Check the diode bridge with a multimeter
As of today, you hardly find a home appliance, which would not have used a diode bridge (Graetz circuit). And frequently, namely the breakdown of the diode is broken or cause failure of the device. In this scheme, I will demonstrate to you how to perform a full scan of the diode assembly.
A bit of theory
Before embarking on a direct verification, let us remember (learn) the main characteristics of the diode, and the diode bridge directly.
Due to P-N transition unit and the good diode conducts current only in one direction. A Graetz circuit is a combination of four diodes in sequence:
Moreover, the conclusions indicated by "~" AC voltage is applied, and on the "+" and conclusions "-" occurs eat rectified DC.
Note. In addition to the sign "~" input "recess" may also be abbreviated «AC», which stands AlternatingCurrent (literally - AC).
So, the basic principle of the scheme and clear. Now you can safely take any diode bridge and check it out. For these purposes, I chose "BKZHI.758713.010-01 I4" assembly of the diode bridge for clarity, because there can be visually trace the chain links.
Full Scan
In order to make it even easier to navigate when checking Draw a diagram and enumerate our diodes 1 to 4.
Take a multimeter and translate it into a mode so-called "continuity"
Now, let us verify the integrity and serviceability in the diodes by the numbers 1 and 2. For this probe multimeter red color put on a negative terminal of the bridge, and black soot on the output marked "~". Thus, we will check the first diode.
Because in this way we do with you direct on, we see the display parameter 561, the aforesaid points to a value in millivolts. This value is the threshold value for the successful opening of the P-N junction, this value is necessary to overcome.
To check the next diode move the black lead to a different conclusion under the symbol "~". The numbers on the display should be as close to each other.
And this diode is good with a direct connection.
But in order to complete the verification of the pair of diodes, it remains to verify that the reverse connection, they do not pass current.
Therefore, the "-" our conclusion with you bridge connect the black instrument probe and red soot on the line for both of output "~". In this case, on the display you should see the following option:
The unit of the display will inform you that in this area P-N junction is closed and no current flows.
Conclusion - the pair of diodes is fully operational.
But that it is our check is not completed. It remains to show that a pair of 3 and 4 the same function.
To do this on the "+" bridge plant the black test lead and the red one by one put on a "~". At the same time we carry out direct inclusion of diodes and should see the following picture:
From the above presented figures it is seen that the diodes 3 and 4 intact. Now we check the reverse inclusion in analogy to check the first and second diodes.
If you see on the display "1" in two versions, then these diodes are fully operational.
You probably say that this is a long time. Yes, this test is complete, but only in this case you are 100% sure of the good condition of each bridge element. You can, of course, to perform a so-called rapid test, but it does not give you the guarantee of health of each element separately.
A quick check
To quickly check the diode bridge, connect the "-" Graetz circuit plus the multimeter (red end), and the "+" schema black end of the device. And since diodes 1 and 3 are connected in series, the display you will see their total voltage.
And since diodes 2 and 4 in relation to the 1 and 3 have a parallel connection, then it will also flow current and it turns out we checked all at once diodes. And if even one of them is broken, then the option will be lower at least twice. But we will not know what the normal value for these specific diodes, so we can erroneously conclude at too low a value and a voltage supply device known in the defective detail.
Output
As you can see only a complete check of each separate diode guarantees that the bridge. Therefore, rather spend the extra 10 minutes on the meticulous checks and you will be one hundred percent sure of serviceability of the diode bridge.