: JohnPen on February 14, 2019, 09:34:54 amThe switches are strange and fragile. RTFM to find the approved way to clean the contacts. In most cases it involves IPA, shiny paper, and delicacy
Bad IC's experience. - Page 1
Forum section: electronics / repair

author: powerchisper
author_rank: Contributor
timestamp: February 15, 2019, 07:04:19 pm
content: Hello friends.Sometimes you can find bad chips that show no external signs of damage, but ...How often does it happen to you ?I am currently repairing a game system from the nineties that has lots of battery damage . IC's pins were all green and rusty , but no external signs of being in bad condition.At least one of them seems to be dead (PAL16L8), and it doesn't either show damage beyond the green legs, which I did clean up. Someone told me days later that those things have a twenty year life expectance ( parameter retention time )So..can you tell your experiences in this subject ? Which is the weidest thing you have found ?Thanks and once again excuse me for my English.

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: February 15, 2019, 07:41:15 pm
content: LoL...And don´t forget.... women fart too... but you only get them by the smell...The world of electronics is not always spectacular unfortunately...

author: bsudbrink
author_rank: Frequent Contributor
timestamp: February 15, 2019, 08:00:38 pm
content: Quote from: powerchisper on February 15, 2019, 07:04:19 pmIn a word: frequently.QuoteI restore "vintage" computers. In my case, computers from the 1970's. I am currently restoring a rare S-100 card and have identified five dead 7400 series chips with no visible signs of damage, not even any corroded or tarnished pins. My understanding is that the board was stored "well" and was operational when stored.I have heard that moisture can infiltrate some plastic carriers and wreak havoc inside.
Fluke 32 takes a while to zero out - Page 1
Forum section: electronics / repair

author: Axtman
author_rank: Regular Contributor
timestamp: February 13, 2019, 06:49:51 am
content: I have an old Fluke 32 Clamp Meter that works but takes a long time to zero out. This issue occurs on all the settings (600v, 220v, 200 ohm, 600A, 200A). My guess would be because of it's age that the capacitors are probably shot. What are your thoughts? Thanks!
Remake JBC HD-2B under C245 cartridge - Page 1
Forum section: electronics / repair

author: alex.br
author_rank: Newbie
timestamp: February 12, 2019, 08:18:45 pm
content: Good evening.Is it possible to correctly remake JBC HD-2B under C245 cartridge?https://www.fingers-welt.de/phpBB/viewtopic.php?f=14&t=9327https://www.mikrocontroller.net/topic/408786- these solutions are imperfect.Thanks in advance.

author: Rasz
author_rank: Super Contributor
timestamp: February 12, 2019, 10:32:18 pm
content: http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=5264
Beaten by Tektronix 7834 LV Regulator problem - Page 1
Forum section: electronics / repair

author: perdrix
author_rank: Frequent Contributor
timestamp: February 10, 2019, 01:29:48 pm
content: The supply was shutting down because the output voltages weren't correct. There is a resistive network with all supplies connected which should sum to zero at pin 2 (BAL SENSE) of the controller IC. If it isn't 0V the IC outputs a stop signal on pin 8 which goes to base of Q1254 to shutdown the supply. This was shutting the supply down, and removal of Q1254 on the Cap/Rectifier board allowed the supplies to run so I can fix the output levels (in theory).The voltages I observed wereSupply Measured-50V -50V+50V +46.9V-15V -14.58V+15V +13.8V+5V +4.275V-50V is the reference for all the other supplies. The other part of that story is "reference ground" which is connected to chassis ground with a 47 ohm resistor (R1591).In my supply reference ground was 0.45V below chassis ground which was definitely messing up the output voltages.Shorting R1591 and readjusting the -50V rail to exactly 50V I see the following:Nominal Actual+5V +4.75V-15V -14.21V+50V +47.70V+15V +14.32VInterestingly all of them are nigh on exactly 95% of what they should be! I'm sure that this fact plus the issue of reference ground being at -0.45V without that shorting link should be telling me what's wrong but I just can't see it.For reference they should be:Supply Limits-50 -49.8 to -50.2-15 -14.85 to -15.14+5 +4.9 to +5.1+15 +14.85 to +15.15+50 +49.5 to +50.5The raw supply voltages from the Cap/Rectifier board are: -17.6, +17.5, +54.4, -54.4, +7David

author: perdrix
author_rank: Frequent Contributor
timestamp: February 10, 2019, 02:50:25 pm
content: Problem solved - one of the sense bypass resistors had a "suspect" solder joint (specifically R1499) once that was touched up, all voltages measured between Reference Ground (TP1592, *not* TP1591 which is chassis ground) and the voltage test points were within specification. The approx.. 0.5V between reference ground and chassis ground was a "red herring" and would seem to be normal!David

author: David Hess
author_rank: Super Contributor
timestamp: February 10, 2019, 10:58:06 pm
content: The sense bypass resistors do not do anything when the loads are connected because the force and sense lines short them out. They prevent the regulated outputs from running away if the loads are disconnected. This safety feature was not included on earlier Tektronix power supplies.

author: perdrix
author_rank: Frequent Contributor
timestamp: February 11, 2019, 09:00:35 am
content: I was running with a dummy load that didn't have a sense connection so was relying on the sense bypass resistors presence.PS I've not heard from you on TekScopes since we moved to groups.io. Did you not approve of the move?D.

author: David Hess
author_rank: Super Contributor
timestamp: February 11, 2019, 11:45:28 pm
content: Quote from: perdrix on February 11, 2019, 09:00:35 amNo, I approved of the move but gmail started throwing fits with duplicate and deleted messages which make it very difficult to use email lists.
About screws for Fluke 10, 11 & 12 - Page 1
Forum section: electronics / repair

author: Falkra
author_rank: Regular Contributor
timestamp: February 02, 2019, 03:04:02 pm
content: Hello,I repaired two Fluke meters, model 10 & 12, and the most of the case screws are missing.The service manual says H 1-4 SCREW,PH,P,THD FORM,STL,5-14,.750 832246832246 Being the fluke part.In another topic I discovered if I remember well that those screws are custom made.Are they some possible replacements with standard models ? Did you try it ? I can't find matching screws in my parts box and don't want to damage the plastic.

author: Falkra
author_rank: Regular Contributor
timestamp: February 10, 2019, 11:19:01 am
content: Anyone ?

author: Shock
author_rank: Super Contributor
timestamp: February 10, 2019, 01:55:00 pm
content: https://www.ebay.com/itm/330853729963

author: coromonadalix
author_rank: Super Contributor
timestamp: February 10, 2019, 02:28:41 pm
content: yep thoses were the one ive bought too

author: Falkra
author_rank: Regular Contributor
timestamp: February 10, 2019, 02:37:59 pm
content: Thank you for the link, the seller does not ship to France.

author: ModemHead
author_rank: Frequent Contributor
timestamp: February 10, 2019, 03:02:02 pm
content: I've never been able to find anything in my junk hardware box or in the hardware store with the same pitch and profile. At least they're common to most late-model Fluke series (8x, 17x and some 7x [edit: also 18x]), so they can be scavenged from various parts units.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 10, 2019, 03:19:47 pm
content: Well just found out i have 4 kits of them, after posting Flule 187-189 battery clips on the buy sell page ........ anyone interestedworldwidePaid 4.95$ usd from Fluke usa ....... plus shipping ... and other feesThis is what ive bought, had to go thru crossborder pickup tho have them shipped to me in Canada.https://www.ebay.com/itm/Fluke-Multimeter-Bottom-Case-Screw-Set-4-51-52-70-73-75-76-77-78-79-Series-123-/370622492030?hash=item564ad26d7eThey fit on Fluke 187-189 too

author: ddcc
author_rank: Regular Contributor
timestamp: February 11, 2019, 04:32:55 am
content: If you don't plan to switch back to the original screw in the same plastic boss, I've successfully used No. 4 rounded-head thread-forming screws as a substitute, which are readily available on McMaster-Carr:https://www.mcmaster.com/#tapping-screws/=082385dbf5c14f938feb2f7f804a6e75jrzu5tp2. Typically, the original Fluke screws don't extend the full length of the plastic boss, so in the past I've repaired a Fluke 189 with sheared plastic bosses by using a longer 1" screw, and padding out any excess length using a plastic washer on top:https://www.mcmaster.com/91545a210.

author: Falkra
author_rank: Regular Contributor
timestamp: February 13, 2019, 12:03:56 pm
content: I will have a look, thank you very much.
Thrift store smell...? - Page 1
Forum section: electronics / repair

author: Tetzly
author_rank: Regular Contributor
timestamp: February 08, 2019, 05:45:25 pm
content: I recently purchased a very cheap clone 858d hot air station from Ebay. For $36 shipped the thing works so far, no issues there. My problem is the thrift store smell of it. It smells like second hand clothing, really strong...beyond the "first time you use it odor will be produced..." I sprayed a vinegar solution on it last night and it didn't really help too much, the stink is coming from inside the unit and the hand held blower. I would rather not have to smell Goodwill store while i'm working.Anyone have any ideas about what I can do to get rid of the CCC warehouse stink? Baking soda? Kitty litter?...ugh.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 08, 2019, 07:58:54 pm
content: I have a commercial HEPA air filter that has 2 UV-C germicidal lamps in it and they produce a tiny bit of ozone so when I get stinky stuff I set it on top of the air outlet on the air filter and in a day or two the ozone seems to kill the mildew or whatever is causing the odor. For old books, I used to put baking soda in a salt shaker and sprinkle it between every page in the book and that also killed the odor.

author: soldar
author_rank: Super Contributor
timestamp: February 10, 2019, 11:25:38 am
content: That musty smell is often tobacco and sometimes mildew and other stuff that grows in damp places. Items from a smoker's home sometimes have, not only smell, but also a layer of gook which is disgusting.Airing in dry air and time will help. Ozone, Chlorine, UV, all help.Chorine bleach will get rid of anything and everything but, of course, it cannot always be used depending on the object to be cleaned.

author: tkamiya
author_rank: Super Contributor
timestamp: February 11, 2019, 02:55:49 am
content: I don't know where you are, but leaving it under direct sun for a day or two takes care of most smells. Ozone generator works well, too. I have a cheapo from Amazon and it's amazingly effective. Just don't over-do it, as it is bad for plastic.

author: tooki
author_rank: Super Contributor
timestamp: February 11, 2019, 08:35:01 pm
content: Quote from: soldar on February 10, 2019, 11:25:38 amI don’t think he’s saying it’sfroma thrift store (or even that it’s used), merely that it smells similar.

author: Tetzly
author_rank: Regular Contributor
timestamp: February 11, 2019, 08:44:35 pm
content: Quote from: tooki on February 11, 2019, 08:35:01 pmCorrect. The item was sold as new, but stinks like a second hand store. I did a little research on what exactly that smell is, but still am uncertain. Combination of mildew and fungicide, or mothballs perhaps, although i'm not aware of any commercial product that smells like that. It might be fading a little bit, at least in the handset.
Laser projector with blurry spots - Page 1
Forum section: electronics / repair

author: elektrinis
author_rank: Regular Contributor
timestamp: February 11, 2019, 01:58:11 pm
content: So I have this LG 1080p "laser" projector:https://www.lg.com/us/home-video/lg-HF80JA-projectorI have it mounted on a ceiling, projecting to a 100" screen. All, is good, however...I can't get a good focus: either top part of the screen, or bottom part and corners are blurry. Looks like it's focus point is spherical, not on a plane...It is not tragic and is fine for movies, but any on screen menus and smaller texts are blurred in places.Also noticed it having a different focus point between left side and right.I also have a 720p LED "mini" prjector (wowoto H8) in the bedroom and it is suffering similar symptoms.So the question is: is this considered normal and is there some adjustability inside, like moving the matrix a little?

author: dzseki
author_rank: Frequent Contributor
timestamp: February 11, 2019, 02:59:18 pm
content: Don't even think about to adjust the panel inside... instead, make sure it is installed as per the manual's suggestion? Do you happen to use excessive keystone correction?

author: elektrinis
author_rank: Regular Contributor
timestamp: February 11, 2019, 03:01:25 pm
content: Quote from: dzseki on February 11, 2019, 02:59:18 pmI have no correction. I did my part to install it correctly, so it is perfectly aligned to my screen without any correction, only zoom and focus were adjusted...

author: dzseki
author_rank: Frequent Contributor
timestamp: February 11, 2019, 03:22:30 pm
content: If you can try to exchange in warranty. Otherwise it very well can be that the construction of the unit is such poor by design...

author: elektrinis
author_rank: Regular Contributor
timestamp: February 11, 2019, 03:26:05 pm
content: Found one review with similar issue, so it may be the design.I did not expect optical issues at $1500....

author: dzseki
author_rank: Frequent Contributor
timestamp: February 11, 2019, 03:36:25 pm
content: As I see in these days with consumer electronics features are more important than functionality, regardless of price...Perhaps it is possible to tilt the projector such way the projected picture remains sharp throughout.