- VCF South West - June 14 - 16, Davidson-Gundy Alumni Center at University of Texas at Dallas
- VCF West - Aug 2 - 3, Computer History Museum, Mountain View, CA
- VCF Midwest - Sept 7 - 8 2024, Schaumburg, IL
- VCF SoCal - Mid February 2025, Location TBD, Southern CA
- VCF East - April 2025, Infoage Museum, Wall NJ
-
Please review our updated Terms and Rules here
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Trs 80 disk error
- Thread starter jonathancox
- Start date
Druid6900
Veteran Member
What is this connection for? I've seen it there but there doesn't seem to be anything that it goes into...
http://www.flickr.com/photos/34069486@N04/4268767431/
I don't have a Model 4 handily open right now, but, power connectors should go to each of the floppy drives, the main board, the FDC board and the RS232 board (the other one behind the main board). I don't recall any spare connectors that weren't used.
One thing to check for is that the ribbon cables are right way around in the connectrors for the FDC and RS-232. There are only "fingers" on one side of those connectors and they have to match up, on both ends, with the bare metal side of the ribbon cables.
I spent a lot of years fixing Tandy equipment and I don't recall ever having to change an FDC board. I had to align a few when someone screwed with the pots on the board, and, a couple of 1793? chips had to be replaced, but, never the entire board.
pavery
Experienced Member
Thanks Druid...
I did notice that when I took the ribbon cable out of the Floppy controller, some of the metal strips bent back. I put them back in carefully and I think they make a connection. But just in case, I swapped the RS232 cable, which is perfect.
I've had similar trouble with my Model III (which, for the purposes of this discussion is very similar to a Model IV), whenever I've disconnected the FDC in the past. Often when I reassembled the machine, I'd get the CASS message - as the FDC wasn't being recognised. It can be most difficult to align the ribbon connector connecting the FDC to CPU board. In my experience the ribbon has to be *centered* in the connector to ensure all pins connect, not merely inserted using the edge of the connector as a guide. In fact on mine, I have to have a gap on each side of the connector to get all pins connecting.
If visually all pins look connected, and you're still having trouble - verify each connection with a multimeter, using the soldered side of the connectors as test points.
Philip
jonathancox
Member
Thanks guys---
I don't have access to the machine at the moment. I remember testing the connections with a multimeter and they all came out good. Maybe some had bent over and shorted the connection somehow? I don't know. I will try it again... but after exams.
Sorry to be ignorant, but what's a "pot?"
I don't have access to the machine at the moment. I remember testing the connections with a multimeter and they all came out good. Maybe some had bent over and shorted the connection somehow? I don't know. I will try it again... but after exams.
Sorry to be ignorant, but what's a "pot?"
Last edited:
The two pin connector that jonathancox is refering to in his photo weblink from a previous post of his, is for the optional Tandy hi res graphics card. This connector proved the 5volts power to the hi res graphics card, and was only ever included in the Tandy M4 loom in "Non Gate Array" models, later "Gate Array" models did not come with this piece of extra wiring loom. So unless you have a optional Tandy Hi Res card, the connector will remain unused. Not even the Microlabs Graphics Solution cards required the use of this connector for power.
Hope this solved the mystery.
Hope this solved the mystery.