DarkNDubby wrote:So here goes:
- How easy is it to fry a transistor? How can I tell if my transistor is fried? I have a Cen Tech DMM that I bought from BYOC's site, can I use that to test? - I see a lot of people are testing the values on the transistor. How do I do that? Is there a resource you can point me to so I can understand what is going on and how to test?
- If I use the continuity test on the DMM, can I touch input and output on the vero and should I get a reading? Or am I supposed to test small segments at a time?
- Is it likely that I could damage other components? For example, can I ruin an electrolytic if I put it in backwards? Or can I just turn it around and it will work fine?
- Are there any tutorials out there that talk about using a DMM for troubleshooting in general? I have looked up videos and the manual, but they didn't help me much.
- Is it possible to overheat components and make them non-operational? Sometimes, I turn up my 5-40watt soldering iron close to full once I start to troubleshoot because i find it is much easier to desolder when the iron is hotter.
Sorry for all the terribly noob questions. I have been reading all over this site and others, but I am still a little lost. I guess I just need the basics of trouble shooting. Any answers or resources you can point me to would be greatly appreciated. I'd really like to grow and get better. (And not be so lost and frustrated...)
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WOW!!!! You don't ask for much, do you?
1a.) Resistors control the amount of current flowing through a transistor. They are selected based on desired parameters
and the limits of the transistor. If a circuit has a collector resistor of 12k (12,000) ohms of resistance and you make a
mistake and insert a 12 ohm resistor.....yes you will fry it.
1b,c,d..etc.)It appears your meter has a transistor tester built into it. Testing is simple. Turn the selector dial to "hfe".
There is a socket for npn and pnp transistors with labels EBCE for each one. These correspond to the transistor legs.....
emitter, base, collector. It is laid out for two primary layouts....EBC and ECB. The reading should tell you the gain. If it
is not in the range you would expect, then it's bad.
2.)A good way to test continuity is to use the smallest setting on your resistance scale (ohm). Put one probe on point A,
the other on point B. If it reads a short ( 0 ohms ) then you have excellent continuity. If you read anything higher, then
there is resistance in the path. This is an excellent way to test the cuts on your vero boards. Dial in a resistance setting,
place the probes on opposite sides of the cut and read. It should show high resistance (infinite) on a good cut. If there is
a small sliver of trace left you will read a low or "0" resistance.
3.)The simple answer is "yes". Almost assuredly with diodes. Caps....I've seen caps in backwards and worked somewhat.
They could probably be turned around and still function. But this was in a low voltage situation. My advice is be careful
and not do that!
4.)Basic DVM is rather easy to use. There are three main functions: Ohms; Volts (DC and AC); and Amps.
To read resistance (ohms) use the lowest scale for most accurate reading, if it goes off the scale switch to the next highest
scale.
When using this scale make sure the power is off on the device being tested. Place the probes across a
component and read the resistance....easy!
Volts: DC and AC. If you are going to stick the probes in you house wiring outlet, make sure to have the selector dial
set for AC Volts.....don't do that! For stompbox circuit select DC Volts 20. Clamp the black probe to a ground connection.
The circuit will be live to test voltage. Carefully place the probe at strategic locations and measure the voltage. These
locations will be like the collector of a transistor, or the base of a transistor. You could place the probe on the voltage
supply rail to make sure it's there. Most of the time your voltage readings will be in respect to ground, so I can say for
the most part just clamp the black probe to ground and read away with the red one.
One thing though, be extremely
careful with that red probe and do not touch two points with it.....you will cause a short in a live circuit and can do much
damage. Amps: Mainly used when breadboarding a circuit. It measures the current flow through a divice, circuit, etc. It requires
that you break the circuit and insert the probes at either side of the break. The meter actually becomes a part of the
circuit in this case, but it does allow you to measure current if you need to. Most of the time you can just calculate the
current and actual measuring is not necessary.
5.) Overheating.....most definately yes. Easy to do with germanium transistors especially. Components can be damaged
from overheating by too much current flow. They can be overheated by taking too long to solder. That's why some people
use sockets for delicate, rare, etc. components. When soldering transistors, you can take precautions like clamping an
alligator clip or hemostat to each leg as you solder. They will act as heat sinks while you solder. Place the heat sink between
the solder point and the main body of the component so any excess heat will warm up the heat sink before it reaches the
component body.
I hope this makes sense and helps a little. I don't have time to proof read it, so there are probably lots of errors.
Hopefully you can make some sense from it anyway, and get something out of it.
PP