Hi all,
I have a Yamaha P-2200 amp that's VU meters jump to, and remain at 100% when powered on.
The VU meters were working find before taking it in for a service, and to have the power supply changed from 100v to 240v.
After I received it back, the VU meters jump straight to 100%, and remain at 100% until powered off..
Any ideas on how to resolve would be appreciated!
I have a Yamaha P-2200 amp that's VU meters jump to, and remain at 100% when powered on.
The VU meters were working find before taking it in for a service, and to have the power supply changed from 100v to 240v.
After I received it back, the VU meters jump straight to 100%, and remain at 100% until powered off..
Any ideas on how to resolve would be appreciated!
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Do you mean they jump and stay at 100% ? or do they fall back to zero after a few seconds.
The change in operating voltage from 100 to 240v is a big unknown in all this. I would be doing some investigating to make sure the supplies are at the correct voltage before doing anything. There look to be a large number of options for voltage and you would have to measure a couple of representative voltages to check all was OK.
Some of the options:
I would begin by measuring the AC voltage here which is shown as 13 volts (measured between these points)
And these voltages of around 56 volts AC are measured from ground.
If you are not confident on working on anything like this then the advice has to be DON'T 🙂 and get help from someone who knows how to do this. There are highish voltage inside and it would be easy to cause damage to the amp and to you.
The change in operating voltage from 100 to 240v is a big unknown in all this. I would be doing some investigating to make sure the supplies are at the correct voltage before doing anything. There look to be a large number of options for voltage and you would have to measure a couple of representative voltages to check all was OK.
Some of the options:
I would begin by measuring the AC voltage here which is shown as 13 volts (measured between these points)
And these voltages of around 56 volts AC are measured from ground.
If you are not confident on working on anything like this then the advice has to be DON'T 🙂 and get help from someone who knows how to do this. There are highish voltage inside and it would be easy to cause damage to the amp and to you.
After power-on they jump and remain at 100% until powered off.
Thanks for the guidance. Definitely not confident to take this on myself.
I was hoping it might be a simple screw to turn to reduce/recalibrate back to 0.
Thanks for the guidance. Definitely not confident to take this on myself.
I was hoping it might be a simple screw to turn to reduce/recalibrate back to 0.
Mooly has given good advice. If you're not confident working on it yourself, you need to take it back to the person who serviced it. I would advise against turning it on again before you give it back to them, in case something is being overloaded. If you have a large variac, you could try running it at lower voltages and seeing if it stops the issue, but you'll need a large one.
I do not imagine it's the case here, but moving coil meters are prone to sticking at the end of scales, especially as they get old. The bearings can wear over time, and if a meter is 'pegged' it will stay there. It is plausible that an amp might have spent its life in a club, with the meters pegging for hours every night, damaging the movement over time and making it prone to sticking when pegged. But I think it's unlikely that both meters would have the issue. Meters often jump when something is turned on due to offsets stabilising, but it would be bad design for them to 'peg' and I would not expect it from a serious OEM such as Yamaha. These are respected amps. My feeling is that there is a DC offset feeding the meters for some reason (I haven't seen the driver circuit, but I'm guessing it's a peak meter, which is a lot more complex than a simple rectifier arrangement used on VU meters). Meters can hit the end stops with only a couple of hundred mV, so a slight offset can completely render them useless. They can also be damaged when pegging. Do be careful.
NB- meters can also stick due to static build up. It's not the case here, but worth knowing.
I do not imagine it's the case here, but moving coil meters are prone to sticking at the end of scales, especially as they get old. The bearings can wear over time, and if a meter is 'pegged' it will stay there. It is plausible that an amp might have spent its life in a club, with the meters pegging for hours every night, damaging the movement over time and making it prone to sticking when pegged. But I think it's unlikely that both meters would have the issue. Meters often jump when something is turned on due to offsets stabilising, but it would be bad design for them to 'peg' and I would not expect it from a serious OEM such as Yamaha. These are respected amps. My feeling is that there is a DC offset feeding the meters for some reason (I haven't seen the driver circuit, but I'm guessing it's a peak meter, which is a lot more complex than a simple rectifier arrangement used on VU meters). Meters can hit the end stops with only a couple of hundred mV, so a slight offset can completely render them useless. They can also be damaged when pegging. Do be careful.
NB- meters can also stick due to static build up. It's not the case here, but worth knowing.
Keep the amplifier well away from speakers until you're absolutely certain there is no DC on the outputs. Even if that's okay the funky meters do not inspire great confidence in the tech who did the initial work. Didn't the amp get a good look afterward, or at least a smoke test?
No, they didn't turn it on and show me that it's all working, they just gave it back to me. This is the number #1 premium HiFi shop in Sydney, so I thought it was in good hands.