hybridfree/eevblog-posts huggingface dataset:
Need help to repair Hot Rod Deluxe transistor switching circuit EDIT SOLVED - Page 1
Forum section: electronics / repair

author: Planobilly
author_rank: Regular Contributor
timestamp: February 19, 2017, 05:02:21 pm
content: Hi,The issue: The "more drive" circuit is not working.Three amp techs have looked at the amp without results. Link to schematichttp://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Hot-Rod-Deluxe-Schematic.pdfI have replaced many of the components in this circuit.Test point readings:Per schematicTP 31+1.37 +1.07 +1.07ActualTP 31+1.36 +1.09 +1.09Per schematicTP 32+.548 +9.76ActualTP 32+.498 +9.78Per schematic TP 33 +16 -13.5 -13.9Actual TP 33 +16.37-10.17 -10.17Per schematic TP34 -13.0 -5.46 -4.96Actual TP34-11.88 -12.11 - 12.11Per schematic TP 35 -.54 -10.0Actual TP 35 -.51 -9.5Per schematic TP 36 -16 -16 +16Actual Tp 36 -16 -16-16I have verified all resistors and zener diodes and changed any that were out of value. I replaced the op amp which was a 4558 on the board from the MFG but shows a 4560 on the schematic. The only difference in the two op amps is the slew rate. I replaced the two JFETs and Q3 and Q4 transistors. The push button switches are working correctly.It is obvious that the voltages at TP33, pin 7 of the op amp are not correct. TP34 is not correct, and the voltage at TP36 does not change to positive.I can provide any other measurements that may help.Anyone have any ideas of what to do next?Thanks,BillyEDIT...sorry about the schematic...you will need to go to the link2nd EDIT...the 4558 op amp that was in the amp would not work correctly. I installed a 5532 and that works. Other strange issue...the combo LEDs are not red and yellow but red and green which makes yellow when both are lit and shows red when the green LED is turned off.
HP 3455A AC or DC same reading - Page 1
Forum section: electronics / repair

author: ebaker
author_rank: Newbie
timestamp: February 09, 2017, 04:50:22 pm
content: I have three 3455A's that I recently ebay'd. They all seem to read fine DC wise, but with a DC supply on the front or rear terminals (2-wire), one reads almost the same on the AC setting while the others converge to nearly zero as they should. Anyone encountered this before?I have checked the supply voltages and they look to read within the tolerances. I did notice this one has a darker display than the others but it also looks darker when off like it has a darker tint to the filter in front of the LEDs.

author: Krytron
author_rank: Contributor
timestamp: February 11, 2017, 01:15:47 am
content: Its been a long time - I donated my 3455A - but I believe it had AC and DC coupling that could be selected in the AC mode. A real True RMS meter will read DC on the AC input. I think it had a switch that allowed this.On one of my hand held meters, a Beckman true RMS unit, this is also a check for the True RMS converter, to apply DC instead on AC and verify it reads the same.I think the 3456A was a close made unit to the 3455A, which I ended up with several of them.Check the manual on the 3455A and see what the coupling options are on the AC mode.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: February 11, 2017, 02:54:09 am
content: On the rear of the meter there is a hidden switch to choose between AC or AC+DC modes. I bet the AC+DC mode switch is enabled on that meter. The info is located in the manual inside section 3.

author: ebaker
author_rank: Newbie
timestamp: February 17, 2017, 01:50:01 am
content: I wanted to swing back around and let you guys know that you nailed it. So why would you want to bypass the ac coupling cap on the true RMS circuitry - LF AC? It was interesting that when measuring DC with this switch enabled did not quite yield the same value as when it was open. Many thanks for the help.
TTi PL303QMD-P PSU displaying "Fail 4" - Page 1
Forum section: electronics / repair

author: KSP
author_rank: Regular Contributor
timestamp: February 21, 2017, 08:40:03 am
content: The PSU powers up just fine, will even output voltage for a short time, then will cut the output, freeze up, and just display "FAIL 4" on both channels. I can't seem to find any info on this failure, even the guy I spoke to at TTi didn't seem to know (granted, I believe he was more of a sales rep than a repair engineer).Anyone got any insight into this one? This is the second PSU I've had with this fault.

author: voltsandjolts
author_rank: Unknown
timestamp: February 21, 2017, 08:52:50 am
content: Might be worth re-flashing the firmware to eliminate that - firmware on TTi site.Could it be related to the network interface? I say that because normally a short time after power on (30 secs?) LAN ERR will flash up if there is no network connection.Is the delay you see (until FAIL 4) the same as the delay to the usual LAN ERR message?

author: KSP
author_rank: Regular Contributor
timestamp: February 21, 2017, 09:48:07 am
content: Thanks for the input, but reflashing the firmware was the first thing I tried, to no availBut yes, the time between power up and the failure is pretty reminiscent of a LAN timeout, so maybe you're on to something! I shall investigate

author: KSP
author_rank: Regular Contributor
timestamp: February 21, 2017, 10:15:36 am
content: My mistake, I was thinking of the other PSU I'm working on! This one refuses to flash the firmware, the firmware flasher just freezes up. And yes, I did remember to put it in firware update mode (holding LAN reset on power up). But also worth noting that this one isn't detected at all by NI-MAX via usb (windows doesn't see it either for that matter), or LXI Discovery Browser by LAN connection.So is the interface board dead then? If so, any recommendations for an attempted repair?
DC Boost Converter Repair - Page 1
Forum section: electronics / repair

author: raf13005
author_rank: Newbie
timestamp: February 16, 2017, 10:06:32 pm
content: Hi Everyone, I am building a secondary battery system to charge my main hybrid battery while i am driving (2006 insight).I am using two isolated battery packs to power two non-isolated 1.5kW boost converters wired in series (Any thoughts on this approach?). Anyways i accidentally reversed the input polarity to one of the boost converters and a chip exploded...Unfortunately for some reason this chip and the main controller IC are defaced so there is no visible part number. It would be really nice if anyone recognized what the broken chip might be?In the pictures the chip that is damaged is U3. The first 4 pins of the chip are attached to the negative of the input capacitor bank. pin 6 is attached to a small inductor, tiny surface mount cap, and a diode, pin 5 is attached through a via to the positive rail of the input capacitor bank. The chip labeled U2 is a lm358 op-amp maybe used for CCCV regulation or possibly temp monitoring.There is a NCE 80h16 mosfet directly under the board. I am wondering if the mosfet, inductor, electrolytic capacitor, D5, and the broken IC make up a buck circuit for the fan to run?I assume the chip covered under the white glue is a dc-dc boost converter management IC...Anyways I am mostly hoping someone will know of any common chips that could have 4 pins wired together that could be used in dc boost converter management circuit.the board is only 25$ but seems like a waste to throw it out if just one tiny IC is broken...This board btw.http://www.ebay.com/itm/like/131945193257?lpid=82&chn=ps&ul_noapp=true
Keithley 213 Quad Voltage Source - GPIB - Page 1
Forum section: electronics / repair

author: k1mgy
author_rank: Regular Contributor
timestamp: January 27, 2017, 08:19:51 pm
content: I've removed a Keithley 213 Quad Voltage Source from the shelf with a thought that perhaps it might be made useful at last. It sat on the shelf because I could never talk to it over the GPIB and that's the only way to enable outputs.Anyone here have experience with this?I can't afford the National Instruments software, which seems to be the only option...

author: Assafl
author_rank: Frequent Contributor
timestamp: January 28, 2017, 10:45:00 am
content: NI offer Labview for makers for 50$. It is the 2014 version and works really well.I also got the original Agilent 82357B for about 90$ (local electronics junkyard).And got the raspberry pi for metrology project (see on the metrology forum). I use it control and log a DMM and power supply using Python scripts.Turns out RPi comes with a free version of Mathematica so I am now trying to see if I can connect the two.

author: k1mgy
author_rank: Regular Contributor
timestamp: January 28, 2017, 01:40:10 pm
content: Assafl: Thank you very much.I did a bit more research and found the NI Drivers (I have the NI USB interface) and a GPIB toolkit by KE5FX. In the toolkit is a command line tool called query. The Keithley is at address 9 and I see it on the buss when using another tool.When I send the 213 a command, I consistently get back a reply that looks like it's trying to send me some data.A1C0P1R0V+00.00000The error LED on the 213 is lit after sending any command. If I ask what the error is using E? I get the same:C:\Program Files (x86)\KE5FX\GPIB>query.exe 9 E?A1C0P1R0V+00.00000Any clue what this is?

author: k1mgy
author_rank: Regular Contributor
timestamp: January 28, 2017, 02:15:40 pm
content: Never mindI got it.Had to power-cycle the Keithley 213.Also, am now using EZGPIB, which provides a simple programming interface. Quite powerful.http://www.ulrich-bangert.de/html/downloads.html

author: k1mgy
author_rank: Regular Contributor
timestamp: January 29, 2017, 01:45:50 pm
content: A1C0P1R0V+00.00000 is a status output. It's listed deep within the Keithley 213 manual.

author: cncjerry
author_rank: Unknown
timestamp: February 15, 2017, 08:52:43 pm
content: PM me if you need help. I have a 213 and have done a lot of GPIB with it with Visual Basic. I started to write an entire app for controlling it, got part way, but I know the device inside and out.Jerry

author: k1mgy
author_rank: Regular Contributor
timestamp: February 15, 2017, 09:09:00 pm
content: Thanks very much!Maybe we can port your VB stuff to C.
R&S FSEB30 Display Backlight - Page 1
Forum section: electronics / repair

author: phillip.hodges
author_rank: Newbie
timestamp: February 15, 2017, 09:03:26 am
content: Hi, I recently bought an FSEB30, however, the screen has started to go very dark. I believe it is the backlight tube!? The actual picture is perfect so I don't think it is an issue with the LC.Does anyone know where I might get a replacement set of tubes? Or if there is an alternative available? - I did see a thread a while back where someone replaced the tubes with a strip of LEDs.Thanks in advance,Phil

author: CJay
author_rank: Super Contributor
timestamp: February 15, 2017, 12:33:06 pm
content: Certainly seems to be an issue with the R&S LCD panels, I started a thread for information more than anything with some detail on the CCFL in the CMU200 but my fault was the reflectors around the tube had broken loose and were masking the the light output.There's a link in the last reply from another member who had successfully replaced the CCFL with LEDhttps://www.eevblog.com/forum/repair/rohde-schwarz-cmu200-lcd-backlight-success/http://www.rbarrios.com/projects/LCD2LED/
HP 3312A function generator sweep/FM modulation not working - Page 1
Forum section: electronics / repair

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 14, 2017, 10:40:30 pm
content: I just acquired a rather clean HP 3312A and the thing is working pretty well bar the sweep and FM modulation. AM is working absolutely fine.Does anyone know of any usual issues/bugbears in these before I print out the SM and dig into it?Have some porn for now:
The Led TV LED - Page 1
Forum section: electronics / repair

author: naldo
author_rank: Contributor
timestamp: February 12, 2017, 06:32:53 am
content: On a LED TV if instead of replacing the LED put 1 DIODE in place if you notice any difference in the brightness (image) of the tv ??, and when it is 2 leds (1 away from the other) ??. What are the types of glue that can be used to attach the LED deflector? Thank you 1 return!

author: naldo
author_rank: Contributor
timestamp: February 12, 2017, 09:27:05 pm
content: Good evening, friends, any tips ??

author: Rasz
author_rank: Super Contributor
timestamp: February 12, 2017, 11:42:11 pm
content: 1 no image2 google translate?

author: BMack
author_rank: Regular Contributor
timestamp: February 14, 2017, 05:26:23 am
content: If the TV is full array, you might notice but probably not. If it is edge-lit, there is no chance you will notice.A lot of the LG and Samsung full array TVs I've replaced LEDs on have had multiple bad, they only fail if the LED blows open. If the LED shorts you will have a dead LED but the TV will still work.
Tracing the failure source on a mosfet RJK0389DPA (Motherboard repair) - Page 1
Forum section: electronics / repair

author: Stonent
author_rank: Super Contributor
timestamp: February 12, 2017, 08:33:33 pm
content: I have an HP Elite 8300 motherboard that I purchased off of ebay that worked great for all of about 10 minutes and then released the magic smoke on a MOSFET (RJK0389DPA). The board was on an insulated surface with a known good power supply.It's past the return point because I ordered it before several other parts that I ordered much later before I could test it.I want to hopefully determine which direction from the chip to look where there could be a problem. There are no schematics for this board so I'm working blind in that respectRight now the board powers up and I see the BIOS text for about 3 seconds and then the board powers down.Here is the datasheet:https://4donline.ihs.com/images/VipMasterIC/IC/RNCC/RNCCS17891/RNCCS17891-1.pdf?hkey=EF798316E3902B6ED9A73243A3159BB0The Magic Smoke hole appeared between Pin 4 and 9.Based on the design with the two internal MOSFETs are they trying to spread the load or something else?I've attached a picture of the board (not my exact board but an identical one)All 12 MOSFETs in the top right corner are identical. I'm guessing they are lined up with the inductors that they are feeding into it and then the CPU.http://imgur.com/a/OJxTs

author: Rasz
author_rank: Super Contributor
timestamp: February 12, 2017, 11:37:18 pm
content: first remove that fried partbooting for 3 seconds means there is a very good chance its easily fixable. It might even start working fine after removing this mosfet alone(obviously at a cost of bigger load on the rest, should be a problem with weak cpu like pentiums), or bios enables power saving modes and disables half the CPU power rails (standard on never intel platforms). There are bioses that let you control for that (all ASROCK for example), but hthis is HP so no options for you.
Help to identify manufacturer / line of European threaded connector - Page 1
Forum section: electronics / repair

author: rbm
author_rank: Regular Contributor
timestamp: February 24, 2017, 01:27:01 am
content: Hi, I picked up a Greiner watch microphone stand (Swiss made) which has a female threaded electrical connector in the base. I'm looking for the mating male end that will allow me to hookup the amplifier lead. The receptacle looks like this:A complete stand with a mating cable appears like this:It is an M8 x 1.0 thread with a single coaxial style contact in the centre. I've searched Mouser and Digikey catalogs for a similar item but have failed to locate anything. The closest I've come is a Switchcraft 2501F or Amphenol-80-75-MC1M but they are too big. Maybe one of the European members of this board will be able to ID the manufacturer for me.

author: Unknown
author_rank: Unknown
timestamp: February 24, 2017, 04:59:43 am
content: Any chance it's not M10 but 3/8"? That might make it a Switchcraft 5501 series, which was sometimes used on smaller gear.

author: rbm
author_rank: Regular Contributor
timestamp: February 24, 2017, 10:28:30 am
content: I will attempt to verify that the thread is a 3/8" x 32 instead of M8 x 1.0. If so you may be correct. Thank you very much for the lead.

author: Armadillo
author_rank: Super Contributor
timestamp: February 24, 2017, 10:46:34 am
content: you can easily custom make it. Just use a suitable size cable gland with the thread and a spring test pin in the centre, epoxy the assembly with wire out of the assembly.

author: rbm
author_rank: Regular Contributor
timestamp: February 24, 2017, 11:18:34 pm
content: Tac:I made some more measurements and conclude that the Switchcraft 5501M won't fit. The thread size on the connector is too fine (32) for the pitch in the base (24 or 1.0mm).Armadillo:That's the path I'm going to take. Surprisingly, I found a threaded plastic housing in my stash that fits perfectly in the thread. I'm going to use a spare Amphenol connector for the center conductor and spring copper for the ground contact which I'll locate in the slots so that they brush up against the threads in the base. I'll encase that assembly in epoxy as you've suggested and bring it out to a shielded twisted pair. Thanks for weighing in on this discussion.
Lowe HF-125 resistor identification - Page 1
Forum section: electronics / repair

author: jkf1000
author_rank: Regular Contributor
timestamp: February 10, 2017, 08:30:07 pm
content: I am just in the process of checking my receiver prior to sale and I found a burnt resistor R6 top right on the keypad interface board. I have looked through the manual and googled for more info but have not been able to identify the correct value for a replacement. If there is any one out there with the same or similar receiver could just pop the lid and check for me it would be greatly appreciated. The receiver itself appears to be working 100% and the current measured value accross the resistor in circuit is around 73ohm. Thanks in advance.. Karl

author: Andy Watson
author_rank: Super Contributor
timestamp: February 11, 2017, 02:48:48 pm
content: Looks to be either 56\$\Omega\$ or 560\$\Omega\$ in this picture:http://radiopics.com/By%20Make/Lowe/Photos/Lowe_HF-125_Keypad%20Option.jpgI favour 56\$\Omega\$ because I think the ring colour looks black and also it would be difficult to fry a 560\$\Omega\$ with the 12V supply of the radio. Does this radio use the same keypad as the HF150? - If it does you could possibly compare the schematics - I'm guessing that that resistor is used to supply power to the keypad and will be overstressed if the jack-socket is shorted.

author: jkf1000
author_rank: Regular Contributor
timestamp: February 11, 2017, 05:17:29 pm
content: I made the same assumption about powering the keypad. It may be that it has been shorted by plugging in the keypad while the unit is powered. I am not sure if it is the same as the 150 model and I haven't done any reverse engineering but I will explore deeper before replacing it. Personally I still think it is a 560but not 100% certain. May try that first and check for full operation but with only a shortlist of two values it should be a fairly straightforward fix.. Karl

author: jkf1000
author_rank: Regular Contributor
timestamp: February 11, 2017, 05:52:38 pm
content: Just checked the HF-150 and 225 manuals which supply a full schematic for the keyboard interface (same interface in both) but unfortunately they are different to the earlier 125 model. I am going to try a 560 ohm first and if that works ok leave it at that. On the later models the keypad is fed from a 150 ohm resistor but running off a 8v supply line. Nothing to lose by trying.. Karl

author: RayRay
author_rank: Frequent Contributor
timestamp: February 11, 2017, 09:45:06 pm
content: You might find the schematics handy!http://www.dream-machine.myzen.co.uk/Lowe/HF-125%20(Schematics).pdfGood luck.

author: jkf1000
author_rank: Regular Contributor
timestamp: February 12, 2017, 12:35:16 am
content: Thanks for the link but unfortunately the interface board isn't included on any of the schematics I have found, only the main board. I have measured a few voltages and have fitted a 56ohm as a replacement and now everything is back working perfect. thanks to all for their input.. Karl
SMSL MINI5 Audio Amp Repair - Page 1
Forum section: electronics / repair

author: sean0118
author_rank: Frequent Contributor
timestamp: February 21, 2017, 11:45:50 am
content: I recently repaired a 50W SMSL MINI5 Audio Amp. The symptoms were the speakers only emitting a strange static sound and the amp would start to heat up and smell burnt.All four solder joints were broken on the header connector for the speakers. However, resoldering did not fix the amp.It appears that a very corrosive epoxy had been used to glue down the inductors to the board! This stuff was so corrosive that it had started to eat into the copper of the PCB, making it flake off and expand, creating shorts in the output stage.In the image below the corrosion has been scraped off the PCB where the top inductors were soldered (they were really bad) and then polished with Silvo. You can still see some corrosion on the bottom inductor footprints.The copper under the top left inductor was still shorting out after I took this photo, so I used a knife and tweezers to widen the clearance gap. Under the copper PCB material had turned to a grey powder, nearly eaten through the board from heat etc.Anyway, this is just a heads up because it might be a common problem with this model?edit: forgot to mention, it works perfectly now the corrosion has been removed...
Makita dc18ra repair - Page 1
Forum section: electronics / repair

author: reisrdok
author_rank: Newbie
timestamp: February 01, 2017, 04:15:52 pm
content: Hello!I am trying to fix coworker's Makita charger. Originally it started to show "faulty battery" with all batteries. I noticed that a 0.1 ohm (0.25 watt?) resistor was blown from pcb because a diode had shorted out.Now I need to identify that diode. Markings on the side are: F16VB1. Pic (bad) attached.Can someone help a noob out? Is it a zener, or can I just throw 1N4007 there?

author: reisrdok
author_rank: Newbie
timestamp: February 10, 2017, 06:12:21 am
content: Replaced D3 with 1N4007. R64 is a fuse for this diode, covered in heatshrink.Charger seems to work now.
Racal-Dana 1992 voltage selector pinout - Page 1
Forum section: electronics / repair

author: kyleaudio
author_rank: Contributor
timestamp: February 09, 2017, 03:17:43 am
content: I just picked up a broken Racal-Dana 1992 frequency counter and the input voltage selector is missing. I assume that it is just a small circuit board with a card edge connection.Does anyone out there have one of these counters and can upload pictures and/or a pin-out?Thank you,Kyle

author: bitseeker
author_rank: Super Contributor
timestamp: February 09, 2017, 03:57:20 am
content: Hi Kyle,Here's the voltage selector PCB from one of mine. I've composited the photos of both sides and numbered the PCB holes so you can tell how the two sides align. Metric ruler scale included for reference.Hope that helps.

author: kyleaudio
author_rank: Contributor
timestamp: February 09, 2017, 04:46:45 am
content: Hi bitseeker,Perfect! That'll give me what I need to make a new one of my own. Thank you getting these pictures!Kyle

author: bitseeker
author_rank: Super Contributor
timestamp: February 09, 2017, 04:51:18 am
content: Quote from: kyleaudio on February 09, 2017, 04:46:45 amSure thing. I look forward to seeing how your replacement board and the rest of the 1992 turns out.

author: CJay
author_rank: Super Contributor
timestamp: February 09, 2017, 06:32:00 am
content: Looks identical to the one in the 1998 as well.Just as reference in case anyone else stumbles across this thread.

author: bitseeker
author_rank: Super Contributor
timestamp: February 09, 2017, 06:44:41 pm
content: Good to know. Thanks, Jay.

author: kyleaudio
author_rank: Contributor
timestamp: February 10, 2017, 02:01:39 am
content: Good news, I temporarily soldered some wire across the right pins and it powered up! All of the buttons are working well too! It appears to have been dropped on the rear panel where the power cord connects, so I have to replace the power connector and the fuse holder but that'll be easy.Thanks for the help!

author: bitseeker
author_rank: Super Contributor
timestamp: February 10, 2017, 02:55:30 am
content: That's great news, especially that the keyboard is working properly. Enjoy it!
What is this - Page 1
Forum section: electronics / repair

author: dan3460
author_rank: Frequent Contributor
timestamp: February 09, 2017, 02:44:04 am
content: I'm pretty sure that Dave made a video of something similar but cannot find it. It looks like the transparent surface is some kind of crystal. The thickness of the "crystal" is about 2mm. There are two pins that connect to something on the edge of the lower part of the oblique cut and two that do the same thing on the top part.Whatizit?

author: dan3460
author_rank: Frequent Contributor
timestamp: February 09, 2017, 02:54:35 am
content: Found ithttps://commons.wikimedia.org/wiki/File:Glass_delay_line.jpg

author: isometrik
author_rank: Regular Contributor
timestamp: February 09, 2017, 03:04:48 am
content: FYIDave has covered glass delay lines in these videos:(from21m00s)

author: dan3460
author_rank: Frequent Contributor
timestamp: February 09, 2017, 12:12:09 pm
content: Is there anything cool that could be done with them, I found an old box with electronic parts and I probably have 25-30 of them. Maybe that can be a contest, What to do with a bunch of glass delay lines?

author: Ian.M
author_rank: Super Contributor
timestamp: February 09, 2017, 12:41:33 pm
content: http://hackaday.com/2012/11/09/storing-32-bytes-of-data-in-a-piece-of-glass/You could build a 1Kbit memory with 16 of them, reshaping the pulse in between each unit. Its the perfect accompaniment to a discrete transistor CPU.

author: Theobald
author_rank: Contributor
timestamp: February 09, 2017, 01:40:24 pm
content: Hi,it was also used in analog TV set for chroma decoding.Theo.

author: tronde
author_rank: Frequent Contributor
timestamp: February 09, 2017, 08:35:02 pm
content: Hi-tech from the early 1970's.Chroma delay from Philips K80 chassis. Grandad of the type in the first post.K80 was the last of the glow-in-the-dark type chassis(tubes).Obviously no beancounters at Philips back then.120 x 49 x 19mm, weight 176g. The metal chassis is made of 0.75mm steel.Last two pictures shows the piezo transmitter and receiver attached to the glass.Service manual for the K80http://www.philipstv.org.uk/blog/early-philips-colour-tv/continental-cousins/continental-manuals/philips-k80-service-manual/The chroma delay is TD570 i lower left part of this diagramhttp://www.philipstv.org.uk/blog/wp-content/uploads/2012/03/img048.jpg
FIXED: JBL BALBOA SUB/230: diagram needed - Page 1
Forum section: electronics / repair

author: Theobald
author_rank: Contributor
timestamp: February 09, 2017, 02:58:46 pm
content: Dear All,this JBL Balboa Sub is quiet. Voltages +/-45V and +/-15V seem OK , Power On led is bright, PCB clean, no smoke, but ... in silence.Do you have the schematic ?Fixed : An LM358 was running hot, replaced.Theo.
Hung Chang 5502 Oscilloscope problem - Page 1
Forum section: electronics / repair

author: davefigueroa
author_rank: Newbie
timestamp: February 06, 2017, 10:16:04 pm
content: Hello!:My name is Dave Figueroa, i am from Chile and I am 16 years old.I have a HUNG CHANG 5502 OscilloscopeMy problem are the following: When I finish the calibration of the INVERT knob, I try to leave the trace at the middle of the CRT, at a first time the trace stays in the middle, but when I close the enclosure of the oscilloscope, the trace moves up or down. I do not know how the oscilloscope decalibrates itself!I done the calibration again and I have the same problem.The other problem is the movement of the trace when the oscilloscope turns on, because, when I finish using the oscilloscope, the trace is in the middle of the CRT and I shut down the oscilloscope, BUT when I TURN ON the oscilloscope at about 5 minutes or less, THE TRACE MOVES UP OR DOWN. And I think What's happening here?.Awaiting your expert answeringsDave Figueroa OssesOther day I gonna post a photo of this oscilloscope

author: davefigueroa
author_rank: Newbie
timestamp: February 08, 2017, 05:05:31 pm
content: First Photo: The OscilloscopeSecond Photo: The trace when I turned onThird Photo: The trace at about 3 minutes(the traces maybe is shorted because the camera is not faster than the trace)

author: Armadillo
author_rank: Super Contributor
timestamp: February 09, 2017, 12:15:19 pm
content: Hi;Please read and follow the instructions as attached.Push in knob 22 [no magnification].then update us again. Also tell us compare to file "hc.jpg", what were your button or knobs position.
Services Manuals or Manuals - Page 1
Forum section: electronics / repair

author: davefigueroa
author_rank: Newbie
timestamp: February 08, 2017, 05:07:05 pm
content: Hello!I am searching the Services Manuals or only manuals for:HUNG CHANG 9100 multifunction counter (I dont know how can I calibrate this machine)EZ DIGITAL FG-8002 Function generator (I need to calibrate a little)Thanks

author: Andy Watson
author_rank: Super Contributor
timestamp: February 08, 2017, 07:34:30 pm
content: The Hang Chang 9100 looks very similar to the Maplin MF1000, Elenco F1000, Atten F1000 and the Hung Chang HC-F1000.See if this thread holds any information for you:https://www.eevblog.com/forum/repair/wanted-tenma-72-465-multifunction-counter-manualservice-manual/
CRTU: Repair/Calibration - Page 1
Forum section: electronics / repair

author: Bicurico
author_rank: Super Contributor
timestamp: February 03, 2017, 04:51:11 pm
content: Hi,The CRTU I received fails on some tests.For instance, on the Internal RF Loop Test, about half of the values are off tolerance, for example:1->1 Ok : 2200.000 M, Bd.4, Exp. -73.0 dBm, Meas. -82.9 dBmIs this configurable? An error? Something broken?Sometime an error message says "Reference Board Not Locked" (or something similar, it flashes quickly).Is there any point in extracting each module, opening it up for just cleaning purposes?Is it normal that the modules look worn out/oxidized on the outside?Regards,Vitor

author: mjs
author_rank: Regular Contributor
timestamp: February 08, 2017, 11:31:42 am
content: Have you configured the CRTU to use the internal reference from the settings ?The modules are probably silver plated and look oxidized outside - there's no point in opening themIf you want to see what's inside, see my pictures athttps://www.dropbox.com/sh/zgwzbpt91o9p1it/AACC-1YIhZs6Y-2iTAEGV1kCa?dl=0

author: Bicurico
author_rank: Super Contributor
timestamp: February 08, 2017, 11:36:44 am
content: I am currently waiting for a second (broken) unit and hopefully I can assemble a working one out of both. Until then I will refrain from opening what so ever...Thank you for the great pictures!Regards,Vitor

author: CJay
author_rank: Super Contributor
timestamp: February 08, 2017, 01:07:48 pm
content: There most definitely is a point to opening them, those connectors on the 'protocol board' in the Dropbox pictures are the reason why.They're used for additional hardware options in a few of the modules and the connections on those option boards oxidise.On my CMU cleaning those connections resulted in a working machine.YMMV of course but I would say it's worth looking into.
Phillips PM2434 DC-Microvoltmeter question - Page 1
Forum section: electronics / repair

author: jkf1000
author_rank: Regular Contributor
timestamp: February 07, 2017, 10:11:16 pm
content: Not really a repair as such, but I have recently aquired, and have restored the above mentioned microvoltmeter, it looks stunning with its huge analog meter and has an incredible range from 10 microvolts full scale upto 1000 volts.What I need to know is specific details about the built in coin style battery which is used to generate the calibration voltage. It looks as if similar in size to a standard CR20XX but I suspect that it may have a raised section on its body, which would be a little smaller in diameter, to locate it in place in a hole on the PCB. No battery was fitted to the unit when I received it and I have read the manual a few times and found no specific details about the type of cell or its voltage that should be installed.Any help or guidance greatly appreciated.. Karl

author: Gyro
author_rank: Super Contributor
timestamp: February 07, 2017, 10:18:54 pm
content: Mercury button cells were quite commonly used as relatively stable 1.35V references in some older test equipment:https://en.wikipedia.org/wiki/Mercury_batteryYour simplest solution would probably be to use a cheap 2.5V bandgap reference and a resistive divider as a substitute.

author: jkf1000
author_rank: Regular Contributor
timestamp: February 07, 2017, 10:32:32 pm
content: Looks like you are onto something with that. Annoyingly it is not really required for full operation, I can calibrate it with other standards I have. Its more to do with the fact that its not 100% completely restored without it and I am a little OCD with my test equipment. (I guess I am not alone with this!!)Thanks for your input, I will look into it.. Karl

author: Gyro
author_rank: Super Contributor
timestamp: February 07, 2017, 10:44:27 pm
content: QuoteI think I'd me more annoyed if it did!I know what you mean though, completeness is nice in a restoration. Time for pictures...
I need help with g751jy - Page 1
Forum section: electronics / repair

author: tsu20000111
author_rank: Newbie
timestamp: February 15, 2017, 05:30:29 pm
content: HI! I ve a problem with a ASUS ROG g751jy. This computer don´t power on, i checked the mother and i found near the cmos baterry a lost resistors but i don't have any idea where it are from? Can you help with a photo or schematic? I need a photo with it 8585gv and resistors. Thank you a lot.
Help with connector? - Page 1
Forum section: electronics / repair

author: 4cx10000
author_rank: Regular Contributor
timestamp: February 07, 2017, 09:06:15 pm
content: Hi!Anyone out there seen this connector? Have tried to source it all over the web, but to no avail. As seen on the photos it is a right angled 4 pin circular connector with thread. Pictures not taken by me and not my fingersI would be more than happy if someone has something that could lead me to the right manufacturer.Thanks in advance!

author: DC5AJ
author_rank: Unknown
timestamp: February 07, 2017, 09:16:52 pm
content: Looks like a standard M12A connector, for examplehttps://www.binder-usa.com/products/partsdetail/91939

author: 4cx10000
author_rank: Regular Contributor
timestamp: February 07, 2017, 09:44:23 pm
content: Thanks for quick reply DC5AJ!!It sure looks very much like Binder! I did not find the exact Binder - that can be seen on the photos - in their datasheets, but mine could be an old model they do not fabricate anymore. I will have to get my hands on the connector to measure the size though...
Keithley 410A Picoammeter, Teardown, Repair - Page 1
Forum section: electronics / repair

author: HighVoltage
author_rank: Super Contributor
timestamp: February 04, 2017, 04:01:46 pm
content: I bought thisKeithley 410A Picoammeter, really cheap because it was listed broken and I was not sure if it could be repaired.RepairThe problem was found fast, so it can not even be considered a real repair. The mains power cable was so old and the insulation was broken off from the conductors, it made a shortage. New mains cable is installed.TeardownSince I had it open anyways, I took some pictures of the inside as well.Now I need to find a way to test it.I do not have a real pico amp source.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 04, 2017, 04:02:55 pm
content: Inside 1

author: HighVoltage
author_rank: Super Contributor
timestamp: February 04, 2017, 04:04:47 pm
content: Inside 2

author: testmode
author_rank: Regular Contributor
timestamp: February 04, 2017, 04:22:54 pm
content: Quote from: HighVoltage on February 04, 2017, 04:01:46 pmYes, you know youneedone! (Sorry can't help it after just coming from the TEA group therapy thread)Congrats on the good find!

author: TimFox
author_rank: Super Contributor
timestamp: February 06, 2017, 04:17:46 pm
content: I have also repaired several old Keithleys where the power cord rubber had failed badly. Past that, most of the problems were solved by cleaning the rotary switches. (Be careful with switches in high-impedance locations, such as the main range switch on a picoammeter.)PS: the easiest way to get a proper diameter cord was to start with a cheap IEC computer cord and cut off the IEC female connector.

author: Assafl
author_rank: Frequent Contributor
timestamp: February 07, 2017, 07:46:26 pm
content: Strange guarding on the high value resistors. Can't say I understand where the guards are connected to.

author: Vtile
author_rank: Super Contributor
timestamp: February 07, 2017, 09:13:31 pm
content: So the smallest resolution is 5 fA and the deltaA you can notice is <1 fA ?? Nice find.

author: edpalmer42
author_rank: Super Contributor
timestamp: February 07, 2017, 09:31:06 pm
content: Quote from: HighVoltage on February 04, 2017, 04:01:46 pmAll you need is a few gigaohm resistors. I was surprised how cheap they are on ebay. I searched for <resistor (gigaohm,gohm)> and got over 100 hits. One vendor sells a set that claims to go up to 1000 Gohms!That would be interesting to test, but at those levels, be sure to think positive thoughts or you'll upset the reading!
HP 17B II Calculator Bad LCD - Page 1
Forum section: electronics / repair

author: dexters_lab
author_rank: Unknown
timestamp: February 07, 2017, 05:27:08 pm
content: I have this HP 17B mk2 with a bad screen, as you can see from the pics there are a couple of columns out and there are often a couple more than in the pic.I have not opened it up yet, but i wondered if this is a common problem and if they can be nursed back to healthif it's zebra strip on the LCD then i guess i am in with a chance but if the LCD has a hotbar to flat flex or something it might not be so easyanyone with any experience doing this?

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 07, 2017, 05:49:27 pm
content: They're a complete bastard to get inside. Peeling and drills. It does however have zebra strips so cleaning may work. There's a tear down for one here to give you an idea of the process:http://suna-jebem.blogspot.co.uk/2015/02/hp-17b-ii-tear-down-it-doesnt-power-on.htmlHP tend to make things difficult for repairers. I've given up now. When my 48GX display packed in I just got a 50G rather doing the dame jig. I actually bought a spare 50G today by coincidence as insurance against this one going to shit as there is no viable successor to it.

author: dexters_lab
author_rank: Unknown
timestamp: February 07, 2017, 06:06:30 pm
content: heat stakes FFS!?maybe i'll leave it, if i whack it on the desk it fixes it for a short time

author: Armadillo
author_rank: Super Contributor
timestamp: February 07, 2017, 06:14:07 pm
content: Maybe you have dropped it before, Try tightening the screws to compress the casing.

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 07, 2017, 06:15:42 pm
content: I did that with an old Motorola L7089 phone I had. Everytime I smashed it on the table it worked for another couple of weeks. After about 3 months I popped the LCD

author: Armadillo
author_rank: Super Contributor
timestamp: February 07, 2017, 06:38:45 pm
content: Quote from: Armadillo on February 07, 2017, 06:14:07 pmOops! Sorry, I read somewhere it plastic heat rivet....no screws....I would leave it not opened.
Remove/resolder TQFP - Page 1
Forum section: electronics / repair

author: alank2
author_rank: Super Contributor
timestamp: February 09, 2017, 04:28:28 pm
content: I've got a friend who has a bunch of pcbs with the tqfp64 180 degrees rotated from what it needs to be. He is going to get hot air to remove the chip. I've done this a few times, but he has around 100 of these to do. I think he is planning on using hot air to remove the chip, and then resolder it manually. Is that the best way? Can you use hot air to remove it, add flux, and then use hot air to resolder it? Any other tips? Would a preheated be of help or not much?

author: Armadillo
author_rank: Super Contributor
timestamp: February 09, 2017, 05:09:55 pm
content: Invest in the hot air with the QFP type nozzle. This IC is with the leads, so its much easier than the leadless IC.such quantity, I will go for solder QFP stencil to apply the paste and oven all the boards. Its much easier, predicable and faster.

author: Cupcakus
author_rank: Contributor
timestamp: February 10, 2017, 06:57:38 am
content: All you need is the air, other tools can help a bit, but you can just throw flux all over it, hot air it off, wick clean the pads, reapply flux and solder to the pads then hot air it back down, it's very easy.You can lookup any Louis Rossmann repair videos on YouTube as this is all he does every day.Of course the proper way to do it is to use paste and a reflow oven with the proper temperature curve, that will take longer and cost significantly more.

author: Lunasix
author_rank: Regular Contributor
timestamp: February 10, 2017, 09:23:41 am
content: I've done this on a batch of about 50 boards on which the processor (tqfp 100) had an earlier date code, and blocking errata, than the processor used on the prototype. I remember it took less than 5 minutes to remove the bad processor and to solder the new one. For this, I always use a simple nozzle (2mm) : move rapidly all around the processor, works with all sizes of tqfp, I don't like specific nozzles, I don't see nothing and never know when it is hot, never had succes with those things. To solder, a simple iron, solder and desoldering braid.
Power line cord for Heathkit IM-2202 meter - Page 1
Forum section: electronics / repair

author: Ric
author_rank: Newbie
timestamp: February 04, 2017, 08:45:13 pm
content: I'm looking for a Power line cord for my IM-2202 meter. 3 round pins in a triangle. Anyone know where I can find one.Ric

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 04, 2017, 10:11:11 pm
content: Ugh been there. Never found out what it was. If there's enough room left in the case it might be easier to use a nibbler to reshape the hole and stick a standard IEC socket on it. Have done this to a couple of Heathkit things over the years.

author: TimFox
author_rank: Super Contributor
timestamp: February 06, 2017, 04:16:04 pm
content: They show up on EBay from time to time. I believe the original use for these connectors was on "business machines", such as adding machines. They were used on medical equipment, until someone managed to connect a set of EKG leads (with banana-like plugs) into one and electrocuted a patient.

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 06, 2017, 06:10:20 pm
content: That actually doesn't surprise me. Humans are silly animals.

author: GreyWoolfe
author_rank: Unknown
timestamp: February 06, 2017, 06:57:10 pm
content: Quote from: SingedFingers on February 04, 2017, 10:11:11 pmGood Lord, haven't seen one of them in years. I second Singed on the IEC socket.
BK Precision 1745A  Now working BUT...... - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: February 06, 2017, 04:49:25 pm
content: Many thanks for your help. I now have my BK 1745 DC Power supply nearly working. My problem now is that when I try to adjust the voltage below 5 volts the voltage gradually drops to zero unless I add a load across the output posts. It seems like a capacitor is holding a charge. Is this normal? I have attached a schematic for a 1746 which is almost the same (only schematic I could find).Any input would be greatly appreciated.Thank you in advance,Chuck

author: Kleinstein
author_rank: Super Contributor
timestamp: February 06, 2017, 05:59:43 pm
content: In the shown schematics there are 4.7 K resistors as a minimum load. So the voltage will not go down instantly, but also not that slow. I don't see a reason it should be significant slower below 5 V - just the normal exponential decay. Of cause the 1745 might be different (e.g. different resistor values for R1 and R3) at this detail.

author: james_s
author_rank: Super Contributor
timestamp: February 06, 2017, 06:37:28 pm
content: Could it have a dead spot in the adjustment pot?
Spring connectors identification from a LeCroy scope - Page 1
Forum section: electronics / repair

author: owiecc
author_rank: Frequent Contributor
timestamp: February 06, 2017, 03:03:53 pm
content: I am making an add-on to the LeCroy scopes we have in the lab. I would like to use the power from the scope probe interface. LeCroy uses short pogo pin connectors in their probe adapters. Can you help me to identify this spring loaded connector? It has 2mm pitch, 1mm diameter.
Hung Chang HC-L202 oscilloscope, no display - Page 1
Forum section: electronics / repair

author: Depaj
author_rank: Newbie
timestamp: February 04, 2017, 12:28:01 pm
content: Hi!This is my first time on this forum.I have been using this oscilloscope to work on Hifi equipment but this morning it died on me. The power indicator does light up but the display stays dark (when I powered it on there was a faint line, than some flickering and than nothing). It did smell very faintly burnt. I let it sit for a while unplugged (I'm not used to touching HV stuff) and opened it up, there seemed to be no charge anywhere so I started digging in. In the future is it necessary to discharge anything ?I got the power supply out and started checking things : Q301 is shorted collector to emitter. I swapped it out for an original 2SB596 I pulled from an amp, mounted the thing back in and turned on the oscilloscope (on a current limiter). I still don't have any display but I noticed some of the neon bulbs in the high voltage supply were flickering from time to time accompanied by small "pops".I don't know if this is a great oscilloscope but it has been working great so far and I don't really have the budget to buy a new one, so I would love to get it repaired.Any help would be welcome

author: orbanp
author_rank: Regular Contributor
timestamp: February 06, 2017, 12:25:51 pm
content: Hi Depaj,Do you have the manual/schematics for the scope?That would be really helpful!Without it there is very little help we can offer, basically just generic comments.So if you have it, make it available somewhere.Regards, Peter
ELK VIKING 103 Guitar amplifier - Page 1
Forum section: electronics / repair

author: diydidi
author_rank: Contributor
timestamp: February 05, 2017, 06:09:15 pm
content: HI Guys.I'm in need of a schematic for this Solid state guitar amplifier.Someone's been in here and really messed things up.Any help will be much appreciated!!Maybe another ELK solid state schematic will be close enough if you're willing to share.Thank you!

author: oldway
author_rank: Super Contributor
timestamp: February 07, 2017, 10:31:26 am
content: http://www.electro-tech-online.com/threads/elk-viking-103-guitar-amplifier.150050/
Rigol DS1102E Power Switch Replacement - Page 1
Forum section: electronics / repair

author: RadicalAns
author_rank: Newbie
timestamp: February 04, 2017, 07:14:05 pm
content: In trying to replace the fan in my DS1102E I botched it, forgot to take the cap off the power switch, and ended up cracking the switch. It broke in 2 places so super glue isn't really holding too well. I came across these on ebay and they look like they're just about the right size. My only concern is that they're rated at 250V 5A, while the original is rated at 250v 8A:http://www.ebay.com/itm/282103368319Judging by the fact that it has a 2A fuse, and isn't terribly power hungry anyway, I think I might be able to get away with this switch, but I wanted some other opinions before I go and solder it in.Edit: I should also note that I'm running this off of US mains power.

author: eblc1388
author_rank: Frequent Contributor
timestamp: February 05, 2017, 04:25:43 am
content: The eBay picture shows the switch to be an old stock, which is good and perfect for the replacement. You will be fine as the switch has a stamped 80A surge rating for inrush current.If the replacement switch is brand new and from China, then who knows.