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Starving Student PCB's
Jun 18, 2013 at 8:21 PM Post #32 of 392
Mine just arrived in the mail today. Needless to say I'm very excited to place an order at Mouser and hunt for some cheap tubes on eBay :) Thanks again, Howard!
 
Jun 24, 2013 at 9:01 AM Post #33 of 392
My package just arrived today, thanks Howard for fast shipping. Soon me and my friends will buid it..
beerchug.gif

 
 
Jun 25, 2013 at 9:26 AM Post #34 of 392
I put my amp together today, everything was looking great , I'd even found a working power supply in a junk bin for $2 and some nice 1960's tubes ..... final job mounting the Mosfets to the heatsinks .... Doh! I realised that I don't have any of the ceramic mounting kits. Does anyone know where I can buy them or have any to sell? or maybe there is a work around? I can't find any on ebay and Mouser are really expensive for shipping to Japan.
 
Thanks, Andy
 
Jun 25, 2013 at 12:05 PM Post #35 of 392
Quote:
frodo said:
I put my amp together today, everything was looking great , I'd even found a working power supply in a junk bin for $2 and some nice 1960's tubes ..... final job mounting the Mosfets to the heatsinks .... Doh! I realised that I don't have any of the ceramic mounting kits. Does anyone know where I can buy them or have any to sell? or maybe there is a work around? I can't find any on ebay and Mouser are really expensive for shipping to Japan.
 
Thanks, Andy
Click to expand...

 
You mean a TO-220 insulation kit? Like a mica and a plastic shoulder washer?
 
Here you get 10 kits for 3.50 USD. I'm sure the shipping from Hong Kong to Japan would be reasonable.
http://www.ebay.ca/itm/TO-220-Transistor-Mica-Insulation-full-set-for-TO-220-Transistor-X-10-/261144589902
 
Otherwise simply search for "to220 insulation" or similar keywords.
 
Jun 25, 2013 at 6:15 PM Post #36 of 392
Quote:
frodo said:
I put my amp together today, everything was looking great , I'd even found a working power supply in a junk bin for $2 and some nice 1960's tubes ..... final job mounting the Mosfets to the heatsinks .... Doh! I realised that I don't have any of the ceramic mounting kits. Does anyone know where I can buy them or have any to sell? or maybe there is a work around? I can't find any on ebay and Mouser are really expensive for shipping to Japan.
 
Thanks, Andy
Click to expand...

 
Dont forget you only need to insulate the heatsinks if they are grounded, if you dont ground them and use a wooden or ABS type case it's not a problem
 
cheers
FRED
 
Jun 25, 2013 at 6:35 PM Post #37 of 392
Quote:
fred_fred2004 said:
 
Dont forget you only need to insulate the heatsinks if they are grounded, if you dont ground them and use a wooden or ABS type case it's not a problem
 
cheers
FRED
Click to expand...

 
I beg to differ. Here's two reasons:
 
First, there can possibly be some 50 volts on these. With the amount of capacitance on the rail, it can be quite a dangerous zap if conditions are met (you just got out of the shower, your feet are wet and your arm brushes the heat sink...). It's simply not something that should be left to chance. Oh and you don't want to be responsible for someone's cat getting killed by such an advice. Not good for business.
 
If the sinks are not grounded, they become antennas. They'll pick all sort of RF crap that could then be induced on the gate of the fet. Not good. If you ground them, they become shields that actually block RF from reaching the transistors. Much better.
 
It is therefore preferable to ground the heat sinks and then electrically insulate the transistors from them. It's not that hard to do, and the only argument I can see for not doing it is laziness... at the risk of your own safety... and your cat's.
 
Jun 25, 2013 at 11:43 PM Post #38 of 392
I've never had any problems, but if you want to take the precautions , fair enough
 
cheers
FRED
 
Jul 10, 2013 at 8:30 AM Post #41 of 392
everybody seems happy no losses so far :)
 
Jul 24, 2013 at 7:41 PM Post #43 of 392
Bump :)
 
Jul 25, 2013 at 4:34 AM Post #45 of 392
Hi Chris
Italy is a challenge it seems to take 2-3 weeks as a letter,
but there is no hard and fast rule they are all over the place :)
 
FRED
 
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