Realistic TRC-421A distortion

[luRaichu]

https://youtu.be/le70OrKchHs
This is a car mount CB transciever that I've had for about 6 months, the handset was broken so I used it as a monitoring rig. Tuned to channel 1 and listening 24/7.
Today I recieved a new Radio Shack handset so I can TX properly from this transciever. TX from it sounds fine on my friends' radios but now I notice RX is super distorted and unintelligible.
The previous owner has installed a 0-400 Hz lowpass filter on B+.

[luRaichu]

Ok so turns out the problem lies with the built-in speaker. Sounds fine with aux headphones connected.
Even when squelched the built-in speaker makes a really quiet static noise when the radio is on. Could it have been damaged from constantly running?

[old_tv_nut]

Does the earphone output come from the same final stage as the speaker or an earlier point? Is it possible the problem is the final output amplifier stage?

[luRaichu]

Yes, earphones are driven from the same stage as the speaker.

I've isolated the distortion problem to a failure of the built-in speaker. I took it out of the radio and attached it to a hi-fi amplifier. Any audio you play with mid-range volume gets obliterated, but not anything very loud or very quiet.

The speaker must be replaced. How do I prevent this failure from occurring again?

[Alex KL-1]

Basically, no worries with new speaker, unless leaving it 24/7 at maximum volume (I think)... must be ok and last "forever" with normal use.

[old_tv_nut]

Originally Posted by Alex KL-1

Basically, no worries with new speaker, unless leaving it 24/7 at maximum volume (I think)...must be ok and last "forever" with normal use.

Agree. Failure probably due to paper getting very old and deteriorating.