ampfixed

Crown XLS 202 Amplifier Repair – Part 5

I found out you can flip the main PC board (saving me from removing all PSU and ribbon cable wires)!  This is very convenient and just made this repair task so much easier and faster.

pcbflip

These are the locations of the Channel 2 Power Transistors.

channel2

Doing some resistance testing using a multimeter, I confirmed that one of the NPN transistor was shorted (due to it’s very low reading).  But since we’re already here, I decided to just replace ALL Power Transistors of the affected channel. The NPN/PNP power transistors were only $4.60 each at Mouser.com, so it’s better to replace them all now while I have the PCB right in front of me.

A Hakko Desoldering gun is a godsend for this job. I just use the desoldering gun to remove the Power Transistors soldered to the board, then unscrewed the heatsink from the board. powertransistors

Heatsink successfully removed from board. Now, it’s just a matter of unscrewing the TO-3 transistors, cleaning the heatsink, applying some fresh thermal compound, and installing new transistors back. mj15025

So after replacing all Power Transistors in Channel 2 (again, only (1) NPN transistor was bad, but I just decided to replaced them all and give it a “fresh start”), put everything back together, and power up the amp.

Fingers crossed…. the amplifier stayed on, and didn’t shut down! No more FAULT lights. Yay! The amplifier seems fixed.

ampfixed

In my excitement, I didn’t bother connecting it to a signal generator and oscilloscope, I just went ahead and connected it to my speakers and fed it some audio signal.

YES! It’s fixed.

The final step is replacing all the tiewraps I cut, making sure all the cables and wires are secure inside the amp, double check all screws are tight, and replaced the cover shut.  Done.

Thanks for reading!

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Crown XLS 202 Amplifier Repair – Part 4

My hunch is there’s DC output voltage triggering the DC protection circuitry and automatically shutting down the amplifier.

So we need to measure if there’s any DC voltage at the output of the amplifier.   Note, you cannot do this check by sticking your meter at the output binding posts… because those are connected to the relay terminals — and you won’t be able to get any useful reading.

We need to measure where the RED arrow is pointing in the schematic below.  (Of course, the negative or BLACK probe of our meter should be connected to Ground. There is a common ground point on the amplifier, just right below the power transformer location.)

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Crown XLS 202 Amplifier Repair – Part 3

On my last post, I have a theory that DC protection is kicking in for this Crown XLS 202 amplifier and that is what’s causing the FAULT condition.

So now, it’s time to open up this amplifier and verify that theory.

NOTE: You need star-security bits to open up the cover on this amplifier. Good thing I have some of that special screw driver heads in my shop.

They basically look like this:

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Crown XLS 202 Power Amplifier Repair – Part 2

On my last post, I agreed to take a look at an XLS202 power amplifier brought home by my daughter.  It belongs to a friend of hers, and it needs fixing.

First, we need to know what the problem is with this amplifier. So I plug the power amp, and turned it ON.   It came to life, power lights on, fans running at full speed, all LEDs also turned on, including the SIGNAL, CLIP and FAULT light, and then everything turned OFF automatically.

Okay…. So I tried turning it on again, and this time it’s dead… nada. The fan didn’t even moved.  Hmmmm….

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First Post – Welcome to the new DIY-Central.com website

Hello all, and welcome to the *NEW* DIY-Central.com website…. 2.0.

Yeah, this  site is basically a re-incarnation of my previous DIY-Central (which died of neglect).  It’s where I used to post my personal electronics (and non-electronics) hobby projects and experiments back in 2005/2006?  I’m grateful to say one of the projects blogged from the old DIY site turned into a side-business back in 2007 — just around the time the recession started.

As they say, if you want to kill the fun out of any hobby, turn that hobby into a business!  So now, you have your regular day job, and what was previously a fun hobby you do on the side, is also now “work.”

So this *new* DIY site is my attempt to bring  the fun back to my    electronics hobby. On this site, I’ll be posting projects I’ve been working on, or want to work on, or stuff that currently interests me.

I’m not really talking to a specific audience here,. This is not a company blog site.  This site is more for ME, my online note taking, my  online build diary.

If you stumbled upon this site, and enjoy reading other people’s thoughts and adventures in their DIY projects, or looking at electronics project build pictures, or finished DIY projects, then maybe you’ll find this site interesting.  If you have something to add to the discussion or topic, or have tips or additional information for the project, I’d love to hear from you guys.