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Model 4 problem

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phogren

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Joined
Apr 24, 2009
Messages
583
Location
Eagle River, WI
I recently got a large amount of TRS-80 stuff. Trying to get a Model 4 to boot.

I can get into the model III basic mode. I can write a short basic program and it runs and works correctly.
I can get the Diskette? prompt
I have a boot disk that will boot up a 4p
I have tested the disk drive on a MSDOS system and it works correctly.

In the Model 4 the drive light will come on, the drive spins, but then it stops and I get nothing. They are DSDD drives and testing the drive on another machine it works correctly.

Is there a different disk to boot the model 4 with 128K and DSDD drives?
 
Screen issue perhaps? IIRC Model 4 sets a higher screen res and the sync circuitry drifts.
 
Ok do you have a Model 4 or a 4D? Are the disks the full height drives? If so they are SSDD not DSDD if it were a 4D then the drives would be half height with a twist lever to close the drive latch. They were DSDD drives. At least that was the standard configuration.

Let me phrase this if the dsdd are only formatted on one side of course they will work in the older drives. Sorry if I caused any confusion.
 
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They are half-height drives. I'm not sure if there is an additional way to identify the 4D.
I am sure they are DSDD.
 
@phogrem

If you could try with only One drive connected configured as Drive 0 and see what happens.
also do a restart with a disk in Drive 0 BUT don't close the lever on the drive, the screen should have a Diskette request ??.

Again Good Luck Ray
 
With the lever up I do get the Diskette?
closing the lever results in some drive motor activity (but no head movement) and a blank screen.

The front label does not say 4D, just 4.

I tried with a single sided drive with all the same results.

One of the other systems with this lot is a gray model 4 that says model III on the bottom but model 4 on the upper case. It works correctly but is currently waiting to have the magic smoke replaced. I got the impression that when I bought the lot (6 systems and some other stuff) that the previous owner was a university professor and quite the quintessential "Tandy Guy" back in the day.
 
The silver model 4 is actually an upgraded model III. Tandy sold a kit whereby you could have your model III upgraded to a model 4. And this was usually done at a Radio shack computer center. So it's an odd beast. If you look at the bottom of the Model 4 it should have catalog number 26-1069 or 26-1069a. which is it? Also pics would be helpful as well.
 
Re-seat the FDD cable, the white cable which connects the motherboard to the FDC, and all the parts on the FDC. If you have a parts machine try a different FDC.
 
Its a gate-array - the cost-reduced version of the Model 4 with everything on one board. It came out about 18 months after the original Model 4.

You need to check your FDC chips, the are the large 24 and 28 pin devices in the lower left hand corner.
 
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