Sorry for not posting for so long, replaced all capacitors it seems fixed but both channels now show me around -0.01 when nothing is connected at all. I suspect something is still broken or something.
OSXuser Service manual would be awesome to have with my Lenco A50, maybe sometime later i will think of a solution how to get more power from this unit(maybe raise voltage, or add another pair of power transistors or something) 🙂
P.S. it also fixed the rapid heating problem. because earlier it heated up very very fast. now it heats up in like 1-2h on -18db volume, loudness Off, treble bit more than half, bass middle positions. but still not enough bass for me 😛 at this volume 😀
OSXuser Service manual would be awesome to have with my Lenco A50, maybe sometime later i will think of a solution how to get more power from this unit(maybe raise voltage, or add another pair of power transistors or something) 🙂
P.S. it also fixed the rapid heating problem. because earlier it heated up very very fast. now it heats up in like 1-2h on -18db volume, loudness Off, treble bit more than half, bass middle positions. but still not enough bass for me 😛 at this volume 😀
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A-50 schematic
Hello ozracing,
in the meantime I did some scanning with some of the Lenco Manuals I have. They can be downloaded for free from my hompage Rainbow Electronics
You will find them under 'Downloads' and all of them are available in 2 Qualities.
I hope you will get to work your A-50 properly.
Just for your information about modifying your A-50 for more power: The limitation for more power in the case of the A-50 is the power transformer. The successor of the A-50 is the A-600 and according to the service manual the A-600 has 52 watts per channel with a nearly equal power stage but with a larger power transformer........
Max
Hello ozracing,
in the meantime I did some scanning with some of the Lenco Manuals I have. They can be downloaded for free from my hompage Rainbow Electronics
You will find them under 'Downloads' and all of them are available in 2 Qualities.
I hope you will get to work your A-50 properly.
Just for your information about modifying your A-50 for more power: The limitation for more power in the case of the A-50 is the power transformer. The successor of the A-50 is the A-600 and according to the service manual the A-600 has 52 watts per channel with a nearly equal power stage but with a larger power transformer........
Max
Thank you very much OSXuser will do some research on power transformer, etc. also i've been searching for a decent service manual for months 🙂
According to the schematics, the A600 is a more modern design using higher voltage components that the A50. 2N3055 output transistors limit the A50 amplifier to about 45W/8R. Above that means transistor failure.
In practical terms, even doubling the power only increases the volume level by 3 dB. Increasing the power to 52watts will not be noticed. You need to make large power increases before you can perceive higher power. Our ears are logarithmic in response so even a 100W amplifier will not seem much louder and that is why adding a few more parts will be ineffective. You may increase power capability at low impedance by doubling the output transistors but there are other factors like redesigning the VI limiters, drivers and reducing added distortion, finding suitable components and extra heatsinks.
Is it really worth it for 2dB at 4R only?
In practical terms, even doubling the power only increases the volume level by 3 dB. Increasing the power to 52watts will not be noticed. You need to make large power increases before you can perceive higher power. Our ears are logarithmic in response so even a 100W amplifier will not seem much louder and that is why adding a few more parts will be ineffective. You may increase power capability at low impedance by doubling the output transistors but there are other factors like redesigning the VI limiters, drivers and reducing added distortion, finding suitable components and extra heatsinks.
Is it really worth it for 2dB at 4R only?
i completely agree but treble is loud enough for me i just need more bass out of this thing so i see only one way to get that..... make a50 more powerful in terms of power 🙂
Add a cheap 200mm Subwoofer, it will be much more cost effective, assuming
you don't already have good, efficient bass speakers. !
you don't already have good, efficient bass speakers. !
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clarification
Hi again,
just to clear things. The A-50 does not have 2N3055 Transistor's in the Power Stage. They are 2SB558 and 2SD428 (100V/7A - PNP/NPN). The A-600 has the same Power Transistor's.
There is a mistake in the A-50 Service Manual on page 3 but in the Part's List and in the schematic diagram the power Transistor's are named correctly.
Max
Hi again,
just to clear things. The A-50 does not have 2N3055 Transistor's in the Power Stage. They are 2SB558 and 2SD428 (100V/7A - PNP/NPN). The A-600 has the same Power Transistor's.
There is a mistake in the A-50 Service Manual on page 3 but in the Part's List and in the schematic diagram the power Transistor's are named correctly.
Max
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