Took out left and right fuse in turn. No difference to the fused side, same hum. So the toroids are radiating equal amounts to their driven side??.
By disconnecting pcb ground?
If your donut leads are long enough you could also try moving them out of chassis (just as a test) and see what happens with the noise.
I guess running one channel at a time eliminates ground loops and lifting the ground should't be any different.
Best bet will be to take your time getting the transformer output shorted to ground.
I had to pull some of the caps on each side anyhow to get to the pcps so I added shielding for the input trafos and as I was using mic cable on inputs I disconnected the shield from the input side so now the input cable shield is not connected either side. Still have hum, unchanged. Shielding the input trafos changed nothing. My Altec compression drivers are very effective so if there is hum I will hear it. Its to much for late night listening. Will play around with this in the coming days. Its a powersupply problem. Im going to do simple things like reroute the 230v supply, move rectifier bridges further from the pcbs and see if that has some influence on hum. Dont think its a ground loop.
Asking because I dont know. Can I measure ( or estimate ) powersupply ripple with multimeter?. Or do I need an oscilloscope.
If your mm can show AC in the mV range you can, but an oscilloscope is probably more accurate. I think PSUD2 predicts ripple in the order of 50-100 mV for a standard FirstWatt CRC PSU with F6-like current draw.
Thanks silasmellor, Ill see what I can measure with my multi meters this evening. The toroyds are vibrating slightly as I can hear mechanical buzz from them. Could this be the culprint for the hum?
with speakers efficient as yours , every detail in wiring is important
can you post a picture showing cap banks little more detailed ?
if it's possible - make Al plate for 4 caps ground , little extended on end , and take GND point for amp pcbs exactly in middle of back , away of line which connects last two caps screws
that way take out point (central GND point) is moved from area with high pulsating currents
though , by test I wrote , I concluded that magnetical coupling is main problem , not ripple
Thanks ZM Ill post pictures this evening. I hear you and will conduct the test this evening. If the culprint is a magnetic field, screening the edcors in a box (faraday cage ) drained to the heatsinks should have had some notisable effect.
What about the rectifiers, their environment is quite dirty (EM vise) isnt it? The alupates for ground are on the agenda, need to get some plate. And you if I understand your description ground scould be furtest from the rectifyers on the smoothed side.
What about the rectifiers, their environment is quite dirty (EM vise) isnt it? The alupates for ground are on the agenda, need to get some plate. And you if I understand your description ground scould be furtest from the rectifyers on the smoothed side.
only proper test for magnetic coupling is - moving away everything , observing (hearing, measuring) is there any difference
unfortunately , caging Edcors is weak remedy if problem is big enough from start
besides that - just a thought , didn't tested it by myself - those big caps are also pulsating devils , and foil in them is wound spirally ....
can you unbolt one heatsink in any easy way , and move it sideways , then compare two channels for hum ?
unfortunately , caging Edcors is weak remedy if problem is big enough from start
besides that - just a thought , didn't tested it by myself - those big caps are also pulsating devils , and foil in them is wound spirally ....
can you unbolt one heatsink in any easy way , and move it sideways , then compare two channels for hum ?
just nitpicky - avoiding two different materials and further oxidation due to that
in praxis I found it the same - copper or Al
If I lengthen the V+- and Gnd to pcb I can do that. Would it help putting some alufoil between caps and pcbs?
🙂
The easiest way to check if proximity of the caps to the pcbs is a problem is to reconfig the supply as stereo ie with 1 donut, 2 bridges and the 4 middle caps. Then I also have space to play with shorting this and that 🙂
I will also clean up my mains in solution which is a kludge ( connections between swich, fuses and trafos) I used a very stiff wire in a small space.
The easiest way to check if proximity of the caps to the pcbs is a problem is to reconfig the supply as stereo ie with 1 donut, 2 bridges and the 4 middle caps. Then I also have space to play with shorting this and that 🙂
I will also clean up my mains in solution which is a kludge ( connections between swich, fuses and trafos) I used a very stiff wire in a small space.
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that's the same logic , as I was taught - easiest way to catch a Wabbit is - to put some salt on his tail
my father taught me that when I was 5 or 6 ....... never wanting to clarify ..... I was thinking who knows what kind of process is there
probably 10 years later I realized that's practical joke , not something unknown about Wabbit's relation with salt
my father taught me that when I was 5 or 6 ....... never wanting to clarify ..... I was thinking who knows what kind of process is there
probably 10 years later I realized that's practical joke , not something unknown about Wabbit's relation with salt
Difference is, that when I say it and beleive it - its the truth - from my point of view 🙂
Logic ( truth) and personal belief (truth) dont necessary go hand in hand 🙂
Its our irrationality and unpredicability that makes us human and capable of art and invention. ( need a spellchecker).
Logic ( truth) and personal belief (truth) dont necessary go hand in hand 🙂
Its our irrationality and unpredicability that makes us human and capable of art and invention. ( need a spellchecker).
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I was commenting just alu-foil issue , with Wabbit story , we probably typed in same time ... or I just typed too long 🙂
regarding reconfig to stereo PSU , I believe there is no need for that
just use any trick you know to test proximity (Donuts to everything else) question
regarding reconfig to stereo PSU , I believe there is no need for that
just use any trick you know to test proximity (Donuts to everything else) question
No problem ZM. Its quite easy for me to reconfig for stereo as the psu is mostly put together with connectors and screws ( caps ).