ZX Hard #00 31 августа 1998

Железо

Measurements - a very useful shemka for testing printed circuit boards.

             Measurements.


(R) VTS'98
(C) an engineer A. Belousov, YUT'1 / 86.

Now I draw a very useful
shemku for testing printed circuit boards from
magazine UT (Junior Technician), 1 / 86 ".
In parentheses are given ratings for the supply of +5 V (the 
original - +3 V). 



      R1 R2 R3 R4 R5 VD2

                            >

                                     about

            \ / R7 +3 (5) v

           

           e e gnd

             VT1, 2 R6 / about

  <> \>
 Probes VD1 e

  <

                            VT3

VT1 ... 3 - KT315, VD1 - D9, VD2 - AL307
R1 - 300 (510), R2, 4 - 5.1k, R3 - 51k,
R5 - 3k (5.1k), R6 - 100, R7 - 100 (300).


Principle: if the resistance
between the probes (Rx) of less than 10 ohms, the LED lights. 
This allows you to check the track for an open or a closure. 
Because of the low test voltage, limited diode VD1 (about 0.3v),

all the transitions n / n devices on the board will
locked (R>> 10th), also in a thin
equipment no resistor below the 10th (the exception - Coil / 
Choke) that can be used to probe

'Stuffed' board, and for repairs, but the circuit should be 
deenergized! 

When testing large capacitors probe will give a unit impulse and
damped (aka - kondyuk samples).

3lementy R1, Rx, R5, R6 form a measuring bridge, in which the 
diagonal includes a comparator for VT1, 2. At VT3 collected for 
the indicator buffer (VD2). 

Acts, I must say, not bad. Before
I always had to look at the tester. It will be necessary to 
attach a sound ;-). (To the next number).



12.08.98 00:01 msk is-dos