Alpine amplifier issue

[transcendent]

Hi guys,

I've bought a car recently with Alpine amplifier and I got an issue with channels turning on/off randomly when driving through uneven road. Sometimes the sound is gone for a while from one side and comes up when the other channel goes off.

I am quite sure the issue is somewhere close to amp or amp itself, because some speakers are driven by head unit and it all works fine.

Today I took the amp out to see what's inside and it all looks quite good TBH. No moving parts, all looks solidly built - see attached photo.

So my question - is there anything I can check inside or should I assume the issue is elsewhere?

Thanks in advance

 

[Perry Babin]

With an insulated probe (wooden dowel, plastic end of ink pen...). push and tap lightly on all of the larger internal components. Does that cause the problem to show up?

 

[transcendent]

With an insulated probe (wooden dowel, plastic end of ink pen...). push and tap lightly on all of the larger internal components. Does that cause the problem to show up?

Will try it - thanks ! I am leaning towards that white connector to the amp though, how likely some wires are disconnected or broke there?

 

[barber02]

I haven’t worked on many alpine amps yet but from the picture it looks like pin one on the white connector close to the fuse holder may have a cracked solder joint.

Most likely, based on the symptoms you’re describing, a bad solder joint or a broken leg on one of the larger components is going to be your issue or a component overheating. If tapping on components with something none conducive doesn’t produce anything, then heating and cooling individual components may reveal the culprit.

Hope this helps,
David

 

[transcendent]

I haven’t worked on many alpine amps yet but from the picture it looks like pin one on the white connector close to the fuse holder may have a cracked solder joint.

Most likely, based on the symptoms you’re describing, a bad solder joint or a broken leg on one of the larger components is going to be your issue or a component overheating. If tapping on components with something none conducive doesn’t produce anything, then heating and cooling individual components may reveal the culprit.

Hope this helps,
David

Thanks for your input David !

I haven't actually tried yet to do some testing on individual components due to weather conditions and lack of garage :/ I noticed one more thing though. It seems like the sound coming though one channel is not directly related to shaking or moving the amp. It seems like it is related to amount of volume I put. So increasing the volume the sound starts coming through the right channel. Also after driving ~20-30min it stabilizes and seems no longer be dependent on the volume and plays fine.

So question still stands if there's still some bad connectivity @terminals or bad solder joint. It could also be affected by heat since driving a while it heats up.

Just few observations, hopefully someone can make something out of it. Otherwise I will proceed with tap/heat tests when I get some better weather for outside work

 

[Perry Babin]

When two conductors are in physical contact (no solder connection or a broken connection) a layer of oxide (insulator) can develop between them. This layer is weak and voltage (from higher signal levels) can break through it. It's also possible that movement can scrape the connection between the components, allowing them to make a connection. Sometimes the connection remains working normally for a while.

 

[transcendent]

Today I had a chance to do some testing while connected. Some parts at terminal seemed to react on taps, but one thing stood out. The switch board at the top that I do not know the purpose (see pictures). It seemed to impact the sound most consistently. Especially when I push the switch toggle further to position it supposed to be. Almost like it does not have proper contact, but works when forced.

I'll try to remove the cover of the switch to see what's inside. Do you think it might cause the problem?

Oh yeah, and don't mention the two custom pins on that small board - I broke two legs when removing and replaced afterwards.

 

[Perry Babin]

Just try cleaning the switch first. Flood it with contact cleaner and work it back and forth about 40-50 times.

 

[transcendent]

Just try cleaning the switch first. Flood it with contact cleaner and work it back and forth about 40-50 times.

Sure, will go through the cleaning first. Will report back. Thanks!

 

[transcendent]

Got the switch cleaned and contacts it attaches to the main board. Installed everything today and it seem to work now ! Going to give it couple of days before I'm sure it doesn't go back to the way it was, but so far it looks promising.
Thanks much Perry for the help