Doh. My P.A. is dead.

I just got my new PA I bought from Ebay.

No volume.

I have tried both speaker jacks, I have tried all mic inputs (1/4" type... i have none of the other type of cable). I have tried many combinations of knob/eq settings.

One other weird problem.

It has low and high eq knobs. If I turn the low eq knob up on more than one channel at a time, the speakers start pulsing. ... Like every second they go pop, pop, pop... But if I turn up just one of the low eq... it does not do that. All of the other knobs produce no result at all.

The speaker cab works. If I plug my mic into my Carvin amp, and into that speaker cab... it works fine.

Any tips or whatnot would be greatly appreciated. I told the seller of this already and he said he would work with me either on getting it repaired, or returning it... whatever.

I am pretty disapointed.

 

First let me say I am really, really sorry to anyone who thought that I was saying that my father died. I didn't mean to cause any confusion. My Dad is alive and well and he still kicks my ass at basketball anytime he wants to.

Bruce, I am using a guitar cable. I the only amp cables I own are on my Carvin rig. I didn't think to try them, but I sure will.

Some more info:

My cab is currently setup as a 2 ohm load. This PA on the back of it says that it supports down to 2 ohms. So I am using just one jack (it has to speaker jacks), but my speaker load is 4 8 ohm speakers all in parallel. I have tested the speaker cab in my bass rig. I can get output, running my mic through my bass amp into the cab in question.

The exact model is a Crate PA B4150. It has 4 inputs and 2 speaker jacks. It has both types of inputs, 1/4 and XLR (is that the right word?). It has a 5 band eq. It has the following knobs: gain, reverb, monitor, low eq, high eq. It also has some jacks in the front for monitor, main, reverb footswitch, um... I think 2 others. And it has monitor, main and master volume knobs also (sepperate from the individual channel ones).

The cab is plugged into the speaker jack on the back with a guitar cable.

The mic is getting plugged into any one of the 1/4: inputs.

All the knobs are set to 1/2 way up except low eq.

low eq are all left off because when more than one of them are turned up at once the speakers start pulsing.

Thanks Bruce, and everyone else who reads this!

 

Howdy Bgavin,

Thanks for your input!

I will check the fuses. I can check the other components to some degree (as far as looseness or obvious breakage). I used to be an Electronic Technician in the Navy, so I do have some knowlege of working with circuitry... however it's been more than 10 years so I will go slow and quit if I feel above my head.

The amp does say that it will handle 2 ohm loads. It has 2 4 ohm speaker jacks and claims a 2 ohm min. I can certainly change my speaker config to a 8 ohm load though.

Do you have any thoughts on the pulsing sound?

Thanks,

gabu

 

50 amps! I just need two or three....

You are right, I should really invest in a few now that I have two amps and a PA and one true speaker cable.

But anyways, I have decided to let the UPS take this one back. They will give me $100 insurance for my troubles. I had one heck of a time trying to figure out how to get inside of the thing... There are 15 screws in the back. I took off the outter six... but the cover only wobbled. I was worried about the last 9 because they seemed to hold some componants on the inside. In short, I chickened out.

But I don't think it was a fuse issue, because I do get power to the unit... just no output to the speakers. (and the weird low eq problem)

If UPS pays me and leaves me with the unit too then I will get more adventurous... Otherwise... it's back to ebay for me. (or Carvin perhaps)

 

http://www.speakerhole.com/Store/product/view.cfm?ProductID=775

This will be my pa replacement. It seems like a great deal. I have a buncha cash in my paypal account so it won't be much out of my pocket.

The guy who sold me the crate pa was very cool and refunded my order.

Thanks for everyones help. If you need a smaller PA check out this speakerhole one... it seems cool!

 

I finally decided to just push my luck and undid the screws again, then pulled... pulled... pried and finally Ka-Boink! The front panel came off.

Shortly thereafter, the back panel came off too. I eventually found the fuse, and examined it. It was fine. I looked for any more and was not able to find any more fuses.

Both the front and the back circuitboards are screwed on to the front and back panels upside-in... So when I took off the panel, it was kind of hard to see all the circuitry... But I did get a fairly good gander and nothing was obviously loose or burnt.

Between the two boards, screwed to the bottom of the case (with rubber shock absorbers even) was a metal box. It had two cables connected to it, one saying out and the other saying in. I unscrewed that and looked under it. The cables connected to what looked like a small transformer and between the two transformers were a couple of springs. These springs had a bunch of support wires attaching them that seemed to keep them from moving around too much. Weird! Well, I didn't see anything loose or burnt so I put it back together.

Next, the great experiment:

Okay, the power light does come on. Also, when I turn it on, the speakers give a normal sounding pop. So I thought, maybe something that I can't see is just loose. So I lift the pa about an inch off of the cab and drop it. It makes a really funky boooiiinnnggg sound through the speakers. That much be those springs I saw imbetween the circuitboards. Now that would indicate to me that the back circuitboard is probably working. Since it is what handles the power, and also is what the speakers connect to.

What's next?

Frankly, I have no idea. What is it that might be wrong with the front circuitboard that is killing the signal before it gets to the back circuiboard? The preamp maybe? Hmmm...

 

Done! I have replaced the instrument cable with speaker cables I bought yesterday. No change yet.