Paul_J Posted October 20, 2006 Report Share Posted October 20, 2006 I replaced a STK3062 in a Marantz PM-52SE power amp with another module. The output DC offset voltage is 0 but the quiscent current in 700mA. :oWhat should I do to reduce it to 70mA?Here's a list with the values of the components of the replacement module:R1______________47K 1/4W ResistorR2_______________4K7 1/4W ResistorR3______________22K 1/4W ResistorR4_______________1K 1/4W ResistorR5_____________330R 1/4W ResistorsR6_______________1K5 1/4W ResistorR7______________15K 1/4W ResistorR8______________33K 1/4W ResistorR9_____________150K 1/4W ResistorR11_____________39R 1/4W ResistorC1_____________470nF 63V Polyester CapacitorC2_____________470pF 63V Polystyrene or ceramic CapacitorC3______________100uF 63V Electrolytic CapacitorC4_____________100nF 63V Polyester CapacitorsC5______________10pF 63V Polystyrene or ceramic CapacitorQ1,Q2,Q3,Q4,Q5_____MPSA42 300V 500mA NPN TransistorsQ6___________MJE340 200V 500mA NPN TransistorQ7___________MJE350 200V 500mA PNP TransistorSTK_3042-3062-3082-3102-3122-3152_III_-_Sanyo.pdf Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 20, 2006 Report Share Posted October 20, 2006 If your amplifier circuit has a trimpot to adjust the amount of idle current then it will connect to a transistor or couple of series diodes connected to the outer of the 3 pins of your new module. Probably the new module passes a different amount of current through the adjustment part so it causes a higher idle current.Attach a schematic of the output circuit to see the adjustment trimpot and what can be changed to get a better current adjustment range. Quote Link to comment Share on other sites More sharing options...
Paul_J Posted October 20, 2006 Author Report Share Posted October 20, 2006 Because it's a rare amp I don't have a schematic. It's hard to guess it by looking at the PCB tracks because there's also a circuit that detects if there's DC at the output. I think the value of the trimpot is too large. The trimpot connects to a transistor.If this doesn't work I'll use a couple diodes. Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 20, 2006 Report Share Posted October 20, 2006 I think the value of the trimpot is too large. The trimpot connects to a transistor.Maybe Marantz copied Sanyo's circuit. Increasing the value of the pot turns on the transistor, then the idle current is reduced. A resistor is on the other side of the transistor to turn it on, reduce its value to reduce the idle current.It would be difficult to find a trimpot the same physically but with a higher resistance. Quote Link to comment Share on other sites More sharing options...
Paul_J Posted October 20, 2006 Author Report Share Posted October 20, 2006 The circuit is different from Sanyo's. The trimpot is an ordinary one, nothing special. I could easily find a replacement if I had to. The output stage seems to be a triple Darlington - all TOSHIBA.I'll find a way to fix this. Thanks anyway. Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 20, 2006 Report Share Posted October 20, 2006 Marantz was an extremely high quality [q]American[/q] hi-fi equipment manufacturer, probably the very best. Now they are Japanese-owned and use cheap Sanyo and Toshiba parts. Their owners also bought McIntosh and Boston Acoustics. Amazing. Quote Link to comment Share on other sites More sharing options...
login
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.