ZX475ti hum with car off

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macky322
Posts: 8
Joined: Thu Jan 23, 2020 9:07 am

ZX475ti hum with car off

Post by macky322 »

I wanted to get some feedback on my hum issue on my ZX475ti. Its installed in a 2007 BMW 328i.

It hums....
with car off
with car running
with RCA inputs disconnected
through all 4 speakers

Its been sitting for a while.
I worked the static and popping out of the cross over pots.

I even noticed my halos on my headlights were blinking a little...not sure if the amp was causing feedback or noise into the BMW.

It seems to change with the sensitivity pots if I wiggle and/or increase gain.

Not sure if there is anything else I can check.

Have a feeling the Sensitivity pots needs cleaning? I saw the post about taking them apart. Did anyone have a part number for part of it? Or at least if i try to take it apart and clean it. Is there a specific grease to use? Thanks.
lilviper
Posts: 270
Joined: Tue Nov 06, 2012 9:30 pm

Re: ZX475ti hum with car off

Post by lilviper »

macky322 wrote:I wanted to get some feedback on my hum issue on my ZX475ti. Its installed in a 2007 BMW 328i.

It hums....
with car off
with car running
with RCA inputs disconnected
through all 4 speakers

Its been sitting for a while.
I worked the static and popping out of the cross over pots.

I even noticed my halos on my headlights were blinking a little...not sure if the amp was causing feedback or noise into the BMW.

It seems to change with the sensitivity pots if I wiggle and/or increase gain.

Not sure if there is anything else I can check.

Have a feeling the Sensitivity pots needs cleaning? I saw the post about taking them apart. Did anyone have a part number for part of it? Or at least if i try to take it apart and clean it. Is there a specific grease to use? Thanks.
Have you changed the psu caps?

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ttocs
the Floor Sweeping Hack with Golden Ears
Posts: 14783
Joined: Fri Dec 19, 2008 9:53 pm

Re: ZX475ti hum with car off

Post by ttocs »

try disconnecting the remote turn on just for shits and giggles and see what happens.
what else can I say I am a grumpy asshole most of the time.
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Jacampb2
Mad Scientist
Posts: 1562
Joined: Sat Apr 19, 2008 11:57 pm
Location: Beaverton 48612

Re: ZX475ti hum with car off

Post by Jacampb2 »

For clarification, you are saying that while the audio system is running, there is a hum coming from the speakers which remains even with the engine switched off?

First, definitely check to see if have the Panasonic caps in that amp. Many ZxTi amp had them, it's not likely your problem, but it's going to be a big problem if you don't get them taken care of.

My guess would be that the resistors from RCA shield to secondary ground have burned open in the amp. They are very close to the actual RCA inputs, do you can inspect the board to see if you have any toasty ones.

Aside from that, since you say it happens without the rcas attached at all, the only other real possibility send to be a more serious issue with the amp.

Normally the dirty pots result in static, dead spots, unequal gain, and unanticipated crossover phase shifts. They do not normally cause humming. Aside from that, the ZxTi and TI potentiometers are still widely available and there is no need to try to disassemble them.

Good luck,
Jason
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
macky322
Posts: 8
Joined: Thu Jan 23, 2020 9:07 am

Re: ZX475ti hum with car off

Post by macky322 »

Made a mistake. I looked at the cover...its actually a ti500.4 which I thought was almost the same as the zx475ti. And for the caps they are Nichicon. I didn't see anything visually wrong inside either. I tried to isolate and noticed the hum came from the Left. I also played around with the crossover settings and I switched the config knob on the front inputs to bypass and the noise went away.
lilviper
Posts: 270
Joined: Tue Nov 06, 2012 9:30 pm

Re: ZX475ti hum with car off

Post by lilviper »

macky322 wrote:Made a mistake. I looked at the cover...its actually a ti500.4 which I thought was almost the same as the zx475ti. And for the caps they are Nichicon. I didn't see anything visually wrong inside either. I tried to isolate and noticed the hum came from the Left. I also played around with the crossover settings and I switched the config knob on the front inputs to bypass and the noise went away.
Bad switch?

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Jacampb2
Mad Scientist
Posts: 1562
Joined: Sat Apr 19, 2008 11:57 pm
Location: Beaverton 48612

Re: ZX475ti hum with car off

Post by Jacampb2 »

If the noise goes away with the crossover bypassed then it's possible that it is a faulty pot in the stack of pots. Did you try cycling the frequency control to see if the noise changes or goes away? If it is one of the 10 pots in the stack then you should hear some changes when you cycle it.

If there is no change in the sound, then it's going to be a lot harder to track down. I mentioned via pm that it might be a bad coupling cap in the crossover but unless it's been abused, I would say that's unlikely. I mean, random failures happen, but the ti amps are still fairly recent to be seeing these issues...
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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paulmichelsen
Posts: 55
Joined: Fri Oct 10, 2008 6:24 am
Location: San Francisco

Re: ZX475ti hum with car off

Post by paulmichelsen »

Damn, now I'm wishing I had tried to repair my 475, over the weekend I found it in a box and couldn't remember what was wrong with it so I put it out on the curb in front of my house.
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