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Old 29th July 2005, 06:02 PM   #3471
K-amps is offline K-amps  United States
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I'd rather like 1w versions if the spec is 0.25w to 0.6w unless anyone things they won't fit the PCB.

K-

Troy, I see lots of good info, is this waht you wanted or is there too much info? If the latter, I'd say it's not worth your time to source if from 7 different places, I would not mind paying a little extra if it makes it easy for you, after all you are not getting paid so we should make it easy for you.
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Old 29th July 2005, 06:25 PM   #3472
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would it make sense to have a capacitor like C110 or C111 rated for more than 16 volts when it has its leads across a 27 volts Zenerdiode ?
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Old 29th July 2005, 06:49 PM   #3473
AndrewT is offline AndrewT  Scotland
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Hi,
the small resistors do not have a heat dissipation problem.
The quiescent dissipation for all the resistors from R101 to R130 and all RB & RV are less than 100mW and most are less than 28mW (Vrail=38V).
The exception are the output resistors which see peak dissipations into the Watts range. These are R127 & R128, R204 & R205, all Re.
Have I missed any?
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Old 29th July 2005, 07:15 PM   #3474
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Hi guys,

In an earlier post I asked:
Quote:
On another note, I have just about completed my case and will be ready to install everything into it. I've got a question about fuses. How many do I need, what values and where in the circuit should they go?

May I assume one main fuse and two per channel, (one for each rail)?

What ratings should be used for each?

Thanks, Terry
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Old 29th July 2005, 07:26 PM   #3475
AndrewT is offline AndrewT  Scotland
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Hi Still4given,
How low do your speakers go?
I recall you said 4ohms, then the DCR will be about 3R and peak current will be about (42-4)/3 = 13Apk. For this I suggest a rail fuse of about F7A 250v.
For a mains fuse start at T5A(240V) or T10A(110v) and reduce it so that it blows at switch on then go back up one size. You may find that T3A250v (240v) or T5A250v (110v) works with a slow start circuit.
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Old 29th July 2005, 08:36 PM   #3476
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Al,

I was not totally happy with your BOM because you subbed in some of the parts values because you had them handy... while thats all find for your project we still would want to keep any parts group buy as true to the original as possible. Except for the current limiting junk Jans list is the most accurate so far for a MK-2 KSA-50 hence I reccomended Jans BOM.

Mark
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Old 29th July 2005, 08:39 PM   #3477
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Default line fuse

Terry, I've been using a 7A fast blow fuse on the AC inlet and CL-60 soft start, so far have not blown in in about 20 starts. I'm going to try dropping to 5A so that's where I'd start if I were you.
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Old 29th July 2005, 08:41 PM   #3478
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Quote:
Originally posted by AndrewT
Hi,
the small resistors do not have a heat dissipation problem.
The quiescent dissipation for all the resistors from R101 to R130 and all RB & RV are less than 100mW and most are less than 28mW (Vrail=38V).
The exception are the output resistors which see peak dissipations into the Watts range. These are R127 & R128, R204 & R205, all Re.
Have I missed any?

Andrew, my Vrail=80 to 100vdc ;-)
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Old 29th July 2005, 10:52 PM   #3479
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Arif,

even with 100v rails resistors like r103 and r107, with a voltagedrop of 99.4v, still need less than 0.25 watt.
Even with 1 watters, others will die without Stuart's extra's, like R108/109.
So why the need for 1 watt resistors ?
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Old 29th July 2005, 11:03 PM   #3480
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Default power...

Once the 6ma CCS is in place, none of the front end resistors are power stressed. Without it, the whole front end will die at more than about 60v rails.

Once the front end voltages are held stable the voltage over the rest of the resistors is held quite constant regardless of the supply voltage. Thus the majority of the extra dissipation is in the transistors, and because of this the pre-drivers (q107/108) will need to be heatsunk for complete reliability.

Once the rails are beyond 60v the 2sa970 and 2sc2240 don't have enough Vce to be completely safe, and I substituted the mpsa types for my tests.

Stuart
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