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Received a question about an internal cable for replacement. Model III

NathanAllan

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The cable that is needed is the internal flat ribbon that is similar to the one included here:

http://www.ebay.com/itm/Tandy-TRS-8...609?pt=LH_DefaultDomain_0&hash=item51886ee3b9

That machine is not in my collection, so I dont' know of a generic replacement for it. Does anybody here have a Model III that can tell me what kind of header it has so I can figure out a replacement cable?? It doesn't have to be original equipment (that would be nice but not totally necessary), just a working way to get it fixed. Thanks!

Nathan
 

Chromedome45

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It's similar to a card edge. A "flex" cable slides into it to make the connection. One on the rs-232 board and the same thing on the floppy then to the mainboard. They usually last a while as long as they are not removed or inserted to many times. But over time they do wear out. It is a 20 conductor cable.

What I usually do especially with the floppy controller is remove that connector from both the motherboard and the floppy board by way of carefully desdoldering them. On the floppy board I put in a 20 pin right angle pin header with pins pointing up. It looks like a single row IDC cable connector. On the mainboard end I also put a 20 pin pin header but one that is pointing straight out. I then use a fully pinned old IDE cable and use one row to make the connection. Just make sure you use the same row on the other end.

Also if the person has never soldered before find someone who has! It is easy to destroy the runs on these. They are very thin!

See the 2 Pics. On the left is the standard flex type plug. On the right is the single row 20 pin connector. Sometimes called stacking pins.

Hope this helps you out Nathan.
 

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leeb

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I'll see if I can find the thread I made ALL THOSE YEARS AGO when I built a cable for my 4p..

SHOULD be the same TANDY 3/4 configuration...

:D
 

Al Hartman

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I'm the person that Nathan was helping.

I bought a Model III from the M.A.R.C.H. Swapmeet a few weeks ago, and it booted to a garbage screen. In diagnosing it, we pulled the interconnect cables to the RS-232 board, and Floppy drive controller.

Both are now hosed.

I have to replace them.

The garbage problem was bad RAM. The pins on the RAM were oxidized, so removing the ram, cleaning the pins and reinserting them fixed the problem there. I now get a Mem? prompt.

The next task after fixing the interconnects is to repair the broken hinge on the top floppy drive. Then, I should have a working Model III.
 

Chromedome45

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I wish you luck, Al. Yes those flex cables are not very robust. Considering the Model III is about 32 years old they were probably already seperating the metal fingers from the plastic background as were the contacts on mine. So i did the pin header install. More reliable for sure and working great.

Now the broken hinge on the floppy you mean the door latch isn't locking down? Most likely those drives are either Texas Perpherals or Tandon's. I might have some spare parts to fix the problem. if you need them let me know Also send me pictures. PM me and I will give email to send pictures to. Or post them here is you wish so we can see what is going on.
 

Al Hartman

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Yes, the door hinge is broke. My friend Tom just puts in a small metal hinge and that fixes it.

Just in case, I picked up a Tandon TM 100-2a from eBay for $9.95 + S/H. It has the IBM logo on front, but I can always change the faceplate.

I'll try the pin header fix as soon as the parts arrive.
 

Chromedome45

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Ok cool yes some of the drives used cheap plastic pins in the door latch. Batter ones used the metal one. Glad to hear that the door is working.
 

Al Hartman

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I decided I'm going to remove the connectors for the flat cable, and install 4 single row pin headers and use two cut down IDE cables (using only one row of the female on each end to replace them.

After beating my head against the wall at Mouser and Digi-Key, and finding another place that had them had a $14.00 minimum order (I just placed an order with them last week.) I thought to check eBay, and got 10 pcs of a 40 pin breakaway header for $3.89 with shipping. So, I'm in business.

Someone sent me a RAM test program, so I'm set there (though I have Super Utility which also has one). I need to repair the door on the upper drive, and assuming the RAM and Serial board both work, the Model III will be on it's feet.
 

ldkraemer

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Al,
Either my Kaypro or Model 4 had a Tandon Drive that had the same problem with the door latch. I bought a new door latch back then, but found a better fix.

I just dug though a stash of Brass Brazing rods to find one that was a very snug fit on the door latch to replace the two plastic pins with a full length Brass one.

It's still working.

Your Local Welding Supply guy will most likely let you test a few Brazing Rods to find the best one too!

Larry
 

Al Hartman

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Model III Connectors are replaced. But, as it turns out the second power supply is bad. My friend wants to replace both supplies with a newer switching unit. So, when that happens I'll have two extra Model III Supplies to sell on eBay. The buyer can probably recap and fix the second supply.

We made up a composite cable for my Model I, which is now not working correctly. It just comes up with blocks on the screen. Maybe I killed it trying to attach it to my dodgy E/I. *Sigh!* (Edit: When attached to TRS-80 Monitor, it works fine. Needs more sleuthing.)

We dug out the power supply for my Atari ST and tried it out. It's a little flaky. Sometimes it boots to multiple bombs. I removed the 2.5 mb Easie-ST Ram Board which hasn't been working, and that didn't change anything.

I have a Mega ST, but it looks like my trusty old 520 has also bit the dust. (Edit: After reseating the MMU, the ST appears to be OK.)
 
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Chromedome45

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Al, When you made the composite cable you used only 2 wires correct? One of the wires in the video cable that goes to the official monitor carries 5 volts through it to power the OPto-Isolator. Should have signal on pin 4 and ground on Pin 5. Nothing else and those are the only 2 connections you need.
I made one and worked like a champ. And some modern LCD's that have a composite input won't sync on the signal so if possible use an actual composite monitor. Hope this helps you out
 

TRS-Ian

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Al, can you post a picture of the screen you get connecting your cable to the LCD TV?

Also, I see you have an Amiga 1000, can you connect the Model 1 to your 1084 monitor into the Yellow socket and see if you get the same image on the screen.

Ian.
 

Al Hartman

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Also, I see you have an Amiga 1000, can you connect the Model 1 to your 1084 monitor into the Yellow socket and see if you get the same image on the screen.

Ian.

Model I works fine with Magnavox Monitor I bought for my LNW as I'm afraid to power on the Amiga Monitor currently attached to it. I guess I'll have to try it eventually. I paid $75 for it over 20 years ago. It had been dropped then, and a friend repaired the circuit board and it has worked ever since.
 
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