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Subject: Re: [korgpolyex] Poly 800 A/C Adapter Issue

From: Karl Williams <williams.karl50@...>
Date: 2009-03-10

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.datasheetarchive.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@...>
To: korgpolyex@yahoogroups.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