Magnat Phantom Mono-block car amp

[stj]

Re: Magnat Phantom Mono-block car amp

got a frequency counter?

the amp has a switching psu that steps up the voltage, you could be hearing that because of a bad cap.

[jansiu]

Re: Magnat Phantom Mono-block car amp

No, I dont have frequency counter..

Is it some of those "RAIL-side" 1000 uF / 100V?
Or some of those whitch are in power input side (2200 uF / 25V)?
Any suggestions?

[stj]

Re: Magnat Phantom Mono-block car amp

the 1000uf 100v are the main smoothers, i dont want to think those are all bad.

that then feeds a 15v regulator that feeds the op-amps.
maybe that could be checked first.
lower right section of page2, c83,84 100uf 63v and c93,94 100uf 25v

what make and series are the 1000/100 and the other 4 caps?
because they should be low esr to handle the psu frequency or they wont last!

and check those 4 double-diodes d51,52,53,54

[stj]

Re: Magnat Phantom Mono-block car amp

btw, test it from a battery, not a mains supply - just to eliminate external noise.

[jansiu]

Re: Magnat Phantom Mono-block car amp

I have already checked all of those diodes- they are OK.
I check those caps tomorrow. I have fluke with cap-testing function at work.
And also I post info about those 1000/100 caps...

[CapLeaker]

Re: Magnat Phantom Mono-block car amp

Take IC14 out and see if the noise is gone. Do you have an oscilloscope?

[jansiu]

Re: Magnat Phantom Mono-block car amp

I replace those caps. (C83,84,93,94)
And remove IC14 -> no hum or other "extra" sounds anymore.
Should I replace IC14?

All caps are made by HZC.
No other info..

[jansiu]

Re: Magnat Phantom Mono-block car amp

I replaced both IC13 and IC14.
No hum noise anymore.
When audio input (or even cable, with or without anything on other end) is connected to phonos, it makes "blip" or "bliiip" noises randomly. It is very annoying.
If there is no audio input or even phono cables connected, it is silent.

[CapLeaker]

Re: Magnat Phantom Mono-block car amp

So when you had IC14 out, there was absolute silence, correct? That was to prove the noises are coming from the sub sonic filter. I figured that there may be IC13 bad too. But its good to change them all. I think that the blip blip crap is still coming from the input circuit. I'd change out caps C107, C207, C103, C203 and C105 and see if there is a change. If it isn't than the problem is after C105, around the sub sonic filter, I think. Kinda hard trouble shooting without a scope. Does this blip crap change in volume if you turn the amp gain knob?

[jansiu]

Re: Magnat Phantom Mono-block car amp

So when you had IC14 out, there was absolute silence, correct? That was to prove the noises are coming from the sub sonic filter. I figured that there may be IC13 bad too. But its good to change them all. I think that the blip blip crap is still coming from the input circuit. I'd change out caps C107, C207, C103, C203 and C105 and see if there is a change. If it isn't than the problem is after C105, around the sub sonic filter, I think. Kinda hard trouble shooting without a scope. Does this blip crap change in volume if you turn the amp gain knob?

When I have IC14 out, there was absolute silence.
I earlier changed caps C107 and C207.
Now I have changed caps C103, C203 and C105.

I think it is working right now.
I need to put it back together and test it in my car... someday..
I inform you, if there is still some problems.

Thanks for everybody who helped me!

[CapLeaker]

Re: Magnat Phantom Mono-block car amp

Good to hear!