Hi All,
I have noticed that when the volume is tuned down with no sound that the left Vu meter on my Luxman M03 is showing a reading of (0.01) and the right is (0.00). There are no issue with sound etc and the Vu eventually went back to (0.00) after a short listening period. I have however noticed after starting up again a while after that the left VU is reading (0.01) again.
Any ideas on what could be causing this.
Thanks in advance.
I have noticed that when the volume is tuned down with no sound that the left Vu meter on my Luxman M03 is showing a reading of (0.01) and the right is (0.00). There are no issue with sound etc and the Vu eventually went back to (0.00) after a short listening period. I have however noticed after starting up again a while after that the left VU is reading (0.01) again.
Any ideas on what could be causing this.
Thanks in advance.
It is common for meter movements to sometimes be a bit sticky mechanically. If it reads 0.01 then turn the power off and see what happens and also give the meter a light tap or two and see if it falls back to zero.
If that proves it is not mechanical in nature then you would have to look at the circuit and do some simple tests. Worst case scenario would be the amp oscillating at HF and causing a deflection but that is unlikely. Mechanical issues are most likely at this point.
If that proves it is not mechanical in nature then you would have to look at the circuit and do some simple tests. Worst case scenario would be the amp oscillating at HF and causing a deflection but that is unlikely. Mechanical issues are most likely at this point.
Sorry I should have mentioned that the VU metres on the Luxman M03 are electronic.
Thanks for the reply.
Regards
Thanks for the reply.
Regards
That's a whole different ball game then.
We need to see a circuit but the basic tests remain. You need to verify by measurement (with scope and meter) that the input to the meter circuitry is zero, no DC, no noise, no oscillation.
We need to see a circuit but the basic tests remain. You need to verify by measurement (with scope and meter) that the input to the meter circuitry is zero, no DC, no noise, no oscillation.
This is an FL meter assembly. IC703 controls it. A leaky driver transistor or impurities on the PCB in that area can allow leakage current. Do the simple things first, clean the PCB with a zero residue cleaner. Clean out any dust first.
Otherwise Karl is right. Any noise at the input of that circuit will be interpreted as a signal. So simple things first, then drag out the test gear.
Otherwise Karl is right. Any noise at the input of that circuit will be interpreted as a signal. So simple things first, then drag out the test gear.
Thanks for the replys. I will check the basic then if no luck handover to my tech.
Great site always good advise.
Regards
Great site always good advise.
Regards
The Lux M-03 metering circuit is a complex thing. Microprocessor controlled with A/D lines and any leakage in the various coupling/buffer/signal conditioning front end to it, can cause an offset on the display. Even a fluctuating DC offset on the amp stage itself can do that.
I have a few of those amplifiers myself and you really don't want to be spending time on the metering circuit, especially if you are paying a technician. And that micro is custom and NLA (if it ever was). One slip of a probe and he could kill the entire meter.
This is just the power meter schematic in the M-03.
I have a few of those amplifiers myself and you really don't want to be spending time on the metering circuit, especially if you are paying a technician. And that micro is custom and NLA (if it ever was). One slip of a probe and he could kill the entire meter.
This is just the power meter schematic in the M-03.
Last edited:
It's just a complex A/D circuit and scaling. The display is high impedance (around 30 VDC probably) bias. Leakage will cause segments to glow. Of course noise on the input of the A/D will do the same.
Look after the simple stuff first. Then relax and break out the instruments. A tech use to these will have an easier time. I'll admit I haven't seen this before, and I was authorized warranty for Luxman. But just because it uses a large chip doesn't mean it is complicated.
Look after the simple stuff first. Then relax and break out the instruments. A tech use to these will have an easier time. I'll admit I haven't seen this before, and I was authorized warranty for Luxman. But just because it uses a large chip doesn't mean it is complicated.
Not easy to follow on a small diagram but it looks like the signal input is at the bottom left . Quick scope check on the inputs to see they are clean and zero and then a quick follow of the signal path through the opamps and confirm still clean and zero coming out.
Thanks everyone for the replies. One final update.
I disconnected all connections tonight and hit the on button, after several attempts of doing this there was about a 1 minute delay before the relay clicked and the digital led came on again showing a very slightt reading on the left channel noting that the reading on the VU decreased with time. I have read in another thread that this caused fault was diagnosed by an issue with the speaker protection unit and repaired through replacing out of tolerance resistors (R273/274).
The Luxman M03 is a very good Amp, in fact I own two. Could this be also a possible with my amp.
Thanks
I disconnected all connections tonight and hit the on button, after several attempts of doing this there was about a 1 minute delay before the relay clicked and the digital led came on again showing a very slightt reading on the left channel noting that the reading on the VU decreased with time. I have read in another thread that this caused fault was diagnosed by an issue with the speaker protection unit and repaired through replacing out of tolerance resistors (R273/274).
The Luxman M03 is a very good Amp, in fact I own two. Could this be also a possible with my amp.
Thanks
Hi Karl,
https://archive.org/details/manual_M03_LUXMAN It's available on the 'net. I have the original and PDF, but they are large.
Hi ddf1969,
Yes, they were. I have a pair of M-02 and an M-05. I have too much stuff! lol!
https://archive.org/details/manual_M03_LUXMAN It's available on the 'net. I have the original and PDF, but they are large.
Hi ddf1969,
Yes, they were. I have a pair of M-02 and an M-05. I have too much stuff! lol!
Thanks @anatech
Well they are easy enough to change or simply to isolate and measure. The normal voltages on these show they are not highly stressed as they have little voltage across each.
The left channel is the same but with different reference numbers, the numbers you quote are in the right channel.
Well they are easy enough to change or simply to isolate and measure. The normal voltages on these show they are not highly stressed as they have little voltage across each.
The left channel is the same but with different reference numbers, the numbers you quote are in the right channel.
Thanks Mooly appreciate your help.
There is a bit of work involved to get access, however as you mentioned simple enough to test.
Now to find the time.
There is a bit of work involved to get access, however as you mentioned simple enough to test.
Now to find the time.
Have you tried cleaning the display switch (CH703, input 6) and the speaker terminal switch (CH701, input 4)?