Left loudspeaker keeps blowing

[crusch3000]

Hello, as you might soon recognize I am no audio expert but signed up here because of conflicting advice.

My pair of Mission 770 speakers and SONY TA-E868 Power amp and SONY TA-N868 Pre-amp have worked wonderfully since 1984. A few weeks ago my left speaker ceased working. A friend of mine had a look and said it might be the pre-amp, suggesting a repair shop that had a good reputation. Took it there and $75 later I took it home. The man in the shop said it was the pre-amp, but I did not ask what exactly was the problem. Connecting it at home, there was no change. The left speaker still did not have any sound. I called the guy and he came over. He exchanged the fuse and it worked. Yes, I did not challenge him about what the supposed pre-amp roblem was. Maybe I was too stunned. Anyway, this lasted for about three CDs then the right speaker stopped. I bought a supply of fuses (thinking that after 25 years, this might be quite natural) and it worked.

Now, I have replaced the left speaked fuse twice since that original replacement. It blows after about 2 CDs worth of music. The one on the right has been good.

Before I call the oriiginal repair man again I would like to have a more intelligent approach, i.e. some suggestions what might be the problem.

Can anyone help? My apologies if I come across dumb.

Thank you

[MadMutt]

Lets start with a basic test.
You say that it's the speaker fuse that keeps blowing.

Swap the speakers over (left to right) and see which fuse blows.
If it's the same amplifier fuse, the speakers can basically be ruled out and more 'fault finding' can start.