BOOT ERROR DC on TRS-80 Model II

[MikeS]

Yeah, I'm trying to make as much money per year as a pampered programmer did LOL

Everybody knows that programmers are neither pampered nor do they make any money (unless they have the right stock options).

(BTW, for anyone taking our banter seriously Dru is actually a pretty nice and generous fella, and gives excellent service.)

 

[Druid6900]

Everybody knows that programmers are neither pampered nor do they make any money (unless they have the right stock options).

(BTW, for anyone taking our banter seriously Dru is actually a pretty nice and generous fella, and gives excellent service.)

And Mike, while slow as a glacier, is a great and knowledgeable guy who lives in a castle made entirely out of Vintage and Legacy computer equipment piled up meticulously and adhering to all the Ontario safety standards.

(oh, and he lies about not making any money as a programmer, but, we all know better....)

 

[Lorne]

Update: BOOT ERROR DC – the plot thickens……..

The BOOT ERROR DC message is supposed to be caused by three things:
- Bad floppy disk
- Bad DC board
- Bad disk drive

In order to start eliminating/ruling things out, I sent two boot disks that I’d made from images to ChuckG who tried the disks in his Model 16. They both worked in his Model 16, so it isn’t the disks.

I also sent ChuckG my DC board, and he tested that in his Model 16, where it worked fine, so it isn’t the DC board either.

I tested my Shugart drive. It can make a disk from an image (using TeleDisk), and I can then get a directory of that disk (using22Disk). There’s still a problem with the drive though. As soon as I eject the disk, and re-insert it, I can no longer get a directory of the disk which is probably due to a disk centering/clamping problem. I’m going to swap out the hub clamp assy and spindle hub assy along with their bearings and see if that fixes it.

But when it comes to the Model II, it isn’t a disk drive problem either.
ChuckG modified the DC board I sent him, to allow it to boot from a 3 ½” floppy drive.
It works on his Model 16, but on my Model II the 3 1/2" drive is accessed, then the in-use LED lights, and that is followed by a BOOT ERROR DC message. So, I suspect there’s something other than the three problems that are listed in the troubleshooting section of the Model II service manual. I suspect it’s either the backplane (on which I have already reflowed every solder joint), or the CPU board.

Many thanks to ChuckG for the testing/modifications - who else would have been able to figure out how to, or that you even could, boot a Model II from a 3 ½” drive?

SoupWizard has generously shipped me a backplane and the four other boards from a Model II parts machine he had, so I can do some swapping around of boards to see what’s what.

I’m getting there – I’m just not sure where there is.

 

[Lorne]

The TRS80 documentation is incorrect, and has caused a wild goose chase in this case.

The Model II Boot Errors Table saysthe BOOT ERROR DC occurs because of:1) Defective diskette – try a differentdiskette
2) Floppy disk expansion unit not on –turn on the floppy disk expansion unit
3) Defective FDC Chip or drive – ContactRSSC

That information above, is in fact, incorrect.

A bad RAM chip on the memory board will also cause a BOOT ERROR DC (even if your DC is fine) !

I received the boards Soupwizard sent me, and first replaced the backplane.
Next up was substituting the CPU board.
That provided the same problem as previous (ie: boot error DC).
With a working disk controller board modified by Chuck(G) to boot from a 3 1/2" floppy drive (to rule out the 8" Shugart drive), I didn't need to substitite that.
Next to be substituted was the memory board, and when that happened the machine booted from the 3 1/2" floppy drive with no problem at all.

I put my backplane, and boards back in, and using Soupwizards memory board, it booted again with no problem.
Put my memory board back in, and I got the error again.

So, don't believe everything you read in a TRS-80 manual.
If you do, you might just get sent on that goose chase.

I sure am glad I only bought solder from Rat Shack in the 80's, and none of their computers.
Having been through this mess now with one of their "business" machines, I'm glad I stuck to an Altos8000, a Kaypro 10 and a few PC compatibles.
Business could have come to a halt if I had one of these POS's.

Hopefully someone else who comes across a BOOT ERROR DC problem will see this post, and not follow the manual.

I'm starting to notice that weird prblems that don't seem to make any sense, are quite often related to a RAM problem.
It's going to be one of the first things I check from now on - no matter what the manual says.
It sure would have been handy if Rat Shack who designed the thing had the correct design info in their manual - now I'm wondering if they didn't know what they designed, or if they didn't know how to design.

 

[Catalyst52]

I am having the exact BOOT ERROR DC problem with my TRS-80 Model II. Any help is appreciated!