Max number of side car addons

Chuckphd53 · Post by **Chuckphd53** » Mon Mar 16, 2020 6:58 am

If this issue becomes an 'issue' and there are enough folks that would like a fix...
I can make a small PCB with SMT resistors that would fit flat against the backside
and easily attach with small jumper wires....
as the Resistor fix that I did in the previous email works fine, it is cumbersome and takes a bit of work
to dress everything out....
if you need to contact me pcjr@terradock.com feel free I am happy to help with questions on this..

Chuck

KenG · Post by **KenG** » Mon Mar 16, 2020 3:17 pm

Could this be included in a revision? Also, could something be made to plug into the sidecar similar to the SCSI termination to go on the last sidecar in the chain?

Chuckphd53 · Post by **Chuckphd53** » Tue Mar 17, 2020 2:32 am

I have included the resistors in my Rev 'C' of the JRIDE and it works.

Yes a plug in ( scsi ) as you mentioned is what I did when I tested this fix, but it hangs off the JR connector and you cannot put the side car cover on.
It is just looks tho, if you dont mind that.

I dont think alot of the folks suffer from this issue, as I am guessing they just have the JRIDE on the Jr only, or in the First position that does
offer some reliability in my testing...

alanh · Post by **alanh** » Wed Mar 18, 2020 11:30 pm

If anyone is to make a board revision, please fix it with a proper 245. The totem-pole setup is a bit of a hack.

Chuckphd53 · Post by **Chuckphd53** » Thu Mar 19, 2020 3:13 am

Already being done, but the Pullup/Pulldown is a viable solution for the existing users.

FortMax · Post by **FortMax** » Sat Mar 21, 2020 9:34 am

Do other people with this issue get two beeps and a black screen (which usually indicated a power issue)? I've found that resetting the PCjr by inserting a ROM cart gets it to boot properly every time.

DoctorOctal · Post by **DoctorOctal** » Sat Mar 21, 2020 2:54 pm

FortMax wrote:Do other people with this issue get two beeps and a black screen (which usually indicated a power issue)? I've found that resetting the PCjr by inserting a ROM cart gets it to boot properly every time.

Do you have a jr-IDE attached? If so, what POST code is it displaying when you get two beeps?

FortMax · Post by **FortMax** » Sat Mar 21, 2020 6:26 pm

DoctorOctal · Post by **DoctorOctal** » Sun Apr 05, 2020 2:37 am

Chuckphd53 wrote:How many side car add ons did IBM spec was the limit.
I understand it depends on the design and power consumption, but was there a Rule Of thumb from IBM on this subject…
My quest is the Data and Address Control line Fan out /signal propagation degradation.

I just ran across this:

The I/O Channel signals have sufficient drive to support five I/O Channel expansion-adapters and the internal modem and diskette drive adapter, assuming one standard TTL load per attachment.

—PCjr Technical Reference, 2-21

OldComputerGuy · Post by **OldComputerGuy** » Sat Jul 04, 2020 10:32 pm

If you do a power supply conversion, do you still have to use power sidecars, or will the new power supply be enough?

Mike's PCjr Page

Max number of side car addons

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