Stuck on an MA Audio power supply problem - Page 2

Scanlines · 13th June 2011, 01:23 PM

Perry;

Those last shots were taken at 2V?Div.
At this point I'm thinking shorted transformer.

Perry Babin · 13th June 2011, 06:46 PM

Generally, if you have a primary to secondary short, you will have 12v on the secondary center tap. If you have a primary to primary short or a secondary to secondary short, it will be impossible to develop a square wave on the primary.

What's the oscillating frequency? Has it possibly drifted?

Scanlines · 14th June 2011, 02:31 PM

Perry;

The PS is running at 42.1khz
Thanks for the advice, there are no pri to sec shorts.

Interestingly, I pulled the drains of the power FETs out of the circuit and connected them to an outboard transformer in the same configuration and I got a pretty clean and sharp square wave when powered up.

I'm concluding that there's something on board that is still open or leaky causing my problem.

I found these 2 resistors RF3 and RF4 on the front end near the input that have suffered some distress and are burned out of recog.
They both measure 32 ohms but I don't know if this is the correct value.
Didn't see this amp on Ampguts.

here;s a pic.

MVC-120F.jpg picture by UCN_photo - Photobucket

13th June 2011, 06:46 PM	#12
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Generally, if you have a primary to secondary short, you will have 12v on the secondary center tap. If you have a primary to primary short or a secondary to secondary short, it will be impossible to develop a square wave on the primary. What's the oscillating frequency? Has it possibly drifted? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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
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 HK-302sx power light flashes???	Redrocker	Car Audio	4	6th November 2010 08:16 AM
Simple Power Supply for Audio Amplifiers. (Why? This is for audio)	AP2	Power Supplies	10	30th March 2010 12:02 AM
Sundown Audio SAE-1200D stuck in protect	spooney	Car Audio	16	12th March 2010 09:35 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


	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

13th June 2011, 01:23 PM	#11
Scanlines diyAudio Member Join Date: Dec 2007	Perry; Those last shots were taken at 2V?Div. At this point I'm thinking shorted transformer.

14th June 2011, 02:31 PM	#13
Scanlines diyAudio Member Join Date: Dec 2007	Perry; The PS is running at 42.1khz Thanks for the advice, there are no pri to sec shorts. Interestingly, I pulled the drains of the power FETs out of the circuit and connected them to an outboard transformer in the same configuration and I got a pretty clean and sharp square wave when powered up. I'm concluding that there's something on board that is still open or leaky causing my problem. I found these 2 resistors RF3 and RF4 on the front end near the input that have suffered some distress and are burned out of recog. They both measure 32 ohms but I don't know if this is the correct value. Didn't see this amp on Ampguts. here;s a pic. MVC-120F.jpg picture by UCN_photo - Photobucket

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