Skar audio RP4500 need help!

[Perry Babin]

It shouldn't be shrieking. It should play normally up to a reasonable level.

Does the bulb light up when it shrieks?

Do you see excessive noise on the rails?

Do you see a strange signal on the input of one inductors while the other is a clean square wave?

I forgot a previous question. On the oscilloscopes page, start reading at 'Scope Display Markings:' and read the next few sections. There are likely many sites online if you still don't quite understand. Basically, you use the scope display to determine the time for a complete cycle and use the formula F=1/time.

 

[Basshead1989]

Ok Perry the bulb has not lit up yet.

I don't see any excessive noise on the rails.

And the inductors there's a clean sqaurewave on one side and the other side the signal im not sure about pic below to help both inductors are identical.

SCOPE SETTINGS FOR PICS 50mv / 10us x10

 

[Basshead1989]

Oh perry i forgot to mention that the screeching and that signal in the pic above are in sync with each if it screeches the signal move in sync with it

 

[Perry Babin]

I don't think you can hear anything with that high of a frequency. Put the scope on about 1ms to see if anything shows up.

 

[Basshead1989]

Here's a pic below of scope setting 50mv / 1ms x10

If i touch on the driver board around r4 & r5 it makes the screeching turn into a squealing/ static

 

[Perry Babin]

Do you have a capacitor that you could parallel with the speaker to see if that stops the noise?

 

[Basshead1989]

Is there a specific type of capacitor or size I need to use

 

[Perry Babin]

Anything suitable for an output filter capacitor. Mylar of 10uF is very good. Two polarized caps in series but with a reverse connection is also OK. 22uF or larger (I've used up to two 220uF).

 

[Basshead1989]

Ok so when you say two polarized caps in series but with a reverse connection are you meaning to put the two caps in series and put in reverse on the speaker terminal?

Does voltage rating matter on the caps

 

[Perry Babin]

The negatives are generally connected together when they are connected in series. This is a fairly common practice in amps that need any significant filter capacitance at high voltage.

Voltage isn't an issue when working with the low rail voltage.

Attached shows one example.

 

[Basshead1989]

So hook them up positive to positive instead of negative to negative?

Messing with the amp more I've found that the c6 cap on the driver board is connected to r4/r5 and when pushed on it's causes a lot of noise as well as the LPF potentiometer wiggling the potentiometers when you cut your finger on the LPF it makes the amp Buzz

 

[Perry Babin]

Positive to positive?

 

[Basshead1989]

Sorry don't mean to ask so many questions but in the diagram you sent there in series with the negative sides together should I do it like in the diagram or in reverse

When you said a reverse connection is ok also it threw me off a little sry

 

[Basshead1989]

Will this work better perry

 

[Perry Babin]

That will work.

 

[Basshead1989]

Ok so just hook it across the + and - speaker terminals with sub still hooked up as well just wanna make sure I'm getting right

 

[Perry Babin]

yes

 

[Basshead1989]

It still screeching it sounds like old dial up internet is the best way I can describe it but the audio sounds clean and strong other wise

LPF potentiometer if you touch it in anyway it's buzzes crazy no other potentiometers does it though

 

[Basshead1989]

It almost like a ground issue or something feedback of some sort because if a hold the power supply wires to amp in my hand and move em around ita goes away then back

 

[Perry Babin]

It's possible that you have other issues. Are the RCA shield grounds intact?

At the output of the op-amp that drives the driver board, do you see the noise?

Did the capacitor reduce the visible noise on the output of the amplifier?