boy ....... what a mess 
twist every AC pair
go to 6moon and look at every FW amp you can see opened
when you tighten that wire harness - if you have some residual hum - put fat wire bridge between L and R pcb main gnd points
twist every AC pair
go to 6moon and look at every FW amp you can see opened
when you tighten that wire harness - if you have some residual hum - put fat wire bridge between L and R pcb main gnd points
I've had a quick skim through but can't find the answer I'm looking for. Can anyone tell me the approximate cost of building an F5 including power supply but not the chassis?
acumos - Short the input. Does it still hum?
Despearce - Of course things are variable, but I've always quoted $500-600US with chassis, so maybe 200-250GBP without.
Despearce - Of course things are variable, but I've always quoted $500-600US with chassis, so maybe 200-250GBP without.
The most elusive hum problem in my builds was caused by a tiny solder bridge between a power trace and the mounting hardware. I see some spots that appear to have excess solder, so I would suggest checking for same on both sides of, and the full length of the power traces on the F5 boards.
Attachments
You must make your wiring neater and shorter, twist all pairs together as best as possible.
Where is the purple transformer lead (the shield) connected in the amp? It should be directly to the chassis floor.
Where is the purple transformer lead (the shield) connected in the amp? It should be directly to the chassis floor.
Yes, or just to the chassis wherever you can attach it. The shield needs to be at chassis potential, not PSU gnd.
Removing the speaker protection? Good idea for now.
Get the amplifier working and quiet, then add the protection later.
Shorting the input quasi works. What does it means?
with no input connected from source it's silent
with no input connected from source it's silent
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the shield of the input wire. I tried without it no change. Have read my last edited post?
shields of signal routes need to be connected to audio gnd , not chassis
did you read my previous post ?
however - use either twisted pair of wires , or one coax ;
not twisted coaxes
did you read my previous post ?
however - use either twisted pair of wires , or one coax ;
not twisted coaxes
Ok now shields are disconnected, I'd thought two twisted coax would be the best choice, because they are shielded from each other. I can use 24 awg solid core twisted but not shielded. Can this cause this hum, what I should check? What can I attempt?
Measure it, don't guess.
An ordinary DMM (not an RMS meter) set to 199.9mVac is perfectly good at reading a voltage @ 0.1mVac over an adequate frequency range.
The hum + noise of a shorted input power amplifier should be less than 0.1mVac, i.e. you should see a reading of 0.0mVac indicating less than 0.05mVac.
The bad. I've burnt the left q4 irfp240 cause I tried the boards without the heatsinks...
The good? The other channel is working no hum. I'm going to buy a new mosfet. Can I try at this moment to connect the other gnd wire to search for any loop?
The good? The other channel is working no hum. I'm going to buy a new mosfet. Can I try at this moment to connect the other gnd wire to search for any loop?