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Hi,
I have just finished building Sympatico.
When I turn it on, I hear hum(quite loud white noise) and heat sink gets very hot quickly.
Is this normal? Or something might be wrong?
I am feeding Sympatico with Buffalo32/Volumite directly and speakers are 4ohm.
Power sources are two AN-4222s and R10 is open.
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No, that is not normal. Check for continuity between the V- rail and the heatsink (there should be none).
Does this happen on both channels?
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Please post photos if you can. Something is definitely wrong.
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Yes, it happens on both channels and there is no continuity between the circuit and heatsink. Please tell me how to upload a photo. hkminn attached the following image(s):  phpXJiMWEPM.jpg (96kb) downloaded 591 time(s).You cannot view/download attachments. Try to login or register.
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What is the orientation of the opa1632. Is the white bar facing the rectifier or the heatsink?
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Also please measure the voltage across C11 and C12.
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You could try another source. I also got white noise when i hooked up my squeeze box to the Sympatico but it was fine when I used my ipod (both single ended).
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Russ White wrote:What is the orientation of the opa1632. Is the white bar facing the rectifier or the heatsink? The white bar is facing the rectifier. I will measure the voltages across caps as soon as possible. Is it OK to connect power sources to Sympatico when heat is building up very fast? I am wondering whether I have connected transformers correctly. I read 40v btw AC1-AC2, 20v btw AC1-CT1, 20v btw AC2-CT2. Edited by user Wednesday, July 7, 2010 6:06:23 PM(UTC)
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Your transformer voltages seem to indicate that it is attached correctly.
Can you get a closeup shot of the 4780 pins (top and bottom)? I know it's tough to do at this stage.
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sureshm wrote:You could try another source. I also got white noise when i hooked up my squeeze box to the Sympatico but it was fine when I used my ipod (both single ended). You need to remember to connect IN- to GND when using a single ended source. Cheers! Russ
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Russ White wrote:Also please measure the voltage across C11 and C12. Btw 13.8v and 14v across both caps. I measured ( + cap - ) with heatsink farther away with all the connectors disconnected. Is polarity correct? Edited by user Wednesday, July 7, 2010 8:47:55 PM(UTC)
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Brian Donegan wrote:Your transformer voltages seem to indicate that it is attached correctly.
Can you get a closeup shot of the 4780 pins (top and bottom)? I know it's tough to do at this stage. hkminn attached the following image(s): chip1.jpg (60kb) downloaded 516 time(s). chip2.jpg (40kb) downloaded 517 time(s).You cannot view/download attachments. Try to login or register.
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Russ White wrote:sureshm wrote:You could try another source. I also got white noise when i hooked up my squeeze box to the Sympatico but it was fine when I used my ipod (both single ended). You need to remember to connect IN- to GND when using a single ended source. Cheers! Russ Sympatico is connected balanced to B32, which I have been using for almost a year w/o any problem. My main concern at this stage is more about the heat than the noise. The size of the heatsink I am using is not very big(4"x4"x2" for each 4780). But even when it is idling, LM4780 heats up very quickly and become abnormaly hot, just like when a tube amp is biased too high.
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Russ White wrote:Please post photos if you can. Something is definitely wrong. Something must be wrong!!! I replaced 4ohm speakers with 8ohm speakers, then there was a high frequency beeping instead of white noise. It sounded like a mic feed-back when the mic is placed too close to the speakers on a PA system. Edited by user Thursday, July 8, 2010 2:25:34 AM(UTC)
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One other thing, ALWAYS when testing a new power amplifier connect the inputs to GND. Not a real source.
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hkminn, to help me understand if we both are having the same problem, could you please connect both IN+ and IN- to GND (as Russ suggested) and measure voltage from OUT+ to GND and OUT- to GND when the power is on?
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