From Brian Willoughby Sent Mon, Sep 30th 2019, 01:23
From Brian Willoughby Sent Mon, Sep 30th 2019, 01:23
Hi Ben, I haven=E2=80=99t looked at the schematic, but 4.5 V would be the = virtual ground reference for a +9 V power supply. That M5218L could be = working properly, because 2x =E2=80=9C0=E2=80=9D equals =E2=80=9C0=E2=80=9D= (substitute 4.5 V for =E2=80=9C0=E2=80=9D when working with virtual = ground). Your problem may be earlier in the signal flow. Brian On Sep 29, 2019, at 5:32 PM, Benjamin Clark <xxxxxxxxx@xxxxx.xxx> wrote: > Hi all, >=20 > I turned on my MC-202 today and it didn't seem to be making any sound. = After cranking up the output, I could hear the synth was working at a = very low volume. It's the same situation from the headphone jack. >=20 > Anyone run into this issue on a MC-202 or SH-101 before? I'm guessing = the M5218L dual op amp is bad since it amplifies the synth for the = headphone and output jacks. The power supply input to the chip is good = (9 V) and these are the measurements I'm getting from inputs and = outputs: > =20 > non-inverted input 1 and 2: 4.3 V > inverted input 1 and 2: 4.5 V > output 1 and 2: 4.5 V >=20 > They are setup as non-inverting opamps with a 100K input resistor and = 100K feedback resistor, so I think the output is supposed to be 2x the = input? Any help would be appreciated. >=20 > Thanks, >=20 > Ben =20 >=20