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Old 19th February 2011, 10:06 PM   #111
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Last week was some discussion about tapping the mounting holes for the power transistors - some people do have a tough time with it and sometimes leave a raised edge, holes at wrong angles, wrong position because of broken taps, etc, etc - most of us have been there, done that, ...

There are quite a few "Transistor Mounting Spring Clips" & "Transistor Clamp Bars" readily available that'll take much of the drama out of the whole mounting exercise, particularly useful if you remove the transistors more than once - also, pressure is applied directly onto the centre of the back of the transistor, a good thing - basically, retail versions of the common mounting bar/bracket idea.

I find them very useful, perhaps other's may also ......
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Old 19th February 2011, 10:58 PM   #112
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Originally Posted by tinitus View Post
you dont need to know very much, or how to calculate anything

its all in the F5 manual, in every detail

even a supply schematic clearly showing 18Vac trafo
Even though I don't need to know very much, I would really like to know how everything in an amp works. I'm working my way there but still need more! And thanks everyone.

Hows the amp coming 6l6?
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Old 20th February 2011, 12:58 AM   #113
6L6 is offline 6L6  United States
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Originally Posted by crazycody1993 View Post
Hows the amp coming 6l6?
So that's what this thread is about...

The amp PCB for the 2nd channel has been stuffed, but other than that, I haven't done anything since the last post with photos.

I am going skiing for a week+ starting Monday, so you will not see any updates from me until a few days into March. Unless something bizarre happens tomorrow and plans fall through, I will not have any time to work on it at all.

Stay tuned in, this project will be completely documented as it gets completed.
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Old 20th February 2011, 01:38 AM   #114
anilva is offline anilva  India
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Default Question about silpads

Hi,

I have built 2 F5 and 2 Aleph J so far in order to run some of my speakers in active configs. In my experience, F5 has been the easiest to build if one were to build the stock design of Mr. Pass.

I have also used mica washers and goop (heatsink paste) for heatsinking the outputs. But it is quite difficult to manage with mica and goop if you are replacing the outputs or do some changes with other output variants such as Toshibas.

I have bought a bunch of silpads, but wasn't happy with the heat transfer compared to goop. Do I need to use goop with silpads too? How about keratherm? Do they need goop as well?

Cheers.
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Last edited by anilva; 20th February 2011 at 01:40 AM. Reason: Spelling errors.
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Old 20th February 2011, 02:36 AM   #115
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Quote:
Originally Posted by anilva View Post
Hi,

I have built 2 F5 and 2 Aleph J so far in order to run some of my speakers in active configs. In my experience, F5 has been the easiest to build if one were to build the stock design of Mr. Pass.

I have also used mica washers and goop (heatsink paste) for heatsinking the outputs. But it is quite difficult to manage with mica and goop if you are replacing the outputs or do some changes with other output variants such as Toshibas.

I have bought a bunch of silpads, but wasn't happy with the heat transfer compared to goop. Do I need to use goop with silpads too? How about keratherm? Do they need goop as well?

Cheers.
My understanding is no. I know that for sure about sil pads, and that's what I've been told about keratherm. Someone can verify this?

Russellc
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Old 20th February 2011, 07:57 AM   #116
Zen Mod is offline Zen Mod  Serbia
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Keratherm doesn't need goop
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Old 20th February 2011, 09:38 AM   #117
AndrewT is offline AndrewT  Scotland
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if the insulator is soft or squiggy then it is almost certainly designed to fill in all the scratches in the heatsink and the active device. No goop needed to fill the scratches a second time.
Many of these "dry" type need heat to make them "flow". This will happen at first warm up. second operation may turn out to run slightly cooler, i.e. heatsink slightly hotter due to better transfer of heat through the "prepared" insulator.

Hard insulators, like mica, metal oxides, Kapton do not fill the scratches. These need goop to exclude air from the interfaces.
If Kapton is treated on one side with a flowable goop then the bare side will still need goop.
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Old 20th February 2011, 09:53 AM   #118
EUVL is offline EUVL  Europe
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Mica and Goop

And Keratherm is not based on two-phase wax, so no need to heat to flow.

I have written an article for Jan Didden's Linear Audio on thermal design of Class A amplifiers, for those who want to understand and then onto design their own. Probably out in the second half of the year, as far as I know. There is a detailed comparison of all commonly available insulator types. The simple conclusion is that Keratherm is still the best solution to-date that money can buy (off the shelf).


Patrick
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Old 20th February 2011, 10:32 AM   #119
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I hope your FETs are still okay after handling them so much...
ESD is a nuisance, especially in winter.
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Old 20th February 2011, 11:06 AM   #120
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Quote:
Originally Posted by jameshillj View Post
Last week was some discussion about tapping the mounting holes for the power transistors - some people do have a tough time with it and sometimes leave a raised edge, holes at wrong angles, wrong position because of broken taps, etc, etc - most of us have been there, done that, ...

There are quite a few "Transistor Mounting Spring Clips" & "Transistor Clamp Bars" readily available that'll take much of the drama out of the whole mounting exercise, particularly useful if you remove the transistors more than once - also, pressure is applied directly onto the centre of the back of the transistor, a good thing - basically, retail versions of the common mounting bar/bracket idea.

I find them very useful, perhaps other's may also ......
I used a very simple method, all by hand. It was my first attempt at working with aluminum, and my first attempt at tapping drilled holes. I very carefully used a hand held drill and used a little oil designed (or at least sold as such)
for tapping. Tapped the holes, 4-40 and 10-32 with an inexpensive hand held tap. Then removed the "edge" by using a bit designed to make cone shaped holes so screw heads of that shape can fit flush. I didnt cut a cone shaped hole, just used it to remove the raised edge, and it worked perfectly!

There are a lot of more precise methods I'm sure, but this worked for me with minimal tools.

Russellc
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