Archive of the former Yahoo!Groups mailing list: Korg Poly800/EX800 Users

I tested at the 9v DC in point with the A/C adapter plugged in and batteries in place. The voltage came to 18V which I understood as the adding of the batteries and the A/C adapter. Any thoughts as to why that would/should be? Should there be a cut off of the batteries once the 9v adapter is plugged into the socket? Thanks for any further thoughts. By the way Diode 2 which prevents against reverse polarity was fine. -Johnb --- On Tue, 3/10/09, Karl Williams <williams.karl50@ yahoo.com>wrote: From: Karl Williams <williams.karl50@ yahoo.com> Subject: Re: [korgpolyex] Poly 800 A/C Adapter Issue To: korgpolyex@yahoogro ups.com Date: Tuesday, March 10, 2009, 4:58 PM I just picked up a Poly-800 II for $15 because of the same problem. I'm not sure if the design of the power input circuit is the same on the MkII as the original but the culprit is usually a blown diode that is meant to protect against someone plugging in a power supply with the polarity reversed. If the wrong adapter is used and the voltage is too high then I'd bet that the diode is dead. Another part that is bypassed when the batteries are used is a filter, with the part number ZJK5103-00, meant to eliminate noise in the supply (http://www.datashee tarchive. com/ZJK5103- 00-datasheet. html). If that part was overloaded it might be dead too.. I had to replace both the diode and the ZJK5103-00 on mine.   Take care, Karl From: Gordon JC Pearce <gordon@gjcp. net> To: korgpolyex@yahoogro ups.com Sent: Tuesday, March 10, 2009 6:45:43 AM Subject: Re: [korgpolyex] Poly 800 A/C Adapter Issue thetravelsource wrote: > My Poly-800 works fine on batteries but I have not been able to use the A/C adapter for years. I think someone once fried the circuit with the wrong adapter or polarity and I am wondering if anyone has had a similar problem and knows where to begin to repair.  Are you sure the power supply is working? If it's not, then there's  your answer. I think they're negative-to- middle, 9V - same as  Boss/Roland/ Kawai, not like Yamaha. The power connectors on the Poly-800 (and indeed anything that uses that  type of connector) are usually pretty reliable, but tend to fail such  that the batteries don't work and an adaptor does! What happens is that  there's a pin up the middle for one connection and a springy metal strip  that touches the outside of the plug when it's in, or another metal  strip connected to the battery (so it acts as a switch).. The only way I  can see for the thing to work on batteries but not with a working mains  PSU is either the pin is broken, or there is a bad solder joint between  the tag with the pin and the board. > I am finding it hard to search the group messages via yahoo for similar problems. Perhaps there are no other posts but if someone knows of an answer on this group, please point me to it. Yahoo Groups search is knackered. Utterly useless. Gordon