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Netronics Fastvid 64 Repair

falter

falter

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Jan 22, 2011
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Finished cleaning up and checking out my second Fastvid terminal that came in a blue Netronics case. So far it seems to power up okay with blinking cursor, but does not respond to keypresses. I checked out what was happening with my breakout box, it appears that when you press a key, TX lights up.. and stays lit. It does not flash quickly and go back to dark afterwards. It only goes off if you hit the same key again or another key. So it's operating like an on/off switch, which is weird.

I've not been able to find a schematic for this.. it uses a COM8017 chip. I note the board has inputs for -16V DC (I am running off the AC inputs).. that would imply to me that it it might be using -12V or such somewhere as serial machines often do.. but going through the major ICs I couldn't find anything that wasn't single 5V. I'm not really sure how this one works.. it doesn't use the MC1488/1489 combo I'm used to.

Pic of the board here: https://drive.google.com/file/d/1O09WHlDJCshWmuSFfdeJ4d3fG0m86nYm/view?usp=sharing
 
Many thanks to Doug on the cosmacelf list, I got this schematic of my terminal. Off the bat, the SMC COM8017 proved to be bad. I swapped with a known good and immediately RX/TX was doing what it should be. I have connected the terminal to my Thinkpad 380XD running Hyperterm, and with the default settings at the correct baud rate (9600), 8 bits, 1 stop bit, no parity.. I can successfully type whatever I want on the Thinkpad and it shows up without issue on the terminal side. *However*, if I type something from the terminal, it's weird. Initially the right characters will appear, but after a few keypresses suddenly it goes to junk.. and then it's throwing up random characters every time you type. The only way it will work on both sides is if I force Hyperterm to 7 bits incoming. I feel like this isn't right.. like something is flaking out and sending an extraneous bit or something that throws off whatever the receiving side is getting.

The schematic to me seems to imply this is a pretty simple design.. basically keyboard input into the UART and then out to the PROM. I'm thinking maybe a stuck bit coming out of the PROM?
 
I seem to have it working now with a different cable. I have it hooked up to my Ex85 and a legible prompt comes up. The only problem I when the cursor returns to the left it doesn't line feed. Not sure why.
 
I'm a moron.

I went to the manual again looking for information on the keyswitches used in the keyboard. Of course, it wasn't in there because the manual is for the Fastvid terminal, not the keyboard which is a separate product. But in looking around, I stumbled on a line in the fastvid manual right below the ASCII table that says essentially that unless you have some software means of slowing things down so the terminal can catch the control codes, you are best to stick to 1200baud, otherwise it will miss things. Ironically I was onto that earlier and had switched the terminal down to 150 baud, but thought it wasn't working because I had a flaky space bar and the computer wasn't receiving the 'go' signal.

Anyway.. for those that tangle with this beast and attach an actual Netronics computer to the Netronics terminal, that's where you might get tripped up. Always RTFM. Thrice.

https://drive.google.com/file/d/1c0T...ew?usp=sharing
 
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