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Arcam Diva A85 question
Arcam Diva A85 question
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Old 11th September 2019, 07:34 PM   #11
chinpok is offline chinpok
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Thanks.

First I want to clean it as it is very dirty and for that I need to take it apart.
What is a safe way to remove the heatsink from the mosfets? They are kinda glued there... I'm not sure if it is because of time or it's some sort of adhesive thermal paste.

Btw I see the fluctuation(left side) on output terminal too, not too much but might be enough to ruin the image.
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Old 12th September 2019, 02:34 AM   #12
Ian Finch is online now Ian Finch  Australia
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Are you sure the fluctuation you see is not that of the DMM? Not all digital instruments are capable of stable, precise measurements, so what is the voltage and the amount of fluctuation you are reading?

BTW, don't try to disassemble the amplifier before you are certain that it is working properly. Otherwise, you will almost certainly end up with a bin full of scrap or a non-working amplifier. Unless you are experienced with the assembly of electronic equipment, this will end in having nothing of value to sell.
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Old 12th September 2019, 04:33 AM   #13
aparatusonitus is offline aparatusonitus  Croatia
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Quote:
Originally Posted by chinpok View Post
First I want to clean it as it is very dirty and for that I need to take it apart.
What is a safe way to remove the heatsink from the mosfets? They are kinda glued there... I'm not sure if it is because of time or it's some sort of adhesive thermal paste.

There are no mosfets in this amp, output stage is pure BJT darlington.


I second Ian regarding disassembling amp...do not take it apart!


Quote:
Originally Posted by chinpok View Post
Btw I see the fluctuation(left side) on output terminal too, not too much but might be enough to ruin the image.

The readings you see on DMM is amplifier output DC offset and is normal (a few +/-mV depending on amp construction and opamp used in DC servo roll.
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Old 12th September 2019, 09:41 AM   #14
chinpok is offline chinpok
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Fluctuation: It happens only on one side. I tested it with both multimeters I have and the oscilloscope(all cheap but it's not the multimeter's fault). But if you say it's normal then I believe you and consider the amp working correctly and then it is just a bad sounding amp(no other obvious problems).

Disassembly: I've already done the preamp but that was easy, I'll see how brave I am with the rest(probably not worth the hassle anyway).
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Old 12th September 2019, 10:32 AM   #15
aparatusonitus is offline aparatusonitus  Croatia
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Quote:
Originally Posted by chinpok View Post
Fluctuation: It happens only on one side. I tested it with both multimeters I have and the oscilloscope(all cheap but it's not the multimeter's fault). But if you say it's normal then I believe you and consider the amp working correctly and then it is just a bad sounding amp(no other obvious problems).

TI TL072CD datasheet says intristic Vio (input offset voltage) for is +/-3mV typ. up to +/-10mV max. so your amp is ok regarding output DC offset.

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Originally Posted by chinpok View Post
Disassembly: I've already done the preamp but that was easy, I'll see how brave I am with the rest(probably not worth the hassle anyway).

Please, do not be brave...be smart-)...choose battle you can win.
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Old 12th September 2019, 10:56 AM   #16
chinpok is offline chinpok
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Quote:
Originally Posted by aparatusonitus View Post
Please, do not be brave...be smart-)...choose battle you can win.

Alrighty then.. you won this time Arcam Diva A85 but next time... no there will be no next time bye.

Arcam Diva A85 for sale in perfect condition, one of the best amplifiers ever made based on multiple trustworthy reviews, don't miss it!
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