The Cast Iron Griddle Amp - a Budget Conscious Heatsink Solution

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#22
These are the cables I use. They improve the sound without question compared to 16ga. Very soft and supple for 12 gauge and ready made. I like that “cables with Pants”. 🙂

Mediabridge 12AWG Ultra Series Speaker Cable w/Dual Gold Plated Banana Tips (6 Feet) - CL2 Rated - High Strand Count Copper (OFC) Construction - Black [New & Improved Version] (Part# SWT-12B-06B) Amazon.com: Mediabridge 12AWG Ultra Series Speaker Cable w/Dual Gold Plated Banana Tips (6 Feet) - CL2 Rated - High Strand Count Copper (OFC) Construction - Black [New & Improved Version] (Part# SWT-12B-06B): Electronics
 
#25
Interesting, I wouldn't have thought that the surface on a griddle would be particularly flat or smooth. Looks like it works though. How does it handle driving a 4 ohm dummy load at 3/4 power?

So, as another cheap heatsink solution, what about using a piece of 3" x 0.75" (sorry to use the dumb units) 80/20 extrusion? The 0.75" wide stuff has some parts that are pretty thick. Aluminum is easy to tap (even more so than cast iron). WD-40 or kerosene is a good cutting fluid for aluminum (one of the few things WD-40 actually works well for).

I'm not sure how flat the surface would be, but even for those who don't have a milling machine in their basement, you could use a surface plate (or even a piece of glass- it's flat enough for this) with some 320 grit sandpaper glued to it with spray adhesive.

This stuff is fairly cheap, and I see pieces of 80/20 sold at surplus auctions all the time so you might get it for even less.

Something like this:
80/20 3" X .75" T-SLOTTED EXTRUSION | WOOD Magazine

A 3" wide piece should fit in a standard 2u chassis.
 
#26
That profile could work too. Just need to have it log enough to dissipate the heat. The griddle is big - lots of surface area but lacks real fins.

My experience is cast iron drills and taps easier than aluminum. About 4x easier. I did like 20 holes no problem.

A 300mm length of the 100mm profile is great for heatsinks. Can flow water or air inside the channels.

Bosch Rexroth
 
#30
wtnh said:
X - what brand of Faston connectors are you using? I like the look of the insulated part - do they crimp well?

Thanks
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I use these:

Yueton 100pcs Female Fully... Amazon.com: Yueton 100pcs Female Fully Insulated Wire Crimp Terminal Nylon Quick Connectors Wiring Spade (Female): Home Improvement

They do crimp well, with the right crimpers. I use a Klein to do the initial “bite” in the internal metal part, then I use the compound jaw crimper to finish it off with a lot of pressure that squeezes the metal and the plastic. It’s very secure - I have not had one pull apart yet.

Klein 1005 tool step 1 (Use the “uninsulated” jaw even though insulated);

Klein Tools 1005 Cutting / Crimping Tool for 10-22 AWG Terminals and Connectors, Terminal Crimper for Insulated and Non-Insulated Terminals Klein Tools 1005 Cutting / Crimping Tool for 10-22 AWG Terminals and Connectors, Terminal Crimper for Insulated and Non-Insulated Terminals - Crimpers - Amazon.com

Then step 2 is a compound jaw generic brand like this for example:

Wire Stripper and Crimping Tool Meterk 0.14-6mm² Adjustable Crimping Range With Carbon Steel + Alloy (Crimping Tool Wire Crimpers) Wire Stripper and Crimping Tool Meterk 0.14-6mm2 Adjustable Crimping Range With Carbon Steel + Alloy (Crimping Tool Wire Crimpers) - - Amazon.com

Probably can skip the Klein but I like to know that it’s the best crimp possible.
 
#31
xrk971 said:
That profile could work too. Just need to have it log enough to dissipate the heat. The griddle is big - lots of surface area but lacks real fins.

My experience is cast iron drills and taps easier than aluminum. About 4x easier. I did like 20 holes no problem.

A 300mm length of the 100mm profile is great for heatsinks. Can flow water or air inside the channels.

Bosch Rexroth
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As long as you use some form of cutting fluid (aluminum is very prone to chip welding), it's pretty easy. Tapping cast iron should be quite easy, you are correct, though I hate milling or turning cast iron because it make such a huge mess.

Call me an idiot, but I like to power-tap most of the mounting holes for transistors with a hand drill. The smaller 12V drills work well for this. For work I managed to do about 100 4-40 holes in about an hour this way. (excluding the time spent cleaning the finished parts and test-fitting them). I certainly wasn't interested in hand-tapping all of those.
 
#32
it make such a huge mess.
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So true! My hands looked like I worked in a coal mine or those of an auto repair mechanic and there is black iron dust everywhere. A magnet picks up a lot but ultimately, a huge mess compared to aluminum.

I have broken too many taps to trust my skills at power-tapping. Although, last time I broke 3 taps on a surplus Dell solid copper heatsink. Never working with copper again.
 
#37
 
#39
xrk971 said:
Thanks! $26 for 100 vs $7 is a bit more but probably worth it.
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I honestly wish Wago made their PCB-mount CAGE CLAMP products more readily available. Having used the Wago 221 series of connectors and their DIN rail terminal blocks, I almost don't want to use anything else. That technology is unbelievably good.

*I have no relationship with the Wago company, or any of its parent or subsidiary companies*.

Oh, looks like a GB company actually sells them online. 745-821 | Wago, 1 Way PCB Terminal Strip | RS Components
 
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#40
xrk971 said:
So true! My hands looked like I worked in a coal mine or those of an auto repair mechanic and there is black iron dust everywhere. A magnet picks up a lot but ultimately, a huge mess compared to aluminum.

I have broken too many taps to trust my skills at power-tapping. Although, last time I broke 3 taps on a surplus Dell solid copper heatsink. Never working with copper again.
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If you're using a regular drill press, cleaning up after cast iron is annoying but not that big a deal.

In my case, I do almost all of my drilling on the mill, and after doing anything with cast iron it's a significant process to clean and re-lubricate the ways. As such, I only use cast iron when I need to, which is pretty rare. Now and then I have to make a back plate for a lathe chuck or do modifications to a piece of cast iron tooling, but for the most part I'm able to avoid it.

Copper is always difficult. It tends to be very gummy. It's a bit like brass, only much worse. Drills tend to grab, and tapping is no fun.

Power tapping is something I mostly do when there's repetitive work, and I usually only do it in Al with high-quality taps.

More on topic, whenever I have devices that are dissipating a lot of heat, I use a clamping bar. The mounting screw in TO-3P and TO-264 packages doesn't make for very even clamping. When I do this, I usually also take the time to make sure the heatsink is flat and smooth, and sometimes I even do the same on the transistors. Most amplifiers do not need this kind of thing.

As a side note, some microprocessors (Intel is terrible about this) have heat spreaders that are pretty far from being flat. One of my friends couldn't figure out why his overclocked CPU was overheating even with a water cooler, until I checked it against a surface plate and demonstrated that the high spot was high by nearly a millimetre. Lapping the top of the heat-spreader improved things by almost 35 C. I've seen similar things with transistors as well.
 
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