Stock subwoofer ringing when powered.

[hiimnofun]

Lets start with my setup, I own a 1995 Celsior with stock amp and a stock sub, all with the pioneer system.

My system started cutting out under load and I assumed that it was because of my cassette to aux and didn't think much of it, until I noticed it was happening with an FM transmitter and my CD player. 

It's only really noticable when the bass hits and I'm on the highway where I have to crank er' a lil' to drown the road noise. 

I recorded a video to show what was happening and increased the volume, after that the subwoofer began ringing and would only stop if I turned the car off completely. (If I shut the radio off and shut the car off, and then turned the car on again, it wouldn't ring again until I powered on the system)

Another odd thing I noticed was that this ringing would increase in pitch if the RPMs increased.

It stops when I remove the grey plug on the amp(music will still play through the door speakers) and it stops when I pull the orange plug (music wont play at all) ((this probably doesn't really matter, as the grey plug is likely to do with the sub, and the orange plug is for the rest of the speakers, but I just wanted to add this observation.))

My first guess is that its likely a ground, but I'm fairly certain it might be the amp, although for only having 50k Kilometers on it, I'd really hope not.

 

 

If you guys know where this amp is grounded, please let me know, and if you have any advice or have encountered a similar problem, I'd love to hear your solutions as I don't really want to get rid of my factory sound.

[BigBoomer]

Sounds like either a broken ground or else a noise filter somewhere in the electronics has died. Must be on the input side of the amp as if on the output side you would never hear the noise. Are the amps on the 400 prone to capacitor failure like some of the ECUs are?

[hiimnofun]

4 hours ago, BigBoomer said:

Sounds like either a broken ground or else a noise filter somewhere in the electronics has died. Must be on the input side of the amp as if on the output side you would never hear the noise. Are the amps on the 400 prone to capacitor failure like some of the ECUs are?

I don't know to be honest, I've only put 5k on this thing so I'm somewhat new to these things.

Any idea where the grounds are that I'd need to readjust?

[Cotswold Pete]

Not aware that the 400 suffers from any capacitor failure in the radio (well as bad as the ECU issues).

Could be an earth problem, but from your description I would say an earth problem inside the amp unit.

When you say 'ringing', not quite sure what that means, and chance of dropping a copy of the recording on the post.

 

[hiimnofun]

8 hours ago, Cotswold Pete said:

Not aware that the 400 suffers from any capacitor failure in the radio (well as bad as the ECU issues).

Could be an earth problem, but from your description I would say an earth problem inside the amp unit.

When you say 'ringing', not quite sure what that means, and chance of dropping a copy of the recording on the post.

 

Heres a clip of the ringing/humming/buzzing? Or whatever you would wanna call it.

 

Sorry what does earth problem mean? Grounds?

 

i found 2 grounds ungrounded in the engine bay, grounded em, didn't help. For the time being I have the grey plug unplugged on the amp and it appears to be working fine.

[hiimnofun]

***by working fine I mean, it isn't powered so it isn't screaming at me.

[steve2006]

It sounds like feedback, possibly the sub amp section. The problems are getting it repaired and/or finding a replacement with it being a Celsior unless the system is the same as UK models.

The grey plug is as you correctly mention for the sub woofer.

As the other speakers are working OK with the grey plug disconnected this eliminates any problems with the input signals from the radio , CD etc and the outputs to the speakers. 

It may be worth seeing if you can fit a replacement UK unit.

Has the radio got a frequency changer fitted so you can pick up more than a couple UK stations and is the amplifier under the passenger seat?

My 1994 Celsior had the Premium Sound System fitted (Pioneer) and the amplifier failed on that at around 50,000 (converted) miles, I ended up fitting aftermarket myself but retained all the original speakers including the sub.

[hiimnofun]

19 minutes ago, steve2006 said:

It sounds like feedback, possibly the sub amp section. The problems are getting it repaired and/or finding a replacement with it being a Celsior unless the system is the same as UK models.

The grey plug is as you correctly mention for the sub woofer.

As the other speakers are working OK with the grey plug disconnected this eliminates any problems with the input signals from the radio , CD etc and the outputs to the speakers. 

It may be worth seeing if you can fit a replacement UK unit.

Has the radio got a frequency changer fitted so you can pick up more than a couple UK stations and is the amplifier under the passenger seat?

My 1994 Celsior had the Premium Sound System fitted (Pioneer) and the amplifier failed on that at around 50,000 (converted) miles, I ended up fitting aftermarket myself but retained all the original speakers including the sub.

Radio does not have a FM band extender, although it did have an aftermarket analogue tv/nav system in there that I've unplugged but haven't fully removed yet. (I'm going to try re-plugging everything in and see if that does anything, but this problem started a couple weeks after I unplugged it all so I sort of doubt it's related.)

The amp is located under the drivers seat (right side of the car) 

I'm sure I can find a replacement, I just wanted to diagnose the issue first before I started throwing cash into it. I plan on going aftermarket anyways, but I wanted to wait till 75k on the ODO to tear apart the interior.

Any ideas on a few things I can try before bringing it into a professional or just straight up replacing it?     

[Cotswold Pete]

That sound seems like somewhere in the AMP section a feedback control circuit has gone a little AWOL.

Usually feedback paths are simple resistors that when they go open (as opposed to shorting) the amplifier oscillates just like that noise on the video.

A specialist might be able to pin-point which component(s) has gone faulty, but sometimes not easy to repair depending on how it is soldered to the amp boards.

What I meant by Grounds, was that what the electronics in a car prefers is a common ground, so the lights might all go to a common ground point, and the ECUs (might) go to a common ground point, and the audio systems go to a common ground point.  Audio systems without common grounds tend to have noise or instability as small currents move around the grounds points and the amps just amplify the noise.

If you are able to plug in a speaker to the sub amp that is not touching and other metal parts and you still get the noise, that to me indicates the sub amp is the problem. 

[steve2006]

I have checked the part numbers and it seems the LS400 uses the same amplifier so replacement will be plug and play. Just check the part number matches to yours.

I have also found this one for £30.00 (or best offer) which is a good price as you would pay more than this just for someone to take a look at your faulty one.

https://www.ebay.co.uk/itm/Lexus-LS400-Stereo-Radio-Headunit-Amp-Amplifier-LS430/254766966719?hash=item3b514b67bf:g:6FwAAOSwEWldYxJJ

[hiimnofun]

3 hours ago, steve2006 said:

I have checked the part numbers and it seems the LS400 uses the same amplifier so replacement will be plug and play. Just check the part number matches to yours.

I have also found this one for £30.00 (or best offer) which is a good price as you would pay more than this just for someone to take a look at your faulty one.

https://www.ebay.co.uk/itm/Lexus-LS400-Stereo-Radio-Headunit-Amp-Amplifier-LS430/254766966719?hash=item3b514b67bf:g:6FwAAOSwEWldYxJJ

You're a ****' legend man, cheapest replacement I've seen.

 

Appreciate the info and help 🔥

[BigBoomer]

I'd be very surprised if this was feedback as it varies with engine speed (2nd video).
I'm still betting on a busted earth in the amp or possibly a noise filter in the amp has failed.
I assume that with the engine off the sub works normally if plugged in?

A cheap replacement amp is still your best bet though