Sonance DSP 8-130 schematic

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ubxf

Well-known member
Joined
Sep 3, 2004
Messages
796
Location
los angeles
Hello,
i just got one of those amps but it won't power up. I called the company for support but they don't repair or have the schematic .
It has 8 Hypex UCD250LP so it should be pretty good. My repair skills are quite basic and i'm more comfortable around tube gear , this
is definitely over my head.
I opened it up and looked at the power supply and didn't see any obvious burned component, the fuse is ok, is there anything else to look for.
 
Mains input fuse? NTC? Any smaller transformers in addition to the main one, in case the power supply is a switchmode one?
 
Thanks, the main fuse is ok, when i apply power no current is being drawn
 

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Those symptoms would lead me to believe that the standby supply may very well not be working. I see the small capacitors are of the "wonderful" JH brand (some nearly random chinese crap, wouldn't trust them as far as i could throw them), so the first step i'd take is investigating that area (C950 & co. on the primary side, and C955 and its neighbour, on the secondary.

And/or the PWM controller of the standby supply itself, the 7-pin hidden behind U906 in the second picture. What part number IS U906, by the way?
 
Thanks Khron, i'll investigate according to your suggestions. Here is a picture unfortunately not great of U906. I'll get a better one later today
 

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So i changed the the JH electrolytics (955,954,950,949,927,920,926and the 2 10uf 400v) and the 7pin THY287PG that is behind U906 and unfortunately the situation is the same. If you have any other suggestions could you please let me know and i would be happy to give it a shot.
 
D921 IN5822 is ok (was ok but i put a new one in just in case)
still no change unfortunately. When i power up i reconnect everything to provide a load then i bring it up slowly on a variac and monitor the voltage and current. Would it be better to try the power supply by itself?
 
It can't hurt. Not sure winding the voltage up slowly is the best idea for switchmode supplies though; a series-bulb tester might be more useful.

Did you at least wind it up to full mains voltage? And is everything else on the primary side ok? Fuse, common-mode chokes, varistors, bridge rectifier?
 
Yes a bulb tester would be better, i brought it to full mains voltage. Everything seems ok on the primary. Now it powers up but it is in a weird cycle loop, the relay keep clicking every 3 or 4 sec and the lights flash (that is with everything connected)
 
Can you connect the power to each of the 8(?) amplifier modules individually? Might be worth trying one at a time, to begin with.
 
i was about to dismantle everything so i could test each amp by themselves but i noticed that the power supply is only good on +55V the minus 55V side is giving 0.7V .
btw i finished recapping and the supply is not cycling anymore.
 
No unfortunately i couldn't but all the amps are ok by themselves . The power supply is still not working correctly.
 
Sorry to hear. Sadly there seem to be very very few on the internet who are repairing and posting about it anywhere. :/
 
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