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MAC 600 chip heatsinks


Mr Steve

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Hi,

 

I am resurrecting a MAC 600 which has a dead tilt system. Swapping the pan and tilt wires over the thing tilts and no longer pans, so I want to replace the drive chip on the board. However the old chip has a metal heatsink soldered on to the legs of the chip. Is this metal fin a heat sink? If I unsolder it off the dead 3772 chip and on to the new one, will heat from the soldering iron damage the 3772? Or, will the new chip be fine without a this fin/heatsink attached? Any help from those with more experience would be appreciated :)

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Yes, the metal fin is indeed a heatsink. The driver chips dump their heat partly out of the ground pins and usually require a large patch of copper on the PCB to use as a heatsink. Since there isn't space on the motherboard, Martin have gone for the next best option of adding a heatsink to the chip. You may be able to un-solder the heatsink, but keep in mind that the job of a heatsink is to get rid of heat! This will make un-soldering/re-soldering a bit more tricky. A temperature-controlled iron, capable of higher heat levels will help you, but be careful not to cook the chips.
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Do not be afraid, it's actually quite hard to "cook the chips". The worst thing is uneven heat which can crack them by one end expanding more than the other.

As Gyro says, using the right soldering iron will help. You need a high powered iron (40W or bigger) with a big fat tip.

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Solder Wick is probably your friend. Or a hot-air rework station ( I have one here if needed).

 

I think (not sure) that the driver chips were through-hole chips on a Mac 600. If so the best way to get them off the board is to cut all the legs off with some fine wire cutters, then use a solder sucker to suck the pins out of the holes. Once the old chip is off you can remove the heatsink from it.

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They are socketed.

Hmmm, that won't be helping with heat dissipation.

Presumably why they have a big metal fin soldered to the ground pins on the chips.

Curiously I have found a few photos of the Mac600 mainboard and the driver chips do not have any heatsink fins on them...

 

e.g. here

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Curiously I have found a few photos of the Mac600 mainboard and the driver chips do not have any heatsink fins on them...

I was surprised that they were socketed; I can't see a manufacturer doing it as standard. Sounds like they've been replaced before and someone is playing safe.

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Curiously I have found a few photos of the Mac600 mainboard and the driver chips do not have any heatsink fins on them...

I was surprised that they were socketed; I can't see a manufacturer doing it as standard. Sounds like they've been replaced before and someone is playing safe.

 

The standard Martin spares picture shows them socketed (with no heatsinks). They did used to blow up quite a lot, any damage to the motor wiring harness would kill them, so I guess they were socketed for easy servicing.

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We should point out to the OP that as per post #12 you need to ensure the fault that originally caused the driver chip to blow has been remedied as otherwise you're likely to blow the replacement chip too. There are plenty of previous threads on here that tell you how to check.
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