ATC SCM7 . . . with Papa's diy amp? - Page 22 - diyAudio
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Old 15th November 2008, 06:20 AM   #211
Formerly "jh6you". R.I.P.
 
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You will get much better knowledge than I have

Here I am re-drawing F5 circuit with component values I have.

- Increased R3, R4, R15 and R16 to 2.4K
- Increased TH1 and TH2 to 5K
- Reduced P1 and P2 down to 2K

These will provide me with adjustable resistance value of 0~950ohms between the +rail and the drain of Q1 and between -rail and the drain of Q2. So, these changes should be okay.

- Changed Q1 to 2SJ74 and Q2 to 2SK170
- Increased R19 and R20 to 160 as I have number of this resistor. This will provide the amp with reduced max. output current of about 9A.
- Increased R21 and R22 to 18K. Papa recommends 22K, but I have only 18K of the value near to 22K.
- Changed R5, R6, R7 and R8 to 2W-rating as I have number of 100ohm-2W resistors

I will go ahead with the re-drawn . . .

Cheers,

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Old 16th November 2008, 08:01 AM   #212
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Default Resistors

I will probably increase R21 & R22 as well, but that will be about for me.

My biggest hurdle is the case and the amp board.

If you can get someone to make up a case for you, that's great, go for it.
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Old 16th November 2008, 11:01 AM   #213
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Quote:
Originally posted by enzedone

I will probably increase R21 & R22 as well, but that will be about for me.


I wonder . . .
R21 and R22 are arranged to prevent too much power dissipation in the Mosfet in case the output is shorted by mistake and the short current exists during certain time length. Nevertheless, Papa recommends to increase R1 and R2, saying that it's for a marginal better sound. (Sacrificing the better safety of the short circuit . . . ?)
>><<

I misunderstood myself as I had TH1 and TH2 of 5K ohms. I was wrong. So, I tried to find 5K ohm thermistors from few dealers located near to my place, but . . . but . . . uhhhhm . . .
>><<

I'm thinking to replace 5K ohm thermistors with 10K which is easy finding here for me.

Cheers,

>>PositiveWay<<
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Old 16th November 2008, 07:45 PM   #214
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Default NTC Thermistors

I found these ones at Farnell

Part No.
RL1004-2910-97-D1


http://nz.farnell.com/ge-sensing-the...tor/dp/9771336

What Value Thermistor are you using on the power supply/Star ground? I was told about 25 Ohms should be o.k?Edit: Just found these:

http://nz.farnell.com/ge-sensing-the...tor/dp/1707188

If you can't order them, let me know and I will put an order in for you from here, and wack them in the post for ya.
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Old 16th November 2008, 08:23 PM   #215
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Default And..........

These

http://newzealand.rs-online.com/web/...duct&R=5167827
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Old 16th November 2008, 09:45 PM   #216
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Default Re: NTC Thermistors

Quote:
Originally posted by enzedone

What Value Thermistor are you using on the power supply/Star ground? I was told about 25 Ohms should be o.k?Edit: Just found these:

If you can't order them, let me know and I will put an order in for you from here, and wack them in the post for ya.


I am using CL-60 type (5 ohms/10A) between the star ground and the power socket earth point.

Thanks for your kind offer
But, sure, I can order the 5K ohms zener from here to Farnell. I just thought of easy mwthod . . . Tks again!

Cheers,

>><<
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Old 17th November 2008, 04:00 AM   #217
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Okay, I got 5K thermistors . . .

By the way,
I'm thinking to make a new thread separately from this one.

"New-building of my F5"?


Cheers,

>><<
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Old 18th November 2008, 10:11 AM   #218
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Default Opinion

Babowana

Sorry to be asking you again, on your thread
What is your comment about this board please.
If this seems o.k I will not trouble you again

regards

Brett
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Old 18th November 2008, 10:23 AM   #219
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Brett,

The PCB arrangement looks very good (I did not see all details tho). I want to copy your's. But, I already finished my ugly board, eeng . . .

Cheers,

>><<
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Old 18th November 2008, 06:07 PM   #220
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Default Thank you

Thanks for the help.
I will try and print this off and then use photo paper to copy to board.

I am looking forward to seeing how your project turns out as you are such a fast operator.:smash
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