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shadow_rusty

Scalextric Digital Chip Repairs

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Just ordered myself a mosfet to repair my dead chip... (Stupidity induced failure... lol)

 

As I couldn't find a ZXMC3A16D on ebay, I ended up ordering a AF4502C as it had slightly better specs than any others I could find that were suitable...

Mosfet%20Comparison.JPG

http://www.users.on.net/~shadow.rusty/Slot%20Cars/Mosfet%20Comparison.xls

 

At this stage, I'm not going to replace the diodes with shotky's, as that gives the chip an unfair advantage... (0.6v extra to the motor)

I will only consider it if I was to upgrade all of my chips, and all of my brothers chips at once as we often race together...

 

A big thanks ti RichG for his outstanding work in providing analysis of these chips...

http://www.slotforum.com/forums/index.php?showtopic=17259&st=0&p=184648&&do=findComment&comment=184648

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Should work Ok, but only trial will show...

 

Bigger drivers do imply an increase in capacitance of the mosfet and so can be a bit slower/laggier to respond - especially when switching from full power to braking, and back. If the two drivers take longer to respond, then you can end up with a dead short across the power rails. That can then cause an overload through them and they can blow. I know that from testing the InCar stuff, where I wasn't delaying enough for the mosfets to decay one driver before turning on the other.

 

Ian


Linux: A '90s reincarnation of a '80s Operating System based on a '70s design philosophy

Website: www.electricimages.co.nz

InCar-PRO: Chip Main Page

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Here's hoping I guess...

At $3 for 2, and the chips already dead, I don't have a lot to lose...

 

Thanks heaps for your input Ian...

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Hi SR, I have an old oscilloscope over here if you need any help with fault finding the decoder chip.

 

I could not have fixed my PB4 without it!.

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No worries Phil... THanks heaps for the offer... I'll definately keep that in mind...

My biggest issue is going to be removing the old transistors...

Edited by shadow_rusty

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Well, I've fitted it, and so far, so good...

Mind you, I've only run it for 30secs or so, just enough to know it works...

 

The Revision 'G' version chip I have is slightly different arrangement of components to the chips in Rich's link above, but they are the same components.

Also, being a DPR chip, it was VERY hard to fit it in such a way as to still allow it to work as a DPR module...

But it is done, and hopefully I never have to do another one... lol.

 

I will have to build a track on the weekend for some more serious testing...

That's going to be weird... I haven't run digital for ages...

Edited by shadow_rusty

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