audioguru Posted September 3, 2005 Report Share Posted September 3, 2005 What do you mean "wired separately"?Don't just use a single wire from the heatsink to the common point of the pcb and assuming that their cases and tabs are properly connected together on the heatsink. Solder each one's common terminal to the pcb or use a separate wire from each one to the pcb. If there is a resistor an the tab of the TO-220s and the heatsink is soldered to the neutral of the board, won't we have unwanted current flowing through the heatsink?You might have a small "ground loop" kind of current in the heatsink but your wires should be thick enough to reduce their voltage drops.So you propose that the best place for an ammeter in this circuit is the one in the picture?Correct. ;D Quote Link to comment Share on other sites More sharing options...
Staigen Posted September 4, 2005 Report Share Posted September 4, 2005 Hi thereAudioguru, placing the ammeter between the rectifier and the smothing cap just dont feels right, the resitstance of the ammeter reduce the charging current a lot, its only short pulses with a lot of current, compared to the total current going to the regulators. The ammeter should be placed between the 2200 cap and the caps connected to the inputs of the regulators. And use an ammeter with a low voltage dropout, 50 or 100 mV!//Staigen Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 4, 2005 Report Share Posted September 4, 2005 Hi Staigen,You have a good point! ;DI agree with you. Quote Link to comment Share on other sites More sharing options...
Staigen Posted September 4, 2005 Report Share Posted September 4, 2005 Hi there AudioguruIn an earlier reply you also say that the caps across the rectifier diodes is removed in newer equipment. They are suddenly not, only in cheap suplies! An examle, i bought a pair of speakers to my computer, cheap ones, 160(2*80) whats, they where powered by a 6 VA, 12 Volt wallvart(hehe), and have problem with hum when the volume was turned up, not much, but it was there. I then replaced the wallvart with an another one, 12 VA, 12 Volt, and the problem was gone. I then pryed the old wallvart apart, and found that the caps was not there, it was place for them, and the mounting holes was there, so i mounted 4 caps and the wallvart worked as it should, the hum was gone. Now i use the 12 VA one, i belive the other was a little bit to small for the 4 ohms speakers. Hehe, a 6 VA wallvart for a 160 Watts Amp! Ridiculous! The speakers inside is 5 Watts ones, and i belive that the amp put out less than that, with a decent sound!//Staigen Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 4, 2005 Report Share Posted September 4, 2005 Hi Staigen,He, he. They should never put Whats ratings on audio equipment. ;D ;DIf the rectifier diodes have a quick reverse recovery rating, then I don't think they would cause mains buzz. The slow ones are still conducting when they should be shut-off. ???Maybe it is the opposite. The rectifier diodes switch too quickly. Adding capacitors across them smooths their switching speed. ;D Quote Link to comment Share on other sites More sharing options...
Staigen Posted September 4, 2005 Report Share Posted September 4, 2005 Hi again AudioguruI dont think 1N400X diodes are either fast or have a quick recovery rating, but they are good at causing mains buzz and hum and all sort of noice ;D ;D//Staigen Quote Link to comment Share on other sites More sharing options...
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