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Old 5th January 2013, 12:00 AM   #12761
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that is correct. but also join the + and - side for the 0 point.
and make sure your rectifiers are cooled. and all soldering in the PSU are good. a cold solder will apear as a foult when a high temp is at place.
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Old 6th January 2013, 09:19 AM   #12762
WalterW is offline WalterW  Netherlands
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Join Date: Oct 2012
Location: Utrecht
Default Front panel design ??

Just finished my standard F5 on a test-heatsink, and connected some old B&W speakers. Wow it sounds terrific!!! Didn't knew that this old speakers could sound so good.
Here are two pics, I use the softstart board and have a total of 352.000 uF/ 35V for the two boards

Now I'd like to build the F5 into a 3U or 4U Hifi2000 chassis, but I'm looking for a nice frontpanel design.
Does anybody have an example? Maybe even a .dxf or .dwg file format?

I am not that creative, and think drilling and sanding in the nice 10mm frontpanel won't make it any nicer, if I'm doing it myself.

Thanks in advance !

Walter
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Old 6th January 2013, 09:25 AM   #12763
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i would move the 4.7K NTC's a little bit. let them tuch the screw for the fet or the center leg.

Quote:
Originally Posted by WalterW View Post
Just finished my standard F5 on a test-heatsink, and connected some old B&W speakers. Wow it sounds terrific!!! Didn't knew that this old speakers could sound so good.
Here are two pics, I use the softstart board and have a total of 352.000 uF/ 35V for the two boards

Now I'd like to build the F5 into a 3U or 4U Hifi2000 chassis, but I'm looking for a nice frontpanel design.
Does anybody have an example? Maybe even a .dxf or .dwg file format?

I am not that creative, and think drilling and sanding in the nice 10mm frontpanel won't make it any nicer, if I'm doing it myself.

Thanks in advance !

Walter
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Old 6th January 2013, 10:00 AM   #12764
Koeniwo is offline Koeniwo  Austria
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Join Date: Aug 2008
Servus Walter,

Attach the NTC's with a thermal bonding glue to the MOSFET.
For your configuration (1 pair MOSFETs for each channel) you need only 3U HiFi2000 chassis. I have tested this config with a 3U chassis. The heatsink warm up only to appr. 50 degrees Celsius.

I'm looking also for a nice frontpanel design.

Kindest Regards

Wolfgang
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Old 6th January 2013, 10:48 AM   #12765
WalterW is offline WalterW  Netherlands
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Join Date: Oct 2012
Location: Utrecht
Thanks for your reply Audiosan.
Touching the plastic cover of the MOSFET isn't enough? Even when I glue it with thermal glue in the definitive version?
Touching the center leg is easier and would look nicer I guess...

Wolfgang, that's what I was hoping for, I like the 3U chassis over the 4U.
The heatsink I'm using right now, Fischer SK56 20x30x4 cm, is becoming too hot, with this stereo setup. Aprox. 128 Watts on a 0.3K/W.
So on the back is a little quiet fan right now

Walter
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Old 6th January 2013, 11:00 AM   #12766
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it will work. but center leg is a safer way. if you have already glued it, then just leave it be
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Old 6th January 2013, 11:29 AM   #12767
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Join Date: Feb 2005
I'd suggest a couple of things also, hopefully without appearing to be a "smart ***".

It appears that you have fuses on the power rails but no dc protection on your O/P - suggest adding one, even if it's a basic unit, as fuses have been known to fail without cause.


If that's a GB bridge (general purpose 35A/200V) feeding your power caps, suggest changing it to an IXYS Shottky bridge or discrete diodes - those GB bridges are convenient and cheap, but this is an easy upgrade for a noticeable improvement in the sound. You have to keep them as cool as possible.

That's a lot of capacitance - 22mF Panasonics? Perhaps an additional small 470uF Nichicon KZ or FG on the pcb (rails) could be beneficial to the sound ....

I can't see any problem about using thermal glue to hold the thermistors to the power Fet's bodies (I hope there's some insulation on the thermistor's leads).

However, AudioSan mentions it's better to glue them directly to the Fet's middle leg - this is interesting and I'd like to know why ...
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Old 6th January 2013, 11:39 AM   #12768
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it is where the fets are hottest. afterall. this is a thermal protection.
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Old 6th January 2013, 11:54 AM   #12769
WalterW is offline WalterW  Netherlands
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Join Date: Oct 2012
Location: Utrecht
You're no smart****
I like feedback, it can only make things better...
The fuses are there for initial testing, cause I don't have a variac. They are removed when the amp is build into the chassis.
I will leave out a speaker protection circuit, I even think of cutting out the 10 Ampere limiting circuit...

How are those IXYS Shottky bridge's going to improve the sound? I'm always open for suggestions, but I think all the current will be taken from my indeed large buffercaps, ( yes they are 22mF panasonics from digikey) and the rectifier diodes will not be so important???
I will do some reading about that subject...

Putting a small cap on the PCB is a good suggestion yes, It's a pitty it is not on the PCB already.
Me being a "HAMradio" builder also, I always like to put a lot of decoupling cap's on power rails
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Old 6th January 2013, 11:59 AM   #12770
WalterW is offline WalterW  Netherlands
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Join Date: Oct 2012
Location: Utrecht
Quote:
Originally Posted by AudioSan View Post
it is where the fets are hottest. afterall. this is a thermal protection.
I think you're right, this leg is probably directly connected to the substrate inside... so that is where 'm gonna glue mij NTC's.

Anybody a suggestion for a nice frontpanel design?
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