ElectronicNoobBlog

Today i got broken li-ion Bosch PSR Select screwdriver.

Repair was very easy, access to battery (common 18650) great.

Less than 5 minutes and tool work like new.

Tip: Always when You come across dead li-ion battery inside any rechargeable device always:

1. measure current drawn from battery when device not in use (failed battery might be caused by failed component on PCB drawing constant small current so for example after 3 days Your new battery will go bad again) – so this is very important step
2. measure charge cut-off voltage – plug charger and make sure it not go over 4.2V on battery terminals – failed charging circuitry might also cause battery fail – and broke new battery after couple of charges

I got keyboard to fix with strange symptom, pressing space delete last entered character… acting like pressing backspace key…

Very strange, very unusual but after opening case, i easy found what’s wrong… there is jumper that allow you to select action of space key… just replace jumper and will work ok.

Here are some pictures of this unusual job.

My heating element in soldering station WEP 968DB+ finally fail.

I got replacement and go for this simple repair.

1)

First is check if heating element is failed (check resistance between red leads from heater – my read infinity what’s mean fail open).

2) Mount new heating element

3) When i first run soldering station displayed temperature was 300*C and real temperature was almost 400*C so i need to calibrate it.

I was thinking it’s a MCU controlled station so i tried pushing + – temperature buttons, powering on / off while pressing buttons but i was unable to enter calibration from front panel… after opening i found that calibration is done by multi turn potentiometer…

Calibration pot is blue one, close to soldering iron switch (and side) opposite will be probably or hotair heater.

Tips while calibration:

– Avoid cleaning / apply lot solder just before measurement – when You do this You lower temperature of tip and station will send more power to make constant temperature and You will get higher temperature that will drop in seconds giving false positive high.

– Avoid testing just before plugging in – it send more power while starting and temperature will be false high – will drop later

– Try to calibrate as close to Your working point temperature (if You work at 315*C calibrate to 315*C) not for 200*C. The fare You will go from calibrated temp there will be more difference!

Here are some pictures from job.

I’v got my old hairclippers made by Philips but they suffering short work time… sometimes i had go over wire.

I decide give them a try to fix.

It turn’s out that model of Philips hairclippers was quite easy to open without damage enclosure after putting everything back.

I feed it by the best (in my opinion) possible of shelf battery NiMh Eneloop.

Here are some pictures of that simple repair:

Hello all Electronic Noob Blog viewers.

Today i was doing calibration of DDM 235 made by Sinclair Multimeter – quite vintage 🙂

I plug it to my bench power supply, witch floating ground (insulated from earth).

I made simple repair and after finishing calibration of DC, Resistance, Current i went to AC voltage.

I decide to quick measure AC voltage in outlet (230V 50Hz) and compare result to my analog meter to decide is it need any adjust.

I’m always take caution while doing witch live voltage and have my own power on method.

First i make sure that device under test is disconnected, i made adjustments, turn power on on device panel, take few steps back and plug device into power strip witch another switch … from few meter i switch power strip, i something smoke i hit switch again… that’s save me many times from breathing smoke from cooking capacitors, hitting via starting motors etc. and today save me from being hit in my face via semiconductor parts… that’s might sound funny but i think no-one want to be hit in the eye…

About DM235 i will write another post… but find why it’s exploded ?

It exploded because electric found way from power outlet -> threw multimeter -> threw power supply back to grid network closing circuit…

I do a quick check  grid “hot wire” -> bulb 100W -> isolated power supply output = full bright light 🙂

Of course that should not happen because my PSU is floating ground… and that’s mean it should be separated from grid threw transformer…. but it is not…

After opening power-supply i found blown “ceramic capacitor” with was connected between GROUND and NEGATIVE post terminal…. blown ceramic capacitor have full short patch… and that’s the way how current pass threw DDM to grid…

After removing blown capacitor my PSU start being floating again 🙂

Take big lesson from me… if your PSU is floating and You want use it as floating… check if there is capacitor across terminals… because when apply AC voltage it will blow and will damage Your device if it need to be isolated…

Historical images of using thermal transfer method.

Working very well. Old pictures, i don’t have any information. I downloaded board from internet.

Another experiment – of course not working

That pictures have few years. I was trying to develop own lead-alum battery for solar purpose. Without success.