Phoenix Gold Phorum

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.

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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try disconnecting the remote turn on just for shits and giggles and see what happens.

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

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.

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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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...

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.