74ac74

Hi, I finally find the problem, at reading with multimeter, suddenly is no more reading on V+ pins TDA1543. It was the floatng lead that carries 6.7v. to Dac board. Bad connexion due to extensive handling at modifications.

Hello everybody, I finally fix the problem, I got faulty transistor, nothing related to modifications on the DAC output. So I can confirm now, I run only one IC TDA1543 and left the other seven remaining shokets unused.  As I/V resistor substituted 340R for 2k7 Riken and then got a major...

To check an IC health must proceed as any transistor, position diode/continuity on meter, there it beeps when shorted the leads, and "1" when no signal. Then tie the black wire to ground (pin 4) on TDA1543 and read the remaining pins.  Mines eight IC read very close to the following values...

47k are output resistors (signal to ground) two small SMD after the 10uf. the last components before signal leaves the board.  I found this values completely wrong. Concerning the capacitor substitution. I proceed as resistor explained before, with two more wires soldered on capacitor...

1-"plate choke"    I reach to lower the output impedance and place a 50k pot to substitute the SMD 47k at the circuit. A trick is soldered wires on tested component and terminated with alligator clips. Then raise the value turning the pot while listen music. I test the value chosen, and...

Hi, mine is valab 3.0. I successful modify the signal output, from 10uf. down to 2.2 uf. cap. russian k75-10 modified, and from 47k to 2k7ohm/200Henry plate choke (signal to ground). And enjoy so much this way. Now what happens is my unit is faulty, and don't know how to test the TDA1543 ic...