I have a Technics PR-305 Digital Piano, I was playing some songs on it, then one day I went to play on it and the speaker and amplifier blew. I saw that the foam Surround was gone, it had perished wit

Attempted to clean? Not a good idea obviously...Take it apart like you did before and look at the wiring and imagine that you can divine the thing to reveal some logical explanation. If you used a contact cleaner or spray to clean, that could be death to that piano my friend.

I would suggest taking it into the nearest factory authorized repair center. Go to the Technics web site to find one in your area.

it can be repaired or replaced if the boards are still available
Take it to an authorized service to have it repaired and failing that some shops that repair micro wave ovens have the technical ability to repair items of this nature
may be a good radio technician or radio repair shop could also do the repair as it is basically an electronic ( wireless/radio) that is controlled by keys

Sometimes the contacts under the keys get dirty and must be cleaned. To do this you have to disassemble the keyboard,
carefully remove the PCB under the whole keyboard, locate the not sounding notes, remove tre siliconic stripe with the contact and gently clean the inside black conductive rubber pills with a cottonfioc and alcool.
Also clean the contacts on PCB.

Yes, can be repaired. Sounds like sound output power chip has gone bad.

Also, in addition to more info I need; look on p 91 of the online owner's manual linked below. Pay attention to Sounds and Effects, the first section therein. Follow the directions closely, esp., read pp. 26, 83, and 86 which are referenced for detailed help w/ sound issues. TECHNICS SX PR305 Manual Page 91

Yes it can.....but you will need the schematics and some test gear in order to do it.....and a soldering iron....what do you mean by no surround on the speaker?? Can you post a pic??

The Speakers can be replaced with any brand. The thing you need to know is the OHM rating for the speaker. OHM is also called impedance. Unless the sticker has fallen off the back of the speaker that information will be on that sticker. OHM rating MUST match the old speaker. For instance 4 OHM, 8 OHM, 16 OHM are common ratings. All different ratings but VERY important to get this correct otherwise you could damage the electronics of your instrument.

it will be wise to replace the speakers.