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Old 1st February 2011, 09:53 AM   #10211
Marra is offline Marra  United Kingdom
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Thanks Andrew will do when I can use my workbench [dining table]. The wifes sorting Avon at the moment.
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Old 1st February 2011, 10:00 AM   #10212
AndrewT is offline AndrewT  Scotland
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you live dangerously !

A friend asked me to build an engine for him.
He presented me with his workshop: The kitchen worktop !!!
and his wife was in at the time.
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Old 1st February 2011, 11:07 AM   #10213
Marra is offline Marra  United Kingdom
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Brave; not really. After my undergoing heart surgery 2yrs ago Elizabeth is just happy to see me building things again. Not that I'm recommending that as a means to get round the wife to let you use the dining room as a workshop you understand
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Old 1st February 2011, 11:45 AM   #10214
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Quote:
Originally Posted by lhquam View Post
Here is my new stereo F5 build, using a single HeatSinkUSA E007, cut in half and reassembled to make a heat tunnel. Airflow is provided by a Noctua NF-S12-B fan shown in the images. With this arrangement the heatsink temperature rise is only 30 degrees F (17C) with 12 volts to the fan. The MOSFETS are mounted with 1 mil thick mica and Thermalcote.

Since these fans are so quiet, especially at lower RPMs, it seems obvious to me that higher wattage class A designs should take advantage to the 3X increase of wattage for the same heatsink by using airflow from a quiet fans.

BTW: With the addition of some insulated mountings, the 2 heatsinks can be electrically isolated from each other and ground, if you are inclined to mount your MOSFETS without any insulators.
Great assembling! Silent fans are a great way to achieve big amounts of power in an small confined space. People don't really realize how silent can a fan be if it is well designed and running at low RPM. Truly inaudible with your ear further than 30cm.
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Old 1st February 2011, 11:51 AM   #10215
AndrewT is offline AndrewT  Scotland
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Hi,
is a DC motor fan just as quiet if the reduced speed supply is PWM (pulse width modulated) rather than reduced voltage?

I saw a circuit based on a 555 that provided variable speed by changing the duty cycle as the sink temperature changed. All that switching must create electrical interference, but does it also cause mechanical vibration in the motor and/or fan blades to make noise worse?
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Old 1st February 2011, 05:12 PM   #10216
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Hello,
I have problem with F5 amp. When I set P1, P2 voltage to 4.2V, across R11, R12 shows 0,15V (must be 0,6V). The amp is working.
When I increase P1, P2 to 4,8V, across R11, R12 shows 0,55V, but now an amp works with a low level signal. If I Increase a signal, amp is “closing”, and it begin to heat at Q3,Q4. After several tries, the 2sk170 were “killed”. I changed it. but I killed it also.
I put 2sk170bl and 2sj74bl.
Please help.
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Old 1st February 2011, 08:27 PM   #10217
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Hi everyone,

I plan to finalyse my BoM and then purchase the last little things I need.
Nevertheless, I have 2 questions about 1) the transformer 2) the case.
  1. according to several threads on several forums I read, it seems that a 400VA instead of a 300VA would be better. Is that true?
  2. I plan to buy either a HiFi2000 4U 300mm or a 4U 400mm. According to the attached file, a 4U 300mm should be ok, but isn't it a little bit too tight?
Thank you very much in advance.
Attached Files
File Type: pdf Hifi2000.pdf (27.5 KB, 75 views)
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Old 1st February 2011, 09:43 PM   #10218
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Nevohteeb View Post
Hi everyone,

I plan to finalyse my BoM and then purchase the last little things I need.
Nevertheless, I have 2 questions about 1) the transformer 2) the case.
  1. according to several threads on several forums I read, it seems that a 400VA instead of a 300VA would be better. Is that true?
  2. I plan to buy either a HiFi2000 4U 300mm or a 4U 400mm. According to the attached file, a 4U 300mm should be ok, but isn't it a little bit too tight?
Thank you very much in advance.
1. for stereo build, 400VA would be better, for mono amps 2x 300VA equally good

2. stick to 300mm, and 5U being the best choise
boards are small, so 300mm should be fine
just place your trafo close to front plate, maybe preferably in upright position
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Old 1st February 2011, 09:49 PM   #10219
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Quote:
Originally Posted by tinitus View Post

just place your trafo close to front plate, maybe preferably in upright position
Just make sure the trafo bolt does touch the top of the chassis as well or you will have a shorted turn.
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Old 1st February 2011, 09:56 PM   #10220
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Quote:
Originally Posted by tinitus View Post
1. for stereo build, 400VA would be better, for mono amps 2x 300VA equally good
Ok, then 400 VA it is/

Quote:
Originally Posted by tinitus View Post
2. stick to 300mm, and 5U being the best choise
boards are small, so 300mm should be fine
just place your trafo close to front plate, maybe preferably in upright position
Hmm, actually, I was first thinking about taking a 4U 400mm. Hence, I saw that 4U 300mm would be ok, which would save me about 40 euros... 5U is too expensive for me. Is the latter is not too tight, I'll take it but I'm not so sure...
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