I've gone through a bunch of threads and didn't find a direct answer but sorry if this is a redundant post. I have an amp I've been running for 6 months now with an 18-0-18 500 VA antek transformer and a DIYaudio store power supply with an Aleph 3 clone board for months. I recently updated it to an Aleph J which is wonderful! However, after a couple of hours, the transformer starts to buzz noticeably (it is silent until then). This is a mechanical buzz not through the speakers. Is this likely a heat-related problem?
Although the transformer itself doesn't get warm the Aleph J does run warm inside the box and the rectifiers (KBPC3xxx) are getting to ~50 degrees C. The heat sinks for the amplifiers are well within reasonable limits less than<40 C in most places I measure them <50 C in the "hot spots". There is plenty of space on the bottom and both sides and warm air is flowing out the top vents.
Should I try a fan or better heatsinks on the rectifiers? Any other suggestions???
Although the transformer itself doesn't get warm the Aleph J does run warm inside the box and the rectifiers (KBPC3xxx) are getting to ~50 degrees C. The heat sinks for the amplifiers are well within reasonable limits less than<40 C in most places I measure them <50 C in the "hot spots". There is plenty of space on the bottom and both sides and warm air is flowing out the top vents.
Should I try a fan or better heatsinks on the rectifiers? Any other suggestions???
Thanks, ZM. Is it strange to you that I can run it for two hours without a buzz? I took the lid off to let some heat out and it seemed to help.
Was the amp cooler when you were using the Clone Aleph 3 boards? IIRC, a properly biased A3 shouldn't be any cooler than an Aleph J.
It seemed to run a little cooler maybe up to 5 degrees C on some of the hotter areas (I never tried to track air temp inside the chassis but it seems warmer now). The previous "A3 boards" were questionable designs that I wanted to replace after becoming a member DIYAudio. The bias resistors on these boards were 1 ohm biased at .65 amps. I'm not sure comparing it to a real Aleph 3 is valid.
The amp sounds great, dead silent, and seems to operate within specs. One point of view is to try a fan and see what happens. (I do hate to add one though).
The amp sounds great, dead silent, and seems to operate within specs. One point of view is to try a fan and see what happens. (I do hate to add one though).
I found the problem (at least I'm pretty sure). I had a bad connection to ground at a screw terminal. I've been running for 3 hours and no buzz yet (fingers crossed).
not exactly that I actually helped anything here..... though
that leads me to think that you either have screw connection or crimped spade-plug there
that's why I always cringe - solder that, solder that!!!
that leads me to think that you either have screw connection or crimped spade-plug there
that's why I always cringe - solder that, solder that!!!
I prefer solder too but wanted to be able to change amplifier boards easily so I have a mix. I work in an industry that has proven screw connections on stranded wire can be just as good as solider when you tighten them correctly. The technicians can get it right, engineers like me are the ones that screw it up.
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Fantastic! Could you shed some more light on the likely cause? Where exactly was this bad connection to gnd, and how weak was it? Pics?
Regards,
Andy
Sorry, I didn't take pics but I used screw terminals at the power supply and the amplifier (soldered to the boards). The ground connection on the PS board to the amplifier board was extremely loose (Like some idiot didn't tighten it at all). I think the amp was getting ground through the XLR connection and not from the power supply. I'm not sure why this caused the transformer to buzz rather than causing a buzz through the speakers but that is what happened. As you can find everywhere on this forum grounding is critical and not doing it right is trouble. I've played the amp for maybe 8-10 hours and no buzz since I fixed this.