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....
Those two resistors supply the differential pair and the VAS stage if they are overheating then you have a s/c type fault in those stages.
Check out the BJT,s in those stages, if not then the diodes.
Check out the BJT,s in those stages, if not then the diodes.
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?
Little PCB preview... I think I should be able to put there simple spk protection, hmmm...
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Your right if you are putting your own protection in then then the green line components can be removed .
Yes reinstate the orange sector it contains the zobel network you need that
Yes reinstate the orange sector it contains the zobel network you need that
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 🙂
So, second PCB version will be finished I guess tomorrow.
If anybody knows the answer for https://www.diyaudio.com/forums/parts/356957-transistor-ktc3911s-gr-replacement.html
that would be cool!
If anybody knows the answer for https://www.diyaudio.com/forums/parts/356957-transistor-ktc3911s-gr-replacement.html
that would be cool!
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. 😕
Logically if those two resistors are "going up in smoke " and they feed the input end then you have an over-current problem .
I would disconnect that section and feed it with a bench power supply to trace out the fault.
I would disconnect that section and feed it with a bench power supply to trace out the fault.
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?