I’m a 78 rpm collector with a collection from early 1920s until 1950s.

Playing 78 rpm records can be easy but also a little bit complicated. If you have a record player with that speed and a standard 78 rpm stylus (e.g. Ortofon), you can play all of them. This is the way how most people play 78 rpm records from time to time just for the fun of it. Usually, they are not serious collectors but looking for some nostalgic moments. One thing is still important even in that level. You need at least one 78 rpm stylus for your record player. I guess you don’t have such a stylus at all. You can’t play 78 rpm records with an ordinary stylus for vinyl records.

Serious collectors even use different types of styli. The size of a stylus starts at 1.8 thou and it goes up to 4.0 thou. The reason for the different sizes of styli is that the grooves of the records don’t have the same size because the stylus, which cut the record (the matrix) doesn’t have necessarily the same size like others.

A Coral record is from the 1950s or even 1960s. Such records need usually a 4.0 thou size stylus. If you want to play the majority of 78 rpm records, I would recommend the styli sizes 2.0, 2.5, 2.8., 3.2 and 4.0.

The speed of a 78 rpm record is by the way not always really 78 rpm. Sometimes, it’s 76.2 rpm and sometimes even 80.0 rpm etc.. Usually, you can’t hear the difference though. I play my "Alligator Crawl" by Louis Armstrong and His Hot Seven on OKeh 8482 with 78 rpm instead of 80 rpm, which would be the correct speed, and even as a hardcore collector, I’m very happy with the result.

Another thing for a better sound quality is to play your 78 rpm records in mono and not in stereo. This will reduce the noise considerably. Your Hi-Fi seller should be able to switch the cables of your record player in order to make it play mono.

Your problem has nothing to do with the fact that you have a modern player. My player is very modern…

Cleaning 78 rpm is another long subject. I make it short. Use only lukewarm water!!! Never use chemicals, not even those for vinyl records!!! Dry your records with a jogging shirt (the silky ones) and watch out that the label doesn’t get while washing the record.

The second question… I do agree, Coral makes very fragile records. But, i am not expert on faults, or sound mishaps on records, so all i can say is, get it cleaned as soon as possible.
Hope i helped a bit.