hybridfree/eevblog-posts huggingface dataset:
Need header/wire housing manufacturer... - Page 1
Forum section: electronics / repair

author: gotwood
author_rank: Contributor
timestamp: November 28, 2016, 07:32:35 pm
content: Repairing my wiring harness and pcb from my Kohler house generator's transfer switch.I need to figure out the manufacturer of the header/wire housing, any help would be appreciated.

author: helius
author_rank: Super Contributor
timestamp: November 28, 2016, 07:51:19 pm
content: Looks like Molex Mini-Fit Jr, but check the key shapes of those housings.

author: gotwood
author_rank: Contributor
timestamp: November 28, 2016, 08:08:16 pm
content: its not molex....molex has three keys on the 6 positionthe one I'm looking for only 2also molex headers have 2 positioning pins(snap in)this one only has one...

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: November 28, 2016, 09:20:36 pm
content: What about this ?http://www.digikey.com/product-detail/en/te-connectivity-amp-connectors/1-770875-0/A32589-ND/1091170TE Connectivity 1-770875-0

author: gotwood
author_rank: Contributor
timestamp: November 29, 2016, 01:00:11 am
content: thanks...looks like thats it...though when I used that site and tried to find it i didn't pull that up
Fitbit Charge HR charger pinout - Page 1
Forum section: electronics / repair

author: 0b01010011
author_rank: Regular Contributor
timestamp: December 05, 2016, 05:45:02 am
content: Hi guys,The wife has lost her Fitbit Charge HR charger lead, and has asked me to see if I can at least charge it until she gets another one.I did do some searching and could not find the pinout - there are some of other Fitbits but seems they all have different charge connectors. What I am after is the pinout of the one in the attached image, circled in red. I'm pretty sure one will be 5v and one will be GND.Thank you...

author: brainwash
author_rank: Frequent Contributor
timestamp: December 05, 2016, 11:34:07 am
content: I normally run a diode test on the device and if I see a conduction path (600mV or so) then it usually means that the polarity is reversed (protection diode). Then I would feed 5V at a very small current (10-20mA) to see if anything breaks.However a google search shows this:https://community.fitbit.com/t5/Charge-HR/Temporary-USB-charge-lead/td-p/732222"I just tested my charging cable and if I hold the cable with the bend/notch to the top the left pin is negative and the right is positive according to my voltmeter."Make sure you current-limit everything before testing.

author: Postal666
author_rank: Regular Contributor
timestamp: December 05, 2016, 08:29:50 pm
content: Please excuse the crude MS Paint...Both pins show as short (both directions) in diode mode.Vcc is 2 OhmsHope that helps

author: 0b01010011
author_rank: Regular Contributor
timestamp: December 05, 2016, 10:19:10 pm
content: Fantastic thanks for the info guys, yes if I didn't get any info I would have tried a current limited PSU at first, but as you suggest brainwash a diode test is a good idea so I'll remember that for the future.I am guessing the FitBit must have either reverse diode protection or a series diode as minimum as it is possible to 'fudge' the connector backwards, not sure if it makes contact though.Will give this a try tonight.
SMPS Repair - Page 1
Forum section: electronics / repair

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 28, 2016, 02:04:30 am
content: Hello everyone, I have a TV in my garage that I need to get working. It was working fine, but I think the manufacturers didn't screw the PSU down hard enough. The heatsink on the power supply touched the metal mesh that shielded the PSU, and that heatsink was connected to the negative capacitor through two 0 ohm SMD resistors, which exploded. It also made a mess around the feedback traces from the optoisolatosr, so I cut those traces and cleaned the area, running bodge wires where they needed to go instead. I replaced the exploded 0 ohm resistors with wire.Powered it on, and it just sits there ticking. Its a 3 rail PSU, one rail handles the backlight, and the other two are in a group (they were the damaged ones) and they run the mainboard.I figured that the PSU's driver chips were probably bad, so I just bought a replacement PSU from ebay. However, it arrived damaged. I messaged the seller about it, waiting for a response. Some traces on the output side were broken, so I repaired them before connecting the PSU.After repairing them, I installed it into the TV, and applied power. But the new PSU makes the ticking noise as well....So I unplugged the backlight and mainboard (so the only thing left is the mains input) and both PSUs STILL made the ticking noise.What could be at fault here?

author: carl_lab
author_rank: Frequent Contributor
timestamp: November 28, 2016, 12:56:20 pm
content: Ticking sound (hiccup mode) is probably shorted PSU output (or short on PSU itself).Can you measure resistance from +supply voltages to GND at the TV side (with PS unplugged)?You also tried PSU only (without load)?Some SMPS need a minimum load to start...
Chassis connector - Page 1
Forum section: electronics / repair

author: akis
author_rank: Frequent Contributor
timestamp: November 27, 2016, 07:06:35 pm
content: I am looking for a wire to chassis connector. The chassis could be the steel frame of a PC enclosure for example, or some steel plate protrusion in the boot of a car for another example.Of course I can use a crocodile connector but vibrations will knock it off, I need something much more secure.I do not want to dril a hole on the chassis.I am imagining a g-clamp style of small connector (rather than a crocodile one) with a screw that secures the g-clamp onto the plate, and the same screw also secures the wire.Is there something like that and what is it called?

author: The_Penguin
author_rank: Regular Contributor
timestamp: November 28, 2016, 02:17:36 am
content: Why not a crimp-on lug remove an existing screw, add the lug, and re-install the screw?

author: Monkeh
author_rank: Super Contributor
timestamp: November 28, 2016, 04:19:38 am
content: Something like this?Radiator earth clamp. Fairly large, though.

author: akis
author_rank: Frequent Contributor
timestamp: November 28, 2016, 07:40:25 pm
content: Yes that's precisely it... I have used a heavy duty crocodile connector in the interim.
best practice to safely repair old oscilloscope with vacuum tube and crt - Page 1
Forum section: electronics / repair

author: crazyhog
author_rank: Regular Contributor
timestamp: November 28, 2016, 02:45:20 am
content: I brought an old timey Tektronix 564B storage oscilloscope.http://w140.com/tekwiki/wiki/564Note that my B variant is built using semiconductors. However, the vertical amplifier plugin, the time base plugin and the CRT are based on vacuum tubes.I got it because of the very unusual direct-view bistable storage CRT. If you are curious, this is the technical write up of the technology. It is fascinating!http://www.radiomuseum.org/forum/tektronix_three_kinds_of_storage.htmlI have a newbie question.I have no experience working with high voltage circuits. In fact, I am learning EE on my own at the moment. Before I hurt myself, I'd like to ask the board the following:What are the recommended best practices to safely service and troubleshoot high voltage vacuum tube and CRT equipments?Thanks!

author: jh15
author_rank: Frequent Contributor
timestamp: November 28, 2016, 04:54:49 am
content: #1 keep your left hand in your pocket. Learned that in my pre-teens and likely contributed decades later to saving my life in an industrial accident.Isolation transformer for troubleshooting any line powered item on the bench. Do not isolate a scope Used for troubleshooting, ok for the scope under duress. Not sure if Dave mentioned that .Learn a lot of the line referenced vs line isolated power supply stuff.Look at concepts in Dave's video how not to blow up your oscilloscope.Have someone around. Teach them not to grab you while in process of being electrocuted. Kill power, if in reach, or whip off your belt and pull her away, etc. Unless you have a metal belt.Reply back in a week here.Don't panic, I learned all this early on in the 60's 9-10 yrs or so old.

author: VK5RC
author_rank: Unknown
timestamp: November 28, 2016, 09:28:39 am
content: Tektronix, about the time of your scope, wrote a great paper on "Troubleshooting your oscilloscope". Certainly worth a read. Gives good safety advice, fault tracing algorithms and common faults.
Samsung Galaxy S2 Dropping Service When Using Data - Page 1
Forum section: electronics / repair

author: canadaboy25
author_rank: Regular Contributor
timestamp: November 22, 2016, 05:43:13 am
content: Hey guys, I have a Samsung Galaxy S2 which has a problem I have never seen before. I get decent cell signal with it and I can send text messages without issue. The problem arises whenever I try to use my data connection. If I try to load up a website, it will try to load for a moment, then my service will go away and display a cross sign over my signal strength. After a little wait my signal will return and it will continue to work until I try to use data again.I am on a Koodo contract and the sim card works without issue in my Galaxy S4 so it is definitely an issue with the S2.I found this website which shows replacing the power amplifier IC or the RFMD IC to resolve a few issues that are also listed on the website.http://blog.brokenlcds.com/samsung-galaxy-s2-network-problem/I have a dropping signal issue which they say to replace the RFMC IC in order to fix. In my mind I would think that the power amplifier IC was at fault due to the fact that using data uses more power which my push the old worn out chip past its limits? This is of course pure speculation on my part and I have no experience with cell signal circuits.Just wondering if anyone thinks that either of those chips could possibly be causing my issue? Any help is greatly appreciated.Thanks

author: daveshah
author_rank: Unknown
timestamp: November 25, 2016, 04:42:13 pm
content: Failing power amplifier does sound plausible. What happens if you try and make/receive a call?

author: canadaboy25
author_rank: Regular Contributor
timestamp: November 29, 2016, 01:55:04 am
content: Quote from: daveshah on November 25, 2016, 04:42:13 pmIt's been a while but I do remember problems with the service disappearing when making or receiving calls. I guess it doesn't really make a difference which chip it is if I cannot find a replacement. I searched the number on one of the chips on that website and couldn't find anything. Is this the sort of thing that is sold as a chip or are they specially programmed?
Acer E1-570G motherboard fix - Help me - Page 1
Forum section: electronics / repair

author: core138
author_rank: Newbie
timestamp: November 27, 2016, 10:55:14 am
content: Hello,I need help with a motherboard for laptop acer e1-570g mark on the motherboard LA-9535P. I have included a link to the image that you see. 2 SMD capacitor have fallen. The most important question is whether it can reconnect the wires or something.Thanks

author: senso
author_rank: Frequent Contributor
timestamp: November 27, 2016, 04:05:13 pm
content: That is major failure,your have a burned tract in your dc-in power input protection mosfets.There seems to be a burned mosfet, and those components that you circled are two ceramic capacitors.

author: core138
author_rank: Newbie
timestamp: November 28, 2016, 08:36:00 am
content: Here are better pictures. Only the 2 SMD capacitor went. Whether it can be to bypass
B+K Precision knobs from the 1970s 80s - Page 1
Forum section: electronics / repair

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 27, 2016, 12:51:02 am
content: I just received my 8$ NTSC generator model 1251.Front panel was a bit dented so I want to remove all the knobs and unbuckle the panel.Most knobs came off easy since they are friction fit, there's no set screw.But the only dual-knob is the one that won't come off. Anyone familiar with this type? Has the knob been pushed too far down the shaft and that's why it won't budge?Otherwise all I can see doing is prying it out with a screwdriver but the front panel is clean, I don't want to scratch it too.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 27, 2016, 05:47:08 pm
content: Guess I have to hand in my man card. I was a bit too cautious, thinking the hollow knobs would crack if I used too much force.A Vise Grip with some wood pieces in the jaw helped to pull it off. It was really jammed in tight! Now to unbuckle the panel.
Looking for help with an IFR 1200S - Page 1
Forum section: electronics / repair

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 26, 2016, 05:59:58 pm
content: Hi group,I have an IFR1200s that most of the functions seem to work correctly. One thing that doesn't work is the MODULATION switch which is used to select AM-SSB-FM. I have done some investigations:1) The switch seems o.k.2) I have checked the logic circuit that reads the switch and it looks like the uP never reads the switch.I would like to try new EPROMs. My unit has the 80C31 processor. This means that I need firmware versions 1.4, 1.51 or 1.7.I currently have 1.7 installed, but I think it might be corrupt.Later versions 3.00 and above are for 80C188 uP.Can anybody help me?Regards,Jay_Diddy_B

author: voltz
author_rank: Frequent Contributor
timestamp: November 26, 2016, 10:21:44 pm
content: Hi,If you suspect the EPROM(s) are faulty, try pulling them out and reading them. The chips have their checksum values written on them. Compare values.The Modulation rotary switch has a common +12 rail to it, check that its there.See if the Modulation mode can be changed via RS232 control (see manual for command set).The Modulation switch data is sent to the DVM/IO board and leads to U16 (74HC244) buffer. Make sure switch logic levels reach the pins of that chip. Note RN2 resistor network is used for GND logic low pull down.Hope that helps.PS, yes your particular CPU card will only accept versions below 3.0, cpu's were changed after that.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 26, 2016, 10:57:47 pm
content: Quote from: voltz on November 26, 2016, 10:21:44 pmI thought about. Unfortunately my EPROM doesn't have a checksum on the label. It just says version 1.7.0 maybe a field upgrade?Quote from: voltz on November 26, 2016, 10:21:44 pmI did check the switch, I think that the 12V is a mistake on the schematic. I did measure 5V. It seems o.k.Quote from: voltz on November 26, 2016, 10:21:44 pmThis is a great idea!! It will take a little time to rig up a cable and computer that 'speaks' RS232 but I do have one. I also have the manuals so I know the commands and format.Thank you!Regards,Jay_Diddy_B

author: voltz
author_rank: Frequent Contributor
timestamp: November 26, 2016, 11:19:30 pm
content: Yes, pretty sure its +5 at the switch, not 12.Shame the Eproms have no checksums. Its usually a hand written label written in pen.Is U16 being addressed at all? Pins 1 and 19. If not then could be address bus decoding problems at U13 etc.
Fluke 11 backward battery - Page 1
Forum section: electronics / repair

author: codycode
author_rank: Newbie
timestamp: November 24, 2016, 07:33:31 am
content: So I think that I killed my oldest multimeter today when I accidentally put the battery in backwards. When the battery is installed (correctly) and the meter is turned on it goes into a reset loop, where it turns on everything on the LCD (happens when the meter is turned on normally) then briefly shows a fairly normal screen, but without any numbers at all (not even zeros), then loops. It behaves differently if you put it into the non-voltage testing mode it displays the low battery icon and does not reset (but still does not display numbers, or have any working functionality)I tested all of the components on board, except for the 2 ICs. They all appear to be fuctioning.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 26, 2016, 04:20:46 am
content: I can't read a schematic to save my life, but in the Fluke 12 service manual, the schematic for the Fluke 11 shows a 1N4002 diode (CR1) attached to the positive battery terminal. Is this diode shorted?Have you checked VSS and VDD?
Need a relay - Page 1
Forum section: electronics / repair

author: BobWells
author_rank: Newbie
timestamp: November 19, 2016, 07:43:17 pm
content: Hi all, newby here, I'm repairing a active speaker & I'm pretty sure the relay has gone. Only trouble is I can't seem to find one, Any ideas gratefully received.Bob

author: christopher iles
author_rank: Regular Contributor
timestamp: November 20, 2016, 07:51:04 am
content: Hello,Relays rarely fail. Have you checked for 12v across the coil? You could apply 12v from a battery or power supply just to prove that the relay clicks over.If the relay has failed, it's a pretty standard item and it shouldn't be hard to find one (I probably have some somewhere in the shack).Let me know how you get on with your tests.King regards,Chris. G0VOE, Somerset.

author: BobWells
author_rank: Newbie
timestamp: November 22, 2016, 06:20:55 pm
content: Thanks for the reply Christopher, the relay is switching on / off most of the time when the speaker is switched on, so I'm guessing it's shot, had this before with relays. Never seen one with these markings before i.e. the 8A threw me.Bob

author: BobWells
author_rank: Newbie
timestamp: November 22, 2016, 06:26:35 pm
content: Blueskull, thanks for the info, I got the part number from Mouser & ordered from RS who I deal with regularly, so hopefully it'll be happy day's.Let you all know how it turns out, Bob

author: BobWells
author_rank: Newbie
timestamp: November 25, 2016, 01:33:27 pm
content: Hi all, just to conclude this thread, I found the relay Blueskull recommended & it's a success. Many thanks to the people that helped with my search, and a great forum, hope I can be of help to someone too soon.Bob
Need help locating a replacement transistor - Page 1
Forum section: electronics / repair

author: Heliotropic
author_rank: Newbie
timestamp: November 21, 2016, 12:20:15 am
content: Hi all! New user and first post here. As with most things you usually don't look at joining a forum until you need help with something, which is what brings me here.This will probably be relatively simple for someone who knows what they're looking as... that's not meI'm trying to find a replacement transistor (pictured attached). I've found some SC945's and there seems to be a variety available, but I can't really narrow down which one to choose. The info printed on the component doesn't match-up exactly to what I've found and I can't figure out how to translate/cross-reference to what I have.Can anyone help me find the correct part so I don't end up frying something?

author: voltz
author_rank: Frequent Contributor
timestamp: November 21, 2016, 12:31:29 am
content: Try 2sc945http://www.micropik.com/PDF/2sc945.pdf

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 21, 2016, 12:33:33 am
content: Hi,The pinout for this transistor is ECB, check the datasheet. This is not the standard pinout.It is a 60v 150mA NPN bipolar transistor.Regards,Jay_Diddy_B

author: Heliotropic
author_rank: Newbie
timestamp: November 26, 2016, 06:16:47 pm
content: Thanks for the help guys. I was able to find and order one that would work and it fixed what I was working on.Thanks again!
Repair videos Fluke 6060B and more - Page 1
Forum section: electronics / repair

author: TheDefpom
author_rank: Frequent Contributor
timestamp: November 24, 2016, 11:35:09 pm
content: Hi All,I have a number of repair videos up on my YouTube channel, I have included a few below which may be of interest, these are for a Fluke 6060B RF signal generator, I have many others, for HP, Tektronix equipment etc.Part 1:Part 2:Part 3:Part 4:Part 5:
Fried Bearcat 996XT Scanner - Page 1
Forum section: electronics / repair

author: The_Penguin
author_rank: Regular Contributor
timestamp: November 12, 2016, 02:26:30 am
content: Hi all. I haven't done any repairs for a long time, thought I'd dust off my skills with a really tough one.A Bearcat 996XT radio scanner that got fried by a surge or maybe incorrect power supply.I have no service information, would love to find a schematic, but nothing found so far.Some fried input circuitry was replaced before I got it. I replaced an open 2.2 ohm resistor so far.Symptom is, it's deadLooking at supply voltages it has 6v, is missing 8v and missing 3.3v for the CPU area. I think the 3.3v regulator is fed by the 8v supply, so not surprised it's missing.My specific question for now, is about the 8v regulator. A 78R08F 5 pin TO-252. It's running pretty warm, and only outputting 2v.Looking at the datasheet, Pin1 is input, Pin2 gnd. Pin3 output, pin 4 is NC, and pin 5 is on/off control.Here's the thing, pin 2 reads 10vdc referenced to chassis gnd. And pin 2 doesn't appear to be actually connected to gnd on the pcb.Not sure if this is a multi-layer pcb, pin 2 goes to a via, haven't really tried tracing it too far.So, am I looking at an inaccurate datasheet, or is there something weird about this design?I removed it, and measured the output pad on the PCB, and it's not shorted or particularly low resistance. 12v on pin 1 and still 10v on pin 2 with the regulator removed. Will test the regulator soon.

author: strawberry
author_rank: Super Contributor
timestamp: November 12, 2016, 03:31:52 am
content: KIA78R08F pin 1 input. 2on/off. 3.output. 4. n.c. 5.Gndinto 1A protection

author: The_Penguin
author_rank: Regular Contributor
timestamp: November 12, 2016, 03:44:45 am
content: Well crap, the datasheet I downloaded is wrong. Just looked at another, agrees with you. Even the test circuit diagrams in the first datasheet are wrong. That explains a lot.Thanks!Now to test the regulator out of circuit.

author: The_Penguin
author_rank: Regular Contributor
timestamp: November 24, 2016, 02:12:18 pm
content: Regulator definitely bad. Have a few coming on a slow boat from China.
FLUKE 8840A Multimeter - +5V power supplier in short circuit - Page 1
Forum section: electronics / repair

author: cbarbos2
author_rank: Newbie
timestamp: November 22, 2016, 05:59:46 pm
content: I have one Fluke 8840A that the +5V regulator is with the output in short circuit to ground.I have removed the +5V ceramic caps, the regulator 7805 and I could not find where is the short circuit.Does anybody have any suggestion?It seems a shor circuit by PCI tracks. But the PCI is multlayer.Thanks a lot for any help.Carlos Cesar

author: singapol
author_rank: Frequent Contributor
timestamp: November 24, 2016, 03:33:15 am
content: From the main power supply circuit there is a 7805 regulator if that's what you are refering to but did you check the big electrolytic cap 6800uf C601? If C601 is ok then the short is further down the 5V supply and it feeds manyic chips. Actually before you take out the 7805 powering the circuit to use the touch test to see which ic or component is the hottest might help zero in the fault if there is no apparent burnt parts or evidence of charred spots on pcb. Alternative you can probe with DMM the ic pins especially Vcc to gnd.Of course it is not definitive as you have the check surrounding components. Do also know that there is another 7805 in the IEE-488 circuit.Good luck,
Need Help with Hioki 3454-51 Insulation tester. - Page 1
Forum section: electronics / repair

author: jmcdonald
author_rank: Contributor
timestamp: November 23, 2016, 06:51:37 am
content: 500v was put into the meter in the continuity mode.Would like to get service manual and or schematics?Q14 a 6 pin Sot363 with K1 on it went pop, IC2 is to hot to touch 5 pin sot23 and the unit will not power onhave removed q14 and still no good IC2 could be a voltage regit have the marking of B481
unknown IC - Page 1
Forum section: electronics / repair

author: david69
author_rank: Regular Contributor
timestamp: November 21, 2016, 12:42:00 pm
content: Hi, I could not look for IC /SOT-23-5?/ in switching supply.The SMD mark code is 17 5T 53 or C9, but I think that is notLDO? The chip controlls optocupler in feedback, thanks for anyidea David

author: daddario
author_rank: Regular Contributor
timestamp: November 22, 2016, 10:04:02 pm
content: Pinout would be helpful, but probably a TL431.

author: david69
author_rank: Regular Contributor
timestamp: November 23, 2016, 12:18:03 pm
content: partly scheme, IC control optocupler diode in power source
Marconi Sig gen that wont start up - Page 1
Forum section: electronics / repair

author: Nemo1956
author_rank: Contributor
timestamp: November 21, 2016, 07:52:30 am
content: My marconi 2202 siggen will not go past the start up. all the LED's will come on and the fan will run but now that's all it will do. I have had a look inside but can see any loss cables or connectors. All the voltages are correct as well.I have no idea where to start looking for this fault.

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 21, 2016, 10:45:33 am
content: Start with the processor.Does it get the correct voltage?Is the clock oscillator running?Is the reset line the proper level?Is there activity on the address and data lines?

author: Nemo1956
author_rank: Contributor
timestamp: November 22, 2016, 08:43:04 am
content: I have measured the voltages and that are all fine.Do you know where I can obtain the circuit for this unit?

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 22, 2016, 08:45:31 am
content: Quote from: Nemo1956 on November 22, 2016, 08:43:04 amhttp://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Marconi/Marconi_2022
tektronix 475A trigger slope not working consistently on startup - Page 1
Forum section: electronics / repair

author: crazyhog
author_rank: Regular Contributor
timestamp: November 21, 2016, 09:21:45 pm
content: Hi,I have just brought my first analog scope, a Tek 475A! The scope has a slope switch to select trigger on raising edge (positive slope) or falling edge (negative slope). However, on cold startups (e.g. early morning), the trigger fires on both raising and falling edges regardless of the slope switch. After running for a 15 minutes, the scope would work properly and trigger according to the slope switch setting.Any idea how to fix this? Is it normal to warm up these analog scope before use?I've attached a picture of my scope with an input from a function generator into ch2. The slope switch is set to positive slope (green oval). However, notice I am getting 2 traces with both positive and negative slope. The scope is firing on both positive and negative slope of the input signal.Thanks

author: barry14
author_rank: Regular Contributor
timestamp: November 21, 2016, 09:43:46 pm
content: Two possibilities come to mind. One, the trigger slope switch may be dirty. This will happen with older equipment. Try switching it back and forth a number of times. You may have to open up the scope and spray some contact cleaner on the switch contacts. The other possibility is that the trigger level control needs to be adjusted. Yes, analog equipment, even solid state, usually needs some warmup for full normal operation because the power dissipation of the internal circuitry will cause various components to increase in temperaure until equilibrium is reached. Most analog equipment manuals call for some warmup time, on the order of 5 to 15 minutes, for the device to operate within all of its specifications.

author: David Hess
author_rank: Super Contributor
timestamp: November 22, 2016, 12:13:04 am
content: The 475A uses tunnel diode trigger circuits which sometimes drift enough with age to require adjustment. The detailed procedure is in the service manual.

author: crazyhog
author_rank: Regular Contributor
timestamp: November 22, 2016, 01:02:32 am
content: Cool, thanks all!Even though my Rigol has a lot more features, I have to I admit I like this scope more! Love all the mechanical switches and knobs! No confusing layers of menu is a joy forever!
Repair Keysight E3616A - Page 1
Forum section: electronics / repair

author: sosokruashvili
author_rank: Newbie
timestamp: November 21, 2016, 12:54:06 am
content: Hi all,I purchased HP Keysight E3616A bench PSU 5 days ago from ebay. It was in not working condition and I decided I could fix it.But it became my nightmare. The problem is that it turns on, outputs voltage but very unstable, voltage is floating and has extremely high noise and peaks. Almost 3 vpp and 400mv floating with random waveform. I've got oscilloscope and good measurement staff so I can check almost anything. I have schematic and repair manuals.I have checked reference voltages and they have identical noise as the output, but when I drop output voltage to 0 noise is gone in reference voltages. I checked every part in reference circuits and they are ok. Also checked Constant Voltage circuit parts, main mosfets input voltages, diodes caps they are all ok. +5 volts, -12 volts, +10volts they are all ok. I also disconnected other circuits like SCR controls and OVP circuits and Constant Current circuit but noise is still there.In repair manual there is some check points and there I have huge problem. There is Reference and Bias Circuit Troubleshooting chapter and I cannot pass the check voltage between TP6 and point3 and voltage between TP6 (common of reference voltages) and point5. I am getting -2.5 (should be -5.1) volts with noise and 0.8 volts (should be +5v) also noise. When I disconnect the panel meter from mainboard the voltages are -12 and +8. But I think panel is making some common connections to make circuits.So, I found that when I disconnect the panel meter from mainboard, PSU is more stable and there is no noise in the output. Then I checked pannel meter inputs and there is constant 100 ohm resistance between +5v and 0. Panel schematic is draining 300ma current and making about 70mvpp noise.I need help and some advises. Do you think that panel is causing this problem? And If anyone has the same PSU I will be happiest man in world if will tell me what is the resistance between panel pin 1 and 2 (+5v and 0). These are the panel power pins. Also I forgot to mention, panel is lighting up and showing some +-3 volts difference from output voltage, and current meter displays 1.999, sometimes 1.000 it does not correspond the load.I will provide schematic and measurement data if anyone is interested. Also if anyone has schematic of panel itself please provide, I could not find anywhereNOT Noise OSCILLATION
Sencore VP401 repair - Page 1
Forum section: electronics / repair

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: November 21, 2016, 02:43:46 pm
content: Hi,Through my own error, and lack of knowledge with this circuit, I blew up my Sencore VP401 !Fortunately we have Sencoretech, and through his kindness I was able to obtain all the information, and support, necessary to get it operational once again!Thank you Sencoretech!
hakko fm-2027 - Page 1
Forum section: electronics / repair

author: cmccul002
author_rank: Newbie
timestamp: November 15, 2016, 06:18:17 pm
content: Does anyone have any hi-res pics of the wiring connectors of the hakko fm-2027 or 2028?

author: cmccul002
author_rank: Newbie
timestamp: November 20, 2016, 03:53:41 am
content: I'm trying to rewire a knock-off HAKKO FM-2028 I ordered, for use with my NON-Knockoff FX-951. It caused S-E errors on the base, and upon taking the handle apart, I found wires loose from their connections and wires soldered to the wrong connector pins (Using info from the FX-951 manual troubleshooting section)I'm trying to use pics and info for the FM-2027.Okay, so a lovely fellow on Youtube, BDub uploaded some great pics for me here:https://imgur.com/gallery/hpvvIAlso this gentleman posted some pics for me:http://www.eapbg.com/single-post/2016/07/02/eapbg-20-New-soldering-station-Hakko-FX951So the real FM-2027 has 5 wires, the 3 Primary wires: Red,Black (with a capacitor between them) and Green. The other two are Blue and White, and from the attached pics it looks like the Blue is for the LED in the handle.My knockoff has only 4 wires, which I assume is because there is an LED in the FM-2027, but there is none in my 2028 knockoff.The White is the one Im having trouble with. From the pics, and from what a different owner described to me, the White wire goes to another terminal in the middle of the T12 tip harness, then to the Black wire terminal. His exact description wasIt is wired to the Soldering Tip harness. A small bare wire goes from that point to the black wire. Not sure what it does.?The tip harness on mine doesnt have a middle pin. The white wire was soldered to a little black ball (a capacitor?) that was then soldered to the black wire.Also, on the Connector end, where the Blue wire would be for the LED (Pin 6) is jumpered to Pin 4. I included the troubleshooting section from the FX-951 manual.Trying to figure out how the temp sensor is monitored in this handle. Looking over the homemade drivers for these T12 iron tips, there are 2 contacts for the mains (Red and Black) and the Ground. So what would the White wire be connecting to in the handle?Any help would be appreciated.
HP 3324A Display - Page 1
Forum section: electronics / repair

author: wn1fju
author_rank: Frequent Contributor
timestamp: November 27, 2016, 02:35:37 pm
content: Took a chance on eBay and lost. Although the unit works fine, I can't see what I'm punching in on the front panel for obvious reasons (see photo).Anybody out there have a parts mule and would be willing to sell me the display board?(Alternatively, I could convert mine into a parts mule if there are boards anybody needs.)

author: JoeO
author_rank: Frequent Contributor
timestamp: November 27, 2016, 05:31:00 pm
content: Add your location to your profile. It may help since you are requesting parts.

author: TAMHAN
author_rank: Frequent Contributor
timestamp: November 27, 2016, 06:45:58 pm
content: Hello,on the risk of a beating: this sounds like a fun project for an Arduino and an OLED display.
Rework Exposed pads - Page 1
Forum section: electronics / repair

author: RBeaubien
author_rank: Newbie
timestamp: November 18, 2016, 04:21:07 am
content: Ok, I'm hoping there is a trick to this. How do you remove SMD chips with exposed pads (like the MP1584EN or the MAX7456-EP)? I have boards with defective chips and when I try to remove the chips, I end up having all the other components around them come off BEFORE I can heat the chip up enough for the exposed pad to release. I'm talking 4-5 minutes here at 750°F. Any guidance would be appreciated.

author: rigrunner
author_rank: Frequent Contributor
timestamp: November 18, 2016, 05:22:24 am
content: Hopefully this will help?If the board is densely populated I use the smallest nozzle i have and around 360-380C/680-716F. Circle the IC about 2.5cm away.If that fails i run a fine wire under the legs on one side of the IC and user an iron to melt the solder as i gently pull the wire up, lifting the pins as it goes.If that fails, and it rarely does, i cut the legs from the IC package with a scalpel and remove the remains with an iron.RR

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: November 18, 2016, 05:51:33 am
content: These chips are both SMD TSSOP or SOIC.......Use Chip Quik and an iron or with a heat gun. I found using a iron works well!http://www.chipquik.com/store/

author: Rasz
author_rank: Super Contributor
timestamp: November 19, 2016, 05:06:25 pm
content: preheat the pcb?
Asus Transformer TF300 - Page 1
Forum section: electronics / repair

author: Bondguy
author_rank: Contributor
timestamp: November 16, 2016, 09:21:18 pm
content: I have Asus Transformer TF300 tablet where digitizer( touch screen) does not work. More digitizers were tested yet none worked.So I guess it is a problem on mainboard. The digitizer does not have any Touch Controller on its flat cable so I think there must be one on the tablet mainboard. That touch controller can be faulty but also paths to the digitizer or there can be any other reason why the touch screen does not work.Can anyone suggest a procedure how to try to repair that problem? Thank you for your advice.

author: singapol
author_rank: Frequent Contributor
timestamp: November 17, 2016, 01:51:07 am
content: Check the power supply? But I suspect some smd electrolytic capacitors may have higher esr.Do you have esr meter to check in-circuit?

author: stj
author_rank: Super Contributor
timestamp: November 17, 2016, 02:20:17 pm
content: i had this on a TF103, reflow the controller i.c.can you post a foto with the rear cover removed?

author: wraper
author_rank: Unknown
timestamp: November 17, 2016, 02:32:55 pm
content: Quote from: singapol on November 17, 2016, 01:51:07 amexcept there is none.

author: wraper
author_rank: Unknown
timestamp: November 17, 2016, 02:38:42 pm
content: Quote from: stj on November 17, 2016, 02:20:17 pmyep, if there are no signs of corrosion, likely you would need either replace or reball touch countroller IC. In small portable deices it is not uncommon solder balls coming off on mechanical impact. you could try pressing on it (starting doing so before powering on) and see if touchscreen starts to work.

author: stj
author_rank: Super Contributor
timestamp: November 17, 2016, 04:48:50 pm
content: no need to replace or reball, just put flux under it and re-flow it.it's a "flip-chip" package, and on the T103 is on a sub-board.

author: wraper
author_rank: Unknown
timestamp: November 17, 2016, 04:55:02 pm
content: Quote from: stj on November 17, 2016, 04:48:50 pmUsually this does not help to make a solder joint again, as pad needs to be retinned before solder sticks to it again. Also IC may be underfilled.

author: stj
author_rank: Super Contributor
timestamp: November 17, 2016, 05:19:49 pm
content: your talking theory's to somebody who has already done it.there is no underfill on these, and no oxide issues - just cracked solder joints probably caused by flexing of the pcb with a long and thin chip on it.

author: wraper
author_rank: Unknown
timestamp: November 17, 2016, 06:00:52 pm
content: Quote from: stj on November 17, 2016, 05:19:49 pmYou are talking with one who professionally repaired mobile phones for many years. The thing is, you are left with bare oxidized copper on one side and solder ball on other.

author: stj
author_rank: Super Contributor
timestamp: November 17, 2016, 07:07:14 pm
content: it's not a fone - the chip is not that small.

author: Rasz
author_rank: Super Contributor
timestamp: November 19, 2016, 05:04:57 pm
content: you are both correctreflow, then reball if still broken
HP 16702A won't boot - Page 1
Forum section: electronics / repair

author: Daxxin
author_rank: Regular Contributor
timestamp: November 17, 2016, 06:11:39 pm
content: Looping with this screen , don't have any cd scsi its possible to reinstall by network nfs etc ?

author: PaulAm
author_rank: Frequent Contributor
timestamp: November 18, 2016, 05:43:33 pm
content: Start looking for a SCSI 2 CDROM; you can find them for $15-20 if you're in the US. Don't forget the terminator.AFAIK the only choice of boot devices is the CD or an attached hard drive.I put an 18G drive in mine and added a bunch of open source software to make it usable (bash, gcc, etc). There's still a repository with HPUX 10.2 executables available.Upgrade time
Agilent E3646A repair - Page 1
Forum section: electronics / repair

author: STMartin
author_rank: Contributor
timestamp: November 17, 2016, 04:28:43 am
content: I'm trying to re-repair an Agilent E3646A power supply.I had bought it broken from EBay, and diagnosed the problem to a bad zener diode in the -15V bias supply. I had some confusion with the value of the zener, as they were marked 5.6 on the schematic, and to my estimation should have been 2.4V. Inaccurate schematics aren't unheard of, so I desoldered the surface mount diodes for both the +15V and -15V rails (they have the same part number), and measured the reverse bias voltage.The bad diode was 0.6V both ways, while the good diode was about 0.7V forward, and 1.7V reversed. I measured a new 2.4V through hole zener, and found it's reverse voltage was about the same as the original good diode. I soldered in two 2.4V through hole zeners to replace the old ones, just to make sure it worked before I ordered proper surface mount replacements. The supply fired right up, passed the full self test, and everything worked great.When checking the bias supply voltages again, I accidentally shorted the two zeners together. The magic smoke got out, and despite my attempts to stuff it back in, the only thing I accomplished was to curse and yell for thirty minutes. I replaced both diodes again, and now I'm faced with a new problem.The display test comes on, all the segments light, but then it goes blank and beeps twice. According to the service manual, this is error 601, "Front Panel does not respond".A link to the service manual:http://exodus.poly.edu/~kurt/manuals/manuals/HP%20Agilent/HP%20E3646A,%2047A,%2048A,%2049A%20User.pdfThe diodes I shorted are CR139 and CR140 on page 212In my travels to diagnose this problem, I have:Checked the bias supply voltages as listed on page 171. All are within spec.Checked every voltage regulator, all are OKChecked the ribbon cables and connectors for continuity and intermittent connections, all are OKEnsured the PC board and front panel have the correct supply voltages, and they doPrayed to any deity who might listen, none have respondedAt this point, I'm not really sure what to look at next. Do I start checking op-amps? Poke around on the display board itself? That option would suck since the components are buried behind the VFD and I'd need a mile of solder wick to get it off.Any advice from those better at this than I?
Burn smd resistor - Page 1
Forum section: electronics / repair

author: atgeek
author_rank: Contributor
timestamp: November 22, 2016, 04:43:51 pm
content: I've a thermostat board that is drived by a mcu. The power part consist in a transformerless power supply, the main 220v pass through a 1.5uF capacitor, then from a half wave rectifier diode and finally there are 2 resistor that provide power for a 78l05 voltage regulator. The 2 resistor were burnt, what could be the appropriate resistor value?

author: wraper
author_rank: Unknown
timestamp: November 22, 2016, 05:24:49 pm
content: So you are injecting unlimited voltage into 78L05

author: atgeek
author_rank: Contributor
timestamp: November 22, 2016, 05:45:23 pm
content: Why? There are the resistors in series with 78l05 input

author: wraper
author_rank: Unknown
timestamp: November 22, 2016, 06:05:14 pm
content: Quote from: atgeek on November 22, 2016, 05:45:23 pmSo what? Remove load from the output of 78L05 and you will should have way above it's maximum input voltage. Limited only by current consumption of 78L05 itself (and voltage drop of those resistors you are trying to add). If resistance of those resistors is low enough to provide low enough voltage drop to make any sense, 78L05 will blow up. If those resistors have high enough resistance to protect 78L05 in such situation, they will burn themselves (unless they are high power). What is resistance of those unnamed resistors?

author: atgeek
author_rank: Contributor
timestamp: November 22, 2016, 06:09:50 pm
content: I don't know the resistance since they are burnt

author: kxenos
author_rank: Frequent Contributor
timestamp: November 22, 2016, 06:51:20 pm
content: Assuming you have max 170Vdc in the divider's input you can place a 13k 3W and a 3k 1W. This will give about 32V max in the input of 7805 when it sinks no current and it will give about 7.5V when it sinks about 8,2mA. The current drawn from the source would be about 10,7mA which is 1,5W of power in the 13k resistor and about 0.35W (max) in the 3k resistor.If you power your 7805 from a bench power supply and you determine that you don't need 8mA of current, you can increase the resistor's values accordingly.
Sanyo JCX 2900KR Power Stage Adjustment - Page 1
Forum section: electronics / repair

author: Nebukad
author_rank: Contributor
timestamp: November 16, 2016, 10:13:24 am
content: Hi there,I've been working on an old Amplifier/Receiver for quite a while now. It is the Sanyo JCX 2900KR - the biggest version of this Amplifiert that was available at that time (~1978).I've already done several things to it like replacing the burnt X-Class Caps on the Mains-Input, changed the Output-Relays and cleaned some of the switches.But there is one thing I could not figure out yet, whitch is the Adjustment Procedure of the Power-Stages. Each PowerStage (Left and Right Channel) has two pots on it, one says "BIAS" (SVR702) and the other one says "CENT" (SVR701). Please refer to the attached part of the schematic.Sure enough, the BIAS-Pot controls the Bias-Current for the Power-Transistors. It can be measured by measuring the voltage on the power-resistors on the Emitters (R724 and so on). It adjusted the current to give me about 7mV on each resistor resulting in ~14-15mA bias-current. This is about the maximum bias-current I can get. Since the Powerstages don't get warm at all I think choosing the highest possible bias-current can't be to bad of an idea.Strangely though the CENT-Pot does not adjust the DC-offset as one would think. Both channels have almost no DC offset (-1mV and +3mV) so this is not really a problem. But still I would like to know, what this Pot is doing and how to set it.Sadly the Service-Manual does not deal with the adjustment of these pots. There are several pages about the adjustment of the Tuner-Section but the Pots on the Power-Stage are not mentioned with any word.So if anyone has any information or experience in the Adjustment procedure of these power stages it would be great to get some information on that.Maybe someone, who is more into the design of Class AB-Amps, can figure out what the CENT-Pot is doing in that amplifier-stage and how it should be set.Thanks in advance!
Vintage DECtalk voice synth repair  - Page 1
Forum section: electronics / repair

author: artelse
author_rank: Regular Contributor
timestamp: November 15, 2016, 08:39:17 pm
content: On the desk I am attempting to repair a DECtalk voice synth from about vintage 1990. It sports a 80C186XL10 and a 87C51 and various logic, an AD7541 ADC, etc. Several caps were leaking and replaced all with equivalents. Also a voltage inverter LT1054 died and replaced it. Still the device outputs nothing sensible through the serial port and no voice greeting.I do measure rather high peaks on the databus, up to 10Vpp.. due to ringing? I checked the 5V supply and it got some dirt on it, but can this cause the ringing on the databus pulses? Can these peaks damage anything? See the attached images: databus, Vcc and clock-out from the cpu which isn't that great either.Any advice is greatly appreciated.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: November 16, 2016, 05:37:55 am
content: Where is the probe ground connected compared to the pin you are checking? How long is the grounding wire? There could be some ringing if the ground is too long.

author: artelse
author_rank: Regular Contributor
timestamp: November 16, 2016, 07:46:22 pm
content: Good question. First I had a longer ground wire for easy probing over the board. Then I shortened it to the regular ground wire of approc.10cm and connected it right to the chip-under-test. I saw some reduction of ringing, but not what I hoped to see.Any other idea?Quote from: Tomorokoshi on November 16, 2016, 05:37:55 am