5V Level at the Side Car

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chuckphd53
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5V Level at the Side Car

Post by chuckphd53 »

Last night I was working with the JRIDE rev 'C' and fighting the read clock issue (solved in the JRIDE Thread).

Started looking at the 5V at the JRIDE sidecar and found it to be 4.75 - 4.90 and it varied abit.
I checked the 5V at the JR power supply and it was 4.98V steady same voltage at the Floppy drive power connector.

was a bit worried about this hitting the recommended high end levels for TTL.

I may install the power supply adjust mod I did years back and try to tune up the 5V to about 5.1V at the JR power supply
and see if it helps boost the level at the side cars. This should increase reliability for the side cars...

has anyone looked at their side car 5V Levels ? Be interested to know your results....

It is curious that the side car conn only has 2 pins A06/A26 for the 5V out but is sourced from power plane on the PCB.
But typically these pins can source many amps of current.
I did ohm out from the internal PS conn to the pins and there was no significant Resistance.
So the interface contact from the JR sidecar conn to the Plugged in sidecar is the weak link and a some V-drop is occurring across
these pin conn interconnects.
This is normal in all systems and designs, that is why they use gold plated to try and mitigate this V drop issue...

Increasing the 5V to 5.1V should provide a little bump to the side cars.
I will get this done and give a quick report as to the results when I get to it this week !...

Chuck
“I never commit to memory anything that can easily be looked up in a book.” (AE)
toddvernon
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Re: 5V Level at the Side Car

Post by toddvernon »

Personally, I think you are good at the current levels. TTL logic is pretty forgiving. If you are above 4V everything is going to work IMHO.
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chuckphd53
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Re: 5V Level at the Side Car

Post by chuckphd53 »

Agree, my concern is the transition swings from low to high , and getting the roll off that I saw on the JRIDE without the PULL up Pull down resistors...
and the loading....
I have a Rev B JRIDE that I has no pullup/down and do some testing with the increase to 5.1V. Not sure how much will be afforded on the side car
but it will be a fun test.

(More data please :) )
“I never commit to memory anything that can easily be looked up in a book.” (AE)
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