Behringer Ultrabass BX4500H wanted

[allante666]

Looking for schem for the above. anyone help?

[Enzo]

Can't provide a schematic, but what are you fixing? In my experience, you either have a blown output in the powr amp or a bad op amp in the preamp. Close? Usually can find a bad op amp by going down the row and reading for DC voltage at each output pin.

[zero cool]

I have the front end schematics for that. but forget which power amp module is in that. I probably have that too.


Zc

[Enzo]

The P3000. Also used in the BX4210 and the BX3000. It has three 5200s and three 1943s as outputs.

[allante666]

Zc anything would be a bonus! its the one Enzo said with the six output trannies.
Thank you

[zero cool]

Dang that's one i don't have! Sorry, But i will hunt for it. if i find it i will let you know.

[knutknut]

Did anyone ever find a schematic for this series of amps. Need schemes for BX3000 if any one can help

[mozwell]

BX4500 pre, BX1200, BX1800, Ep2500 amp
the amp may be close to what you have.
i hope the files help someone

[knutknut]

Hi Mozwell. Thanks for the response. Unfortuneately, none of the schemes are close to what I have. Guess I shall just have to bin the amp and buy an Ashdown

[mozwell]

Dont give up yet. Even without the schematic many amps have been fixed with help from the very kind people who inhabit this forum.

Step 1. Check all output transistors & their ballast resistors for shorts.
Step 2. Measure power supplies, are they all ok, this includes the power supplies to the op amps.
Step 3. Is there DC on the speaker output ? Do not connect a speaker for any testing yet
Step 4. Plug a patch lead into the send & return jacks, does this help
Step 5. Plug a patch lead into peeamp out / power amp in (if these are on the amp), does this help
Step 6. Are you getting signal out of the preamp ? Hint, as Enzo said above, check the output pins of each op amp, are any sitting close to the supply rails or are thay all close to 0V

read post #2 again. and before we go into anything else, what is the actual problem with the amp ?
do you get no sound, or a very distorted sound, has it been over heated, or had drinks spilt through it ?

[MarkusBass]

I'm with Mozwell; don't give up. This is a very simple power amp and it can be fixed without the schematic (in most cases). What is actually the problem?

Mark

[Enzo]

If you give us specific complaints or problems, we can probably give specific advice.

I have the schematic to look at, I am just forbidden to post it. I can answer questions about it and discuss it though.

[knutknut]

The the speaker output goes hard over to one rail. The problem seems to be there seems to be no centre tap to the high power winding on the transformer, so cannot figure out how the voltage rails are maintained equally about 0v

[J M Fahey]

What are the voltage rails?
By any chance, are the transistor collectors or emitters grounded?
Does the big filter capacitors centerpoint go tho the speakers *hot* jack terminal?

[knutknut]

Hi JM.
As you rightly comment, the transistor collectors got to 0v (wherever that is) and the centrepoint of the main caps go to the speaker 'hot' terminal.
All the main transistors check out ok.