Soundcraftsmen 900X2

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:bawling:

Just Bought a Soundcraftsmen 900X2. It worked fine for a test but in my first show it started cutting in and out and died.
There is no output anymore. PS looks ok, input works and clip lights light with enough signal. I'm guessing something with the protection circut. The whole system blew the house circut breaker before we moved it to another circut. I hope that wasn't it.
No dc on output. Anyone got a schematic?
One thing I noticed is the relays do not engage on turn on. Since it's not returnable.....I could use a little help. Will start checking all the mosfets out of circut however initial tests look o.k.
Does this amp have that wierd problem where certain RF will shut it down. I vaguely read about that problem somewhere.

Thanks
 
This is the same circuit as the PCR-800. with beefed up power supplies . My schematic sheet lists the 900x2 amp as well.

If the clip lights arent full on and you get normal clip lights with enough input, then this should be an easy fix as most likely the amp is still working correctly and something in the protection circuit is bad. the clip lights are very sensitive and any amount of dc offset or distortion makes those lights light up.

I will say, these amps are not quite as tough as they make them out to be. a good old QSC will beat the pants off one of these hands down for reliability anyday. these were designed as home stereo amps and they were trying to crossover a bit into the MI market i think. there good for light weight DJ use but dont beat on them.

I posted schematics for the PCR-800 online here a while back i think.


Zc
 
I just found some photo's of the inside of this amp. it is not the same as a PCR-800, but may be similar.

Zc
 

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The 900x2 is very similar to the ProPower 8 - it may even be identical. I have one of each, but have not compared the modules side by side. I have some hand drawn schematics of the ProPower 8 available here .

The problem with your amp may be as simple as a bad connection between the power supply and protection boards. It may be that the protect board is not getting power, so it is unable to turn on the relays to connect the speaker to the amp.

Zero Cool: Where did you find those pictures? My 900x2 looks exactly like that! The connections are soldered rather than using push on connectors. I assumed the previous owner did it, but maybe is was that way from the factory.
 
First thing I would do is measure for DC on the outputs. I would also measure for AC on the filter caps. My first PCR-800 did that and all it needed was new filter caps. My second one had some drivers out on the power supply. I just swapped those out and it plays perfectly. Cost me something like $10.

Blessings, Terry
 
I have a ProPower 4 that did the same thing. Loud buzz, lights, and a horrible stink. One of the filter caps gave out and vented.

Remove the regulator board that sits on top of the caps and check for signs of venting or bulging.

It is a good idea to replace the SCRs and their drivers in addition to the bad caps. At least check them if you don't want to replace. A bad SCR will quickly destroy the caps.
 
Are the burn marks on the bottom of the board? Take a carefull look at the top of the big caps. Compare to this picture . Notice the blown vent of one cap. Some caps have black vents rather than white, so it may be hard to tell if it has vented. Burn marks on the circuit board directly above the vent is a sure sign the cap has died.

SCR is Silicon Controled Rectifier. It is a triggerable diode. There are four along one side of the board, they have a small heat sink. They are used as the bridge rectifier in these amps. Voltage regulation is done by changing the phase angle they trigger at (PCR - Phase Control Regulation).

If you don't have experience with electronic repair, it is probalbly best to just replace the caps. Make sure the polarity is correct (+ to +, - to -).
 
Carlos: Do you build a new amp every week? :D

I have a collection of Soundcraftsmen shematics at www.soundcraftsmen.info

The PCR800 is very similar to the 450x2, and ProPower 1,3,4 & 10. It is rated at 205 W per channel at 8 ohms, and 325 per channel at 4 ohms. This is by far the most common Soundcraftsmen MOSFET amp design.

Hitachi MOSFETs where used until they stopped production, then Exicon MOSFETs where used for a few years.

Most of the MOSFET amps have a Phase Control Regulation (PCR) power supply.


Terry: Do you have a larger version of that schematic that you could send me? Power supply too???
 
oPossum said:
Carlos: Do you build a new amp every week? :D

I have a collection of Soundcraftsmen shematics at www.soundcraftsmen.info

The PCR800 is very similar to the 450x2, and ProPower 1,3,4 & 10. It is rated at 205 W per channel at 8 ohms, and 325 per channel at 4 ohms. This is by far the most common Soundcraftsmen MOSFET amp design.

Hitachi MOSFETs where used until they stopped production, then Exicon MOSFETs where used for a few years.

Most of the MOSFET amps have a Phase Control Regulation (PCR) power supply.


Terry: Do you have a larger version of that schematic that you could send me? Power supply too???


Yes I do. Let me dig them out. A fellow sent them to me through snail mail a while back. Let me search for them and I'll get back to you. Send me an email so I won't forget. These threads get buried sometimes. Out of sight, out of mind. :D

Blessings, Terry
 
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