Shift838

Probably need to convert the PC99 disk if they are that to V9T9 disk image.

So when I moved into the new house I carved out a section out of the garage for all my development and testing for TI/Geneve as well as other projects like Raspberry Pi, Arduino, etc.. It may not be as cool as others, but it works and thought I would share. It helps that I have a dedicated gutted TI mounted too. Let's see yours!

for everyone.. Requires Editor Assembler and 32k Load via EA Load and Run DSK1.LOADS RTPI.DSK

So I went through and tested all the connections between the 99/4A bus and the flex cable connector and then the flex cable connector to the ICs as well as everything on the PEB BUS. All tested just fine. The card did look like either someone replaced the LS244's or someone did not know how solder that well on a few pins of the 244's. Not all the pins, just a few or they had too much to drink. Re-heated those solder points and nada... still the same issue. pulled out my USB microscope and starting checking for anything that would glare out at me.. started looking at each IC and not something I could even see with my nice super magnification solder specs but the microscope picked it up. One of the LS244's pin #3 was (1/2 of the pin) was actually bent under the chip. And whoever put it on the board instead of taking it off and straightening the pin out just put a glob of solder down to make it look like the pin was soldered. removed the chip and decided to remove them all and socket them. plugged all the IC's back in and now another dead flex card has been brought back to life.

So I was digging through boxes last weekend and found a old flex interface card with a post-it note that said BAD, not in my handwriting. Guessing this came from my trip to Arizona probably 15 years ago when I picked up a slew of TI stuff. I first opened it up to see if it had been modified for 5v only (nope all original). Inspected all the caps, resisitors and ICs, which look good on both the card end and the side card end. All traces look good too. I then plugged it in to my test PEB by itself and no smoke. so I plugged it in with a 32k memory card go into XB and it reports the correct memory expansion. Nice..right. Well I remember reading somewhere that even with a bad flex cable you can access 32k depending on what is bad in the flex cable card. So I plugged in a disk controller and trying to catalog a drive I get: I/O ERROR 06 I have verified the CRUCLK lines are good and no broken wires anywhere on the firehose cable. I have also swapped the flex interface out with a original on my daily used system and it all works. I have also swapped out the 74LS245 on the PEB card. Any suggestions where else to look?

I thought I had Rev G, but mine is Rev F

@Tursi I need to solder it together and put in my dev/test system.

@Tursi I think this is your circuit with the switch I believe, correct?

no, the 838-IO is designed after the original flex cable interface card. It is designed to be the last device on the 99/4A bus to the PEB. So the 838-IO will either plug into the side port of the 99/4a itself or a different side port expansion car, like the speech synthesizer, but as said it must be the last one in the chain. The speech requires power to be passed from the 4A, the flex cable side port card (original)as well as the 838-IO side port card does not pass power to anything, both get their power from the PEB via the cable hooked up between the two.

I got around to finishing up a case for the 838-IO Sideport card that connects to the 838-IO PEB card. After a few revisions, it all fits good. the silver top slides in nicely to the black case via some channel cuts. the total time to print both pieces is about 6 hours. the PCB in the case is from the original test run and has the old logo and name on it, the new PCBs will only be simply called 838-IO. I opted to bolt the PCB directly through the case for stability.

I came to a conclusion over this weekend after a some comments around HCT vs LS chips. The naming of the board as Turbo Interface was to take advantage only if the user had installed the 32k ram internally on the 4A's 16 bit bus or if the user has performed a crystal upgrade. Which both of these would allow (according to everything I have read) the data to transfer faster between the PEB bus and the 99/4A bus. But after some thought, how many of us actually have done either of those upgrades or could benefit from it. I have decided to rename the card from 838-Turbo Interface to something more adequate like 838 IO Interface. So if this project makes it to production please be aware the name will change.

as @matthew180pointed out the design is a combination of through hole and SMD components. the PEB card is 100% through hole, where the console side board is a combination of through hole and SMD. all the SMD's are resistors, voltage regulator and 74LS245.

I wanted to throw this poll out there to gauge interest for this card.

I have been able to run down my LED issue described above. I should have tested this first! The schematic has a LS244 controlling the LED via the DBIN signal along with the 2n3904 transistor. Well looks like I had a bad LS244! Replaced it and BAM, no more LED on the PEB card when the 99/4a is powered on by itself. Now for some more testing over the next week or so.

so far I have tested it with a 4 foot cable with no issues. planning on testing a 6 foot next few days, but that is as long as I will test. I have tested with this one: Amazon.com: Antrader 10Ft/3M IDC 40Pin 1.27mm Rainbow Color Flat Ribbon Wire Cable for 2.54mm Connectors: Computers & Accessories