Sorry they are not mosfets. I am writing in to many treads at the time. Have a lot of amplifiers also very exspensive. There is really not many possibillities in the west for diyers anymore.
Succeeded
Yes now it is very very good. Changed input capacitor to Kasai 50 uf 63 v bipolar. Input resistor 100 ohm 0.01 % Vishay. Emitter resistors to Ohmmite. Kasei 100 uf 100 v to Nichicon 470 uf 100 V. Play like a dream. But it was hard work. Several modifications before it got good.
Yes now it is very very good. Changed input capacitor to Kasai 50 uf 63 v bipolar. Input resistor 100 ohm 0.01 % Vishay. Emitter resistors to Ohmmite. Kasei 100 uf 100 v to Nichicon 470 uf 100 V. Play like a dream. But it was hard work. Several modifications before it got good.
Bias
Anybody know how to increase bias on theese moduls? After several hours it is still not hot. Only 34 Celsius after 5 hours.
Anybody know how to increase bias on theese moduls? After several hours it is still not hot. Only 34 Celsius after 5 hours.
Just read in an old dartzeel thread how it's done, should be easy to find, you should twist those speaker wires.
I will soon release the progress of the Model 458, and some test results as well as PCB design.
The PCBs have better quality than Chinese Model 108 clones, I promise. 🙂
The PCBs have better quality than Chinese Model 108 clones, I promise. 🙂
Twist speaker wires does not do anything in my opinion. Twisting or close parralel is exactly same resulting hum. There is absolutely nothing about bias anywhere. Hifi for you? Skruer Selv?
The easiest way is to increase the 20ohm base resistors of the two MJE15033/MJE15032 transistors in the driver stage.
120ohm will double the output transistors bias.
56ohm gives 50% more bias,
this is according to simulations.
Yes I have seen that. I do not know if it is done in this. Better cut them out an see.
I would match the two diodes, to deliver equal voltage over the given resistance.
Not sure if saturation will occure.
Not sure if saturation will occure.
I built a low voltage(32v), higher current version. Outputs run at 260mA, drivers at 130mA. At lower powers where i mostly listen this seems preferable to the standard.
I did that modification and now DC is running up and down very much. 47 ohm instead of the 20 ohm. And the 6.2 Zener instead of 5.1 v . So now I can not use the amp at all. Will mount another 47 ohm across the 47 ohm so it will get down to 23.5 ohm.
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If running at 55v or close i would only change the zener voltage. Resistor values on the original boards appear identical but zener voltage is impossible to read from the pics. At least this is my reasoning if one wants to keep the amp operating as close to the original as possible.
Hi analog sa
Maybe I should try to change the base resistors to a higher value. I mean the base resistors for the power transistors.