Bad voice troubleshooting, part 2

[ddvdave]

Hello again forum,

My other voice problem does follow the voice card, and is a problem with voice 0x06 (voice 7/15 depending on which slot).

The problem appears to be between the F-Chip/DAC/S&H circuitry and the CEM3387. The sound is most apparent with low frequencies as a high frequency overtone/distortion. It does not appear to be SSM-2300 (S&H)-related as I moved all the SSM-2300s from a board which doesn't exhibit this same problem on the same voice to this board and the problem persists.

The sounds can be filtered out, so for example on the 100Hz preset on the UST disk, most voices sound mostly like a single 100hz tone (with a little distortion unfortunately), but the bad voice 7 has a horrible ringing and overtones to it.

Today I replaced the LF356N op-amp (IC36), which is part of the discrete sample and hold circuit coming out of the DAC, with a low-profile 8-pin socket a new LF356N, but the problem persists.

The next thing I shall try to replace is the 74HCT4053, also part of the sample and hold circuit.

Both of these components are easier to replace than the PCM53JG-I DAC IC, which happens to be soldered and not socketed on this voice on this card.

-Dave

[dvdborn]

You may want to have a look at this post of mine.
I've had a similar problem with mine and was able to fix it.

http://eiiiforum.com/index.php?topic=244.msg1933#msg1933

[ddvdave]

You may want to have a look at this post of mine.
I've had a similar problem with mine and was able to fix it.

This is great! Thanks for pointing me to that thread!

Now it makes much more sense to me why some of my DAC chips are soldered (likely original) and some are socketed (likely replacements). I should have some spare DACs in a few weeks to experiment with.

-Dave