Everything was working, then I tried a cable that was larger that had the twist in it. I don't know if that caused the issue, but I untwisted the cable. Now I'm back to testing with the original cable. I have a single Teac drive and its motor no longer runs. I monitored the signal on the control board that tells it to turn on the motor and it does not change from .067V when I try to activate the drive. Does the Tandy 1000 use the motor signal? Or another signal to turn on the motor? Also, where on the motherboard is the FDC chip? I figured it would be near the FDC port, but in the pictures I've seen none of them say the number that is in the technical manual.
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Tandy 1000A Floppy Controller issue
- Thread starter alank2
- Start date
I found the floppy IC, it says R6765P on it.
The motor signal is working however. I followed the pin 16 motor signal from the connector to a 7417 logic IC. This is an open collector IC. I checked the floppy drive and it has a 1K pullup to 5V. The input signal to the 7417 (presumably from the controller IC or other logic from it) does switch between high and low, but the output of the 7417 does not. It stays pulled up and never takes it low when its input goes low. Bad 7417 then, right? Why would they use open collector, is that normal for a floppy interface? The technical manual shows a 7416. It seems odd that it was fine and then the next moment is wasn't.
The motor signal is working however. I followed the pin 16 motor signal from the connector to a 7417 logic IC. This is an open collector IC. I checked the floppy drive and it has a 1K pullup to 5V. The input signal to the 7417 (presumably from the controller IC or other logic from it) does switch between high and low, but the output of the 7417 does not. It stays pulled up and never takes it low when its input goes low. Bad 7417 then, right? Why would they use open collector, is that normal for a floppy interface? The technical manual shows a 7416. It seems odd that it was fine and then the next moment is wasn't.
Chuck(G)
25k Member
The R6765 is the Rockwell copy of the NEC 765 and Intel 8272.
OC is the standard for floppy interfaces. Earlier designs used the 7438 (40 ma sink current). The 7416 is an inverting OC buffer, but obviously, this Tandy design uses a non-inverting one. So, 7407 or 7417; either should work.
OC is the standard for floppy interfaces. Earlier designs used the 7438 (40 ma sink current). The 7416 is an inverting OC buffer, but obviously, this Tandy design uses a non-inverting one. So, 7407 or 7417; either should work.