This is an important detail:
A60+ as delivered has D669 soldered above the plane of the PCB. This is not a great problem if you run the amplifier at low bias. But, as you increase the bias, temperature will rise considerably. This may cause thermic runaway.
Therefore it is of utmost importance to provide negative bias action by placing the D669 on the heat sink along with the output transistors.
Look at the snapshots below:
1. Wrong
2. Correct
A60+ as delivered has D669 soldered above the plane of the PCB. This is not a great problem if you run the amplifier at low bias. But, as you increase the bias, temperature will rise considerably. This may cause thermic runaway.
Therefore it is of utmost importance to provide negative bias action by placing the D669 on the heat sink along with the output transistors.
Look at the snapshots below:
1. Wrong
2. Correct
Yes thank you. On the first two boards, this transistor was soldered on the back of the board, and in the last, just like yours. I corrected it right away. For some reason, with MJL transistors, the radiator heats up more and I could not increase the quiescent current above the equivalent voltage at the TEST points of 10mV. Is the 2SD669 transistor the same as the D669?
There must be something wrong if you can not increase the bias above 10mA. Is there the same problem on the both chanels?
To eliminate hum you must make proper wiring to avoid problems associated with ground loops. Dual mono isn't that difficult but you must systematically go through every aspect.
Here is a link to very useful tread at DiyAudio. Look into the pdf file from the #1 post.
Good luck
PS: D669 and 2SD669 are synonim.
To eliminate hum you must make proper wiring to avoid problems associated with ground loops. Dual mono isn't that difficult but you must systematically go through every aspect.
Here is a link to very useful tread at DiyAudio. Look into the pdf file from the #1 post.
Good luck
PS: D669 and 2SD669 are synonim.
Berlusconi, it seems, begins to come to an understanding of what is wrong with my boards. You can check the values of the resistors R21 and R9 (diagram you published).
My resistors are like that. R21 - 1kOhm (ring colors brown-black-black-brown-brown), R9 - 22Ohm (red-red-black-gold-brown). Then the input is overly sensitive, there is practically no signal division at the input (the ratio of resistors 1000 and 22). I was advised to raise R9 to at least 10 kohm. What do you think?
PS: Technique of the USSR is not a Chinese toy craft. The experience of the former engineers cannot be taken away. Works great, just wiped off the dust. As if not more than 30 years have passed. As a result, I found out that the output signal with a short-circuited input to ground over a cable length of 1 meter completely repeats the signal at the connection point of the resistors R9 and R21. It seems that the Chinese got it wrong with the R9 rating in the new versions of the boards.
My resistors are like that. R21 - 1kOhm (ring colors brown-black-black-brown-brown), R9 - 22Ohm (red-red-black-gold-brown). Then the input is overly sensitive, there is practically no signal division at the input (the ratio of resistors 1000 and 22). I was advised to raise R9 to at least 10 kohm. What do you think?
PS: Technique of the USSR is not a Chinese toy craft. The experience of the former engineers cannot be taken away. Works great, just wiped off the dust. As if not more than 30 years have passed. As a result, I found out that the output signal with a short-circuited input to ground over a cable length of 1 meter completely repeats the signal at the connection point of the resistors R9 and R21. It seems that the Chinese got it wrong with the R9 rating in the new versions of the boards.
You're correct. R9 has even much higher value: 100K. You will see the value on the board when you de-solder it to replace the resistor.
This is why I want to solder myself.
Just look at the snapshots below. It is a snapshot of smaller A60, but that part is geometrically identical. The first image indicates positions of individual components and the next is the silkscreen with values. Just look at the R9.
This is why I want to solder myself.
Just look at the snapshots below. It is a snapshot of smaller A60, but that part is geometrically identical. The first image indicates positions of individual components and the next is the silkscreen with values. Just look at the R9.
Exactly. T-34
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Good question!
No, just 25mm.
By the way: what have you ordered? Let's verify before you order. These things cost and it would be pitty to waste money.
Regards
Hello Paroxod4. I wrote about the boards and the diameter of the capacitors. Only suitable for boards as in the photo below.
I ordered such capacitors, they are well defined by a Chinese tester on ATMEGA. The only thing that is not clear is their ability to deliver a large current in a short time. SAMWHA is now working in the working boards in the assembled amplifier, and in the test board for experiments JCCON. I did not notice the difference, although I did not load the test board strongly at high volume.
I ordered such capacitors, they are well defined by a Chinese tester on ATMEGA. The only thing that is not clear is their ability to deliver a large current in a short time. SAMWHA is now working in the working boards in the assembled amplifier, and in the test board for experiments JCCON. I did not notice the difference, although I did not load the test board strongly at high volume.
Unfortunately, in the first edition of the circuit on the A60 +, mistakes were made due to inattention. I am publishing the revised diagram.
Project Proteus:
https://disk.yandex.ru/d/FOG5ivME6t18rw
Project Proteus:
https://disk.yandex.ru/d/FOG5ivME6t18rw
slavko65
Thank you, I clarify - is this 22000mkf63v, 35x70 suitable for the A60 board?https://aliexpress.ru/item/10050020...18558174274&spm=a2g0o.cart.0.0.6a9f3c00pzATVb
slavko65
OK.These are the only Chinese capacitors that are no worse than Elna and Nichikon. Official supplier. I have 95 percent of the orders, I have no complaints, I constantly compare them with the originals (at work I take apart the equipment, instead of the new one). In addition to them, I can put something branded Japanese.
The translation is a little incorrect. I meant that I bought components for Ali, and mostly good (I also came across fakes for which I received a full refund), I also compared them with the originals that I have from the removed (replacement) equipment. The capacitors that I gave a link have good reviews They are better than the fake Elna and Nichikon who sell even well-rated stores. In any case, the price is not that high to test them.