hybridfree/eevblog-posts huggingface dataset:
BJT controlled relay repair - comfy chair - Page 1
Forum section: electronics / repair

author: plexus
author_rank: Contributor
timestamp: May 01, 2017, 11:07:10 pm
content: Hi. My dad bought an expensive reclining chair that has numerous vibration motors in it. the issue if the motor in the head rest. the chair uses a detachable wired remote with an 8 pin DIN. he was working with the remote and noticed that the head motor will not turn off. in the remote is a simple board with a anonymous µcontroller, with control pins that drive a resistor and a BJT. the BJT is wired out to the DIN with a diode across it on the board. as I suspected the BJT for the head motor was shorted. I am surmising they are using electromechanical relays in the chair to control the motors, although I can't confirm that as I can not see the motors or any circuitry in the chair due to the way the chair is constructed.I can replace the BJT which is an ss8050 PNP 1.5W. I was wondering about using, perhaps, a MOV or some other better component to protect against back EMF - I am speculating this is what may have taken out the BJT. the diode on the board is ok.What are you thoughts and any suggestions on ways to beef this circuit up so my dad doesn't have more problems like this?thanks!

author: james_s
author_rank: Super Contributor
timestamp: May 02, 2017, 07:02:57 pm
content: I would just replace the transistor, a diode across the relay coil is a very common protection method, sometimes parts just fail.

author: plexus
author_rank: Contributor
timestamp: May 02, 2017, 07:25:00 pm
content: I hear ya. That's the plan, to replace the transistor. In terms of using a diode across a relay to catch back-EMF, if there is some length of wire between the switching transistor and the relay, does it matter if the diode is on the transistor end of the remote vs on the relay?

author: james_s
author_rank: Super Contributor
timestamp: May 02, 2017, 07:44:25 pm
content: Oh, there isn't a diode already? I usually put them as close to the relay as possible.

author: plexus
author_rank: Contributor
timestamp: May 02, 2017, 07:46:47 pm
content: Quote from: james_s on May 02, 2017, 07:44:25 pmThere is a diode in the design already however it's in the remote on the trasistor end. I am thinking about modifications to the design to make it more reliable and wondered if there was a reason to have it closer or on the relay as I am typically seen.

author: james_s
author_rank: Super Contributor
timestamp: May 02, 2017, 07:49:40 pm
content: It might help to reduce EMI but in practice I doubt it makes all that much difference. I would say replace the transistor for now and then if it fails again look at modifying the design. It's quite likely just a marginal transistor that was of low quality to begin with.

author: plexus
author_rank: Contributor
timestamp: May 02, 2017, 07:53:45 pm
content: Quote from: james_s on May 02, 2017, 07:49:40 pmThat is a good point. this is a cheap chinese product through and through. I ordered some replacement transistors and I think I will replace them all with the new ones which are name branded from digi-key. thanks for the idea.
Advice needed probing low voltage supply Tektronix 2440 - Page 1
Forum section: electronics / repair

author: adrianni
author_rank: Contributor
timestamp: May 02, 2017, 01:14:19 pm
content: Hello,I would like to probe the LV power supply of my 2440 to see if the waves show the same as the service manual says they should.But the manual also says that some portions of the LVP are at the AC line potential and advise for using an isolation transformer.My question: Is this advice given only to prevent somebody getting electrocuted by touching accidentally a live point in the circuit and thus providing a short to ground? Or it has to do with touching accidentally a live point with the ground alligator clip of the oscilloscope probe?I mean, I would clip the ground lead of the probe to the chassis of the scope and then probe with the tip the points specified in the manual. Am I going to be in trouble if I am careful not to probe all over the place and of course not to touch anything (other than the probe itself...)?I also have a differential probe but I fail to see how this is going to help in this situation.Thank you,Adrian

author: David Hess
author_rank: Super Contributor
timestamp: May 02, 2017, 01:57:10 pm
content: If the probe ground is connected to the chassis ground, which is the only safe place in this case, then the probe tip can be applied anywhere safely.The problem comes when trying to measure the voltages on the primary side because common is *not* at chassis ground potential. So measuring the primary side voltages to the primary side common requires an isolation transformer, floating input, or a differential probe.

author: adrianni
author_rank: Contributor
timestamp: May 02, 2017, 03:08:36 pm
content: Thank you David.This is indeed common sense. But I do see the need to reiterate it now and then.Luckily, I don't need to measure that. But if I did, I would most certainly use an isolation transformer or at least a differential probe or use the two channel math method.Cheers

author: David Hess
author_rank: Super Contributor
timestamp: May 02, 2017, 05:25:06 pm
content: Hopefully you will not have to make any primary side measurements. The critical capacitors on the input side are the large line frequency ones and they wear out last. The inverter operates in current instead of voltage mode so the output capacitors for the preregulator are actually on the secondary side and those are the ones which wear out first.One thing to watch out for when probing on the primary side (or in any circuit) is that the ground ring at the tip of the probe does not short out on something. For safety, insulate it with some tape when not using the witch's hat grabber.
Blinking LED on Schaub Lorenz lt32-353A B - Page 1
Forum section: electronics / repair

author: zero1024
author_rank: Newbie
timestamp: May 02, 2017, 03:40:08 pm
content: Hi to all,I'm having trouble with a Schaub Lorenz lt32-353A B 32'' TV. When I plug the TV to power, the front blue LED comes steady on. After a few seconds the LED starts blinking rapidly and that's it. No matter what I try, the screen never comes on and no response from anything, only the LED blinking.First thing I tried based on Internet search, was to change the PSU (17PW26-4 v1) but still same issue, LED stable for a few seconds then starts blinking.Today I received a replacement for the board of this TV, the board is a Vestel 17MB25-3 v1 bought from eBay from a different TV model unfortunately because it was not possible for me to find from a similar model anywhere. It's the exact same board as on my TV though.As you can guess same issue, nothing changed! I have a new PSU and board but still get the same thing, LED blinking.Any suggestions you may have will be very appreciated! Is my problem on the panel? Or maybe one of the components I bought was defective too? What can I try next?Thank you for your time and response.
Yamaha RX-497 turn off after 10-15 min - Page 1
Forum section: electronics / repair

author: coojoe213
author_rank: Newbie
timestamp: April 28, 2017, 03:58:35 pm
content: Hi all. I have this receiver, but after 10 min turn off.I check the DC/PS values, and i see PS values are low. The normal values in service manual are DC:035, PS:068 . My DC is perfect 035, but my PS is...(my values are 53/52/51....47/46), every 5-10 second they are low. I check all electrolic capacitors in Power supply, but the are fine. C254 (22nf/650v) is 15nf when i check with my multimeter. Is this may be a problem or no? Can you tell what to try? :/EDIT: Now, receiver turn off after 1 minute.

author: Jeroen_Bezemer
author_rank: Contributor
timestamp: April 28, 2017, 08:01:00 pm
content: Check out the zenerdiode on the right part in front of the optocoupler. The led should only light when the voltage is high.Verstuurd vanaf mijn SHIELD Tablet K1 met Tapatalk

author: coojoe213
author_rank: Newbie
timestamp: April 29, 2017, 01:04:51 pm
content: All 3 zener is good and there voltages. I change the 22nf 650v Caps, but no result.On S10 i have 9.7VOn +5M i have 5VBut on the display every 10-15 sec PS is lower :/

author: coojoe213
author_rank: Newbie
timestamp: April 29, 2017, 06:37:18 pm
content: I found part of the problem. My +15V, every second is low. But i can't find which part make problem.

author: mzacharias
author_rank: Frequent Contributor
timestamp: May 01, 2017, 01:34:52 pm
content: Quote from: coojoe213 on April 29, 2017, 06:37:18 pmIs this the +15 volt line that comes from transistor Q121? If so, I would check to see if capacitor C145 might be open circuit. With a 'scope you can look at the collector or Q121 or at resistor R177 and see the nature of your ripple. It the ripple is properly filtered, the cap is OK, and you can look to see if the voltage drops coming out of the transistor. The transistor could be failing, going open emitter-base for example. Seen this problem many times, not on newer vintage Yamaha's but it's worth a check.
SRS DS345 double voltage output or what? - Page 1
Forum section: electronics / repair

author: e-pirate
author_rank: Regular Contributor
timestamp: April 30, 2017, 11:39:29 pm
content: Hi, folks!Just received an SRS DS345 synthesized function generator from eBay. And after some testing I found some strange thing. The output level seems to be double the set value. If I set 1 Vpp on the unit, the actual waveform amplitude between peaks is 2 V (measured with cursors from highest to lowest point of the sin wave with 1 MOhm DC coupled input). OK.. I thought I misunderstood the Vpp thing, but then I did a multimeter test as described in manual. I set generator to output 100 Hz 1V RMS and my multimeter reads 2 V on AC. The gen passes all self test and self calibration routings and fully functional with the exception of double output.I'm doing something wrong or what?

author: ebclr
author_rank: Super Contributor
timestamp: April 30, 2017, 11:49:10 pm
content: Did you note this"into 50? load "

author: e-pirate
author_rank: Regular Contributor
timestamp: May 01, 2017, 08:03:57 am
content: Sure. And there was a "trap for the yang players", as Dave says. When I use internal 50 ohm termination on my scope, the amplitude drops so significantly, that I decided, that I'm doing something wrong. But actually, I start to understand. I don't have a proper 50 Ohm BNC-to-BNC cable on hand, only various scope probes in my Tek pouch and they seem to misbehave (have incorrect impedance) even in X1 mode. Just because the probe has approximately 300Ohm resistance, it forms a divider and therefore the readout was wrong while both the scope and the gen were operating correctly. I simply didn't expect that from X1 probe! When I got a dodgy 50ohm cable with a BNC on once side and a pair of crocodile clips on the other and connected it to the scope that was 50 Ohm terminated internally, I got perfect signal with spot on Vpp. A good lesson for me: it's not your equipment, it's a lack of knowledge multiplies rush multiplies non-thinking-before-doing.
Strange HVAC problem - Page 1
Forum section: electronics / repair

author: Zinger
author_rank: Contributor
timestamp: April 29, 2017, 02:33:59 pm
content: Apologies if this isn't 100% on topic, but if you guys can't help me I'm going to have to find an exorcist.I'm having a truly bizarre problem with my home HVAC system. It keeps turning itself on, switching between heating and cooling, and resetting its temperature. Even if the thermostat is set to off, it will come on by itself. It usually happens in the middle of the night, but it occasionally occurs during the day.Last winter, when it was 20° out, it switched itself to air conditioning and set the temperature to 60°.The HVAC unit is a 6 year old Bryant 313AAV/JAV. The original thermostat was a Honeywell TH6000 series programmable. I switch it out for a TH3000 series non-programmable, thinking the thermostat might have been the problem. That made no difference.Honeywell's help line thought it might be a short in the wiring between the thermostat and the HVAC. I had a technician from John C. Flood check it. He found no problems anywhere in the system and couldn't recreate the problem, of course. BTW, Flood installed the system 6 years ago.He suggested switching out the control board in the Bryant, but didn't sound hopeful.Any ideas on what could be causing this or advice on how to trouble shoot it? I'm literally losing sleep over this. I keep waking up to see if it's done anything funky.Thanks.

author: Samogon
author_rank: Frequent Contributor
timestamp: April 29, 2017, 05:02:06 pm
content: Control board is most probable cause. Chech is moisture gets into it, corrosion, etc.So technician most likely right

author: Armadillo
author_rank: Super Contributor
timestamp: April 29, 2017, 07:34:59 pm
content: Is this thing under remote control? Hide your remote control far away. I had a friend, his remote control gone crazy. A closer inspection reviewed that moisture had gotten into the remote control.

author: james_s
author_rank: Super Contributor
timestamp: April 29, 2017, 08:56:53 pm
content: Look for bad capacitors on the control board, particularly in the power supply. Wonky power supply can cause all sorts of weird stuff.

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 30, 2017, 06:02:31 pm
content: How could capacitors go bad in only 6 years? Are they being abused (IE getting hot, excessive vibration, exc)?It could also be an open control bus (either a wire or part of the circuit board) or a bad bias resistor on a data line to the thermostat allowing stray signals to get into the digital control system.

author: james_s
author_rank: Super Contributor
timestamp: May 01, 2017, 03:22:15 am
content: I've seen loads of bad capacitors that were not even 6 years old, it's very common. Especially if it has a switchmode regulator and cheap capacitors. I think I went through 4 or 5 AC adapters on my internet router before I finally switched to the old iron transformer type. I would expect a HVAC system to be better built than that but I wouldn't count on it.
BK Precision 4040A Sweep Generator  - Page 1
Forum section: electronics / repair

author: softwarejedimaster
author_rank: Contributor
timestamp: April 30, 2017, 08:48:13 pm
content: I just received a used and non functioning unit from an ebay seller. All the internal bnc connectors have been disconnected. Does anyone here have pics of this unit showing where all the 3 pin connectors get connected? Much thanks!
Electronic bathroom scales repair - Page 1
Forum section: electronics / repair

author: martis
author_rank: Newbie
timestamp: April 30, 2017, 05:57:00 pm
content: Hi! I accidentally broke the electronic scales at my local gym while trying to weigh gym weights (Started showing +60kg ). I brought them back home to try and fix them . The problem probably lies in one of the four sensors. While three sensors have a resistance of around 2kOhm between white and black wires, the fourth sensor has a resistance of 6kOhms. What should I do ? Could I just throw out one sensor and connect one of the other sensors instead? ( so that 1 sensor would act as two) . I know that the weight would have to be exactly in the middle to show precise results, but I only need them to work with acceptable precision.The model is sencor sbs 6015 bk.Thanks for the adviceBy the way, now the scales show either ---- or always 81.4kg when you step on them.

author: NottheDan
author_rank: Frequent Contributor
timestamp: April 30, 2017, 07:34:33 pm
content: Unlikely it will work. Even if you find a new sensor to put in it would still need recalibrating and I doubt you find the data for that anywhere.But really, it's a sub-€30 scale. Is the repair effort worth it?
HP 33120A with bad rotary encoder - Page 1
Forum section: electronics / repair

author: JJalling
author_rank: Unknown
timestamp: April 29, 2017, 10:35:45 am
content: Hello all,I have an old HP33120A with a bad rotary encoder. Does anyone know what encoder can be used as a replacement? I would think that it's not worth the effort to try to clean the existing one.Thanks in advanceBR Jonas

author: amspire
author_rank: Super Contributor
timestamp: April 29, 2017, 11:54:09 am
content: If the contacts are not damaged, it is often worth having a go rejuvinating the rotary encoder. It may involve pulling the encoder apart. I have had success with this 2 part Deoxit products:http://store.caig.com/s.nl/it.A/id.2299/.fbut you may be able to find an alternative locally.I had the same problem with my 33120A and Rigol DS1052E scope and both have worked for years without a problem since. I cannot remember the specifics of repairing the 33120A - sorry.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 29, 2017, 12:29:24 pm
content: Bourns makes a rotary encoder with same footprint.The part number is:PEC16-4215F-N0024I have used a few of these successfully.https://www.digikey.com/product-detail/en/bourns-inc/PEC16-4215F-N0024/PEC16-4215F-N0024-ND/3534275

author: JJalling
author_rank: Unknown
timestamp: April 29, 2017, 01:02:32 pm
content: Thank you both of you. I will give it a quick clean, and add a couple of the ones that HighVoltage suggests to my next order.Again, thanks.BR Jonas
Ctek 5.0 Battery Charger - Page 1
Forum section: electronics / repair

author: Gangway
author_rank: Contributor
timestamp: April 09, 2017, 07:49:25 am
content: Just asking if anyone has opened one of these units for repair. Early models had 4 x screws in back case, my later unit, no screws. Need to fix Mode switch problem.

author: tautech
author_rank: Super Contributor
timestamp: April 09, 2017, 07:52:38 am
content: Quote from: Gangway on April 09, 2017, 07:49:25 amScrews under the label ?

author: Gangway
author_rank: Contributor
timestamp: April 09, 2017, 08:05:32 am
content: No, only clear label, think it is a sealed unit, hoping someone has done it before. Thanks.

author: hendorog
author_rank: Super Contributor
timestamp: April 09, 2017, 08:28:18 am
content: I had one of those die, took one look at the weird rivet things they use and it went back. Turns out it was under warranty...The warranty was fairly long so worth checking out as you may get lucky like I did (i.e. > 1 year, maybe 3 or 5 years)Edit: yeah if its one of these then 5 year warranty:http://www.cteknz.co.nz/tabid/319/ProductID/2069/Default.aspx

author: Gangway
author_rank: Contributor
timestamp: April 09, 2017, 08:48:52 am
content: Yes they do have a five year warranty, but as I purchased online in Aust. Cannot find receipt as Ebay records only go back two years. Will try my spudger on it later this week.

author: hendorog
author_rank: Super Contributor
timestamp: April 09, 2017, 08:58:42 am
content: Maybe try contacting ctek direct since you are still covered. It was zero hassle for my replacement at least - I had no receipt either but Burnsco had a record of the sale, you never know.

author: Gangway
author_rank: Contributor
timestamp: April 09, 2017, 10:45:50 am
content: Well it's worth a try, that's why I was reluctant to start trying to open its. Thanks, will update later in week.

author: Gangway
author_rank: Contributor
timestamp: April 10, 2017, 06:33:37 am
content: Rang wholesaler ( Bainbridge Technologies Brisbane), very helpful and they were aware of defunct online store.Told me to send the unit in as should be covered by five year warranty replacement, being a sealed unit.Luckily PayPal history went back to 2014, so they will accept that as proof of purchase.So thanks .hendorog for suggestion, see how I go.

author: hendorog
author_rank: Super Contributor
timestamp: April 10, 2017, 07:31:14 am
content: Happy daysThat is great service from them in both our cases (well so far at least).

author: Gangway
author_rank: Contributor
timestamp: April 28, 2017, 12:01:49 am
content: Good news, received via Express Post complete new Ctek MXS 5.0 today. Brilliant service by distributer.
Computer SMPS hissing, then turning off - Page 1
Forum section: electronics / repair

author: bogdan2014
author_rank: Regular Contributor
timestamp: April 26, 2017, 08:44:09 am
content: Hello,I have a computer switchmode supply that I'm trying to repair.The problem is that it runs for about 10 seconds while putting out a strong hissing sound, and then it stops. I think the sound might be coming from the output inductor.I've checked bad solder connection, bad caps, the secondary side rectifiers, all good.From what I've seen, it seems to be a half bridge converter with the controller on the secondary side.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 26, 2017, 09:36:20 am
content: Hissing is usually a sign of a poorly compensated control loop. Often, the current limiting loop is thoughtlessly designed, and functions crudely (with hissing), or simply shuts down completely (a comparator and latch to disable the output).Double check for shorts, non-functional transistors and diodes, bad caps, etc.Tim

author: gbrettell
author_rank: Contributor
timestamp: April 27, 2017, 08:08:51 pm
content: Sounds like a bad capacitor on the secondary ... does it smell like Tuna??

author: james_s
author_rank: Super Contributor
timestamp: April 27, 2017, 08:36:29 pm
content: Capacitors would be my first thought as well, but he said he checked those so I'll assume they're all good.I encountered a similar fault in the power supply of a TDS340 scope, it turned out to be a shorted rectifier diode in the output, one of the TO220 ones mounted on a heatsink. Says he checked those too, sure there isn't one you missed?Have you measured the outputs while turning it on? That can provide additional clues.
Help me identify this diode - Page 1
Forum section: electronics / repair

author: tonyh88
author_rank: Regular Contributor
timestamp: April 27, 2017, 01:57:56 pm
content: As title says. See photo below in attachment. Marking on diode is 47-10LIs it a 10V zener?I found this seller but there isn't any info :http://www.uuorder.com/Product/37922356213/SMD%20diode%204.7-25L%2047-20%20150-16L%204.7-50%2022-16L%2047-25%20100-10LI accidentally blew it up while debugging....Thanks for the help

author: free_electron
author_rank: Super Contributor
timestamp: April 27, 2017, 02:02:42 pm
content: tantalum capacitor ...

author: daveyk
author_rank: Frequent Contributor
timestamp: April 27, 2017, 02:05:22 pm
content: Quote from: tonyh88 on April 27, 2017, 01:57:56 pmLooks like a 47uf 10v tantalum capacitor to me.Sent from my iPhone using Tapatalk

author: tonyh88
author_rank: Regular Contributor
timestamp: April 27, 2017, 02:12:52 pm
content: Yup it is......... now I feel embarrassed..... sorry for silly question

author: james_s
author_rank: Super Contributor
timestamp: April 27, 2017, 08:33:01 pm
content: Better to ask the question than put a zener diode in there and blow something up.
replacing capacitor - Page 1
Forum section: electronics / repair

author: mensahotoo
author_rank: Newbie
timestamp: April 27, 2017, 03:18:14 pm
content: will it be appropriate replacing a 100uf/450v capacitor with a 450uf/200v

author: helius
author_rank: Super Contributor
timestamp: April 27, 2017, 03:25:07 pm
content: That depends entirely on the circuit in which it is a component.We can generally expect that if a 450V working voltage capacitor was originally used, it was because that rating was considered necessary for proper circuit function. If that is the case, a 200V rated replacement would not operate properly and could fail explosively.Replacing a capacitor with a 4x higher capacitance is also unlikely to function as originally designed, although there are some circuits in which it would be acceptable. You have not provided enough information.

author: mensahotoo
author_rank: Newbie
timestamp: April 27, 2017, 03:40:14 pm
content: the power capacitor is in a smart tv (NASCO 42" smart tv).

author: Jono427
author_rank: Contributor
timestamp: April 27, 2017, 03:53:58 pm
content: Should probably just replace with a cap of the exact same rating. There is probably a reason they are using that one. If you post the model number of the TV and pictures of the board maybe someone can look and see.

author: 4thDoctorWhoFan
author_rank: Regular Contributor
timestamp: April 27, 2017, 05:02:21 pm
content: Don't do it. You are just asking for trouble, especially in a TV.Replace the capacitor with another 450V capacitor. I also would not go higher than about 220uF.You should just get an exact replacement.

author: ollihd
author_rank: Regular Contributor
timestamp: April 27, 2017, 05:11:32 pm
content: When replacing TV caps you should 99% of the time replace the cap with a cap of the same capacitance value. The voltage can be equal to the original or higher, not lower. I usually order the same exact one I'm replacing (same capacitance value, same voltage rating, same temp rating, same manufacturer). The more special characteristics of caps play even a higher role when talking about audio circuits. Hope this helps!

author: mensahotoo
author_rank: Newbie
timestamp: April 27, 2017, 06:06:09 pm
content: thank you all

author: james_s
author_rank: Super Contributor
timestamp: April 27, 2017, 08:29:32 pm
content: This is one of those cases where if you have to ask, then no, you can't. I think it has already been covered but you generally have a fair bit of wiggle room with the capacitance but the voltage of the replacement must be equal or greater than that of the original. Sometimes you don't want to go *too* much greater because higher voltage caps tend to have higher ESR and are physically larger. For example if you need a 16V capacitor you probably don't want to use a 250V capacitor but a 25 or 35V rated part would be fine.
Xl830l multimeter repair  - Page 1
Forum section: electronics / repair

author: atgeek
author_rank: Contributor
timestamp: April 27, 2017, 07:54:40 am
content: I made a mistake by passing more than 200mA in this multimeter, it seem a resistor is blown. Anyone with the same multimeter could give the resistor value? Thanks

author: carl_lab
author_rank: Frequent Contributor
timestamp: April 27, 2017, 08:35:46 am
content: Do you mean the 1R00 resistor (1)?No fuse inside? You should add a fuse (200mA fast) or dump this "quality gear"...

author: atgeek
author_rank: Contributor
timestamp: April 27, 2017, 08:55:44 am
content: No, I mean the resistor near the 1Ohm one, a fuse is still present but it doesn't blownmaybe because it's too cheap
Replace M25PE10 flash memory obsolote from AMS control board vending machine - Page 1
Forum section: electronics / repair

author: brauliochi
author_rank: Newbie
timestamp: April 26, 2017, 05:03:10 pm
content: Hi, I fix a control board from a vending machine, I check that two components is in short, a fram fm25v02, and m25pe10, with the first no problem, mouser have in stock, but the m25pe10 its obsolete, and the only place that they have in stock is aliexpress, and dont trust so much in this supplier, any now any substitute for this chip, best regards

author: Anks
author_rank: Frequent Contributor
timestamp: April 26, 2017, 06:46:17 pm
content: Arrow have them in stock. Have you got the info to burn to it?
Where to buy OMRON connector XC5A-4422 in Europe (Germany)? - Page 1
Forum section: electronics / repair

author: carl_lab
author_rank: Frequent Contributor
timestamp: April 25, 2017, 04:25:45 pm
content: Found it at Mouser, but 3 months delivery time:www.mouser.de/Search/Refine.aspx?Keyword=XC5A-4422
Cheap vape set - ebay - charging - Page 1
Forum section: electronics / repair

author: Matthew98
author_rank: Regular Contributor
timestamp: April 25, 2017, 02:59:18 pm
content: Hey.So I bought a cheap vape set from ebay and the charger is just death trap. (surprise surprise...) It is just a current sensor for turning the diode green, when there is no load at the output. On the output is bare USB voltage. I tried replacing it with TP 4056, but it wont charge the battery, as it has microchip in it and charging sequence, that confuses the TP4056. When I put 5V on the battery, it blinks few times and starts charging. The same with 4.2V. It draws current after the blinking. How to make it safer ? I know it has some protections almost for sure, as it has the microchip in it (So its not THE version just with bare battery inside) , but that may give it only overcharge protection. Not current control. Although it draws 100mah now, as the battery seems to be quite charged...Btw. Im not smoker, I bough it for the same reason as bigclivedotcomThanks !
TDS520D Horizontal position not moving - Page 1
Forum section: electronics / repair

author: Tectonic
author_rank: Contributor
timestamp: April 22, 2017, 01:15:16 pm
content: I can't move waveforms horizontally on my TDS520D. The horizontal position knob isn't moving waveforms. I've tried a few troubleshooting steps to no avail:Factory Reset (normal and DPO)Diag/Err: no failuresPressing the help button then turning the horizontal position knob does display its help textI replaced the front panel. No change.Tried both channels with different probesChecked the zoom menu and tried the different lock/unlock functionsAm I missing some hidden locking function which persists through a factory reset? Should I be looking at the acquisition or processing boards? Any advice is greatly appreciated.

author: capt bullshot
author_rank: Super Contributor
timestamp: April 24, 2017, 01:35:19 pm
content: Did you set the acquisition length to more than 1000 Samples?Did you turn off the "fit to screen" option?Did you turn off DPO / InstaVu mode?

author: Tectonic
author_rank: Contributor
timestamp: April 24, 2017, 11:31:16 pm
content: Did you set the acquisition length to more than 1000 Samples?Set to 5kDid you turn off the "fit to screen" option?It's offDid you turn off DPO / InstaVu mode?It's off
CMU200 service manual available  - Page 1
Forum section: electronics / repair

author: BeO
author_rank: Contributor
timestamp: April 23, 2017, 09:59:48 am
content: HelloI have now a service manual copy if that can help someoneBest RegardsBeO

author: cs.dk
author_rank: Unknown
timestamp: April 23, 2017, 10:07:05 am
content: Please upload it to KO4BB or similar;http://www.ko4bb.com/getsimple/index.php?id=manuals

author: vaualbus
author_rank: Frequent Contributor
timestamp: April 24, 2017, 09:56:55 pm
content: or post it here!
Help me in identifying Component  - Page 1
Forum section: electronics / repair

author: himanshu_hny
author_rank: Newbie
timestamp: April 24, 2017, 10:41:35 am
content: Please help me in finding attached SMD Component in am beginner..Regards,Himanshu Sharma

author: bktemp
author_rank: Super Contributor
timestamp: April 24, 2017, 11:09:08 am
content: 20* is the marking code for BF545A. Maybe they are using the J-FET as a low leakage diode?

author: DTJ
author_rank: Super Contributor
timestamp: April 24, 2017, 11:40:23 am
content: Taking a guess....The DRxx components are resistors.The DCxx components are capacitors.You could make the assumption that DDxx is a diode of some sort.Look at the pins - the bottom two are coupled together, so yeah, it's probably a diode.I can't quite make out the markings on it. Is it "20A" or is it "2D"?Maybe its "20" as BKTemp mentioned.Look through some SMD marking tables and see if you can find something that matches.Tables like this one:http://www.marsport.org.uk/smd/mainframe.htm
E4440A - Page 1
Forum section: electronics / repair

author: Nemo1956
author_rank: Contributor
timestamp: April 24, 2017, 02:00:15 am
content: I have two of these i managed to buy cheap but they both seem to have Similar or same problems.: Calibration fail. Align RF Gain Preamp .I have not worked on this type of equipment before so I need a little help to find the problem/s.Can anyone help???
HP 54601a Oscilloscope - keys suddenly stopped working. - Page 1
Forum section: electronics / repair

author: R Lamparter
author_rank: Contributor
timestamp: April 23, 2017, 07:50:00 pm
content: This was an oscilloscope which had a compressed display that I acquired from a local university . The softkeys (tactile dome switches) under the screen were erratically responsive, so I took them apart and cleaned them. They were working after that. Prior to replacing capacitor C608 to fix the display problem, the display responded to keyboard keys and the softkeys. After the capacitor replacement I was pressing keys - voltage, frequency, print/utility to see what the various screens looked like. The softkeys under the screen were working on the various menus brought up by keys such as voltage, time, etc. IIRC, I pressed the Setup key and the display had a menu of choices at the bottom. I don't remember which softkey choice I made, but I think it was Default Setup, but it could have been Recall. After this the display screen changed to the screenshot below and the scope no longer responded to any keys. I tried shutting the scope off and restarting it. That didn't work. I tried leaving it off longer - over night - that didn't fix it. I assume this is showing something stored in memory, but since I can't get any of the keys to respond, I don't know how to get out of this and get the scope responding again. The first attached photo shows the screen I think I was on before I pressed the softkey that terminated all keyboard responses. The second photo shows the screen it's currently frozen on. I examined the ribbon cables since I had had the front panel off to clean the softkeys and the video board out to replace the capacitor. I didn't see any kinks or loose cables. I reseated the keyboard cable where it attached to the mainboard. The keyboard end was firmly down on its pins. At this point I don't even have a probe to see if it responds to external stimuli. What happened? How do I fix this.

author: JFJ
author_rank: Regular Contributor
timestamp: April 23, 2017, 09:43:17 pm
content: Quote from: R Lamparter on April 23, 2017, 07:50:00 pmHave you tried a key down power-up? That is, hold a softkey down and switch on - release the softkey after the scope has booted.Also, be aware that most keys and control knobs will stop working if any key is permanently stuck down.

author: R Lamparter
author_rank: Contributor
timestamp: April 24, 2017, 12:32:35 am
content: Thank you. The key-down power up fixed it. I had never heard of that.
Brymen BM257s - Out of cal. (C_Er-fault) - Page 1
Forum section: electronics / repair

author: cs.dk
author_rank: Unknown
timestamp: April 23, 2017, 10:03:49 am
content: I've got a Brymen BM257s which suddenly shows "C_Er" when powering up. The meter has not seen any sort of abuse.From the manual;QuoteThis is second time one of my 257s' does it. The first got replaced under warranty. This one is out of warranty, is there something i can do myself? I can send it of to cal, but it will cost nearly as much as a brand new meter.Any thoughts on DIY repair?The meter won't measure DC volts. All other ranges seems to work.Not first time that fault is seen;https://www.eevblog.com/forum/testgear/brymen-257s-lost-calibration-data/
TDS544 Schematics? - Bad -15v Power Supply - Page 1
Forum section: electronics / repair

author: daveyk
author_rank: Frequent Contributor
timestamp: April 22, 2017, 07:36:16 pm
content: I found the service manual but no schematics. The -15v supply J26-7 is only -12.5 with the ACQ board un-hooked. So my problem appears to be that main big power supply. I a not sure how to fire it up outside the scope in order to trouble-shoot it. If I pull the digital board off, the I can not turn it on with the front panel. There is probably wiring to turn on the power supply, but without prints, I don't know how to do that. Even if I can figure out where the -15volt supply is, I could possible shotgun it.If someone has prints could you please send them to me, or reply with a link?Thanks so kindly,Dave

author: John_ITIC
author_rank: Frequent Contributor
timestamp: April 23, 2017, 02:26:02 am
content: Sorry, I don't have any links but I just wanted to suggest keeping this scope repair in a single thread. It appears you've created several threads for the same issue?

author: daveyk
author_rank: Frequent Contributor
timestamp: April 23, 2017, 05:42:16 am
content: Sorry, I'm not sure how but that was with the iphone. I tried deleting my threads and the forum won't let me.
[FIXED] Agilent 34401a repair - dead GPIB - Page 1
Forum section: electronics / repair

author: usagi
author_rank: Frequent Contributor
timestamp: April 18, 2017, 08:47:51 am
content: Picked up a used 34401a off ebay. The unit passes self test without errors.RS232 works but GPIB does not.Is there a common cause of failure for 34401a GPIB ports?I'm guessing either U703 (75ALS162) or U702 (75ALS160) is bad. Is there any way to tell which one?

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 18, 2017, 09:56:49 am
content: Hello usagi,see manual p. 92: 'Only one interface can be enabled at a time'.So I assume, that you have to enable 'HP-IB / 488' first, in the I/O menu, see p. 162, and then it should work.Frank

author: usagi
author_rank: Frequent Contributor
timestamp: April 18, 2017, 05:11:57 pm
content: Quote from: Dr. Frank on April 18, 2017, 09:56:49 ami know this alreadyi had to go into those menus to enable RS232 in the first place, since it came with GPIB interface enabled by default.so I can confirm GPIB is 100% busted.GPIB works on my other devices - keithley 2015 and R&S cmu200.so do you know which exact 34401a IC to verify for GPIB troubleshooting?

author: Tony_G
author_rank: Super Contributor
timestamp: April 19, 2017, 08:38:01 pm
content: I just repaired an 11713A that didn't work with GPIB by resoldering the GPIB connector - Might be worth giving it a try if the connector is soldered direct to the board in those devices.

author: usagi
author_rank: Frequent Contributor
timestamp: April 20, 2017, 07:24:27 am
content: 100% confirmed the connector is perfect.100% confirmed an IC is blown. waiting on mouser order to arrive now.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 20, 2017, 07:39:32 am
content: Once you exchange the GPIB controller it should work perfect again.

author: usagi
author_rank: Frequent Contributor
timestamp: April 20, 2017, 08:25:08 am
content: Quote from: HighVoltage on April 20, 2017, 07:39:32 amU701 is fine.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 20, 2017, 08:44:40 am
content: Quote from: usagi on April 20, 2017, 08:25:08 amAhh, which IC do you think is blown?

author: usagi
author_rank: Frequent Contributor
timestamp: April 23, 2017, 03:16:40 am
content: replaced blown IC, GPIB now works. again

author: TheSteve
author_rank: Unknown
timestamp: April 23, 2017, 03:39:30 am
content: Excellent!!!Please do post which IC you actually changed to make it work though.
Battery maintenance voltage on 732B - Page 1
Forum section: electronics / repair

author: kkayser
author_rank: Contributor
timestamp: April 20, 2017, 03:41:20 pm
content: The maintenance voltage on my 732B is 14.9V. I would like it somewhere in the 13's. Does anyone know which resistors control the maintenance voltage?

author: dacman
author_rank: Frequent Contributor
timestamp: April 20, 2017, 11:34:33 pm
content: Do you mean that the charge indicator is off and it is floating at 14.9 V?

author: kkayser
author_rank: Contributor
timestamp: April 21, 2017, 07:26:19 pm
content: Quote from: dacman on April 20, 2017, 11:34:33 pmYes. The charge light has been off for over a year.

author: Gyro
author_rank: Super Contributor
timestamp: April 22, 2017, 10:13:11 am
content: Do a forum search for '732B battery'. This has been covered in detail in a couple of threads, including charger mods and PCB revisions.
Martin Wisman ULT-400 Audio Amp - Page 1
Forum section: electronics / repair

author: DarkZero
author_rank: Regular Contributor
timestamp: April 21, 2017, 03:49:00 pm
content: if someone has schematic or picture of the output transistors because i desoldered all transistors and didnt see they were not the same now i dont know in what order to put new ones ...
techtronix 475,  U370 does not work?  - Page 1
Forum section: electronics / repair

author: cmcdan
author_rank: Newbie
timestamp: April 21, 2017, 09:36:30 am
content: Hi, Hope to get some info. I am a long time Tek repairman but stuck here. The manual, p26 has a logic chart for U370 inputs. I removed U370 and checked the 4 inputs; logic is correct but U370 does not output signal. I used hairpin loops to bypass ch 2 and all's well. The voltage level hi -2.30; low - 1.49; This IC had a heat sink; it gets warm but not hot? What to do? cmcdan solution: bought a replacement from Greece, yes the country. It worked but scope died; HV pwr supply tap for -150V, 50 kHz kaput; made a Lab pwr supply out of rear 7 inches.

author: tggzzz
author_rank: Super Contributor
timestamp: April 21, 2017, 02:38:10 pm
content: If the IC is faulty, seewww.ebay.com/itm/Tektronix-155-0091-00-Hybrid-IC-400-Series-Oscilloscopes-GOOD-/141983338495
Fluke 8050A decimal point problem - Page 1
Forum section: electronics / repair

author: mellowamoya
author_rank: Newbie
timestamp: April 20, 2017, 03:51:25 pm
content: Hi All,Im hoping someone can help with this my trusty Fluke8050A that has been on the bench for many years and worked very hard, it has developed a problem, it still works and reads but all the decimal points on the display are on all the time no matter what button is pressed, sometimes the last one on the right will be flashing but most of the time they are just all on.any pointers as to fault find the problem would be great.thanksdennis

author: retiredcaps
author_rank: Super Contributor
timestamp: April 20, 2017, 05:26:10 pm
content: 8050A Service manual athttp://bama.edebris.com/download/fluke/8050a/8050a.pdfsuggest for (from table 4-13 troubleshooting guide)All or no decimal points that U16, U17, interconnect may be at fault.

author: JFJ
author_rank: Regular Contributor
timestamp: April 20, 2017, 05:27:11 pm
content: The decimal points are driven by U16 - a four segment LCD driver (CD4054BE). Hopefully, replacing that IC will cure the fault. If not, then it may be game-over, because the decimal point control signal comes directly from pin 22 of U17 (Fluke's own 40 pin controller).If your meter is the 8050A-01 (rechargeable battery option) then the display will have a 'BT' (low battery) indicator, which is also controlled from pin 22 of U17. So, if 'BT' isn't permanently on, then U17 is unlikely to be faulty.Sorry, it's the 'REL' indicator that is "also controlled from pin 22 of U17" (I misread 'Out 4' as pin 4 on the CD4054B datasheet). So, if 'REL' isn't permanently on, then U17 is unlikely to be faulty.

author: ModemHead
author_rank: Frequent Contributor
timestamp: April 20, 2017, 11:46:30 pm
content: Before heating up the soldering iron, disassemble the ribbon cable interconnect and give it a clean, just in case.
How to easy desolder BGA chips (CPU, etc..) in present-day Lenovo laptops. - Page 1
Forum section: electronics / repair

author: Kim_555
author_rank: Contributor
timestamp: March 11, 2017, 09:15:58 am
content: Hi all.If You engage laptops repair, you know hat in Lenovo all BGA chips is with "black compound" and when we unsolder it - we have big chance to damage contacts in motherboard.Fast and safe way before desoldering - is use WD-40. Before desoldering - we add a small amount of WD-40 under chip, and waiting 20-30 min. Then we can desoldering chip on infrared station.We can see this process in my videoIn this video i speak russian, but i think everything will be clear. I wish all successful repairs.

author: 0xreverser
author_rank: Newbie
timestamp: April 20, 2017, 01:08:46 pm
content: This is a awesome video, thanks. You tell waht happened to the sides of the chip but i cant understand russian. Can you tell?

author: Rasz
author_rank: Super Contributor
timestamp: April 20, 2017, 04:07:52 pm
content: he pulled some unused pads, afair nothing to worry about

author: Armadillo
author_rank: Super Contributor
timestamp: April 20, 2017, 09:08:41 pm
content: Thanks, I enjoyed your videos. To increase your subscription to the channel, can you speak in English/text?
HP 9100b Computing Calculator  repair  query  - Page 1
Forum section: electronics / repair

author: rickells
author_rank: Regular Contributor
timestamp: April 25, 2017, 08:54:18 pm
content: hi,Wondering if anyone has repaired an HP 9100a or HP 9100b computing calculator (Core Memory & CRT !).Would appreciate sharing repair notes on this exciting (discrete transistor) vintage calculator.thanks,rick

author: dfrederickson
author_rank: Contributor
timestamp: April 25, 2017, 09:29:31 pm
content: Check The Museum of HP Calculators Forum,hpmuseum.org/forum. The service manual and other stuff can be found at the HP Computer Museum,http://www.hpmuseum.net/display_item.php?hw=50.

author: rickells
author_rank: Regular Contributor
timestamp: April 26, 2017, 05:15:28 pm
content: hi,Yes, have already obtained the manuals and Tony's hand scratched schematics !My issue is No display on the CRT and it is proving to be difficult to find the problem(s).thanks,

author: dfrederickson
author_rank: Contributor
timestamp: April 27, 2017, 04:01:35 pm
content: I've wondered why Tony didn't use schematic capture software. The service manual has better schematics, theory of operation, and troubleshooting procedures.You can also post your question on the MoHPC Forum or email Tony directly.http://hpcc.org/correspondence/index.html

author: kwass
author_rank: Frequent Contributor
timestamp: April 27, 2017, 05:54:49 pm
content: Quote from: rickells on April 26, 2017, 05:15:28 pmThese are really hard machines to repair since almost any failure can result in a blank display. I had a 9100a for some years (pre-Tony's schematics) and was able to get a partial display with X and Y registers showing and some calculations working. While trying to get the rest of it working I ended up with a blank display and could make no progress on repairing it all all. I tested all the semiconductors (hundreds of them) and capacitors and as much wiring as I could. Eventually I gave up and sold it as-is to someone. This person later found that the only issue was a bad resistor somewhere on the core memory board (I think).Good luck with it!

author: rickells
author_rank: Regular Contributor
timestamp: April 28, 2017, 06:16:55 pm
content: hi,Do you have a Web link to the Service manuals that you are referring to ?I have not been able to find any detailed HP schematics nor troubleshooting for the HP 9100, only Tony's.thanks,rick

author: dfrederickson
author_rank: Contributor
timestamp: April 28, 2017, 07:17:45 pm
content: Surf to the HP Computer Museum link, above. Click on Product Documentation at the bottom of the page.Here's a direct link to the Service Manual:http://www.hpmuseum.net/document.php?hwfile=790