MA Audio 4000

Dr Zeus · 11th February 2012, 01:11 PM

I've got this amp which some repair dude didnt know how to fix very well. It appears all the power supply fets were replaced. Nothings shorted, but the amp wont power on correctly. It sorta appears that the drivers were replaced, but then again I'm not 100%.

Pin 5, 9 and 10 of the TL494 look abnormal when the amp is powered through a resistor.

Through the resistor, the amp only gets 6.14v across power terminals. If I supply 13v to rem, the amp tries to power up;

TL494
Pin 1: 0
Pin 2: 3.609
Pin 3: 0.063
Pin 4: 0.055
Pin 5: 1.270
Pin 6: 3.354
Pin 7: 0
Pin 8: 5.93
Pin 9: 2.065
Pin 10: 2.183
Pin 11: 5.92
Pin 12: 5.96
Pin 13: 4.87
Pin 14: 4.86
Pin 15: 4.84
Pin 16: 0.302

I *think* this amp may need new drivers in the ps but not 100% sure

Dr Zeus · 11th February 2012, 02:50 PM

This amp:

I removed the PS drivers and the amp can accept full 13v power. Upon inspection of the TL494:

Pin 1: 0.015
Pin 2: 3.700
Pin 3: 0.078
Pin 4: 0.070
Pin 5: 1.397
Pin 6: 3.507
Pin 7: 0.014
Pin 8: 12.70
Pin 9: 3.210
Pin 10: 3.197
Pin 11: 12.70
Pin 12: 12.75
Pin 13: 5.02
Pin 14: 5.02
Pin 15: 4.84
Pin 16: 0.014

Pins 5, 9, and 10 appear on the scope way way faster than they should, as I can only measure the signals a 1uS which seems odd.

Pin 5 at 2v/div and 1uS:

Pin 9 & 10 at 5v/div and 1uS:

Perry Babin · 12th February 2012, 11:44 AM

Check or replace the timing resistor and capacitor.

Dr Zeus · 12:10 PM

Just checking Film caps: Is 472J100 the same as 4n7J100?

The timing resistor is OK measuring at 3.9k

Perry Babin · 12th February 2012, 12:03 PM

Yes

Dr Zeus · 12th February 2012, 12:13 PM

Cool. I just found this myself too

Thanks perry

Capacitor Chart

Dr Zeus · 12th February 2012, 12:19 PM

OK now I'm cooking. The original 472J100 cap was out of spec and even dropped a legg while pulling it. The new 4n7J100 cap makes the TL494 output correctly.

Dr Zeus · 12th February 2012, 12:46 PM

I think this amp may be OK. It has a tough time powering on my 7A power supply, but on my 12A it comes up without issue. It will not power up with my current limiter.

Regulated voltage is +-12v, rail voltage is +-67v

Think it may be fair game to put this amp back in the sync for some load tests?

11th February 2012, 01:11 PM	#1
Dr Zeus diyAudio Member Join Date: Oct 2010	MA Audio 4000 I've got this amp which some repair dude didnt know how to fix very well. It appears all the power supply fets were replaced. Nothings shorted, but the amp wont power on correctly. It sorta appears that the drivers were replaced, but then again I'm not 100%. Pin 5, 9 and 10 of the TL494 look abnormal when the amp is powered through a resistor. Through the resistor, the amp only gets 6.14v across power terminals. If I supply 13v to rem, the amp tries to power up; TL494 Pin 1: 0 Pin 2: 3.609 Pin 3: 0.063 Pin 4: 0.055 Pin 5: 1.270 Pin 6: 3.354 Pin 7: 0 Pin 8: 5.93 Pin 9: 2.065 Pin 10: 2.183 Pin 11: 5.92 Pin 12: 5.96 Pin 13: 4.87 Pin 14: 4.86 Pin 15: 4.84 Pin 16: 0.302 I think this amp may need new drivers in the ps but not 100% sure __________________ \| Fluke 10 \| Ramsey BS-601 \| Topward 8102 \| RS MiniAmp \| Pyramid PS-15KX \| DieHard \|Big A$$ Resitor \|

11th February 2012, 02:50 PM	#2
Dr Zeus diyAudio Member Join Date: Oct 2010	This amp: I removed the PS drivers and the amp can accept full 13v power. Upon inspection of the TL494: Pin 1: 0.015 Pin 2: 3.700 Pin 3: 0.078 Pin 4: 0.070 Pin 5: 1.397 Pin 6: 3.507 Pin 7: 0.014 Pin 8: 12.70 Pin 9: 3.210 Pin 10: 3.197 Pin 11: 12.70 Pin 12: 12.75 Pin 13: 5.02 Pin 14: 5.02 Pin 15: 4.84 Pin 16: 0.014 Pins 5, 9, and 10 appear on the scope way way faster than they should, as I can only measure the signals a 1uS which seems odd. Pin 5 at 2v/div and 1uS: Pin 9 & 10 at 5v/div and 1uS: __________________ \| Fluke 10 \| Ramsey BS-601 \| Topward 8102 \| RS MiniAmp \| Pyramid PS-15KX \| DieHard \|Big A$$ Resitor \|

12th February 2012, 11:44 AM	#3
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Check or replace the timing resistor and capacitor. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

12th February 2012, 12:02 PM	#4
Dr Zeus diyAudio Member Join Date: Oct 2010	Just checking Film caps: Is 472J100 the same as 4n7J100? The timing resistor is OK measuring at 3.9k __________________ \| Fluke 10 \| Ramsey BS-601 \| Topward 8102 \| RS MiniAmp \| Pyramid PS-15KX \| DieHard \|Big A$$ Resitor \| Last edited by Dr Zeus; 12th February 2012 at 12:10 PM.

12th February 2012, 12:03 PM	#5
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Yes __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

12th February 2012, 12:13 PM	#6
Dr Zeus diyAudio Member Join Date: Oct 2010	Cool. I just found this myself too Thanks perry Capacitor Chart __________________ \| Fluke 10 \| Ramsey BS-601 \| Topward 8102 \| RS MiniAmp \| Pyramid PS-15KX \| DieHard \|Big A$$ Resitor \|

12th February 2012, 12:19 PM	#7
Dr Zeus diyAudio Member Join Date: Oct 2010	OK now I'm cooking. The original 472J100 cap was out of spec and even dropped a legg while pulling it. The new 4n7J100 cap makes the TL494 output correctly. __________________ \| Fluke 10 \| Ramsey BS-601 \| Topward 8102 \| RS MiniAmp \| Pyramid PS-15KX \| DieHard \|Big A$$ Resitor \|

12th February 2012, 12:46 PM	#8
Dr Zeus diyAudio Member Join Date: Oct 2010	I think this amp may be OK. It has a tough time powering on my 7A power supply, but on my 12A it comes up without issue. It will not power up with my current limiter. Regulated voltage is +-12v, rail voltage is +-67v Think it may be fair game to put this amp back in the sync for some load tests? __________________ \| Fluke 10 \| Ramsey BS-601 \| Topward 8102 \| RS MiniAmp \| Pyramid PS-15KX \| DieHard \|Big A$$ Resitor \|

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
MA Audio HK602SX	mike49504	Car Audio	28	8th May 2011 01:06 AM
Crown MA-12000i / MA-5000i / MA-9000i	jack2040	Solid State	4	8th March 2011 01:21 PM
ma audio hk-4000 ,no sound to subs ?MA AUDIO HK-4000,NO OUTPUT TO SUBS	WRENCH030380	Class D	2	7th March 2011 11:38 PM
MA Audio AMP	mike49504	Car Audio	4	23rd September 2010 08:45 PM
MA Audio	Tom7227	Class D	0	31st August 2010 08:18 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read