Dave checks out reports that the Fluke 87V Multimeter is susceptible to GSM mobile phone radiation and can be bricked. He puts his 87V on the line to find out. Can he kill it?
08
Feb 12
Fencing Equipment Repair Toolkit – The Basics to Hardcore Tools
At some point your fencing weapon will break, and then you’ll need to either fix it, buy a new one, or get someone else to repair it for you. The most cost-effective thing to do is to be able to perform at least minor repairs for yourself. Most repairs in foil and epee involve tightening the grips and replacing springs in the tip, but you can end up rewiring the electric blades as well.
Here are a few suggestions for tools that you should keep in your fencing bag to perform some of the regular maintenance and testing.
Every fencer needs a small toolkit for equipment maintenance. The following tools and supplies are essential:
precision screwdrivers for point maintenance and assembly; also handy for body wire repair.
pliers for tightening points; wire cutters are also useful, and are incorporated into many pliers.
Allen wrench, screwdriver, or socket wrench for pommel nuts.
quick-drying (eg. cyanoacrylate) glue for emergency wire repairs.
cloth tape for insulating foil tips.
Fencers who do a lot of maintenance will also find the following tools useful:
metal file for fitting tangs into guards/grips.
hacksaw for cutting tangs down.
blade-bowing tool (see 2.12) for gluing.
scraping tool for cleaning old glue out of grooves; an old jeweller’s screwdriver will do, provided you don’t mind ruining it. Utility knives will also work.
Lighter for burning off wire insulation or softening springs.
vice-grip pliers for heavy-duty work away from a work bench.
Swiss-army knife for everything else.
weapon-tester box.
Serious armourers will need many other tools, including:
workbench with vise.
ohmmeter or multimeter.
mask tester.
metallic fabric tester.
body wire tester.
set of weights and shims.
soldering iron (light for wires; heavy duty for pistes).
Dremel tool.
A common additional tool suggested by some on the Fencing.Net forums is a propane torch. (Though the torch may well do more harm than good.)
05
Feb 12
Ceramic Disc Capacitor – How to Accurately Test It
The last article I mentioned about electrolytic capacitor breakdown when under load. In this article I will talk about the high voltage resin coated ceramic disc capacitor. In computer monitor, it is frequent used in the screen voltage (G2) line at the crt board. When it fails, it can cause erratic or intermittently raster bright and dim and sometimes no display.
Adjusting the flyback transformer screen control will not solve this problem. You can isolate the problem as whether if it cause by a defective fly back or G2 line at crt board. Remove the G2 wire from circuit and measure the screen voltage with a digital multimeter- it should have a constant voltage (will not vary). If the voltage is not stable suspect the fly back. If it ok then trace the screen voltage circuit. Usually this circuit consist of only resistors and capacitors. Sometimes a defective crt socket might cause this type of problem also!
Many times a tech can’t solve this intermittent or no display problem is because their digital capacitance and ohmmeter measured ok on the capacitors. The capacitors in the screen voltage line are usually rated of 102,103, and 472 1kv to 2kv. A ‘missed’ in checking this capacitors will caused the technician can’t solve the problem, unless he direct replace the capacitor. An intermittent capacitor can pull down the screen voltage causing the display problem.
As mentioned earlier, an ohmmeter with 12v output and a digital capacitance with 3v output are unable to accurately check the capacitor that have the rating of 1-2 kilovolt!
If you have the analog insulation tester or meter, the panel will show a short circuit when certain voltage are pump in to check the high voltage capacitor. The voltages that you can select is depends on the brand or model you buy. Some have the range of 50v to 1000v and some have the range from 100v to 500v. It is optional whether you should have one. If you have one then it would be an added advantage for you. The other option that you have is to direct replace the suspected capacitor. In my country, you can get a new one in less than US150.00 or you may bid a used unit from eBay.
As for me, checking the small blue resin coated ceramic disc capacitor that have the capacitor code of 104 50v, besides using digital capacitance meter to check for the value, i also use an analog meter set to times 10Kohm that have the output of 12v to check this type of capacitor. Many times it will revealed the bad intermittent capacitor. You will be shocked to see the capacitance meter checked ok but show a shorted reading when check with analog multimeter.
In the market there is certain brand of analog multimeter that have the range of 100kohm. If you open up the cover, you can’t see the 9v battery in it, what you see only the 2 pieces of 1.5v battery. This type of meter can’t accurately detect the short in the capacitor because the output voltage is only 3volt!
For those of you who involved in repairing monitor, you will agree with me that checking the flyback internal capacitance- quite often you get the right value 2.7nf with digital capacitance meter but when you switch on the monitor, you will hear a ‘tick-tick’ sound from the flyback. This is because the capacitor is breaking down when under load. If you did not do anything with the flyback, gradually the internal capacitance will become shorted and you will need to refurbish the flyback.
27
Jan 12
Test Electronic Components
To be able to test electronic components accurately is essential to identifying faults for any electronic repairer. Top quality electronic testing equipment is therefore much sought after.
If you are involved in electronic repairs, professionally or just as a hobby, you will know just how much time good equipment saves you. Normally, however, this type of equipment to test electronic components can be relatively expensive, especially for do it yourself enthusiasts and people thinking about starting a small or part-time business.
What many people are unaware of is just how easy it is to make your own gear and multimeter to test electronic components to the standards of top of the range brands, but at a fraction of the cost. All you need is the necessary know-how.
There are some guides available to show beginners how to test electronic components and how to repair electronic devices and appliances. You should be looking for the following things when evaluating such a guide.
Good electronic test guides should include the following:
First, check the author’s credentials. Does he perform professional electronic repairs? Is he an electronics testing instructor? Do his instructions appear to be easy to follow and well laid out? Does he offer a guarantee if you are not fully satisfied with his manual? Does he identify being able to test electronic components with electronic repair? He should be aware that repairs are straightforward if you have the correct equipment to identify problems. And is his manual reasonably priced?
Secondly, make sure any guide not only explains how to make your own testing equipment but also explains which equipment to use for particular jobs, how you actually employ that equipment, what to test for and in what sequence. It’s all very well to have superior testing equipment to hand but if there is no methodology to follow in testing, you will just be wasting your time.
Without doubt, working out how to test electronic components can become quite complex. Much like wiring a house or office, without proper plans to work from, even the experts can become confused. If your systems of fault identification aren’t clear and easy to follow, frustration and disaster lie ahead. So, make sure any guide includes easily comprehensible diagrams and descriptions.
Ensure your guide does not just cover the basics. Part of the reason for making your own kit to test electronic components is to give yourself an advantage over other electronics testers. Most equipment that is declared unrepairable is, in fact, eminently repairable. Normally the tester simply has not been able to identify the problem; if he could identify the fault, it is not usually beyond repair.
Ensure any manual also covers testing for faults and shorts using an analogue meter and how to make such a meter. It will prove to be invaluable in cases where a digital meter has its inherent shortcomings.
So, to reiterate, superior testing equipment is essential, but no less important is having foolproof plans of testing to work through so the fault is not missed. The order of testing is important in the sense of saving time by testing for the most common faults first and so on. A good guide should also include a comprehensive troubleshooting section.
20
Jan 12
Testing Capacitor – How To Test A Capacitor When Breakdown Under Load
Have you ever come across power problem where once you switch on the power supply and the fuse blow? You have checked all the components in the power (primary) and secondary section and all the components seems to be ok! Where is the fault? A fuse blown are usually caused by a shorted bridge rectifier, defective posistor, power transistor or FET, shorted primary winding of switch mode power transformer, shorted secondary diode and etc. But in this article I’m gone to show you another secret of electronic troubleshooting tips.
I got frustrated as to where is the cause of power problem. Every time when i switch on the power supply the fuse blow immediately (the fuse became dark color and this indicate that there is a major short circuit in the power supply). I have checked all the components in the power supply and can’t find the culprit! What i do is i desoldered all the suspected parts one by one and replaced with a known good component. I eventually found the caused of the power supply problem. Guess what? It was the main filter capacitor (220 microfarad 400 volt). After replacing the filter cap the power supply worked perfectly fine. I begin my detective work to find out why this capacitor can caused the fuse to blow even though i already confirmed it ok with my meters.
The meters that i used to check the filter cap were analog meter, digital capacitance meter and esr meter. In this article i will not explain about how to check capacitor or testing capacitor and how capacitor work. I believed most of you know how to check capacitors and also generally using this type of meters. Measured with analog it showed capacitor charging and discharge, with digital capacitor tester it showed around 220 microfarad and with esr meter it showed low esr reading!
This proved that the bad capacitor breakdown when under full operating voltage. Then, how do i confirm that this filter capacitor is faulty? By using an analog insulation tester. When i connect the faulty cap to the meter and press the go button-it showed a very low resistance and this is the proved of short circuit between the plate when voltage applied! There is nothing to do with bad electrolyte. A good capacitor will just showed a charge and discharge in the insulation meter just like you are checking a capacitor using analog multimeter. In the market there is quite a number of ranges that you can buy. It has the range of 50v, 100v, 250v, 500v, 1000v and even 5000v! If you want to test a capacitor of 100 microfarad 160v then you have to select 100v. If you select 250v, it will blow your capacitor that is under test.
If you have the SENCORE TEST EQUIPMENT such as the sencore lc meter LC102 OR LC103, these meters have the capabilities of checking any type of capacitors with four tests:
-testing for capacitor values
-checking for leakage
-equivalent series resistance (ESR) and
-Dielectric absorption
It can check aluminum electrolytic capacitor, film capacitor, ceramic, high voltage capacitor and etc.
Conclusion-Different capacitor manufacturer produced different type of quality of a capacitor. Perhaps the bad capacitor that I encountered are from the lowest grade one. A capacitor failure when under load is very rare. Using ESR capacitor meter alone can solve most of the electrolytic capacitor problem.
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