Memphis mojo 16-MC2000D output trouble.

[rhempz01]

I can look at the amp for you to verify. I just got busy a honestly forgot. I take a photo of that section as well as I can at around 1 today.

 

[rhempz01]

C1027 is the transistor on the left top of the driver card

 

[rhempz01]

In this amp I can see my 50hrtz test tone on the speaker terminal, even adjust the altitude with the gain. But it has no audio?

 

[Perry Babin]

Is the relay engaged?

If you connect the test speaker to the secondary center tap and then touch it to both the positive and negative speaker terminals, do you get signal on both?

 

[rhempz01]

I don't think the relay is engaging, everything else seems ok. Not sure I understand what you mean perry.

 

[Perry Babin]

You need to determine, definitively, if the relay is engaging.

Do you have a clean audio signal on the output of the output filter inductors?

 

[rhempz01]

Yes, 50hrtz. Clean there. I just didn't understand where I was jumping from center tap?

 

[rhempz01]

At r500 next to the relay I have the same 50hrtz cleanly

 

[Perry Babin]

If you have clean output from the output filter inductors, the problem is likely in the relay drive circuit. Find the following page of the tutorial. It's a bit different but will show you what you are working with.
repair_tutorial\miscellaneousstuff\memphis\memphis 16 st1000d\repairnotesmemphis1000d.htm


The secondary center tap is covered in section 34 of the power supply troubleshooting page.

 

[rhempz01]

Ok thanks perry I also should replace that 10uf 200v capacitor. Any suggestions on a part?

 

[rhempz01]

Yes it has audio if I jump to the secondary tap. Positive on the red winding and ground and the speaker terminal.

 

[Perry Babin]

#30:
Class D - type 1, scroll down to Replacement Capacitors:

I've tried some of the 10uf BP electrolytics from ebay and they failed. The polyester are better if you can get them to fit.

#31:
If I'm not mistaken, this amp has two independent output sections so you will have signal on both the positive and negative speaker terminals. Get the relay working before worrying about the second output signal.

 

[rhempz01]

I actually still have that 1000 Memphis I failed to repair awhile back and it has 2of them. So that's covered.

 

[rhempz01]

I'll read over the section perry and get it working. Do they ever need to be replaced? Like should I order one in the event I'll need it.?

 

[Perry Babin]

Are you referring to the caps? Yes, they do fail. If you order them, I'd order 3. They commonly fail in pairs and sometimes a 3rd one fails as well.

 

[rhempz01]

Oh sorry I meant the, relay. My mistake. The capacitors I have.

 

[Perry Babin]

I don't remember ever having to replace any in the Memphis amps but I have replaced them in other amps. That said, they're not expensive so it's good to have a couple on hand. They fail in pairs in some of the Power Acoustik amps.

 

[rhempz01]

So I read over the pages perry, I can't find that transistor anywhere. Or any that are open or shorted. Even if it's marked a different number I tested all of them.on the card and surrounding the relay.

 

[Perry Babin]

Follow the trace back from the relay coil.

 

[rhempz01]

There isn't much here and I don't see a 22uf cap or a 1.2 mohm resistor. I assume it's these. and they test ok in curcuit?