Elemental Designs Nine.1

mike49504 · 14th August 2010, 04:57 PM

I recieved this amp in for repair. Inoticed the outputs were shorted (IRF640s')

The 9640's tested fine.

So i replaced the irf640's in the amp. Put it back together and amp powers up fine sits and idles perfect.

So i tested for audio.

The output is very quiet and when a speaker is connected the amp will start drawing excessive like to the beat of the music.

Wondering what might cause this and what do i check for?

mike49504 · 14th August 2010, 05:49 PM

Ok did some checking around in this amp.

On the power supply fets ( IRFP064N)

Theese are the voltages i came up with.

Leg1:0.62

Leg2:13.90

Leg3:0

Shouldnt i have around 5 volts on leg 1??

What do i need to check for at this point?

Perry Babin · 15th August 2010, 08:53 AM

An amp with a regulated power supply can have very low gate voltage (DC measured with multimeter). The reduced pulse width reads lower than the near-full duty cycle.

Do you have ±regulated voltage on the op-amps?

What is the ±rail voltage on the output transistors?

mike49504 · 15th August 2010, 04:07 PM

The rail voltages i got are

IRF640

1:-67.8
2:-1.04
3:-70.3

IRF9640

1:68.4
2:-1.04
3:70.3

I have + 12.2 volts and - 11.8 volts on all op-amps

mike49504 · 15th August 2010, 05:24 PM

Ive got + - rail voltage and + - regulated voltage.

Amp idles perfect. The 640's are new

But as soon as i connected a test speaker to the amp it draws excessive current .

I swapped test speakers but the amp does the same thing.

Wondering what might cause this problem .

I check for dc on the outputs and get like .04 so that normal.

Where would i go at this point?

Perry Babin · 15th August 2010, 09:03 PM

Look at the speaker terminals with your scope. Do you see any high frequency oscillation?

If not, monitor the signal on the speaker terminals when you touch the speaker wires to the speaker terminals.

mike49504 · 16th August 2010, 12:52 AM

Scope set to 10 MS .5 div? or what?

mike49504 · 16th August 2010, 01:16 AM

Perry,

Never mind i have this amp fixed. What the problem was is that i had speaker wire that got pinched inside the encloser causing it to short together.

Thanks

14th August 2010, 04:57 PM	#1
mike49504 diyAudio Member Join Date: Sep 2006	Elemental Designs Nine.1 I recieved this amp in for repair. Inoticed the outputs were shorted (IRF640s') The 9640's tested fine. So i replaced the irf640's in the amp. Put it back together and amp powers up fine sits and idles perfect. So i tested for audio. The output is very quiet and when a speaker is connected the amp will start drawing excessive like to the beat of the music. Wondering what might cause this and what do i check for?

15th August 2010, 08:53 AM	#3
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	An amp with a regulated power supply can have very low gate voltage (DC measured with multimeter). The reduced pulse width reads lower than the near-full duty cycle. Do you have ±regulated voltage on the op-amps? What is the ±rail voltage on the output transistors? __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

15th August 2010, 09:03 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Look at the speaker terminals with your scope. Do you see any high frequency oscillation? If not, monitor the signal on the speaker terminals when you touch the speaker wires to the speaker terminals. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

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14th August 2010, 05:49 PM	#2
mike49504 diyAudio Member Join Date: Sep 2006	Ok did some checking around in this amp. On the power supply fets ( IRFP064N) Theese are the voltages i came up with. Leg1:0.62 Leg2:13.90 Leg3:0 Shouldnt i have around 5 volts on leg 1?? What do i need to check for at this point?

15th August 2010, 04:07 PM	#4
mike49504 diyAudio Member Join Date: Sep 2006	The rail voltages i got are IRF640 1:-67.8 2:-1.04 3:-70.3 IRF9640 1:68.4 2:-1.04 3:70.3 I have + 12.2 volts and - 11.8 volts on all op-amps

15th August 2010, 05:24 PM	#5
mike49504 diyAudio Member Join Date: Sep 2006	Ive got + - rail voltage and + - regulated voltage. Amp idles perfect. The 640's are new But as soon as i connected a test speaker to the amp it draws excessive current . I swapped test speakers but the amp does the same thing. Wondering what might cause this problem . I check for dc on the outputs and get like .04 so that normal. Where would i go at this point?

16th August 2010, 12:52 AM	#7
mike49504 diyAudio Member Join Date: Sep 2006	Scope set to 10 MS .5 div? or what?

16th August 2010, 01:16 AM	#8
mike49504 diyAudio Member Join Date: Sep 2006	Perry, Never mind i have this amp fixed. What the problem was is that i had speaker wire that got pinched inside the encloser causing it to short together. Thanks

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