Hello everyone!
Need help with a Denon PMA-100M amplifier. In the attached picture you can see what kind of noise appears on the left channel in the default situation, as well as a picture of how beautiful the wave is with a 1000 Hz input signal and no noise is heard. Only the left channel does it. Unfortunately, the repair manual is only available on the Hifi engine page, and there is currently no registration there. Please, if anyone can help me download the repair manual or has an idea what could be the cause of this noise in the left channel, please help me! Thank you very much!
Need help with a Denon PMA-100M amplifier. In the attached picture you can see what kind of noise appears on the left channel in the default situation, as well as a picture of how beautiful the wave is with a 1000 Hz input signal and no noise is heard. Only the left channel does it. Unfortunately, the repair manual is only available on the Hifi engine page, and there is currently no registration there. Please, if anyone can help me download the repair manual or has an idea what could be the cause of this noise in the left channel, please help me! Thank you very much!
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Well, you have no positive drive for one. WHat output devices are used?
What history is there? What happened just before it failed?
What history is there? What happened just before it failed?
Here you go.
Did the left channel output get shorted by the speaker wires? Check the back of the speaker also.
Did the left channel output get shorted by the speaker wires? Check the back of the speaker also.
Two Sony speakers (6Ohm) are connected, but even without an output device, the noise is visible on the stroboscope image.
I got it from a friend, it hasn't been used for many years, the inside is a bit rusty and there was a lot of dust in it, I'm trying to clean it, and I'm thinking about replacing the capacitors.
I got it from a friend, it hasn't been used for many years, the inside is a bit rusty and there was a lot of dust in it, I'm trying to clean it, and I'm thinking about replacing the capacitors.
The power supply isn't the problem, since it is shared by both channels.
Perhaps someone shorted the output when hooking up the speaker wires, heard the distortion, and stored the unit away.
That said, you could first try reseating all the connectors, which could be dirty or corroded.
Perhaps someone shorted the output when hooking up the speaker wires, heard the distortion, and stored the unit away.
That said, you could first try reseating all the connectors, which could be dirty or corroded.
Thank you very much for the repair manual! I will try to check the voltages and other parameters.
What is strange to me is that if, for example, you receive a sine signal at the CD input, there is no distortion at the output, the signal is the same as on the right side.
Hi Endreigabi,
Check the signal at the emitter resistor before the relay, then after. If it's bad at the emitters, check at the input to the amplifier stage.
Check the signal at the emitter resistor before the relay, then after. If it's bad at the emitters, check at the input to the amplifier stage.
Hi Endreigabi,
No it isn't the same.
The input signals can be identical, but it is what happens in the next circuits that make them different. Even a bad cable can cause trouble.
No it isn't the same.
The input signals can be identical, but it is what happens in the next circuits that make them different. Even a bad cable can cause trouble.
Do you mean both speaker outputs are good when playing a CD? That would be a very good sign.
Yes, both speakers output good, when playing CD or any source. The problem is only in "idle" status. In this case if increase volume, the max output is about 10Volt on the left side. The sound is like the FM noise between two FM stations.
Do you mean the sound seems ok through the speakers, with no "FM noise" heard,
but the measured output on a sine wave input is distorted, noisy, and low in the left channel?
Is the noise actually distortion of the sine wave, or does it remain when the sine is turned off?
Have you tried re-seating the connectors (with power off)?
Did you check the sine waveform before the series output relay, in case the relay is dirty/corroded?
but the measured output on a sine wave input is distorted, noisy, and low in the left channel?
Is the noise actually distortion of the sine wave, or does it remain when the sine is turned off?
Have you tried re-seating the connectors (with power off)?
Did you check the sine waveform before the series output relay, in case the relay is dirty/corroded?
Oh!
Okay, check the input switching. It varies by volume position so it is before the volume control. The tone amp section maybe too.
Okay, check the input switching. It varies by volume position so it is before the volume control. The tone amp section maybe too.
Corrosion can be a serious problem. You should have seen an Audio Research D51 tube power amp
that spent 20 years on the east coast. It was a total basket case, and unrepairable.
that spent 20 years on the east coast. It was a total basket case, and unrepairable.
Absolutely! Corrosion can be a killer. I've seen all kinds of equipment done in by water and water mixes.
Mind you, car amplifiers were the most frequent victims.
Mind you, car amplifiers were the most frequent victims.
Oh yeah, clean it well. That can cause high leakage currents, your final rinse should be alcohol or Methyl Hydrate.