Backline 600 Troubles

[SpecialGr3g]

I just picked up a GK backline 600 and it doesn't seem to be getting full power out to the cabs. I took the top off and powered the amp on, the fan did a little half rotation like it wanted to start spinning but didn't. With all the eq and volume nobs at 12'oclock and the clean channel selected very little to no volume was coming out the cabinet speakers. I did visually inspect the whole circuit board and nothing is discolored and all the solder looks solid. please if anyone could give some help or advice that would be great.

Thanks Greg

 

[SpecialGr3g]

Don't mind the knobs in the picture, that was after I was done testing. I was cleaning out the pots.

 

[agedhorse]

How are your electronics chops? Do you have any test equipment?

 

[SpecialGr3g]

How are your electronics chops? Do you have any test equipment?

I am not sure what you mean by "electronics chops" and I do have a couple multimeters and a UF tester as well.

 

[agedhorse]

Do you understand signal flow, troubleshooting electronics (things like operating points, level shifting, global feedback)? Do you have a scope (and know howto use it)?

These are things that are likely to be necessary for a successful repair.

 

[SpecialGr3g]

Do you understand signal flow, troubleshooting electronics (things like operating points, level shifting, global feedback)? Do you have a scope (and know howto use it)?

These are things that are likely to be necessary for a successful repair.

cant say that I do.. I am very teachable though and pick things up very fast... but I have a basic understanding of electronics..

 

[fdeck]

I have a BL600 and it's a great amp. But here's my guess.

First, see if you can borrow a friend's amp, to test your cables, speakers, etc. Try with each speaker separately in case one of the speakers is shorted.

Next, see if you can get sound out of it when you plug directly into the effects return. This will bypass most of the preamp.

Sound: Worth taking to a tech. It means that the power amp and power supply, along with your cables, are probably OK.

No sound: Not worth repairing, because you can find a used BL600 for pretty cheap. They were only $300 new.

The fan is designed so it will only spin up if the power amp gets warm.

 

[agedhorse]

If you want to try repairing yourself, now would be a good time to hit the books.

 

[fdeck]

If you want to try repairing yourself, now would be a good time to hit the books.

I've tried repairing myself. I'm beyond repair.

 

[Passinwind]

I've tried repairing myself. I'm beyond repair.

Start with the surface mount stuff, most people will never look deeper anyway.

 

[fdeck]

Start with the surface mount stuff, most people will never look deeper anyway.

That's good, through-hole is much less pleasant.

 

[agedhorse]

No kidding!

 

[SpecialGr3g]

I did try plugging each cab individually and tried different cables in different outputs while doing a power cycle between switching. It still had the same result low volume when turned up and I did play through the amp for a half hour with the top off and the heat sync did get warm and the fan still did not turn on at all.

 

[agedhorse]

Do you have signal at the effects send?

 

[SpecialGr3g]

its dead! today I tried plugging into fx send and now im not getting any sound of the amp at all no matter what is plugged in. thanks for the help guys looks like im just going to spend some more cash on a amp. any suggestion both the cabs are 200w 8ohm. any suggestions would be greatly appreciated.