Tested all following transistors are are Ok
Q401, 402, 403, 404, 405, 406, 407, 408,
Tested all diodes individually and collectively
2* D402(vd1221) two diode in series,
D403(SV-03) three diodes in series. I read that these diodes are used in biasing the transistors with temperature compensation, May NTC or PTC material used in them.
Please guide me what to do next.
Q401, 402, 403, 404, 405, 406, 407, 408,
Tested all diodes individually and collectively
2* D402(vd1221) two diode in series,
D403(SV-03) three diodes in series. I read that these diodes are used in biasing the transistors with temperature compensation, May NTC or PTC material used in them.
Please guide me what to do next.
There is some more information on this amp at: https://groups.io/g/Luxman/topic/luxman_l_100/71950793?p=
Also: https://audiokarma.org/forums/index.php?threads/luxman-l-100-woes.994347/
https://www.diyaudio.com/community/threads/luxman-l100-pointers-needed.401821/
Info on the red light flashing at turn-on: https://forums.stevehoffman.tv/threads/integrated-amp-problem-can-anyone-help.7927/
Also: https://audiokarma.org/forums/index.php?threads/luxman-l-100-woes.994347/
https://www.diyaudio.com/community/threads/luxman-l100-pointers-needed.401821/
Info on the red light flashing at turn-on: https://forums.stevehoffman.tv/threads/integrated-amp-problem-can-anyone-help.7927/
Details about the pins of connector (C11M ~ C18M)
C18M, C17M (+55 VDC) red wire
C16M white wire no idea
C15M (ground) black wire
C14M, C13M (-55 VDV) grey wire
C12M, red wire no idea
C11M grey wire no idea
C09M ~ C10M seems input from preamplifier.
I will check further the details.
Further I tested all the transistors, Diodes & bridge Rectifier of the PCB
PB-647 are ok. These were tested in circuit and my experience tells me that all components that I checked are ok.
C18M, C17M (+55 VDC) red wire
C16M white wire no idea
C15M (ground) black wire
C14M, C13M (-55 VDV) grey wire
C12M, red wire no idea
C11M grey wire no idea
C09M ~ C10M seems input from preamplifier.
I will check further the details.
Further I tested all the transistors, Diodes & bridge Rectifier of the PCB
PB-647 are ok. These were tested in circuit and my experience tells me that all components that I checked are ok.
Okay, good. It looks like these amplifiers have a history of problems with capacitors going bad, and or with the amp not working after a recap has been performed. I would suggest to read the threads I linked to for more information on that.
Regarding the signals on the connectors you are pulling. You could measure the voltage on each pin with only one channel connected. Then connect both channels and measure all the voltages again. It seems likely you will find some voltages are changed when both connectors are plugged in. One or more of the signals that change voltage may be an important clue, especially if that signal comes from a power supply. If so, then we may need to go look at that power supply. That said, I would still suggest reading the other threads first. The flashing red light is a problem other people have seen before. Usually the problem appears to be with capacitors going bad.
Regarding the signals on the connectors you are pulling. You could measure the voltage on each pin with only one channel connected. Then connect both channels and measure all the voltages again. It seems likely you will find some voltages are changed when both connectors are plugged in. One or more of the signals that change voltage may be an important clue, especially if that signal comes from a power supply. If so, then we may need to go look at that power supply. That said, I would still suggest reading the other threads first. The flashing red light is a problem other people have seen before. Usually the problem appears to be with capacitors going bad.
Hi
Now I understand a little bit more about this amplifier and from thread that you shared stating that it has lot of inherent problems. It means not a very good amplifier. What you suggest ?
I asked my office people to print page 15, 16 & 17 on A3 size and that is Schematics of this amp. I hope I will get it repaired provided I could find the output voltages of regulated power supply that is used for driver stage. I noted 1.5 volts DC but capacitor C17 on board is 100 volts and 2.2 uF. It means I must know the voltage out from PCB 647 ( power supply) connector C07S ~ C10S. Let me find and dig it by tomorrow. It's late now in my country. I am really thankful to you and respectful to me.
Now I understand a little bit more about this amplifier and from thread that you shared stating that it has lot of inherent problems. It means not a very good amplifier. What you suggest ?
I asked my office people to print page 15, 16 & 17 on A3 size and that is Schematics of this amp. I hope I will get it repaired provided I could find the output voltages of regulated power supply that is used for driver stage. I noted 1.5 volts DC but capacitor C17 on board is 100 volts and 2.2 uF. It means I must know the voltage out from PCB 647 ( power supply) connector C07S ~ C10S. Let me find and dig it by tomorrow. It's late now in my country. I am really thankful to you and respectful to me.
Today is weekend and working on Luxman L-100. I found that there is no power out from PB-647, connector C07S ~ C10S for driver board of power amplifier PB-649 referred connector C11M ~ C18M. Pin# 17&18.
The power transistors, C116 & A653 of PB-647 are not biased when switch ON the amplifier. According to circuitry both transistors must be biased to make the power supply ready for driver circuits of power transistors (TO-03). I think 48 volts DC will excite the driver transistors of PB-649.
When we switch ON ( amplifier main) 122 volts AC appear on connector C01S ~ C06S pin# 1,2 & 8 Volts AC appear on pin# 3,4. If someone let me know the voltage diagram of PCB PB-647, I can develop much better power supply on the same dimension PCB. If this amplifier got operational then I will made new PCBs with test points and voltage in our will be marked on PCB board complete circuit will be digitised and Gerber files will be available for audiophiles on. So much so the schematics will also be digitised on Proteus software. I have complete facility along with dedicated staff who can prototyping PCBs for L-100 but this all is subject to successful repair. As you told that you repaired many L-100 in the past I will be very much thankful if you please share the voltage IN/OUT as per logic. Mute is also not functioning at the moment.
Audio is my hobby motor control and customised power supplies is my business.
Thanks in advance.
The power transistors, C116 & A653 of PB-647 are not biased when switch ON the amplifier. According to circuitry both transistors must be biased to make the power supply ready for driver circuits of power transistors (TO-03). I think 48 volts DC will excite the driver transistors of PB-649.
When we switch ON ( amplifier main) 122 volts AC appear on connector C01S ~ C06S pin# 1,2 & 8 Volts AC appear on pin# 3,4. If someone let me know the voltage diagram of PCB PB-647, I can develop much better power supply on the same dimension PCB. If this amplifier got operational then I will made new PCBs with test points and voltage in our will be marked on PCB board complete circuit will be digitised and Gerber files will be available for audiophiles on. So much so the schematics will also be digitised on Proteus software. I have complete facility along with dedicated staff who can prototyping PCBs for L-100 but this all is subject to successful repair. As you told that you repaired many L-100 in the past I will be very much thankful if you please share the voltage IN/OUT as per logic. Mute is also not functioning at the moment.
Audio is my hobby motor control and customised power supplies is my business.
Thanks in advance.
Thanks & I will follow the instructions. Only three short questions I will ask you next
Power supply is described on page six of the service manual. There is a start-up circuit to get it going in the dotted area on the left. After start-up, if the power supply voltage drops out then it should stay locked out until another turn-on transient occurs at the input. They say it should be possible to start it up for test purposes using a 5.6k resistor to momentarily bias on the zener stack.
On page 17 of the service manual the actual circuit (which was described on page 6) is shown:
Regarding designing a "better" power supply for the unit, not all power supplies sound the same in audio equipment. Depends on various factors. A more highly regulated supply may end up sounding worse in some cases.
On page 17 of the service manual the actual circuit (which was described on page 6) is shown:
Regarding designing a "better" power supply for the unit, not all power supplies sound the same in audio equipment. Depends on various factors. A more highly regulated supply may end up sounding worse in some cases.
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Thanks for guidance and for corrections.This is totally new for me that in some cases extremely regulated power supply can be a cause of bad sound. I am trying to comprehend why. It is new thought which needs to be explored.
I read that in the document and tried to find the logical signals that biasing the chain of transistors but unable. I really thankful to you. I hope with efforts I will rectify the fault. Just for my knowledge, I feel vintage amps are more musical than new models. Is it my perception or true.
Just out of curiocity - why should the power supply voltage "drop out" during device operation (and thus needing "protection") without that being a a fatal failure (resulting in blown fuse etc)?
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It may be fast transient protection, if due to any reason output of amp clamped, fuse may take time to blowout but protection circuitry may be fast enough to overcome the damaging. It is my guess.
Your point is valid.
It may be fast transient protection, if due to any reason output of amp clamped, fuse may take time to blowout but protection circuitry may be fast enough to overcome the damaging. It is my guess.
My guess is that L-100 designers overengineered themselves.
99% of commercial amplifiers are sold without that kind of "protection" - correct?
If so then why just not eliminate that functionality from the circuit?
Many people seem to agree, but not everyone. Its a matter of personal taste.
"probably" is the keyword.
If most amplifiers survive without that complexity then what is the reason for continuing the personal torment to maintain it there?
I personally would not blink an eye to kick it out.
Basically, or one way to think of it, is that unless the amplifier itself has huge PSRR up to and beyond 20kHz, then the sound of the error amplifier in the power supply will be part of the sound of the amplifier. IOW, some power supply error amplifiers interacting with the amplifier error amplifier and feedback loop may not give the most pleasing result to the ear.
@madis64, If you are a commercial amplifier designer and your amplifier fails for any reason including very poor choice of speaker cables, then speakers may be damaged from DC on the output, or other bad things could happen. If you don't want to get sued or be forced out of business then you need to make sure your products are bullet-proof as reasonably practical. Many amplifiers require a power reset if a safety circuit trips.