No sound (except very faint)

SOURCE: Yamaha PSR-510 Keyboard

There is no need for a manual. It is so easy to operate because it is designed for easy opeating. If you need a manual to operate the PSR-510 then you really won't be able to operate it even after studying the manual. But here it is just in case you can by some miracle!
http://www2.yamaha.co.jp/manual/pdf/emi/english/port/PSR510E.pdf

SOURCE: I have a yamaha PSR 240 and one of the keys (E)

Yep, a key contact has got contaminated... You have to disassemble the unit to expose the keys.

You have to remove the offending key which is OFTEN tied to a bunch of keys. Under the keys you will find strips of silicon rubber with little domes sticking up. Under the domes are two contacts, either two black conductive rubber or sometimes a ring with a pill in the middle. These contact circuit traces with a black coating on the board under the keys. Clean the pills AND the circuit traces GENTLY with ONLY 99% isoprophyl alcohol. Reassemble the keys and the unit.

Be very careful handling, especially the ribbon cables between teh upper and lower halves of the unit.

Note there are TWO contacts per key which one closes before the other and that is how the key velocity is measured by the processor.

SOURCE: My Boss RC-2 Pedal is having a problem with the

Most PROBABLE is the output jack either has been broken (common due to mishandling and accidents with cables such as stepping on the plug while plugged into the pedal) or the soldering of the jack in the pedal has broken loose. Less common is a circuit board crack in the vicinity of the jack. Open pedal and inspect for the above suggestions.

SOURCE: Yamaha PSR-340 keyboard is not

Hi Aspro_uk,

If your Yamaha PSR-430 wont work, it might caused by recent changes on the setting or configuration. The easiest way to correct the issue is to do a factory reset. Please follow the steps below on how to reset the settings of Yamaha PSR-430.

Note: All stored data like User styles, Registration, Multipads, User songs, MIDI setting and User voices will be deleted during the process. I recommend to create a back up before executing the Factory Reset. This can be done by performing a ''Bulk Dump'' to an external MIDI storage device or by saving the user-stored data to a floppy disk via the internal disk drive of the keyboard.

1. Turn off the keyboard completely.

2. Now, press and hold down the rightmost white key (C) while turning ON the keyboard.

3. Once the power is ON, please release the key.

4. The keyboard will reinitialize to the original factory settings.

-->For additional information and guide, please download the user manual below.

Yamaha PSR-430 Manual

Hope it helps.

Thank you for using FixYa.

SOURCE: I'm using a Yamaha FC7

you CANNOT do this connection!!! Period !!! It will not work electronically The keyboards are fighting eachother as each is driving audio into the WYE. If you want to control both levels you need to use a controller that has two separate controls. At one point such a device was made but not sure if they still are... Here is a candidate:

http://www.google.com/products/catalog?hl=en&q=volume+pedal+dual&rlz=1R2ADFA_enUS400&gs_upl=4797l11703l0l12063l17l14l0l1l1l0l1031l4813l0.1.6.3.6-1.1l12l0&bav=on.2,or.r_gc.r_pw.&biw=1203&bih=624&wrapid=tlif131583417165610&um=1&ie=UTF-8&tbm=shop&cid=16799990617547769868&sa=X&ei=RQluTpqgO4fXiAKV09W8Dg&ved=0CCUQ8wIwAQ#