What do you look for when looking for a used piano?
In most cases, something has broken or come unglued and is easily fixed.
When the pinblock goes bad, it cannot hold the tuning pins tightly and the tuning pins will slip. This leaves one of the three strings very flat to the others. A bad pinblock may very well be the end of that piano if it is not a good quality piano enough to warrant rebuilding.
There are some stop gap repairs for loose tuning pins, but generally, it is not advisable to buy a piano with loose tuning pins except on high quality pianos such brands as Steinway, Baldwin, Mason & Hamlin and a few others which would warrant replacing the pinblock.
The soundboard, has ribs glued on it to strengthen it. Sometimes the soundboard gets cracks in it and the ribs will come unglued from it in places. This can allow the soundboard to rattle against the loose rib as it vibrates. This will sound like a speaker distorting when it is played too loudly. Pianos also have a wooden bridge which is attached to the soundboard and have the strings running over it. The bridge has two pins for each string to hold the strings in place. Sometimes the bridge splits and allow the pins to become loose. Bridges are often made in sections that can come unglued from each other which may also caue buzzes and rattles.
Layers of felt can be removed to restore the rounded shape to the hammer but eventually there is not enough felt left above the wooden molding to get a good tone. Hammer replacement is fairly expensive and the piano needs to be of good quality to warrant this work.
You should look at the piano first and be sure it is something you are interested in. Then contact us to inspect the piano to check out the structural condition of the piano. An investment of a service call before buying it can keep you from buying and moving a piano that won't be playable.