I have a Panasonic RAMSA 9110e amplifier that came into my possesion some time ago. As far as I can tell channel B functions normally. Channel A however does not. When channel A is connected to a speaker there is noise. Sounds kind of like white noise, but grainy and not quite as dense in nature if that makes sense. Unfortunately I don't have an oscilloscope to see the waveform of it.
I found a video where somebody else had a Ramsa with a channel A problem. Turned out that corrosive glue had done a number on a component or two.
Like the Ramsa in the video mine also had glue that didn’t look all that great so I pulled the 3 caps with glue under them. Came out real easy. 😅
I've cleaned off the glue now. Some of the glue was on diode legs so I checked the diodes with a multi-meter, but they were fine.
While I was at it I checked the 3 caps that I pulled and they read C120 - 460uf (100V, 470uf spec.), C121 - 460uf (100V, 470uf spec.) and C116 - 550uf(10V, 470uf spec.). The first two are pretty close to spec. Not sure what to think about the 10V one. 470 * 1.2 = 564. I suppose if it is a part with a +/-20% or so manufacturing tolerance and serves it’s purpose in the circuit then it’s fine too. But what is the manufacturing tolerance of an electrolytic capacitor anyway? I googled that and apparently it is typically 20% (source). Same source says that capacitance drifts over time. Would you change this cap for one closer to spec?
Small components around big caps with the glue aside what looked suspect was IC101 - MC-8134.
It’s outer shell had some crystals on it. I cleaned them off with some toilet paper and now it visually looks the same as the IC below it. No holes on it, but the crystals must have come from the inside of it?
I’ve turned the amplifier on and played some music with it 2 times before disassembly:
1)The first time the noise disappeared for a while and then reappeared when I turned it up.
2)The second time the noise was there from the start and followed the level of how high I turned up the amp.
If the noise gets amplified based on how high up the amplifier is turned, then it must be coming from somewhere early in the signal path before attenuation. Thinking this I traced the early signal path from signal input to attenuation.
And what do you know? IC101 or MC8134 sits between the two. (page 31, service manual WP9110c, download link) Haven't seen a difference between the WP9110e I have and the WP9110c service manual yet, btw.
I’ve not seen a part like this before and have only some basic knowledge of how some of the stuff in electronics works. Would you think that IC101 is probably damaged? What was that crystal formation on it? What happened to it?
I wasn’t able to find information on what MC-8134 does so I turned to my last resort - ChatGPT. This was the answer I got: “It functions as a voltage-controlled amplifier (VCA), which allows for adjustable gain control in audio signal paths. This IC is typically employed to manage audio signal levels dynamically, providing features such as automatic volume adjustments, noise gating, or signal mixing in professional audio equipment.” ChatGTP couldn't provide a source, said something like answer derived from general knowledge, but it seems like it might be an accurate one.
Not much else jumps out at me on these boards. There is some brown stuff on the undersides of the boards - old flux residue? (see the 3 images attached to this post) If not IC101 what else could be the culprit?
I found a video where somebody else had a Ramsa with a channel A problem. Turned out that corrosive glue had done a number on a component or two.
Like the Ramsa in the video mine also had glue that didn’t look all that great so I pulled the 3 caps with glue under them. Came out real easy. 😅
I've cleaned off the glue now. Some of the glue was on diode legs so I checked the diodes with a multi-meter, but they were fine.
While I was at it I checked the 3 caps that I pulled and they read C120 - 460uf (100V, 470uf spec.), C121 - 460uf (100V, 470uf spec.) and C116 - 550uf(10V, 470uf spec.). The first two are pretty close to spec. Not sure what to think about the 10V one. 470 * 1.2 = 564. I suppose if it is a part with a +/-20% or so manufacturing tolerance and serves it’s purpose in the circuit then it’s fine too. But what is the manufacturing tolerance of an electrolytic capacitor anyway? I googled that and apparently it is typically 20% (source). Same source says that capacitance drifts over time. Would you change this cap for one closer to spec?
Small components around big caps with the glue aside what looked suspect was IC101 - MC-8134.
It’s outer shell had some crystals on it. I cleaned them off with some toilet paper and now it visually looks the same as the IC below it. No holes on it, but the crystals must have come from the inside of it?
I’ve turned the amplifier on and played some music with it 2 times before disassembly:
1)The first time the noise disappeared for a while and then reappeared when I turned it up.
2)The second time the noise was there from the start and followed the level of how high I turned up the amp.
If the noise gets amplified based on how high up the amplifier is turned, then it must be coming from somewhere early in the signal path before attenuation. Thinking this I traced the early signal path from signal input to attenuation.
And what do you know? IC101 or MC8134 sits between the two. (page 31, service manual WP9110c, download link) Haven't seen a difference between the WP9110e I have and the WP9110c service manual yet, btw.
I’ve not seen a part like this before and have only some basic knowledge of how some of the stuff in electronics works. Would you think that IC101 is probably damaged? What was that crystal formation on it? What happened to it?
I wasn’t able to find information on what MC-8134 does so I turned to my last resort - ChatGPT. This was the answer I got: “It functions as a voltage-controlled amplifier (VCA), which allows for adjustable gain control in audio signal paths. This IC is typically employed to manage audio signal levels dynamically, providing features such as automatic volume adjustments, noise gating, or signal mixing in professional audio equipment.” ChatGTP couldn't provide a source, said something like answer derived from general knowledge, but it seems like it might be an accurate one.
Not much else jumps out at me on these boards. There is some brown stuff on the undersides of the boards - old flux residue? (see the 3 images attached to this post) If not IC101 what else could be the culprit?
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