Showing posts with label Electronics. Show all posts
Showing posts with label Electronics. Show all posts

Wednesday, 22 May 2013

Using a Common mode Choke (differential) as a joule thief transformer (working)

Almost any switch mode power supply has one of these chokes for noise suppression.  The type pictured below is the type that has been tested working.



The prewound choke Coil has even windings on both sides and uses many turns of thick wire around a ferrite core.
Using the standard Joule Thief configuration, it has been tested with a BD139 transistor, 1.4K Ohm Feedback Resistor and a Blue LED.
Starts up easily at 0.6V DC. and is much brighter than the standard joule thief at 1.5 Volts.

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Tuesday, 20 September 2011

AND AD 4326 Digital Weighing Indicator Repair PC2677G AD4326

Symptom: Not working or always switching on by itself.
Cause: Batteries or power connected wrong polarity

Fix:
Check / Replace tantalum cap C20 on display board, 22uF/25V
Check / Replace U1 on display board, LM330T 5V low dropout regulator
Check / Replace Q1 on load cell board 2SA1020





Sunday, 18 September 2011

Acer AL922 19 inch LCD Monitor Repair [BadCap]

Another case of the bad caps.  Would not switch on or just for a second.  The monitor is powered by a 12V 5A switchmode mains adapter.


Opening it was easy, remove the two screws under the rubber feet and pry the case open from the other side, where the adapter cord comes out.


The bad cap was the big mains one, puffy and leaking.

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Monday, 29 August 2011

Kodak Carousel Slide Projector Chattering Buzzing Noise Fix


If you have a Kodak Carousel projector and it is giving a buzzing noise, especially when the slide button is pressed, here is the fix.

It is generally caused by a faulty diode bridge located on the board next to the transformer. 




The faulty bridge can sometimes cause the fuse to blow but this in the extreme case.  Any way, if one of the diodes fails in the bridge rectifier, then there will be a AC component on the DC power rail.  This will mean that the solenoids will buzz, chatter and will be actuating very weakly.

The bridge rectifier in my Carousel was a B125C 1500.  I used a W04 as a substitute.  The secondary rail is about 24v so it is within the 50v rating of the W04.



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Thursday, 23 June 2011

The Jaycar Story, How Australians are being ripped off


In Australia it is customary for businesses to rip off their customers.

This is usually done in a number of ways:
  • Unnecessary increasing prices of products
  • Forcing/conditioning customers to purchase “extended warranties” on products
  • Charging inflated amounts for accessories, which are quietly bundled with the item at point of sale
  • Charging inflated amounts for services such as instillation or commissioning

The pathetic retailer blames their high prices by:
  • Justifying their inflated prices on overheads such as rent and employment of inefficient “customer service” staff
  • Justifying their inflated prices on the geographical isolation that Australia is within
  • Endearing to promote Australian jobs even though the majority of goods sold are manufactured in China
  • Blaming fixed variables such as local taxes put on goods and services

A current example of the price mark-up Australians experience becomes apparent when goods are purchased from a Australian reatiler, Jaycar.

Wholly integrated and operated from New South Whales, Australia; this company also sells the same products to the USA through the American Jaycar online retail website.

Below is two screenshots of a Helicopter toy, one from the AU site and the other from the US site. Exactly the same item, same order number...


As you can see, the US price is $112USD and the AU price is $179AU respectively.

Given that the Australian exchange rate is currently $0.93AU to $1.00USD, there seems to be approximately a $75 difference between the same products being dispatched from the same location.


Given these facts, a point of truth has been realised and it is simply not to shop at Jaycar any-more.

You call yourself a Australian company? You fail, rip off!!!





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Tuesday, 7 June 2011

Reclaiming space taken by plugpacks

I was pissed off the other day with the plug pack from my WD USB hard drive taking up so much space.  This time it was not the body of the plugpack, but rather the adapter for the multiple clip-on plug for various countries.



The 'ears' on this device were much wider than expected and needed to be lopped.





Taking a pair of side-cutters to it, did the trick.



If I collect enough, I will make a necklace just like Dolpf from Universal Solider.

I'm all ears.






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Saturday, 14 May 2011

3 Watt Argon Gas Laser Pictures

Here are some pictures of a 3 Watt Argon gas laser, which we decommissioned recently.

The laser tube and power electronics were water cooled with a pump and radiator.

The tube is a heavy beast, featuring a huge copper magnetic coil around the tube to maintain plasma conditions for lasing.









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