Soundcraftsmen 900X2

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#21
Attached should be a compressed picture of the top of the board. Hopefully it is clear. The orignal picture shows the brown spots clearly.
 

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#23
cygnusxi said:
The burn marks (light brown squiggly lines) I saw were on the top side of the board. I'll try to take some pictures of what I see and post them. I don't recall the caps being vented, but I'll look again and try and take a picture of those too.

Thanks again.
Click to expand...


Squiggly lines sounds like maybe at some time a wire over heated.
Just a thought.

Blessings, Terry
 
#24
The only brown spots I can see on the PCB are at the leads of the big power resistor on the lower left. That is normal for this amp, that resistor runs hot! Is that it, or did I miss some other spot?

The caps look fine, but they are still the primary suspect. Sometimes parts fail without any noticable physical damage.
 
#28
Final analysis

FYI:

To fix the loud buzz and tripping the breaker, I took my amp to Diversified Audio in Tampa, Florida and they found it was a single SCR in the power supply. They advised no reason to replace anything else.

Thanks for everyone's input.
 
#29
Soundraftsmane 900x2 Power supply Help

Greetings and thanks for all the guidance so far.

My 900x2 is running with supply voltages at 102 volts instead of 87. Unfortunately my copy of the schematic does not include the scr board and the power controller/relay board print is unreadable. Anyone have the print for these two boards.
Thanks.
 
#30
My capicitors burned out in my 900x2

does anybody know where i can get the capacitors for the 900x2? i can't seem to find them anywhere... Also, on the top of the capacitors, there are numbers, one is 22 and the other is 13.

not certain where to get these. by the way, i found a guy on the internet who said he sells the orginal schematics for the soundcraftsman amps at http://www.gourmetpa.com/s.html
 
#33
I have 4 PR1800 amps. These are the early production of the model that was later renamed the 900X2 after MTX bought Soundcraftsmen. Some early ones didn't have the later 'soft-start' circuit. The very high inrush current when you first turn them on tends to make the power supply caps explode or is very hard on the caps to say the least. The damaged caps sometimes subsequently blow the regulator SCR.

So anyway I haven't turned on these amps in 5 years; they've been sitting in a stack in my kitchen. Now after reading these posts I'm kind of afraid to turn them on. I do have some really big variacs, but I'm not sure I could power them up slowly to form the caps anyway, since this is a switching-mode power supply. I don't want to have to replace the caps if not necessary. I don't want to have to build a power supply just to form the caps.

Any good advice is appreciated.
 
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