I received an old amp for free. I cleaned up the pots and it works great, but there was a very pronounced and annoying rattle at lower frequencies whenever I raised the volume even slightly.

I took the grille off of the amp and I found the problem was with the speaker.

The speaker has a metallic looking dome in the center, and in the center of that dome was a small hole with a different type of material glued into it. This smaller dome within the dome had it's glue dry out and came 1/2 way loose. I touched it with my finger and it popped out. Now the buzz/rattle is gone and to me the amp sounds great.

Should I attempt to glue the smaller piece back into the speaker or leave as is? Can anyone tell me the purpose of the now missing part of the speaker. See pictures.

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Kong, I haven't seen that before, congrats on the new amp, always nice to be gifted unexpectedly, sounds like you handled the low end issue, play on Bro!

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you can save the world with your guitar one love song at a time it's just better, more fun, easier with a fender solid body electric guitar or electric bass guitar.

Kong,
If I remember correctly from my college audio speaker design days...I am reaching back here...LOL it is a kind of protective screen...that is all. If it is working fine now and you are not throwing stuff at your gear...rock on buddy. Hope this helps. I will do some research tonight and see if I can give you a better answer tomorrow.
Eric

Interesting find!
Is it a closed cab or open back?
That might influence the need for resealing the speaker cone.

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Keep on Truckin, Going full speed ahead down the highway to hades.

It is a dust cover; forget about it.

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You dig?

Thanks for the replies guys. It's nice to know that little dust cover is nothing to worry about.

It's a 1984 Carlsbro Lead 90 Combo - solid state amp. I posted it when I found it a few weeks ago on Freecycle.

It sounds really good now, when I got it the pots were filthy and it made horrible noises. I cleaned them with wd-40, which I later found out is not a good idea, so I sprayed some radio shack electronics lube into them and it now works like new. I also had to clean all the input jacks and solder in a new fuse holder. The spring reverb was not working well so I pulled out the tank and cleaned the RCA inputs, and it now works like a charm.

I am thinking of putting a new grill cloth on it. The cabinet is built like a tank. I get some nice mellow tones from it .

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Wow looks like you are doing some good work to get the old amp working properly again!

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Keep on Truckin, Going full speed ahead down the highway to hades.