korg poly 800 power prblem

[Circuitbenders]

Is Q1 one of those transistors up by the power input in a TO220 case like a voltage regulator? A while back i was modding an EX800 for someone who said it wouldn't turn on after he used an AC/AC power supply on it by accident. I had a look inside and one of those, presumably Q1, actually had a hole burnt nearly all the way through it!

[YashN]

I have a puzzling problem with my Poly 800's power supply.

First, it won't power on using the 9V DC in jack. I do get power inside right after the jack, but anything beyond, e.g. the first resistor seems blank.

Secondly, I can power it on through the battery terminals, I actually extended the leads out and used a 9V battery plug so that I can easily connect 9V batteries outside of the casing. However, the synth drains the battery very, very fast (approximately 10 mins)!

Another thing I noticed is that if the battery is connected, at the same time as the PSU with the input jack, the synth won't power on: there's a short circuit somewhere...

Any pointers on what to look for would be greatly appreciated.

[Circuitbenders]

check the diode up by the DC input. I think its a 1N4001 or something.

For some reason that diode seems to fail on a very regular basis.

[YashN]

Thanks CrustyPaul, how are things?

I tested it with my multi-meter, it looks like it's okay: inf in one direction and a measure in the other, is that correct?