I recently picked up a Tascam Portastudio 424 off of ebay untested and without a power supply. I was able to find a power supply around the house that provided the right voltage (12V), provides more than enough current (1700mA), and has the proper polarity (tip negative). Yet the Tascam won't turn on at all. I'm wondering if there are any obvious places to look for problems on the circuit board. Here's what I've done so far after opening it up and probing with my DMM:
* The caps seem to be fine on the small board with the power jack (I removed them, measured their capacitance with my DMM, and they seem to be the correct values).
* I'm getting 12V as I should from the jack, and from the traces after the power switch.
* Here's the strange part. There's a small cap and resistor in between the power switch and the ribbon cable that connects to the main board. Both of those passive components seem to be fine. But I'm reading only 0.3V going down this ribbon cable, which could be the real problem here. But I'm not sure why that is, if I'm measuring something wrong, or if there's something else I'm not taking into account.
Any ideas of what else to take a look at it? I didn't spend much on this, so if I can't get it fixed no big deal, but if I could...I'd be quite happy!
Thanks!
* The caps seem to be fine on the small board with the power jack (I removed them, measured their capacitance with my DMM, and they seem to be the correct values).
* I'm getting 12V as I should from the jack, and from the traces after the power switch.
* Here's the strange part. There's a small cap and resistor in between the power switch and the ribbon cable that connects to the main board. Both of those passive components seem to be fine. But I'm reading only 0.3V going down this ribbon cable, which could be the real problem here. But I'm not sure why that is, if I'm measuring something wrong, or if there's something else I'm not taking into account.
Any ideas of what else to take a look at it? I didn't spend much on this, so if I can't get it fixed no big deal, but if I could...I'd be quite happy!
Thanks!