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Advice on heatsinks for 7800 from Console5


raymondjiii

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The only ICs that dissipate any notable heat are the 6502, RIOT, Maria, TIA.

 

As you ask which heatsinks would be useful, I'd just like to clarify that you really shouldn't "need" any at all.

I just left my system on for about 15 minutes sitting on the Xevious 'demo' mode and took some measurements.

At an ambient temp of 72F (22.2C) on the case, the 6502 reached 114F (45C) and was the highest temp out of those four chips.

A WDC 65c02 is rated up to 185F (85C) and I wouldn't think atari's 65c02 would be much different.

TLDR: Even if it causes second degree burns on your finger, it is still operating well within normal thermal parameters :P

 

That said, if by useful you mean "I want them" and you want ones that will fit...

These four chips are all 0.6 inch (15.24 mm) wide (top to bottom)

40 pin DIP is basically 2 inch (52 mm) long. The Maria is 48 pin so a bit longer, but that shouldn't matter here. 

 

The site you linked has a 14mm square heatsink that would fit and is far cheaper than the longer ones.

Even getting 8 of them, 2 per chip, would be a third of the cost of their dip-40 sized heatsinks.

 

Only one of their two dip-40 heatsinks lists any measurements on it with a 12mm height.

The electrolytic capacitor next to the Maria is 15mm high, so you should have at least that much clearance.

 

The only other advice I can give is to pay mind to the type of thermal compound you get.

Thermal grease and paste are not intended to adhere the heatsink to the chip in any fashion, they are only intended to create an even layer of contact for thermal conductivity.  These are for use when there is another means to clamp the heatsink onto the chip to hold it in place and keep it from falling off.

Thermal glue and epoxy are intended to adhere the heatsink to the chip with varying degrees of permanency. 

 

In other words, the proper compound is going to permanently disfigure the system.  Be sure you're OK with that before starting.

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I would never epoxy a heatsink to a chip if I could help it- but I have had good results securing them with a thin rub of silicone caulk on the sides of the chip while using a traditional thermal medium between the chip and heatsink like arctic 5 or whatever. The silicone can be pulled off later with no consequence to the original hardware if the heatsink needs to be removed.

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As has been stated, with the exception of the MARIA the others don't require heatsinks. But I believe you are asking as you saw pics of my personal one that has heatsinks installed on each of the main ICs? I did this as a preventive measure once I had a few 7800s come in that had bad TIAs that I could only figure was due to the heat over time. That said, I've never had it requested nor offered to install them for any of my clients. I actually do have the larger 40pin sinks installed on mine, but I think I got a deal on them from Console5 at the time years ago because it part of a much larger order. I actually used thermally conductive epoxy I bought off Amazon to attach them. C5 sells some as well, but it is a one time use tube because once you open it, it just cures on its own even when you put the cap back on it. 

 

 

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11 hours ago, Dissy614 said:

A WDC 65c02 is rated up to 185F (85C) and I wouldn't think atari's 65c02 would be much different.

Just for the sake of clarity here, Atari's vintage 6502 chips are *not* "65c02." That terminology denotes use of more efficient (and thus less current draw and heat) CMOS process in die manufacturing. 


Atari's vintage SALLY version is called the 6502C by Atari. That variant adds a dedicated HALT line to the package and rearranges one or two other signals as compared to the a more standard 6502 or 6502B as designed originally by MOS. 

 

(That said, and in an effort to add even more chaos to things,  I have an MOS-produced 6502C here that I pulled from a spare 5200 system once. And I don't use heat sinks on any of my Atari systems for any chips. :) )

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If you're just looking to remove some heat from inside the case, another option is to replace the existing voltage regulator with a Traco 2-2450 DC-DC converter.

 

As counterintuitive as it may sound, this will involve removing the stock heatsink.  However, it will give the system the ability to pull up to 2A of power, keep the insides cooler, and more consistently provide a solid 5V to the mainboard.  In my 7800, it also cleaned up the (RF) video output a bit.

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4 minutes ago, x=usr(1536) said:

If you're just looking to remove some heat from inside the case, another option is to replace the existing voltage regulator with a Traco 2-2450 DC-DC converter.

 

As counterintuitive as it may sound, this will involve removing the stock heatsink.  However, it will give the system the ability to pull up to 2A of power, keep the insides cooler, and more consistently provide a solid 5V to the mainboard.  In my 7800, it also cleaned up the (RF) video output a bit.

It will only provide up to 2A if the original PSU is replaced to be able to provide that as well. But in reality, this will never be an issue as once you swap over to the DC-DC, the system literally takes half the current to operate compared to what it used to need. In fact you might even be able to save some money on the part if you just use a 1-2450 which, is the 1A output variant. With one of these installed, the 7800 will take less than 500mA of current even with a pokey enabled cartridge. Just make sure that the DC-DC switcher will operate properly with 7v minimum to operate to make sure.

 

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On 3/11/2023 at 7:46 PM, raymondjiii said:

Hi, could anyone tell me which heatsink pieces would be useful for a 7800?

1) As juansolo indicated none of them need a heatsink. If heat was an major issue with regards to required performance or failure then they would have been fitted at the factory, otherwise Atari would be receiving returns for repair almost fast as they were selling them.

2) If for no good reason you just have to have them, then...

a) Check the height first to make sure they will not interfere with anything when it comes to re-assembly.

b) Check the IC case material, if it is plastic then as that is a poor conductor of heat adding a heatsink is really a waste as the plastic does not effectively remove heat away from the silicon die anyway unlike ceramic cases.   

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