What the %$@# is up with links from certain other forums?

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JimDrew
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Re: What the %$@# is up with links from certain other forums?

Post by JimDrew » Sun Mar 19, 2017 1:09 am

Yeah, those sockets being the machine tool type with caps were like $3.00 each for 16 pin parts! Ridiculous - it was way cheaper to solder caps to the bottom side of the board, and of course even cheaper to completely omit them. :\

The original owners of Utilities Unlimited took every short cut possible. I ended up getting 20% of UUI in 1989, so things changed dramatically when it came to hardware production.



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eslapion
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Re: What the %$@# is up with links from certain other forums?

Post by eslapion » Sun Mar 19, 2017 9:33 am

The fact remains, whether it came from you or anyone else, not installing decoupling capacitors on the Supercard+ was a mistake, using 74HC logic ICs was a mistake.

The datasheet of the MOS6502 is very clear, the voltage levels that are guaranteed for low and high logic signaling are those of TTL families. CMOS logic ICs must be compatible by design with these levels if they are to be used safely and reliably with MOS families of processors.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

JimDrew
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Re: What the %$@# is up with links from certain other forums?

Post by JimDrew » Mon Mar 20, 2017 7:21 pm

Like I said before, using HC/HCT chips was not a mistake - it was done deliberately. LS chips do not work (even with proper capacitors) when using the ribbon cable. The boards worked fine with HC and HCT chips. The Supercard+ boards that were for the 1541 only (slightly different design board with no ribbon cable), used LS chips.

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Zippy Zapp
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Re: What the %$@# is up with links from certain other forums?

Post by Zippy Zapp » Tue Mar 21, 2017 2:09 am

Just curious, did the RAMBOard need caps on it too?
Commodore - Changing the world 8 bits at a time.

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eslapion
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Re: What the %$@# is up with links from certain other forums?

Post by eslapion » Tue Mar 21, 2017 3:20 am

JimDrew wrote:
Mon Mar 20, 2017 7:21 pm
Like I said before, using HC/HCT chips was not a mistake - it was done deliberately.
HCT is okay, Gyro couldn't be more clear, using 74HC with digital ICs designed for TTL levels is just plain wrong so you deliberately used the wrong part.
LS chips do not work (even with proper capacitors) when using the ribbon cable.
That's normal, 74LS (that's low-power Schottky) logic ICs use bipolar TTL technology and use considerably more power than CMOS families of logic ICs. The consequence is the voltage drop caused by the ribbon becomes excessive and there is no longer enough voltage for some components on the Supercard+ to operate properly. NOTHING TO DO with BUS NOISE.
The boards worked fine with HC and HCT chips.
HC chips worked by pure luck on that board. ITS THE WRONG PART.
The Supercard+ boards that were for the 1541 only (slightly different design board with no ribbon cable), used LS chips.
It was designed properly. Maybe it's missing the caps...
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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