m250
hienrich kumusta? these sanken transistor you have mention ive been using these about ten years ago with my 150w amp which was taken acctually in the electronics digest... the output stage was using (2sa1216a & 2sc2922a) or (2sa1215a & 2sc2921a) they only differ in Vce. its input stage was using an op amp LM301AN... the low power supply requirement of the op amp was scaled down with the use of limiting resistors and further regulated by zener diodes.....
musta bay?
alan
hienrich kumusta? these sanken transistor you have mention ive been using these about ten years ago with my 150w amp which was taken acctually in the electronics digest... the output stage was using (2sa1216a & 2sc2922a) or (2sa1215a & 2sc2921a) they only differ in Vce. its input stage was using an op amp LM301AN... the low power supply requirement of the op amp was scaled down with the use of limiting resistors and further regulated by zener diodes.....
musta bay?
alan
well, we still have differences in doing things but arrive on the same
place.
many service manuals of knowned manufacturers, places test points
on there service schematics and even voltage drops across these test points
meaning, you place your test probes on those points and measure
those assigned voltages when ever doing a servicing...
when doing it your way it is safe but you should also know the
current consumptions of the input and the voltage amplfier stages,
and add them up together with the output stages so you have your
total current consumption....
but what if there is this someone who knows not more on current
consumptions, without scopes and only done his projects by a given schematic and a PCB layout but without construction manuals.....??
so still VBE measurements are essential no matter which bipolar
are used....
rgds,
macweb
place.
many service manuals of knowned manufacturers, places test points
on there service schematics and even voltage drops across these test points
meaning, you place your test probes on those points and measure
those assigned voltages when ever doing a servicing...
when doing it your way it is safe but you should also know the
current consumptions of the input and the voltage amplfier stages,
and add them up together with the output stages so you have your
total current consumption....
but what if there is this someone who knows not more on current
consumptions, without scopes and only done his projects by a given schematic and a PCB layout but without construction manuals.....??
so still VBE measurements are essential no matter which bipolar
are used....
rgds,
macweb
Hi macweb,
No. What you are doing is incorrect. Period. And another period!
What is important to know is the actual current through each device, so your idea is correct. Your method is totally wrong.
How do I know? I've serviced gear for over 25 yrs. Warranty for many brands and LARGE power amps. The only accepted method (where emitter resistors exist) is to measure and monitor the voltages (in mV) across the emitter resistors. You want to know the outputs are sharing current equally. You pick an average one and set your bias current from that. End of story.
Now, some manufacturers want you to replace a fuse with a resistor and measure the voltage across that. Others (like Fosgate car amps) want you to look for crossover distortion under load, normally something like 20KHz across 4R at low power. I guess you could use a current probe but that's a bit out there for normal techs.
-Chris
No. What you are doing is incorrect. Period. And another period!
What is important to know is the actual current through each device, so your idea is correct. Your method is totally wrong.
How do I know? I've serviced gear for over 25 yrs. Warranty for many brands and LARGE power amps. The only accepted method (where emitter resistors exist) is to measure and monitor the voltages (in mV) across the emitter resistors. You want to know the outputs are sharing current equally. You pick an average one and set your bias current from that. End of story.
Now, some manufacturers want you to replace a fuse with a resistor and measure the voltage across that. Others (like Fosgate car amps) want you to look for crossover distortion under load, normally something like 20KHz across 4R at low power. I guess you could use a current probe but that's a bit out there for normal techs.
-Chris
built my first ss amp in1975!
my first solidstate amp was a pioneer 707 clone! it was a quasi-complimentary design with bootstrap capacitor and a single 38volt rail,
then a complimentary amp with 2n3055/mj2955 in the late or early 80's with a supply voltage of +/-32volts.
i built my first leach super amp around 1984 using japanese transistors and scaled down psu rails of around +/-60volts dc!
with all the years of experience behind me, repairing power amps like soundcraftsmen, GAS, hafler, and many others of japanese make, i think i am qualified to comment about testing methods!
i can spot where something is amiss!
the m250 is typical design topology that is open for a lot of possible modifications.
my first solidstate amp was a pioneer 707 clone! it was a quasi-complimentary design with bootstrap capacitor and a single 38volt rail,
then a complimentary amp with 2n3055/mj2955 in the late or early 80's with a supply voltage of +/-32volts.
i built my first leach super amp around 1984 using japanese transistors and scaled down psu rails of around +/-60volts dc!
with all the years of experience behind me, repairing power amps like soundcraftsmen, GAS, hafler, and many others of japanese make, i think i am qualified to comment about testing methods!
i can spot where something is amiss!
the m250 is typical design topology that is open for a lot of possible modifications.
heinrich, whoever you are. are you the designer of the M250 at Makus M250
can you update the site or something? i really like the m250 and the mcd 1 and i really want the schematics for the mcd 1
can you update the site or something? i really like the m250 and the mcd 1 and i really want the schematics for the mcd 1
They should just drop straight in. They are slower in fT so there should be no stability problems. If you're running it heavy you might want to use 6 transistors per side instead of 4, but that's about it. You could always drop the rail voltages a little to say 50V or 42V if you want to stick with 4 pairs.
" If you're running it heavy you might want to use 6 transistors per side instead of 4, but that's about it. You could always drop the rail voltages a little to say 50V or 42V if you want to stick with 4 pairs."
If they are real, four pair MJ15003/04 will have 2KW SOA at 50V. With ±55V, a 38-0-38 1KVA transformer, and good heatsinking, they will do 500W into 2 ohms.
If they are real, four pair MJ15003/04 will have 2KW SOA at 50V. With ±55V, a 38-0-38 1KVA transformer, and good heatsinking, they will do 500W into 2 ohms.
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