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artcarmo 6th September 2011 09:00 PM

SoundTech PowerSource1300 NOISE
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Hi friends,im a E hobbyst with some test gear,i got this sountech powers source1300(ebay),this one have a noise at the
outputs like a buzz ,everything at the output modules are fine (power trs ,resistors,etc) i put some pics ,the oscilloscope
taken at the outputs with 1khz sinewave at the inputs,and at the power supply with no load (NOTE in power supply i got
same signal at pos,neg hi and low voltage rails,but even at the ground with the ground of the scope at the amp ground..???)

I will try to upload the schematic i get,the noise decrease at outputs when i disconnect one chanel no matter if is A or B

I only notice that the PWM ic's gets really hot ,i change the caps at power supply,one side only,and the signal
in the oscilloscope just 'focus' but the amplitude an freq still are the same (the pictures are taken after the


So if anybody can give some advice ,that will be nice,

artcarmo 8th September 2011 07:25 AM

1 Attachment(s)

artcarmo 10th September 2011 09:17 AM

seems to be no answer on this

gonzothegreat 7th January 2015 06:41 PM

Thanks to the OP for posting the schems. I have a PS-1600 amp that has a very similar power supply and need a schematic for the 1200/1600. This will hopefully help figure out why the 250v 500mA fuse blows immediately without any other fuses or the output modules.

Hopefully it isn't the Samsung electrolytic caps. Never seen their caps used in any other gear and that isn't a good sign IMHO.

JonSnell Electronic 7th January 2015 07:47 PM

Nothing wrong with Samsung Capacitors, they make good road building diggers as well!
I would check the main smoothing in the buzz amp.
500mA fuse blowing. Is JP1 correctly positioned?

gonzothegreat 9th January 2015 01:44 AM

The 120/240 jumper was factory set at 240 and was blowing the 500mA so that wasn't the issue. There are a few caps in the LV psu that are being pushed hard like C408 (16v on a 15v regulator). The 12v zener might be bad as well.

There is a seller on eb-ay that has a repair kit for another Soundtech amp. Can't tell for sure but it looks like the parts rebuild the LV psu ie the linear regulators, caps and a few other passives.

gonzothegreat 16th January 2015 11:09 AM

The fuse issue was the power transformer in the linear PSU. The top of the transformer only has a thin layer of tape protecting it and some monkey tech banged it up. The 500mA fuse no longer blows and the 12v/15v/zener PS section is working. Power light comes on immediately and it doesn't go into protection. All fuses are good as well.

Unfortunately the amp still isn't ready for the show. This was a 240v amp but I need a 120v unit so I moved JP1 to the correct setting for 120 ie both primary windings in series. The linear PSU is working but the SMPS voltages are only half what they should be. The +/- 50v rails are only 25v and the 90v rails are 45v. I thought the SMPS would handle 120v without any other changes but apparently not. There aren't any conversion notes on the above schematics. Does the 120v model use different SMPS transformer(s)?

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