Hello to everybody!
I decided to build Yamaha A-S500 clone. I think it is very exciting (for me)!
I did PCB board is Sprint Layout, I soldered almost all components and I connected it to power. No explosion! Yay! But resistors R136 and R137 got super-hot, so I disconnected it from power. The reason is I did not connected several parts, because I thought they are not necessary, but obviously they are.
The question is: What parts can be removed? I mean parts linked to speaker protection. (I will have an independent module for speaker protection.)
I ignored all parts after 0.22Ohm 3W cement 3pin resistor. Now I know it was not good idea.
Please, see the page 57 of service manual: a-s500.pdf
All what I want is just main board
I will be happy to share PCB and additional experiences.
Thanks! Milan
img for reference:
I decided to build Yamaha A-S500 clone. I think it is very exciting (for me)!
I did PCB board is Sprint Layout, I soldered almost all components and I connected it to power. No explosion! Yay! But resistors R136 and R137 got super-hot, so I disconnected it from power. The reason is I did not connected several parts, because I thought they are not necessary, but obviously they are.
The question is: What parts can be removed? I mean parts linked to speaker protection. (I will have an independent module for speaker protection.)
I ignored all parts after 0.22Ohm 3W cement 3pin resistor. Now I know it was not good idea.
Please, see the page 57 of service manual: a-s500.pdf
All what I want is just main board
I will be happy to share PCB and additional experiences.Thanks! Milan
img for reference:
once i was looking at this schemtic- it seemed to me that the output transistors are very low power (80w each). I don't see the yamahas designers point of such a solution - they don't hold a 4 ohm load for given rails voltage.
at least 4 of them must be set or more powerful output transistors must be chosen....
at least 4 of them must be set or more powerful output transistors must be chosen....
Hello Duncan, see the image please. In orange are things I ignored. Well, I thought less is better after cement resistor, lol. So I am adding them. Please note the green line, it goes to speaker protection. So I assume, R178, C133 and R179 are the only parts which can be ignored if I will be using my own spk protection, right?
I appreciate your confirmation! Thank you.
Some parts are SMD in orange section, so resistors can be standard axial, also diodes. I will keep the one transistor as is.
Interesting thing, I just noticed an extra transistor Q140 output to somewhere, I guess to protection, or some detection of something. Interesting it is not part of the main amp area on PCB. I think I can remove that too.
Yamaha A-S500 has some programme running from some chip on another board. It does basic diagnosis. I don't need a led warning eg input not connected... Well, I am not blind not to see connected cable.
And I will modify PCB so instead of one 3 pin resistors we will have 2 standard cement pieces
I've found totally difficult to find 3 pin resistors.
Your right I have old 3 pin resistors but I took them out of old UN-repairable amps haven't found any yet online .
Personally and I mean personally I don't like power amps with computer controls or safety features that make it hard to trace the fault .
Like you I don't like flashing lights and signal equipment added into an amplifier , if it blows it blows ,luckily all my own designed amps keep on working without all those "bells & whistles "
Personally and I mean personally I don't like power amps with computer controls or safety features that make it hard to trace the fault .
Like you I don't like flashing lights and signal equipment added into an amplifier , if it blows it blows ,luckily all my own designed amps keep on working without all those "bells & whistles "
Update
So here is updated PCB board.
- it is smaller than original board
- 3 pin cement resistor changed into 2x 2pin cement resistor
- some traces without coldermask to improve conductivity
My next plan is check the details one more time, to be sure all is good and I will be ready to order PCB prototype version 2
So here is updated PCB board.
- it is smaller than original board
- 3 pin cement resistor changed into 2x 2pin cement resistor
- some traces without coldermask to improve conductivity
My next plan is check the details one more time, to be sure all is good and I will be ready to order PCB prototype version 2
YAMAHA A-S500 IS READY FOR DOWNLOAD!
So here is the PCB final version *.lay6 of amplifier board only.
DOWNLOAD LINK
I hope you will like my work. It took quite a long time to trace and check everything several times. It was not tested, but soon I will order pcb from China and I will keep you updated.
Meanwhile, if you are bored, you can check the board and compare it with service manual which is here.
Image preview:
So here is the PCB final version *.lay6 of amplifier board only.
DOWNLOAD LINK
I hope you will like my work. It took quite a long time to trace and check everything several times. It was not tested, but soon I will order pcb from China and I will keep you updated.
Meanwhile, if you are bored, you can check the board and compare it with service manual which is here.
Image preview:
So here I am again and quite frustrated. Disappointed. It is just copy. It should work. R136 and R137 (both 47 ohms) are after power on in smoke.
I connected left and right channel output with 50K on both side, from middle (connection to spk protection) over 100K + cap in parallel to ground as is in service manual. (The resistors and caps "in air".) I thought it will resolve the problem. Of course not!
I also opened my original amp to compare diodes direction, transistors and so on. Everything looks ok. I just don't know.
I connected left and right channel output with 50K on both side, from middle (connection to spk protection) over 100K + cap in parallel to ground as is in service manual. (The resistors and caps "in air".) I thought it will resolve the problem. Of course not!
I also opened my original amp to compare diodes direction, transistors and so on. Everything looks ok. I just don't know.
Hello Lucas,
I am not so sure if I have skills to do that that way. But I just fixed Yamaha AX-10 (it had broken pcb, so I re-traced it and ordered new one from jlc). In some way the design is somehow similar. And I am sure I have to add some components extra. I don't know what exactly yet, but I will figure it out (I hope). Basically A-S500 has some extra connections to main board. Maybe some current control?
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