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whit3rd <whit3rd@gmail.com>: Jul 13 01:02PM -0700 > Hi Tim   > So it is a power supply out of a Sun Microsystems SPARC Classic computer. Good info; the date might be 2000 or earlier, so there's a good chance old-line part-number xrefs will help > Sun P/N 300-1101-01 Rev A > Model: PEX643-30 > Made by FDK Fuji Electrochemcical Co Ltd   Lots of Japanese transistors have different pinout from US types; for TO-92, US normal is (facing flat, with wires DOWN, left to right) E-B-C Japan normal is E-C-B You can usually distinguish the two by a multimeter's diode-check function (assuming a working transistor) without desoldering.   > PCB1750 A06-119271D   > Not easy or not marked as to the parts   > the transistors in questions are TO-92 and are all on the low voltage side of the switcher.   If it helps, NTE crossreferences for (P4M) include NTE159, a general-purpose PNP (see <https://www.nteinc.com> and use the crossreference search)   It is usual for one TO-92 item on the low voltage side to be a TL431 voltage reference...

Holger <me@privacy.org>: Jul 14 03:18AM +0200 > Hi Folks   > Having some trouble finding some transistors.   > I am repairing a switch mode power supply and have a number of transistors that need replacing. The issue is I can't seem to find them online....maybe my google fu is out of whack or I have forgotten something obvious.   Try to get the schematic, and then you should be able to figure out, what for a kind of transistor you are looking for. Second bet is, you have to add strings like "2SB" oder "2SA" for "2SA2005" or something similar. Search for the appropriate datasheets, good luck.   Holger

Jeff Urban <jurb6006@gmail.com>: Jul 14 07:02AM -0700 Take some detailed pictures of the board top and bottom. If I can figure out how it is designed I can figure out a replacement fairly fast.   Either upload them somewhere or just send them to me. Hosting is nice, I used to have hosting until Dropbox stuck it up my ass and I don't want them at all anyway because they won't do what I want done. This year I am just going to dig in the old pocket and pay for some decent hosting. Are you in any forums that accept pictures in posts ? If so I can tell you how to hotlink.   Now I need high definition well lit pictures, this is reverse engineering. It's not much fun anymore actually.

Stu jaxon <stankowalski02@gmail.com>: Jul 13 05:14PM -0700 On Saturday, July 13, 2019 at 7:01:56 AM UTC-4, John-Del wrote:   > The way I approach a no-picture issue (with normal backlights) is to scope the differential signals coming out of the main at the LVDS plug to the TCON. These are digital signals and are jibberish, but if they're there, the main is usually good. While scoping, it's helpful to push the TVs menu button and watch for any activity on the differential outputs. If only DC appears on the LVDS output connector, you still have a bad main.   > If the differential signals are there, try removing either of the two ribbon connectors going to the display from the TCON and see if you get half a pix. If not, reconnect the ribbon and remove the other. If you get half a picture from either attempt, you've got a bad display. Still no pic? Prob bad TCON.   > There is a 12V fuse near the power harness you can check, but if it's open, usually a bad multi layer chip cap has shorted although there could also be a bad IC. If the fuse is good, you can check for DC at various points on the board if marked. If nothing is marked, look for small round inductors that identify the handful of buck converters that normally populate TCONs. There should be DC voltages on them and can vary from 1.2 to 24V depending on design. If any are missing with the output ribbons disconnected, you have a bad TCON.   thanks for the info.. the fuse tested good.. I hooked up a scope 5v ch1, on dc coupling I got dc differential signals with the menu button pressed on some pins and not data on others same results with ac coupling, if the tcon board was good was i supposed to see an AC siganl.? and with the ribbons removed no pic on either side.. bad tcon board..?

John-Del <ohger1s@gmail.com>: Jul 14 06:14AM -0700 On Saturday, July 13, 2019 at 8:14:28 PM UTC-4, Stu jaxon wrote:   > > If the differential signals are there, try removing either of the two ribbon connectors going to the display from the TCON and see if you get half a pix. If not, reconnect the ribbon and remove the other. If you get half a picture from either attempt, you've got a bad display. Still no pic? Prob bad TCON.   > > There is a 12V fuse near the power harness you can check, but if it's open, usually a bad multi layer chip cap has shorted although there could also be a bad IC. If the fuse is good, you can check for DC at various points on the board if marked. If nothing is marked, look for small round inductors that identify the handful of buck converters that normally populate TCONs. There should be DC voltages on them and can vary from 1.2 to 24V depending on design. If any are missing with the output ribbons disconnected, you have a bad TCON.   > thanks for the info.. the fuse tested good.. I hooked up a scope 5v ch1, on dc coupling I got dc differential signals with the menu button pressed on some pins and not data on others same results with ac coupling, if the tcon board was good was i supposed to see an AC siganl.? and with the ribbons removed no pic on either side.. bad tcon board..?   I should have asked if you checked for 12V on the TCON fuse.   With the scope on AC coupling, set it for 50mv with a 10X probe and maybe .5ms for the horizontal - neither setting is critical. The signals are digital data and not on every pin. What I've found over the years is that any data visible with a known good input source or menu activation (which guarantees *something* should appear on the screen) means the main is good. Of course, those that produce a picture with issues like off colors, pixelization, gamma errors etc. could be the main and it's nearly impossible to tell if the main or the TCON are causing those problems by scoping the signals. But generally, if you have differential signals to the TCON but no picture, the main is good.   So if you have 12V on the TCON fuse, it sounds like you have a bad TCON. Pull the shield off and look for any shorted multi layer capacitors. These are small SMD caps, have no markings, and are invariably brown in color. The ones most suspect are the ones that are side by side in a parallel arrangement. If one of these caps short, the buck regulator in the circuit will shut down. The problem is that one shorted cap may be paralleled by several and up to a dozen, so picking the offending shorted cap out can take some time.   I can check Monday to see if I have a verified good TCON in the shop.

HW <none@no.no>: Jul 09 12:19AM +0200 >Now you can troubleshoot. If there is a short, the light will limit the fault current.   I actually have wanted to make one of those for a while. Maybe this is the right time. I like the dual outlet idea. That way, I can plug in different power bulbs depending on the type of device.   >Also beware using a scope that the ground in your circuit may be live.   I recently got myself a differential probe.   >I would buy or make an isolation transformer as well for your safety.   That is also on my to-do list.   >Replace the FET and cap and turn it on with the 60Watt bulb in series.   Transistor and capacitor set are on order.

HW <none@no.no>: Jul 09 12:06AM +0200 On Mon, 8 Jul 2019 11:40:51 -0700 (PDT), Terry Schwartz   >There certainly is no point trying to measure a split open capacitor.   Sure. But since I had removed two components and the short went away, I felt it was worth checking them both for a short. It turns out none of them are shorted, which is where it gets interesting.   Some capacitors do fail short. In fact, some are designed specifically to fail short.

HW <none@no.no>: Jul 08 03:52PM +0200 I have an automotive battery charger like this one:   http://www.carstel.com/index/product/product_info/id/100.html   I have not been able to find schematics, and the manufacturer ignores me.   There are two boards, one looks like the power supply section, while the other one contains buttons and LED display. The SMPS board looks like an ordinary flyback arrangement, with a transformer and opto isolator for feedback.   The symptom is that the 5 A input fuse blows as soon as power is connected. The fuse blows with a magnificent blue flash and produces an audible pop, so the overcurrent is considerable.   The SMPS is based on an ST 3845B, driving a 9N90C MOSFET. Across the MOSFET's D/S, there is a 470 pF / 1 kV capacitor, located very close to the MOSFET. The capacitor is split open and has spewed its guts onto the MOSFET. The capacitor measures open circuit with an ohmmeter. I do not have a megger available, so I cannot check the capacitor at high voltage.   I have unsoldered the MOSFET and the capacitor. Now the fuse does not blow. Between the MOSFET's G and S pads on the PCB, I can see a nice 27 kHz square wave with declining amplitude for 7 ms, and then nothing for 17 ms, before another burst of 27 kHz, so it looks like the controller is trying to start from its bootstrap supply.   The MOSFET tests OK on one of those cheap ATMEGA-based component testers.   What is the most likely fault scenario?   What should I check next?   Could the blown capacitor be the only problem, or is it only a result of the actual fault?

Bob Engelhardt <BobEngelhardt@comcast.net>: Jul 08 01:16PM -0400 On 7/8/2019 10:56 AM, John Robertson wrote: >... > I'd use a 'scope and do the math if the readings are critical and you > can't afford a proper AC meter   The readings aren't at all critical - a single-digit correction factor would be good enough.   I wonder if the meter reading has a consistent relationship to the RMS value. E.g., if the meter always used the peak value, the actual value would simply be 0.7 the read value. If it was consistent, I could calculate the correction factor by measuring the peak on a scope. But I wouldn't want to have to generate correction curves.

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Jul 09 12:21PM -0400 On 7/9/19 5:02 AM, Look165 wrote:   > The older one (AMM) were making true measurement with a rectifier and a > filtering cap.   > This is particularly obvious in Amperemeter operations.   You're cracked. (Plus you top-post.)   Rectifier + filter is _not_ a true-RMS meter.   <https://www.walmart.com/search/?cat_id=0&query=true+rms+multimeter>   Cheers   Phil Hobbs   -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510   http://electrooptical.net http://hobbs-eo.com

Look165 <look165@numericable.fr>: Jul 11 09:45PM +0200 DMM work perfectly with sine wave, but not with other signals.

Look165 <look165@numericable.fr>: Jul 10 04:05PM +0200 Not considering losses, The mean rectified signal is 2^^(1.5)/pi the RMS input value 2^^(1.5)/pi is about 0.9.   Phil Allison a écrit le 08/07/2019 à 23:59 :

Look165 <look165@numericable.fr>: Jul 09 11:02AM +0200 NO ; with today's DMM the value is only true with sine wave. Some use triangular signal, other Dirac comb. They sample the signal and then computation and mathematical process. The older one (AMM) were making true measurement with a rectifier and a filtering cap.   This is particularly obvious in Amperemeter operations.   Phil Hobbs a écrit le 09/07/2019 à 00:16 :

Look165 <look165@numericable.fr>: Jul 09 12:01PM +0200 Joule is the quantity of energy neceassar for heatin 1g of water up to +1° at 4°. Watt is the power related to J but per second.   Phil Allison a écrit le 08/07/2019 à 23:59 :

Bob Engelhardt <BobEngelhardt@comcast.net>: Jul 08 05:30PM -0400 On 7/8/2019 5:23 PM, Phil Allison wrote:   >> If I measure a full wave voltage   > ** I wish folk would use correct terminology and not private shorthand.   > Do you mean " full wave RECTIFIED voltage" or not ???   ...   Sorry for the offense. I thought that it was obvious & didn't know that there was any other kind. What other kind of full wave is there, other than full wave rectified?

Look165 <look165@numericable.fr>: Jul 08 08:04PM +0200 I got a problem measuring efficienty on an SMPS unit.   The meter I used was indicating about 50% which was absurd. I brought my personal old analog meter, it said about 85% ! That's why I don't like todays's meters.     Bob Engelhardt a écrit le 08/07/2019 à 16:47 :

Bob Engelhardt <BobEngelhardt@comcast.net>: Jul 08 10:47AM -0400 If I measure a full wave voltage with a non true-RMS common variety DMM*, will it be off by a known factor, from the true RMS value?   Or is there a rule of thumb about the error. E.g., the reading will be high by about 10%.   Thanks, Bob   * - Extech Ex320 if it matters

Bob Engelhardt <BobEngelhardt@comcast.net>: Jul 08 05:42PM -0400 Oh, wait ... the light dawns. The DC that I'm trying to measure is the output of a bridge. It's RMS value will just be the RMS value of the AC input, less 2 diode drops. Unless I'm missing something ... not unheard of.

Look165 <look165@numericable.fr>: Jul 07 10:21AM +0200 In Europe, there are some kind of "socks"" that can fit the exact form of the phone. Some are made out of velvet. Color is your choice. The advantage is reversibility.

Jeff Liebermann <jeffl@cruzio.com>: Jul 07 04:12PM -0700 On Sun, 7 Jul 2019 17:46:00 -0500, Fox's Mercantile <jdangus@att.net> wrote:   >well as my Asterisk PBX. >Which is great, I have an original Stromberg Carlson candle >stick phone with a rotary dial. It works "just fine."   U-Verse voice, cable internet gateways, Magic Jack, and VoIP adapters will NOT work with a rotary dial phone. However, there are dial pulse to DTMF adapters available for about $40: <https://www.voip-info.org/dial-pulse-to-touchtone-dtmf-converters/>   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

etpm@whidbey.com: Jul 07 10:28AM -0700 On Sat, 06 Jul 2019 17:04:59 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote:   >there was a demand for red "hot line" phones. Somehow, I didn't think >of trying to make one by painting or dyeing a phone red.   >Good luck. Too bad it's a black phone.

~misfit~ <shaun.at.pukekohe@gmail.com>: Jul 08 11:53AM +1200 On 8/07/2019 3:52 AM, Fox's Mercantile wrote: >> Putting a laptop on the bed on top of the covers for example   > It's still a problem. A friend got the top of his legs burned by > a laptop.   I keep a piece of 2mm hardboard the same size as my laptop in my laptop bag and always use it under my laptop if it's not being used on a hard surface. It maintains clearances for air gaps. Common sense really... -- Shaun.   "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM" David Melville   This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.

"Percival P. Cassidy" <Nobody@NotMyISP.net>: Jul 07 08:55PM -0400 On 6/5/19 11:37 AM, bitrex wrote:     >> be the last machine I buy from this company just avoid these shit heads.   > It's too bad ThinkPad used to be a quality product when IBM made them > but it's just bargain basement zombie-brand China junk, now.   I have bought still-in-warranty used Lenovo T-series ThinkPads and found them excellent in quality and excellent value for money.   Perce

Bob Engelhardt <BobEngelhardt@comcast.net>: Jul 08 10:38AM -0400 On 7/6/2019 1:31 PM, Jeff Liebermann wrote: ... > So, after reading my analysis and guesswork, do you still think that > they don't deserve any more help?   First I'd like to say that I appreciate the effort that you put into your replies, even when I'm not the OP. You have a great deal of credibility and when there's a long thread that has sidetracks of the "Yes it is" "No it isn't" variety I often skip most of it and read your replies.   But, to the point here: your 1st reply brought up the boiling-under-vacuum problem. Which he totally ignored in his reply to you and repeated his original request for finding the device he thought he needed. If they're not going to listen, I'm not going to waste my time. If he won't listen, he probably can't be helped anyhow.

Fox's Mercantile <jdangus@att.net>: Jul 10 08:24AM -0500 > The simple way to find out if replacing a cap will help is > to bridge it with another cap.   That only works if the cap has gone open.     -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

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