x0x troubleshooting - audio out?

[far gon]

Those last readings of R104 were with my multimeter (which is somewhat inexepensive, and i'm unsure of its accuracy at mV levels). So in cross referencing with the oscilliscope (rigol ds1052e) I get different readings:

5v applied = 60mV ish (fluctuating a little)
0v applied = ~123mv again fluctuating.

When measuring with the oscilliscope, these measurements were fluctating as it seems to be a biased waveform of pretty high fequency. Is this correct?

Sorry if my measurements with the multimeter threw you off... I think its time for a proper meter.

[guest]

that not quite right. with 5V CV, measure the voltage drop across R100, it should be pretty small. then measure the voltage on one side of R100 with respect to ground (doesnt matter which side), it should be 5.3V.

[guest]

the scope readings are even stranger. i would trust the multimeter more at low voltage levels, as digital scopes are pretty noisey below 50mV or so. it should be a DC level, though.

[far gon]

Also I installed fresh batteries in the multimeter just in case...

Voltage drop across R100 = 29.9 mV

Voltage on supply side of R100 to ground = 5.11 V ( I compared this to J4 pin 1 and its 5.11V as well, but with oscilloscope it measures 5.36- so there is slight discrepency between my multimeter and the scope).

[far gon]

Point taken on the scope! Makes sense about the noise.

[guest]

ok, can you repeat that, and measure the voltage with respect to ground at:

1. both sides of R106
2. both sides of R118
3. both sides of R100
4. both sides of D25 (there are 3 pins, only 2 do anything)

[far gon]

R106 = 5.06V, 4.99V
R118 = 5.08V, 0V
R100 = 5.11V, 5.08V
D25 = 467mV, 4.4mV (third pin is 0V as you mentioned)

[guest]

are those D25 voltages correct? are they refrenced to ground? they seem a bit wierd, ill have to think about that for a bit. are these measurements with your meter or your scope?

[guest]

put C33 on the scope, and watch the scope as you measure the voltage at D25 with you meter. if C33 stays at 9.3V, and D25 is still reading 400mV (or anything less than 5V for that matter), then Q28 is probably bad.

[far gon]

I just re-measured the D25 pins, and the values were the same as posted before.

I rechecked a couple other voltages and then went back to the D25. This time measured 430mV, 4.9mv.

I then started writing this post and went back to triple check and got 422mv, and 4.7mv.

So it seems to slightly fluctuate over a few minutes

Voltage to ground measured with the multimeter, not the scope.