Hey I'm new here, my knowledge of circuits is pretty limited but i'm handy with a soldering iron and looking to learn.
I picked up a samson servo 300 off a friend who "upgraded" the case fans and ended up causing a puff of smoke. After taking custody and scrapping the fans, i powered it up and the amp works totally fine except channel 2 has a noticeable high frequency hiss and occasional static burst that's absent in channel 1. It's drowned out if i play a signal through the amp but it's very noticeable when there's no input.
After ruling out cables and anything earlier in the signal chain, my thoughts are that the amplifier's power-amp circuit has been damaged as the hiss is independent of the volume control.
After dismantling and inspection there are slight scorch marks on the underside of what i assume is the power-amp circuit cos of the big reservoir caps. But no visibly burnt or blown components. (can post pics in a bit).
As my knowledge is limited, my plan is to just go through and replace all the components with the scorched underside. But before I do that I thought i'd check with you wise folk to see if anyone has any advice or experienced a similar problem (also will probably need help IDing a few components)
Chime in with your thoughts, i'd love to hear them 🙂
I picked up a samson servo 300 off a friend who "upgraded" the case fans and ended up causing a puff of smoke. After taking custody and scrapping the fans, i powered it up and the amp works totally fine except channel 2 has a noticeable high frequency hiss and occasional static burst that's absent in channel 1. It's drowned out if i play a signal through the amp but it's very noticeable when there's no input.
After ruling out cables and anything earlier in the signal chain, my thoughts are that the amplifier's power-amp circuit has been damaged as the hiss is independent of the volume control.
After dismantling and inspection there are slight scorch marks on the underside of what i assume is the power-amp circuit cos of the big reservoir caps. But no visibly burnt or blown components. (can post pics in a bit).
As my knowledge is limited, my plan is to just go through and replace all the components with the scorched underside. But before I do that I thought i'd check with you wise folk to see if anyone has any advice or experienced a similar problem (also will probably need help IDing a few components)
Chime in with your thoughts, i'd love to hear them 🙂
Please don't just start replacing things. Can you imagine someone trying to get his car to start by replacing, oh, the water pump, the brake cylinders, the fan belt, etc etc?
Photos would help. On MANY amps, the circuit board gets discolored by hot components, especially zener diode voltage regulator circuits. it is normal and not a sign of trouble. Could they have designed it not to discolor? Of course, but like most any commercial product, they design for good enough and no further. Also, some burnt looking marks can just be evidence of solder work.
The fact that the amp works and apparently sounds OK other than this noise suggests to me that the problem is not something overheating.
Good forum etiquette would be to link or post a schematic. Searching, I found this:
http://bmamps.com/Schematics/Samson/Samson_Servo_200,_300,_600_Schematics.pdf
The power amp is likely at fault, but that is a trick finding, as there whole thing is the power amp. That volume control is after only one op amp IC, the entire rest of the circuitry is after that control. SO it doesn't narrow it down much.
Do you have a scope or signal tracer? It would be useful to determine if the noise is actual noise or if it is evidence of a high frequency oscillation.
Photos would help. On MANY amps, the circuit board gets discolored by hot components, especially zener diode voltage regulator circuits. it is normal and not a sign of trouble. Could they have designed it not to discolor? Of course, but like most any commercial product, they design for good enough and no further. Also, some burnt looking marks can just be evidence of solder work.
The fact that the amp works and apparently sounds OK other than this noise suggests to me that the problem is not something overheating.
Good forum etiquette would be to link or post a schematic. Searching, I found this:
http://bmamps.com/Schematics/Samson/Samson_Servo_200,_300,_600_Schematics.pdf
The power amp is likely at fault, but that is a trick finding, as there whole thing is the power amp. That volume control is after only one op amp IC, the entire rest of the circuitry is after that control. SO it doesn't narrow it down much.
Do you have a scope or signal tracer? It would be useful to determine if the noise is actual noise or if it is evidence of a high frequency oscillation.
Thanks for the reply! Ah sorry, i tried to attach a pdf schematic with my first post but clearly i failed to upload it correctly. Ok ha i'll hold off swapping out components (nice analogy). Interesting, I didn;t know that about the scorch marks. I don't have a scope on hand but i'm trying to source on here's a photo of the scorch marks (underside of the board with the reservoir caps) and the top as well if that's any use.
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