Had an x300 radio to fix on my work bench, crackly speakers and some other issues, turned out all but one audio coupling capacitors were completely shot! They are 10uF 16V capacitors just behind the TDA amplifiers. Out of curiosity I pulled my parts radio out and just two out of 8 capacitors were ok on it, at this point decided to take the radio out of my daily driver and lo and behold half of the coupling capacitors were shot, showing just 1uF and leaking badly!

If you're wondering why they are critical, effectively they filter out DC voltage on the speaker outputs, any DC voltage there and you're getting crackly distorted sound, often also quieter, damage to speaker cone is caused by DC voltage too. It also causes high current, therefore extra head and it can lead to amp damage. Since I had 3 radios, each with these faulty capacitors, I strongly recommend replacing them if you want to preserve your radio, I now believe that when all of them eventually fail it triggers overcurrent protection and radio switches completely off(appears dead).

Its a bit of a PITA to remove them but it is doable, most of mine simply pulled out with cap legs still attached to the board which made it easier to remove afterwards.

Of course an ESR meter is needed to test capacitors but even if you don't have one, I suggest replacing them all as its clearly a fault that is present in majority of these radios. Sound of course nicely improved, even when I crank it all the way up, there is considerably less 'crackle'.

Some pics







The lone survivor! Well done Cap!


The lone survivor coupling capacitor




Found this one also faulty

 

Excellent pics as you decoded the mystery.

Too good of an original dash item to substitute ( with mods ) .

I'll have some follow-on questions for you later as I have tinkered in the mater and have a couple of play original Alpine heads.

Joe Barry

Flight line avionics / electronics , American Airlines ( Ret )

 

The radio in my 1996 Sovereign has started to go silent after a few minutes of use! Switching it off and on again sometimes gets the sound back! Any ideas as to the possible causes, and cures?

 

Since you do not have ( Sovereign ) the separate CD changer and separate final power amplifier you are more focused in the stereo head unit

The on / off switch that seems to be intermittent is actually an encoder switch of unknown part # as there are many sizes

But I think someone found a source recently

Some have cleaned their's to no avail from reading

 

I do have the Sovereign with the regular radio. I also have a newer radio donated by Brendan some time back, I think it may be time to exchange the radio ! Alec G.

 

Parker,

Who is this Joe Barry fellow? A retired avionics expert such as yourself? Can he do what Katar83 (aka Luke) did here? Can we trust Joe Barry's advice?

 

This may as well be the overcurrent protection from the TDA amp kicking in, that I've mentioned in the first post. I believe all these radios will have an issue with coupling capacitors at this stage so for best results they will need to be replaced. My own radio been operating perfectly fine, did some rigorous testing over last few weeks, cant complain, sounds great! The owner of the other radio where I've replaced these capacitors reported no issues and commented that the radio never worked so well in all the time he owned the car.

 

Hello from Finland. I have several pieces of AJ9500R, I removed these elkos from one. Their values are 1uF 50v, 10uF 16v, is it possible to have different ones than yours? The problem with this device is that it cannot find CD playback. Tried with several boxes, can't find CD playback. Could you advise on such a problem with the device? Thank you! -Matti-