Ok, i've been reading on these forums for about a year now, but finally come across a problem, that seacrh has no answers too.
I have a class D car amplifier, with 14.4 volts poaring from its RCA inputs.
I've looked for inline caps and found no shorts over any of the caps connected to the input stage.
If I power it up it works fine, but eventually fries headunits.
Not good!
So do you guys have any idea what this might be?
I was contemplating just getting some decent capacitors to check before the rca's, but i thought prevention is better than cure!
Pics of said amp. Will do close ups on request!
Can't find any schematics anywhere!!!!
http://ampguts.realmofexcursion.com/Powerbass_XA-3000D/
Thanks for any help
I have a class D car amplifier, with 14.4 volts poaring from its RCA inputs.
I've looked for inline caps and found no shorts over any of the caps connected to the input stage.
If I power it up it works fine, but eventually fries headunits.
Not good!
So do you guys have any idea what this might be?
I was contemplating just getting some decent capacitors to check before the rca's, but i thought prevention is better than cure!
Pics of said amp. Will do close ups on request!
Can't find any schematics anywhere!!!!
http://ampguts.realmofexcursion.com/Powerbass_XA-3000D/
Thanks for any help
Sorry, i'm a major newb to audio work on amplifiers, so excuse me...
The amplifier does still work! It still hits damn hard! Pushing what i believe to be 3kw rms.
I've had a look for some input caps, but with my simple multimeter i found nothing in the way of conductance from the rca inputs...
Roughly where will these capacitors be?
I've checked the 4 that are right next to the rca inputs, (which i thought would be the problem), but they seem fine... I whacked a 1.5 cell across them and they charged an discharged rapidly!
I know ideally it needs a fix, but as the amp is performing as should except for the dc leak through RCA, i was just looking for a fix to remove this.
Sorry i know little about how these work, but simply using a touch of common sense i followed the tracks but found nothing in the way of the RCA centre pin (singal pin).
I've ordered a couple of 10uF caps, i used f = 1/ 2 x pi x R x C to calc a C value, i hope that was correct.
The amplifier does still work! It still hits damn hard! Pushing what i believe to be 3kw rms.
I've had a look for some input caps, but with my simple multimeter i found nothing in the way of conductance from the rca inputs...
Roughly where will these capacitors be?
I've checked the 4 that are right next to the rca inputs, (which i thought would be the problem), but they seem fine... I whacked a 1.5 cell across them and they charged an discharged rapidly!
I know ideally it needs a fix, but as the amp is performing as should except for the dc leak through RCA, i was just looking for a fix to remove this.
Sorry i know little about how these work, but simply using a touch of common sense i followed the tracks but found nothing in the way of the RCA centre pin (singal pin).
I've ordered a couple of 10uF caps, i used f = 1/ 2 x pi x R x C to calc a C value, i hope that was correct.
Still getting 8v DC across my RCA's folks...
I put the caps inline with a plug and socket either side...
But I'm still getting 8v on the socket side when the rca's are plugged in.
Anything else I can do???
It still works fine, but my RCA cables get melted! Also I'm sure it's not great for my HU!
That was with a 1mf cap, rated at 50v???
My 35v 10mF haven't come yet...
Does the DC get discharged from the capacitor as the AC passes???
Still not got a full grasp of how the capacitor works. It stores a small amount of DC charge, but will allow AC to pass through it yes.... But does the DC charge get discharged as the AC passes??
I put the caps inline with a plug and socket either side...
But I'm still getting 8v on the socket side when the rca's are plugged in.
Anything else I can do???
It still works fine, but my RCA cables get melted! Also I'm sure it's not great for my HU!
That was with a 1mf cap, rated at 50v???
My 35v 10mF haven't come yet...
Does the DC get discharged from the capacitor as the AC passes???
Still not got a full grasp of how the capacitor works. It stores a small amount of DC charge, but will allow AC to pass through it yes.... But does the DC charge get discharged as the AC passes??
agi,
Can you explain exactly how you are measuring the DC on your inputs? A small drawing would help. Also, what kind of measuring device are you using? (I guess a multimeter).
Try adding a resistor to ground before your capacitor, to bleed off any residual DC voltage. If still the DC remains, there is something else at work...
Can you explain exactly how you are measuring the DC on your inputs? A small drawing would help. Also, what kind of measuring device are you using? (I guess a multimeter).
Try adding a resistor to ground before your capacitor, to bleed off any residual DC voltage. If still the DC remains, there is something else at work...
Yes, I'm using a multimeter across the termainals of the socket pins (the none normally visible side of the RCA socket.)
The voltage is present only when i plug in my HU into the amplifier, but i tested the HU for the voltage on the output and got nothing......
The voltage flows form the ground to the centre pin too......
I got -10volts... ish when i put the red connector onto the centre pin and the ground (of the RCA) onto the black connector.
So put a resistor across from the centre pin to the ground then? Leave that in there all the time? Or just a one off?
Later i'll test for a voltage difference when the RCA's are plugged in between the ground of the RCA's (shield or whatever its tech name is) and the ground of my amplifier (cars common ground (chassis)).
The voltage is present only when i plug in my HU into the amplifier, but i tested the HU for the voltage on the output and got nothing......
The voltage flows form the ground to the centre pin too......
I got -10volts... ish when i put the red connector onto the centre pin and the ground (of the RCA) onto the black connector.
So put a resistor across from the centre pin to the ground then? Leave that in there all the time? Or just a one off?
Later i'll test for a voltage difference when the RCA's are plugged in between the ground of the RCA's (shield or whatever its tech name is
) and the ground of my amplifier (cars common ground (chassis)).Ok, just checked and the voltage difference from the amplifiers ground ( The cars chassis ) to the RCA's output and it is 12.whatever my batts floating at's voltage)
So 12.56 right now on my UPS batts....
So maybe I need to change that Capacitor so that its on the ground instead of centre signal pin. Also whats the harm in putting a cable directly from the RCA earth to the earth of my car? I hope that would fix it, yeh?
So 12.56 right now on my UPS batts....
So maybe I need to change that Capacitor so that its on the ground instead of centre signal pin. Also whats the harm in putting a cable directly from the RCA earth to the earth of my car? I hope that would fix it, yeh?
Wait... let me get this straight... Your HU is your signal source yes?
When you measure the output with nothing attached, there is no DC between center pin (signal) and shield (ground) right?
If you measure the input of your sub amp, there is no voltage between signal and ground?
But.... when you hook the two together, a DC voltage between signal and ground appears equal to your battery voltage.
Then the next important bit of info is that between car chassis and RCA signal pin is <battery voltage>... Or is that between car chassis and RCA ground (signal ground)?
If you have a voltage between RCA ground and car chassis then maybe there is a miswiring in your setup.
When you measure the output with nothing attached, there is no DC between center pin (signal) and shield (ground) right?
If you measure the input of your sub amp, there is no voltage between signal and ground?
But.... when you hook the two together, a DC voltage between signal and ground appears equal to your battery voltage.
Then the next important bit of info is that between car chassis and RCA signal pin is <battery voltage>... Or is that between car chassis and RCA ground (signal ground)?
If you have a voltage between RCA ground and car chassis then maybe there is a miswiring in your setup.
No,
When i have the amp wired up corectly as i never had this problem with my old amp, or any of my other 2 wired in the same way...
I get about 8v difference across the RCA plug when i put the cap inline of the RCa signal. ONLY WHEN RCA's are pluged into HU! When caps not in i get 12ish volts here!
When HU not plugged in i get 0v between the rca gnd and signal.
When off i get a 12v FROM the RCA earth to the common earth (amps earth) This may also be the case when on i haven't checked yet...
When i have the amp wired up corectly as i never had this problem with my old amp, or any of my other 2 wired in the same way...
I get about 8v difference across the RCA plug when i put the cap inline of the RCa signal. ONLY WHEN RCA's are pluged into HU! When caps not in i get 12ish volts here!
When HU not plugged in i get 0v between the rca gnd and signal.
When off i get a 12v FROM the RCA earth to the common earth (amps earth) This may also be the case when on i haven't checked yet...
Ok, I bridged the RCA's gnd to my amplifiers gnd.
Tut tut, blown a track inside just by the edge of a toroidal!
Will pull out the iron and fill her back in though
As this was a part to blow I noticed this... hmmmmmmmm.........
What looks like a capacitor which was definatly added on after the construction of the board.
So what this doing there?
Should I remove it? It appears to be connected one side to the track I blew... which leads ultimatly to the RCA's ground....
The other side goes onto a resistor then through another cap one way but god knows where then. I might remove this cap then see what that says???
What you guys think?
Tut tut, blown a track inside just by the edge of a toroidal!
Will pull out the iron and fill her back in though
As this was a part to blow I noticed this... hmmmmmmmm.........
What looks like a capacitor which was definatly added on after the construction of the board.
So what this doing there?
Should I remove it? It appears to be connected one side to the track I blew... which leads ultimatly to the RCA's ground....
The other side goes onto a resistor then through another cap one way but god knows where then. I might remove this cap then see what that says???
What you guys think?
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