Review on Omron Blood Pressure Meter

2 June 2014

Bought this meter from Q0010 for less than SGD$90 including $4.50 shipping charge.  This meter was delivered within 4 days which was considered fast. The first impression was that it looked better than the Osim icheck 100 blood pressure meter I had had for almost 2 years.  I bought this Omron meter as a replacement for the Osim meter as the latter had not been giving accurate readings.  I had  to rely on manual method to get the readings done. 

Model and Features 

The model is BP742,  a lower 7 series of the Omron range.  It was manufactured in Vietnam.   It came standard with 3 main readings,  the systolic,  diastolic and the pulse/min reading.   The screen reading is quite big with characters measuring about 15 mm tall per character which is very easy to read for elderly who has vision difficulties.

Besides the bigger characters,  this Omron meter also has some other features which are useful:- 

1.   Memory storage for 2 persons.  Each person can store up to 30 readings that include time and date signatures.  The memories can be reviewed easily by selecting the front buttons. 

2    averaging the readings taken in the last 10 minutes 

It also comes with hypertension warning indicator. 

It is running on a set of 4 batteries giving a total of 6 volts supply.  It  did not come with a storage bag and a 6 volt adaptor.  The manual came together with the set are just description on how to use the meter. 

Inside the Meter 

Those guts inside the meter are also quite standard.  It has the following components 

1. The LCD display board
2. The electronic control board and the pressure sensor
3. The Pressure pump
4. The pressure header
5. The solenoid relieve valve
6. The orifice capillary valve

How it works

When the start/stop button is pressed,  the electronic control board will start the pressure pump to pump air into the cuff via the pressure header.  The pressure sensor in the control board will give the readings to display on the LCD display board.   At the same time,  air will also be released continuously through the orifice valve at constant speed as the solenoid valve is slammed shut.   The pressure pump will be shut off once the electronic does not detect any pulsing signal through the pressure sensor and the air is allowed to discharge through the orifice valve until the pulsing pressure is detected again and subsequently,  disappears. This is when the solenoid valve will release the air completely and the LCD will display the reading. 

Accuracy Checking 

The meter was checked against a pressure dial gauge which had been calibrated before against a mercury pressure meter. The meter and the dial gauge are then connected in parallel to measure the blood pressures.   

The pressure readings recorded were almost the same for the two types of meters as shown in the following table. 

Dial Gauge (mmHg)	Omron meter (mmHg)
20	20
60	60
80	82
100	103
160	162
180	182

The measurements of systolic and diastolic pressures were also within close limits when compared between the manual dial gauge using stethoscope and the automatic Omron meter.

Overall Verdict

 

It is a cost effective and accurate blood pressure meter that will keep customers happy for a smaller sum.

Safe to Buy Stocks with Little or No Float?

26 May 2014


Someone has been selling on the idea when there is very little float,  for example in the case of China Fishery Group Pte Ltd (CF,  BOZ.SI) in SGX,  there would be little chances of prices falling drastically should there be a sell down;  it is pretty safe to buy and keep so to speak.  Let examine a scenario how things can always happen when everyone is complacent.  That is usually how the contrarians will profit. 

Security Lending and Borrowing 

Like most major bourses in the World,  SGX allows also security lending and borrowing.  This is done through the Central Deposit Pte Ltd (CDP) that keeps the registries of all stock and shares traded in SGX.   Any member of CDP can lend and borrow any amount of a particular stock exceeding a minimum lot  provided there are agreed lenders and borrowers.  The script lenders will get 4% interest which is  better than nothing sitting pretty in the CDP’s vaults.    Once lent out, the lender will temporarily lose the ownership of his scripts although he still has all the rights such as receiving dividends, voting and other rights.  The borrower who becomes the temporary owner of the scripts will pay 6% for the borrowing.  He  can do anything with the scripts such as for “covering” its risk in a margins trade or for shorting purposes.  Under the agreement,  the lender can still sell its stocks and CDP will make separate arrangement to cover until the period of the "loan" is over.

Margin Trade

Margin Trade is like borrowing money from a broker or an institution such as a bank to purchase stocks. It can be treated as a loan.   Margin trading allows one to buy or sell more stocks than one can possibly own using the normal channels. They will need little capitals because of the leverage,  sometimes,  can be more than 1 to 10; in other words,  one can buy $10/= worth of stock with just $1/=.  Margin Trades are governed by laws structural wise but not in the actual trades.  One must have the qualifications to become a margin trader and the brokers or institutions will need to comply with some rules and regulations.   In a way,  Contracts for Differences ("CFDs")  is one derivative of margin trades.

 A Possible Scenario

Trader A,  a prominent business man,   thinks that CF is a good stock and it will move up but he could get little through the normal channel because not much was traded in SGX daily due to very little float.  He goes to his brokers or his banks.  Because he is a big customer who can back up his  “loan  of shares” with his collaterals or cash deposits,  the brokers allow him to purchase the stock on a margins trade.  

Assuming CF went up daily,  Trader A will make tons of money because of the leverage.  There will be no top ups required for his margins trade and he can withdraw some of his winnings.  Assuming CF went down,  Trader A will be asked to top up the margins.  Now further assuming that Trader A could not do the top ups in time,  the brokers will have to right to “call” his margins trade with the brokers recovering the cost from Trader A.

Now,  one may ask how do the brokers “call” the margins.  You guess it right.  Besides threatening to confiscate Trader A’s  collaterals,  the brokers can also through some means,   taking the opportunity to “short sell” CF using  the borrowed  scripts.  They can always sell CF  in a Zombie way (selling without feeling of losses),  making “a pile” while Trader A will be footing the final bills.

Characteristics of Zombie Sale

Besides these zombies sale has no feeling of losses,  the brokers and institutions are also not in a hurry to buy back and return the scripts.  It will usually take a long time before the price can rise again.

 

Catching the falling knife

It has become an even better ground for the brokers to short sell the market using borrowed scripts when SGX started clamping down the short sellers.  First, they said one cannot short-sell without covering within the day; otherwise, the buying-in will start on T+2.  Then, they modified later to say one can short-sell but must cover within T+3.  The buying-in by CDP will start at T+4.  

Either way, greedy investors now turned to CFD or margins trading where investors are allowed to buy or short any amount within the scope of  “limited funds and collaterals ”.  These are all performed and controlled by the brokers and Institutions. 

When the brokers and Institutions started making margin calls and afterwards, short selling the market,  it will create a falling knife pattern where many retailers will trade for profits by buying at low,  then selling at high.  How much will these retailers profit will depend on when the brokers and Institutions will complete their zombie sales.

The final winner is none other than the brokers and the Institutions as they will have the  control of the market and also enough collaterals to cover the damages and losses.  The retailers who rushed in to buy up the stocks think it was a bargain might contribute more to their winnings .

Transcend SSD340 Review

5 May 2014

Got this 256 GB Transcend Solid State Drivefor a Samsung Laptop R440.  Q0010 has a price tag of $159/= and it was delivered within 3 days. 

The Package 

The SSD was packed inside a hard paper envelope.  It contained a 3.5” mounting bracket and some screws.  There was no installation CD except for a mult-language quick installation guide that has little information about the installation procedures.  It tells something about how to upgrade the desktops and nothing about upgrading of laptops.

Software for Hard Disk Cloning

This is one of the most important steps.  To clone the existing hard disk will require special software.  Without any CD and explanation,  I instinctly used the "Acronic" cloning software to clone of the existing hard disk. This required me to dismantle the existing hard disk from the laptop and mounted it as an external USB hard disk together with the Transcend 340 as another USB hard disk.  The cloning process was smooth and all done within 1.5 hours for about 200GB worth of existing data transferred. The start-up also went without a hitch. Windows 7 started up with a 20 seconds from pressing of the start button.

Only when everything was completed,  I saw a little note on the side of the box saying that there is system clone software available from the Transcend website.

Performance

The Samsung R440 has an i5 CPU running @ 2.4 GHz and this laptop has an installed memory of 4 GB and runs on a 64-bit Windows 7 operating system.

Comparing the start up timing,  one can see that Transcend SSD is much faster than  the original Samsung HM321.  The Transcend started up all within 20 seconds whereas Samsung hard disk took about 3 times as much time to start up the same Windows 7 laptop.

  

In term of ASSSD measurement,  one can see that Transcend 340 is 6 times as fast in turn of read and write capabilities as shown in the attached pictures.

The Transcend Software

The Transcend Software that can be downloaded free is called “SSD scope”.  It has about 6 functions as shown below.   Again,  there isn’t much explanation on how to use the software and I found only the “TRIM check" useful besides the “system clone” which I presumed is for cloning of the hard disk of the laptop.  It may allow one to clone the hard disk by mounting the SSD as an external hard disk.

Conclusion

Most 256 GB SSD in the market cost more than SGD$200.  Although the  performance of Transcend SSD 340 might not be as good as those “bigger brothers”,   one should not notice much performance differences without comparing the SDDs side by side.   For a cost of $159/=,  there should be satisfied customers especially when the price come with a 3-years warranty plan plus a free 4GB thumb drive.

A Review on a AC/DC Digital Clamp Meter

17 April 2014

Just bought an AC/DC digital clamp multi-meter from Q0010 for about SGD$18/= including shipping.  It was manufactured in Chinabut it came pretty fast within 3 days because the cost included a QExpress shipment which presumably had the item sent from a local warehouse instead of the usual mail from China which may take up to 20 days.  The package came completed with the testing leads,  an English manual and a set of 2 AAA batteries

Branding

The set has no brand except a model number called DT3266L.  It came “humble” with all the ranges and functions comparable to the other more expensive models available in the market

The Ranges and Functions

The clamp multi-meter is one of the cheapest models manufactured.  It has just the following basic functions

     1. Amperage measurement:  AC only

1. Resistance measurement
2. Voltage measurement:  AC and DC

It has also a live wire detector for voltage less than 400 volts to test which wire is alive. 

The range of each function is listed in the manual attached.

Inside the Box

The clamp meter can be opened up by unscrewing 3 little screws that hold up the cover behind the meter.  Two of the screws are hidden inside the battery chamber and one underneath the “QC Passed” label (Note: The removal of the label may void warranty). 

The circuit board as shown looks simple and tidy.  It consisted of mainly surface mounting components,  one LSI (Large Scale Integration) and 2 ICs and 3 transistors.  It has 3 adjusting resistors for adjusting AC volt,  DC volt and AC ampere ranges and accuracy.

What is lacking?

A fuse for protection of the circuit board in case the meter is accidentally connected to an electrical mains when one had the range set,  for example,  as an ohm meter,  then use it to measure high voltage.  This fuse could however be added if one is handy with a soldering iron.

Reviews 

1. The meter is a handy tool for measuring of  AC currents.
2. It has other functions such as volt,  ohm meter measurement which can be also handy for electricians who does not need sophisticated readings.
3. With the LSI and surface mounted technology,  the meter was designed to last.

It is money well spent if one is just looking for a simple ampere clamp meter that can measure AC currents.  It is an economical handy tool for most electricians.

The Manual

Document (1) by skyjuice123

The COE tweaks

13 April 2014

Singapore controls its car usage and population using several measures.  It used road taxes in earlier days to control car usage as well as air pollution.   It then introduced car registration taxes later to limit the population growth.  When these measures failed,   it  introduced Certification of Entitlement (COE).  In between, Singapore tweaked the COE system,  introducing “weekend cars” for example.  The most recent tweak was to recategorise those cars in Category A. 

What is COE System?

Those who want to own a car in Singapore must first obtain a Certificate of Entitlement (COE) in the appropriate vehicle category. Each COE represents a right to own a car for 10 years.

There are altogether 5 categories for various types of vehicles and the COE are opened for bidding twice a month.  Category A  used to be for car of engine capacity of up to 1,600 cc and category B for those above 1,600 cc.  Category A was earmarked for mass-market buyers and sellers and therefore,  has more  COE available for bidding.  It has always commanded a lower COE prices.  

What is the recent COE Tweak? 

The recent tweak introduced a new element called “engine power” besides the original element of engine capacity of up to 1,600 cc for Category A.   Cars having a powerful engines more than 130bhp will no longer be qualified for bidding under Category A even though they are less than 1,600 cc.  This latest tweak literately “kicked out” more powerful smaller branded cars such as Mercedes and BMW from Category A.

What they said about the recent COE Tweak?

The critics and those in the car sales cried foul but the Authorities went ahead to implement the rule with the understanding that this  rule can be further tweaked for improvements to be made.  After 2 months in operation when the public did not notice a fall in COE prices,  the Authority came out to say that the recent COE tweak has achieved its goal to retain the car models for the mass-market.  Its goal was not to lower the COE prices.

What was the Authority’s Original Goal?

No one quite knew what the Authority’s original goal was although the mass was of the view that the Authority was trying to cap COE price in Category A when it was rising rapidly.  Some thought that owners of the branded cars like Mercedes and BMW usually have deep pockets and therefore,  they could hike the COE prices.

Why the Recent Tweak did not work?

If one were to analyse the recent tweak,  one would find that the recent tweak did not comply with the fundamentals of controlling the car population nor the usage;  instead,  it deviated with the intention to regulate the price of Category A.  It is "designed" to fail.

The basic economic theory always tells us that the price of a product is often controlled by supply and demand and not by product’s other properties such as shapes or dimensions.  

The recent tweak may have managed to “squeezed out” the branded car to the other categories but what good does it serve?  On the other hand,  the recent tweak “punishes” those car owners who wanted to buy more economical, efficient and more powerful branded cars.

Earlier days,  the Singaporeans'forefathers came out with the various categories of  taxes tied to capacity of the cars because cars caused pollution;  therefore,  petrol cars has lower taxes than diesel cars;  cars with smaller engine capacity has lower taxes.  They increased the amount of taxes and introduced car registration taxes to regulate the population at the later stage.  When that failed,  they introduced COE.   The original idea of COE was for bigger car to pay higher COE as it has a bigger footprint;  therefore,  occupying more valuable space.  For ease of implementation,  COE categories and the numbers were tied to engine capacities instead of the cars' footprints. That worked pretty well.   

Electric Cars

These cars will be taken by storm in the future when they have improved the energy storage system.  Electric cars could no longer be ruled by engine capacities nor could it be classified properly using engine horse-powers.  Electric cars may be able to churn out more powers than ordinary petrol engines for the same physical size because the energy driving system will be much smaller.  There would be a need for the Authority to reclassify the  present COE categories in the future to cater for electric cars.   It is hope that Singapore Government could introduce new tweak that would comply with the fundamentals of controlling car population and usage instead of tweaking  around with the COE price.

Conclusion

Singapore  Government has often learnt from its mistakes.  It has progress far to achieve what the people have today.  It is hope that Singapore Government can take the recent COE tweak on engine power as a lesson learnt and refine its future tweaks in order to serve its  citizens well.   

A New Story For the Missing MH370

9 April 2014

 

A tweeter,  by the name of Jonathan Langdale,   got hold of a published ping data and analysed the signal from Inmarsat that tracked the pinging frequencies of Malaysian Airline MH370 that went missing on 8 March 2014.  He has told his “story” to many including CNN but no one listened.

What is his story?

Jonathan Langdale,  a flight simulator fanatic with some flying experience,  believed that MH370 took a large turn back at where it disappeared from the screens on the night of 8 March 2014.  The pilots then dropped the plane down to 12,000 feet with intention to perform an emergency landing at the Terengganu Airportbut they were knocked out completely,  leaving the plane flying south,  passing West of Singapore towards the Indian Ocean on auto pilot in a "kicked off" mode.

 

 
In his March 30^thprediction,  he gave his first prediction without making wind adjustment which he corrected afterwards.   He said this last prediction run on track along the location where the Chinese vessel,  Haixun01,  detected the first pinger signal.  He reckoned that he had over projected the length of the flight path.

His detailed analysis is covered here

How he came to this “story”?

According to his earlier tweets,  he claimed that he followed the published Doppler effect frequency shift data closely.  He said  

1)     The ping data showed that the ping frequency increased from 140 hz to 275 hz,  while it was making a turn back;

2)     The frequency then dropped back to 140 hz which indicated a possible attempt to perform an emergency landing at the Trengganu Airport;

3)     The frequency increased from 125 Hz to 250 Hz,  indicating that the plane flew at constant speed until the fuel run out.  

He claimed that MH370 did not fly west over to Penang as was told by the Military radar.  He said the radar could have tracked another plane.

His timing accounts using the Inmarsat's pinging data is shown below

 

He read also about some villagers at the Marang Beach sighted a very large plane flying around 1:20 am and these villagers made a police report the next morning.

 

 

 

Is his story credible?

Langdale,  by far has the most credible story besides the official one.  Both the Langdale’s and the official ones  ended the flight in the South Indian Ocean except the final destinations varies somewhat due to errors in the educated guesses.  The only difference  is that the official one advocated that there was a deliberate act to fly MH370 to avoid radar detection whereas the Langdale’s story appears to suggest that MH370 may have had some troubles with the plane (fire?) and the pilots had no time to call Mayday.  MH370 then flew South directly without any detection by other Malaysian’s radars as well as the Singaporean’s and the Indonesian’s  radars.

According to many reports,  the investigators who analysed the Malaysian military radar data indicated that the plane did fly at a height of 43,000 to 45,000 feet before dropping down to 12,000 feet.  Because the plane carried about 200 kgs of Lithium batteries,  there were rumors saying the plane could have flown  to a height of 43,000 feet intentionally to extinguish a fire onboard.  Some said the pilot is a technical fanatic who might just want to try this "trick",  choosing to fly another 8.000 feet in 10-20 minutes or another 60 minutes to reach the nearest airport.   As it was not a standard procedure,  the pilots could have switched off the ACARS recording or isolate the fire by switching off the power.  These stories and rumors, though remote,  blend well with Langdale’s story that the pilots were knocked out rather than the official story that there was a deliberate attempt to avoid the radar detection. 

Can the military radars miss the plane?

It is “impossible” for MH370 to avoid all radar detections in all the countries where MH370 was travelling, an aviation analyst said.  Unlike the United States, Britain, Australiaand New Zealand, countries in this region do not have a pact to share their signals intelligence, including satellite and radar data.

Malaysia military primary radar spotted the plane flying west and disappeared from the screen which has a 200 km range.

If MH370 did cross into the airspace of other countries unnoticed, a Weber said it would also mean that the air defense in those countries might be a bit lax in the wee hours of the morning.  The experts pointed out that military radars are expensive to operate and there might be remote chances that these radars were switch off until a trans-boundary tension is building up.  If that is being the case and  in all likelihood,  these countries would not disclose that they have missed the detection of MH370 because it would not look good on them,  especially to their citizens.  It is also a truth to tell others that their radars did not detect any unidentified plane which does not mean the plane did not fly pass through their air space.

Weber continued to say that countries might not be prepared to compromise and put aside their own security concerns to share data that might give away their defense capabilities just for finding a missing aircraft.  They were of the view that “defense is not just about capability, but also about hiding such capability or the lack of it”.   Not many countries will publicly admit to using classified technologies to find the aircraft.  What the public could read would be those non-classified capabilities or technologies;  for example,  the weather satellite images.

 

 

Conclusion

 

There are just too many stories out there in the cyber world including the official ones that said MH370 was deliberately flew west toward Andaman sea and turned south,  ending its journey in Southern Indian Ocean,  West of Australia.  The Langdale’s  story appears to tell similar tale except for the part about MH370 turning  back for emergency landing at Terengganu Airport.   One would never know the likely truth until the where about of the plane is found.

A Review of an Economical Digital Time Switch from Q0010

7 April 2014

Introduction

Bought a digital time switch from Q0010 last week for about SGD $12/= to replace my present mechanical time switch which has been used to control a 3-litres Jojirushi water air-pot that  draws about 3.0 -3.5 amperes.  The digital time switch has no other name on it except “Timer” on its cover.  It is made in China 

Differences between Digital and Mechanical Time Switches

The main difference is in the construction. 

The mechanical time switches on the left have gears and wheels that are driven by an electric motor synchronised to the electrical mains.  These wheels rotate a time dial that can be programmed to activate a level that will turn on or off a micro-switch to control the electricity supplied to the socket outlet.

The digital time switches on the right have no gears, wheels and moving parts.  The timing is driven by a digital clock much like an ordinary quartz alarm clocks except in this case,  instead of activating a mechanical switch that turn-on the alarm circuitry,  the digital time switches have electrical relays that control the electricity supplied to the socket outlet.

Dismantling the Digital Time Switch

It is quite easy to open the casing of the time switch by first finding the two “catches”,  one at each end of the time switch as shown,  then use a small screw driver to carefully pry open the casing which will “pop up” from its base readily. 

The Electronics and Components 

The digital time switch has 3 components 

1)     the switch socket outlet assembly

2)     the supply unit and the output relay

3)     the time clock and display screen

Description of the Circuits 

The supply for the electronics is obtained through a simple transformerless power supply unit that consisted of a 400 volt supply capacitor,  a power limiting 1 ohm resistor and a full wave rectifying bridge.  The power supply unit is supplying a 24 volts dc supply to run the relay circuits as well as 1.2 volts to charge the Nickel Metal Hydride  (Ni-MH) battery and also to run the time clock and display unit as shown in the attached.

The time clock and the programming electronics are hidden behind the display screen’s circuit board

The relay has a name plate rating of 16 ampere @ 240 volts.  The unit has a spare battery chamber which is not used,  probably left over from the older design that used AAA rechargeable batteries. 

The Rating of the Time Switch

Although the name plate of the time switch has a rating of 13 amperes,  the driving electronic has relay rating of 16 amperes. This,  however,  does not mean the time switch can be used for appliances with current rating of  13 amperes so long as it is less than 16 amperes.   This is because most of the appliances have inherited electromotive force (emf)  during starting up or switching on.   For example,  appliances with electric motor can induce current sometimes as high as 12 times the rating of appliances for as long as 10 seconds during starting up.  That back emf induced could easily damage the time switch if there are frequent start-ups even though the rating of the appliance is less than 3 amperes.  As a rule of thumb,  it is not advisable to load more than 4 amperes for most appliances with or without motor start ups.

Heating up of the Time Switch

Time switch will heat up although its electrical components consume little or no electricity.  This is because there are always resistances in the socket outlet's  connection and the wiring.  A typical resistance of 0.3 ohms in the connection circuit will give up about 2.7 watts of heat if the current is 3 amperes.  Try touching an electric light bulb of about 3 watts,  one would always find it warm to touch.     

Comparing to Mechanical Time Switch

This digital time switch was running cooler than the mechanical time switch probably for 2 reasons

1)     The mechanical one consumes slightly more power;

2)     The mechanical one is a bit old giving rise to higher contact resistance.

Programming

The programming is quite straightforward.  The unit has 8 buttons in 2 lines.   The top ones (3 to 7) are for adjusting and setting the weeks,  hours,  minutes and an R/Recall button to cancel or recall the program.  The bottom ones are for setting of clocks and do the programming with an extra button for manual/auto  turning on and off the time switch.

As usual,  the manual coming along with the unit is written probably by a technical guy who assumed everyone if fully versed with function of the time switch.  It is only with trial and error can one started to understand what was written in the manual.  Fortunately,  nothing will destroy the time switch if one is playing around with the buttons without the unit connecting to any power mains.

The Life Span of Battery

All rechargeable battery has a certain life.  For Ni-MH battery, it is not more than 5 years;  after which,  one would have to replace it.  The unit is supplied with a button or coin type of battery which is often seen in laptop/desktop computers for the CMOS circuits.   The battery is not readily from the neighbourhood store.  One might be able to get them  from Sim Lim Tower at a cost of about SGD$6/= each.  Fortunately,  the unit came with a spare battery chamber that one could easily convert the button or coin battery into an AAA Ni-MH battery if one is familiar with soldering.  The AAA battery is easily and readily available from local stores.

Delivery

The track and trace list of Q0010 shows that the unit was prepared for shipment on 31 March and reached the delivery partner by 1 April who delivered it on 3^rdApril.  The cost of delivery is another SGD$4/= or about 30% of the unit cost.

Conclusion

This time switch is a worthwhile investment.  It works very well compare to the mechanical time switch with flexibility of weekly programming which a mechanical time switch cannot offer.   The only snag is that it came with a button or cell Ni-MH battery which is not only expensive to be replaced,  it is also not readily available.   The alternative is to replace the whole unit or convert the battery to the AAA type;  fortunately,  this problem only comes after 5 years.

Manuals

How To Repair Electronic Equipment with Button Switches

3 April 2014

Introduction

These “critters”,  button switches,  are often used in our electronic equipment whenever there is a button designed to be pressed either to reset a program or to do the programming.

These buttons are cheap but they are often not lasting especially those in the cheaper electronics equipment such as door bells or some remote controls. One would need to press the buttons extra hard in order to sound the door bell or to activate the remote control.

Why?

There are 2 reasons:

1. The current that passes through the buttons is not enough to overcome the “dirt” building up at the contacting point. When the contacts of the button are making or breaking, there will be “sparks” no matter how small, these “sparks” will usually “blow” the dirt building up in the contacts.   If the current is too small,  the sparks created will not be able to "blow" off the "dirt".

2. The current that passes through the button is too strong, hence,  causing sparks to “eat away" the metal of the contact surface and therefore, building carbon resistance enough to prevent the passage of the current.

How to Repair?

First, remove the buttons carefully,  making sure the circuit board is not damaged, then

1. Replace the buttons

This is the best option.

2. Open up the button and then clean the contact. 

This will require some skills to break open the cover and then reseal it after cleaning. Not often successful

3. Pass a small current through the button using a torchlight battery with as many pulsation clicks as possible  (i.e to click the button switch as quickly as possible, say 20 clicks) until the ohms meter measurement across the button switch shows consistent low resistance readings. Do not leave the button switch  close for too long as this will short-circuit the battery.

Method 3 may not necessary work when the contacts of the buttons are completely charred and worn. In that case, the only workable solution is to replace the button switch.   However,  method 3 may be a quick method as it could be done "in circuit"  when one can isolate the switch from the circuit. In the case that one torchlight battery cannot do the job and the button switch came back with the same problem,  try maximum 2 nos of batteries working in series.