I know this is going to sound crazy but ... On the M102 system bus connector Pin 1 is marked on the top side of the connector next to the reset button. That means pin 37 should also be on the top row - second pin on the top row of the other side near the printer port.
If I probe a machine with a logic analyzer and press reset, pin 37 (RAM RESET) does nothing. It's neither negative or positive. It is just dead. But if I probe what appears to be pin 37, I get the expected behavior on the reset button - logic low that then goes high while the button is being held. The same thing is happening on pin 32 (RESET). If Pin 1 is marked correctly then pin 32 should be on the bottom row, That pin is active and constantly changing state, so it's clearly not reset. But pin 33 (INT REQ) would have that behavior. Moving to what should be pin 31 (top row) shows logic low normally and logic high when I hold the reset button. Is the IO Bus on my machine wired with the pins already reversed? On Mon, Nov 18, 2024 at 7:22 PM Jerry Davis <[email protected]> wrote: > Seems to be a cable/connector issue. > > I repeated the sequence you described on the M100 and DVI that I have here > and BASIC loads and starts as expected. > > I have a ribbon cable with a broken signal pin at the M100 end and my M100 > does what yours does when I use that cable. Which makes me think you may > have a cable problem. > > Jerry > > On Mon, Nov 18, 2024, 7:20 PM Michael Brutman <[email protected]> > wrote: > >> I powered on the M102 first, then the DVI. After the copyright message >> came up I tried the reset button, power off and then power on, and a cold >> start. The machine restarted but the amount of free memory remained the >> same and the DVI disk light did not turn on. I'm fairly certain the DVI is >> not seeing the reset signal from the M102. >> >> Going to BASIC and using SCREEN 1,1 fails because I'm still on the >> built-in BASIC at this point, as DISK BASIC never got moved into the memory >> on the M102. >> >> >> -Mike >> >> >> On Mon, Nov 18, 2024 at 3:20 PM Jerry Davis <[email protected]> wrote: >> >>> After executing the power-on sequence and getting the "Microsoft" >>> message, did you execute the BASIC command "SCREEN 1,1" from the Model 102? >>> >>> The above command switches output to the CRT on the DVI and displays the >>> key labels at the bottom of the CRT. >>> >>> Jerry >>> >>> >>> >>> On Mon, Nov 18, 2024 at 11:39 AM Michael Brutman <[email protected]> >>> wrote: >>> >>>> I've tried all three methods - power off/power on, Reset, and cold >>>> start. There is no difference. Also, the two machines have no options or >>>> expansions that would alter their behavior. >>>> >>>> The technical service manual has a reasonable troubleshooting guide >>>> which gives specific pins and behaviors to look at. I'd still like to find >>>> a known good cable before breaking out an oscilloscope, but at least the >>>> schematics and behaviors are documented. >>>> >>>> The length of the cable is kind of freaking me out a little bit - for a >>>> bus that's a long stretch. Do you know the length of the original factory >>>> cable? >>>> >>>> >>>> -Mike >>>> >>>> >>>> On Mon, Nov 18, 2024 at 9:19 AM Royce Taft <[email protected]> wrote: >>>> >>>>> One other thing you could try is a cold start (CTRL+PAUSE+RESET). It >>>>> will wipe all your 102’s memory, but maybe it will help? >>>>> >>>>> Royce >>>>> >>>>> Sent from my iPhone >>>>> >>>>> On Nov 18, 2024, at 08:34, Michael Brutman <[email protected]> >>>>> wrote: >>>>> >>>>> >>>>> I had checked the connectors and pins before I wrote, and I was even >>>>> going to check for continuity on each pin but that's going to take a while >>>>> and be error prone with 40 pins. The connector on the underside of the >>>>> DVI >>>>> has the snap-in latches which are engaging. I can't push any further and >>>>> I >>>>> haven't bent any pins. The cable is new from Gregory (Arcade Shopper), so >>>>> I don't have a lot of reason to suspect it. >>>>> >>>>> Besides trying two different 102s I've also tried batteries and wall >>>>> power for the 102s, and I even upgraded one to max out the RAM just in >>>>> case >>>>> I was missing a memory requirement. >>>>> >>>>> The DVI unit itself was pristine on the inside when I first looked at >>>>> it. I'll have another peek inside to check the connector; perhaps it >>>>> experienced some trauma and there are broken traces on it. But I really >>>>> don't want to look for problems where they are unlikely or fix things that >>>>> are not broken .. I've learned that every time I disturb something there >>>>> is risk involved. >>>>> >>>>> Is there anybody in the Seattle area (northern suburbs) with a known >>>>> good cable? If I can eliminate the cable as a possibility then there is >>>>> only the DVI connector, as the rest of it seems to function normally. >>>>> >>>>> >>>>> -Mike >>>>> >>>>> >>>>> On Mon, Nov 18, 2024 at 7:10 AM Royce Taft <[email protected]> >>>>> wrote: >>>>> >>>>>> When I had this issue, it turns out I hadn’t snapped the connector in >>>>>> fully on the underside of my M100. I would disconnect it and ensure no >>>>>> pins >>>>>> became bent and flattened out. If the pins look good, carefully replace >>>>>> the >>>>>> connector and snap it firmly into place. >>>>>> >>>>>> When making my cable, to figure out the location of pin 1 on the M100 >>>>>> and the DVI, I think I used a multimeter and the pin outs in the various >>>>>> manuals to look for ground pins which gave some insight into the >>>>>> orientation of the connectors. >>>>>> >>>>>> Seeing “please wait” followed by a Microsoft copyright is a very good >>>>>> sign that your boot disk was successfully read. >>>>>> >>>>>> Royce >>>>>> >>>>>> Sent from my iPhone >>>>>> >>>>>> > On Nov 17, 2024, at 21:20, Michael Brutman <[email protected]> >>>>>> wrote: >>>>>> > >>>>>> > >>>>>> > Ok, here is the part I hate ... getting things put together and >>>>>> then not having it work. >>>>>> > >>>>>> > I'm using Greg's cable kit with a Tandy 102. I have the twist >>>>>> adapter on the 102 side, red stripe oriented as in the pictures on the >>>>>> Wiki. (The red stripe closer to the 'S' of "System bus".) That goes >>>>>> into >>>>>> the IDE ribbon cable, which is connected to the DVI also using the >>>>>> orientation in the pictures from the Wiki. >>>>>> > >>>>>> > I used Teledisk to create the disk image. I powered on the 102 >>>>>> first, as per the DVI user manual. When I power on the DVI I get the >>>>>> "Please wait!" message, and then I get the Microsoft copyright message. >>>>>> All of this is good so far. >>>>>> > >>>>>> > Where things fail is when I try to load disk BASIC onto the 102. >>>>>> The instructions say to use the Reset button or to power the machine on >>>>>> and >>>>>> off. Neither has any effect, and I've tried it with two different 102s. >>>>>> > >>>>>> > What am I missing here? >>>>>> > >>>>>> >>>>>
