RetroChallenge 2022/10 update #1 NOS is DOA

traidna Retro Challenge 7/2015 - TS 2068 Game Allstar Baseball

Phase 1 of my Retrochallenge project is to get my New Old Stock TI99/4A console set up with the 1mb SAMS memory card, TIPI card/Raspberry Pi Zero WH for drive emulation set up. About a year ago I picked up a TI99 lot with a PEB, several cartridges, a modem, floppy drive and 2 consoles (computers). I was told one didn’t work and one was new in the box. When I go home the non-working one was really an issue with a blown fuse in the power supply pigtail. I ended up selling the PEB and the console. The New Old Stock on had just set in the box until now.

So I unpacked the computer and found everything did in fact look brand new.

I set it all up and turned it on. BEEEEEEEP and no picture. I turned it off and tried again, success.

Awesome things are looking good I think. I put the 1mb SAMS card on and it’s power supply plugged in. This is a known to be good card, I had used it before. I powered up the computer, no joy. BEEEP that just stays on. powered off and on again, no luck. I took the card off, powered up the computer again. BEEEEP that stays on. Not a good sign. My NOS is DOA. I set it aside for a day, tried again no good. Looks like I get a future hardware project out of it. Not sure if I did something by not having the SAMS card just right or it’s just a dodgy 40 year old computer

In the mean time I pulled out my beige TI99, the second generation one and set it all up with SAMS/TIPI and Pi, and it’s up and running. I am using the power supply from the NOS computer rather than the old one that came with the beige console, it works but has a hum sound coming from it. It’s ready for testing Andiar MUMPS which will be run from the SD card on the FinalGrom99 cartridge. More to come…

2 thoughts on “RetroChallenge 2022/10 update #1 NOS is DOA”

  1. If the console beeps when you switch it on, it means that the machine is not really starting to run. One of the first thing that the ROM does when starting is initialize the sound chip, which stops the beeping that is caused by the chip not being initialized.

    In my experience, this problem is most often caused by a faulty ROM or RAM chip on the motherboard. It is also possible that your CPU or one of the TTL chips that connects the CPU to the 8 bit peripherals (sound, video, etc.) causes this issue, or that your clock generator does not work.

    I would check:

    Power supply rails (look at the 4146 chips which have all three, +5V, -5V and +12V).
    All four clock phases going into the CPU
    Reset signal on the CPU going from high to low when powering on
    Select signals on the two ROM chips (they should show activity)
    If everything looks OK, then I’d swap the RAM chips, then the ROM chips. Obviously, you need a donor machine or replacement chip. Arcadeshopper can help with your parts needs.

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