Is this method of heat sinking a good idea? N00b question ahead... - diyAudio
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Old 29th April 2012, 09:34 PM   #1
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Default Is this method of heat sinking a good idea? N00b question ahead...

Hey everyone I finally got a job and even though Im severely under-employed its better than nothing and now I have a small income with which to work on my projects

The following is my beloved Ibanez Toneblaster 25R guitar amp. I got it used from a friend and it is definitely a great bang-for-your-buck amp for heavy music (especially when you trash the stock speaker and hook it up to a decent cab).

Click the image to open in full size.

Click the image to open in full size.

As you can see, the method Ibanez used to heat sink the chips is to hook them both up to a metal plate. This metal plate supports the PCB and is attached to the bottom of the chassis. Also, it looks as though some things have been grounded by being attached to this plate.

Here are my questions:
1. Generally speaking, is this a good method for heat sinking?
2. If not, why? Does it denigrate the sound quality?
3. If not, is there a way I could improve it?

I currently have some eBay bucks that will expire in a few days and was thinking I could buy this in order to improve the Toneblaster. Let me know what you all think Im looking forward to it
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Old 30th April 2012, 12:12 AM   #2
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A couple thoughts- if the chassis is made out of steel, having the heat sink screwed to the chassis accomplishes almost nothing. Steel doesn't transmit heat well, so it doesn't spread and doesn't add much to the area of the heat sink. The aluminum heat sink is good as far as it goes, but could probably be better if it had some fins for more surface area. Now, if the devices are decently attached to the sink, and if the sink isn't getting hot, don't worry about it; it's entirely adequate. If it does get hot, you probably won't improve or change the sound much, but improving the heat sinking will improve the reliability. Maybe. Those little eBay sinks are too small to accomplish much of anything. If I were going to "hot rod" this, I'd make a new heat sink out of a large finned aluminum extrusion. You could also epoxy an extra finned piece to the existing sink if you keep the epoxy joint thin and use a thermally conducting epoxy. That might be the most elegant solution.
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Old 30th April 2012, 09:58 AM   #3
AndrewT is offline AndrewT  Scotland
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Check the device temperatures as Con has advised.
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Old 30th April 2012, 11:16 AM   #4
bcmbob is offline bcmbob  United States
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Home Depot, True Value and the like have a large selection of "L" and square aluminum in several thicknesses. A long chunk could attach to the chips and span the chassis. You could still use those little HS something like the pic.

Al HS.jpg
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Last edited by bcmbob; 30th April 2012 at 11:26 AM.
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Old 1st May 2012, 11:50 PM   #5
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Hey thanks for the advice and comments everyone

I have a feeling the chassis and plate is made of aluminum, as opposed to steel, since the amp wasn't very expensive. However:

1. How can I effectively check the temperature of the chips?

2. Is there a specific piece of equipment I should use? If so, where can I get it?

3. What should be the appropriate temperature of these chips?
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Old 2nd May 2012, 12:41 AM   #6
gootee is offline gootee  United States
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Checking chip temperature: If you put your fingertip on the exposed body of the chip and your skin instantly blisters or smokes, or if you can't hold your finger against it for more than one second, then it's probably too hot. Ideally, you would want to be able to hold your finger against it indefinitely, but five seconds might be OK. Or I guess maybe you could use some sort of thermometer. Either way, you're only talking about the case temperature, not the junction or die temperature (inside the chip) that is probably in the specs.

If it's "too hot" even with a good heatsink, then you are probably either running it too hard or there's a high-frequency oscillation.

Last edited by gootee; 2nd May 2012 at 12:44 AM.
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Old 2nd May 2012, 01:02 AM   #7
bcmbob is offline bcmbob  United States
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Non-Contact Infrared Laser Thermometer

Works great and can be found even cheaper at some tool outlets.
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Old 2nd May 2012, 10:28 AM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by mgcasella View Post
...................However:

1. How can I effectively check the temperature of the chips?..................
Mothers use their elbow, but I'll guess your elbow won't fit. Try the end/tip of your pinkie finger.
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Old 2nd May 2012, 10:34 AM   #9
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by bcmbob View Post
Non-Contact Infrared Laser Thermometer

Works great and can be found even cheaper at some tool outlets.
there is another Thread where the user of this "laser guided" infra red temperature meter swore blind that it was accurate and chastised us for even questioning his temperature measuring method. A few weeks later he came back and announced he was now measuring a much higher and probably more accurate value and now realised his absolutely fantastic laser meter was telling him lies.
Well that not quite how he put it, but it is what is implied in his post.

It must have taken twenty to thirty posts trying to get him to calibrate his temperature measuring method. He would not accept that his method even needed calibration, nor that the calibration would need to be done for every new surface he was trying to measure.

The message from all of this.
You must understand what you need and what you need to do to get reasonable results from any measuring system.
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Old 2nd May 2012, 10:45 AM   #10
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Those infrared thermometers are very inaccurate because of the unknown value of the emissivity Emissivity - Wikipedia, the free encyclopedia
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