TEAC 55-GS SCSI Floppy Drive Issues

[Chuck(G)]

The problem with SCSI floppy drives is precisely the same as with USB floppy drives--they understand a very limited number of formats and are utterly oblivious to anything other than those formats. I know that they were standard on some 80s-90s workstations, but otherwise, not worth the trouble.
Most of this can be traced down to the SCSI convention of using LBA addressing for everything. True, it saves one from the rigors of CHS, but it's also quite limiting.

 

[maxtherabbit]

Is that actually a limitation of the drive firmware or is the CHS to LBA conversion still done in software?

 

[Chuck(G)]

It's part of the controller firmware, just as it's done in USB. As a matter of interest, USB MSC is nothing more than the SCSI device protocol in a USB wrapper. There is no standard SCSI CDB for CHS addressing--it's all LBA.

 

[tyukok]

View attachment 1209013

I can't help but notice you don't have termination resistor packs installed. Do you use an already terminated SCSI cable?
My USBXchange just arrived, and I've been thinking about using it to turn my SCSI 5.25'' FDD into a USB FDD, but the only external-to-internal SCSI cable I have only has one internal plug, meaning I'll have to use termination on the drive itself. Problem is, I don't know what resistor packs should I use (how many ohms). I'm also having difficulties finding 11-pin resistor packs.

 

[Chuck(G)]

Standard SCSI termination per ANSI standard is 220/330 ohm resistor networks.

 

[bolex]

I can't help but notice you don't have termination resistor packs installed

I'm not sure if you're asking about floppy or SCSI termination. However, the last floppy connected to each FC1 (Each FC1 can control 3 floppy drives) needs the floppy termination, and the last device in the SCSI chain needs SCSI termination. The SCSI enclosure I use has a Centronics type terminator.

 

[tyukok]

I'm not sure if you're asking about floppy or SCSI termination. However, the last floppy connected to each FC1 (Each FC1 can control 3 floppy drives) needs the floppy termination, and the last device in the SCSI chain needs SCSI termination. The SCSI enclosure I use has a Centronics type terminator.

Ah, I see. I was asking about SCSI termination. Floppy termination is already there - as far as I understood, it's this resistor pack on the drive right there:

However, on the FC1 board itself there are two empty 11-pin sockets right next to the SCSI connector:

AFAIK if you populate them with appropriate resistor packs they can work as SCSI termination.

Standard SCSI termination per ANSI standard is 220/330 ohm resistor networks.

Ok, so now just have to find 11-pin 220/330 Ohm resistor packs. Easier said than done, because from what I've gathered 11-pin resistor packs are not that common, especially at these values.
I'll see if I can find any.

 

[Chuck(G)]

LIke this?

Not that uncommon, actually.

I'll grant that the 10 pin SIP terminators are far more common--and stupid cheap (usually sold by the 100 lot) on the surplus market. Which is why I use them in my designs needing 220/330 terminators. Even less common are the 12 pin versions--but they exist.

 

[tyukok]

LIke this?

Not that uncommon, actually.

I'll grant that the 10 pin SIP terminators are far more common--and stupid cheap (usually sold by the 100 lot) on the surplus market. Which is why I use them in my designs needing 220/330 terminators. Even less common are the 12 pin versions--but they exist.

Pretty uncommon at my location - the linked website outright refuses to do business with me, and they are nowhere to be found on ebay or aliexpress. In every other online shop it's either out of stock, the shop itself only sells to companies, or sells them in bulk, 1000pcs each.
The only online shop that actually let me order them doesn't have them in stock either, and it will take months for them to arrive.
Hell, even 12 pin versions are more common at my place - some shops actually bother stocking them.

Really, this near-total lack of documentation, sheer rarity of the drives themselves and even off-the-shelf replacement parts for them being really hard to find really contribute to the whole "peripheral from another dimension" feel that I have with these SCSI floppy drives.

 

[bolex]

I just terminated the external enclosure I used with a Centronics terminator.

If you're using this internally, you could always just get a 50 pin cable terminator.

 

[Chuck(G)]

Pretty uncommon at my location

I should probably point out that you haven't updated your profile to give us a clue as to where you live.

 

[tyukok]

I should probably point out that you haven't updated your profile to give us a clue as to where you live.

Oh yeah, I know . But it also does seem they aren't very common in general. I was even thinking about just buying some 220 and 330 ohm resistors and soldering them together - the schematics are publicly available after all.

View attachment 1248475

I actually have one of those! Not sure if still have the right cable, but I'll look for it. Maybe I'll be able to use that until the resistor packs arrive.