TRS-80 Model II

From: Fritz Chwolka <>
Date: Wed Feb 18 18:43:04 1998

Lawrence Walker wrote:
> I've searched the world web over ,but never did I find......
> There seems to be a lot of info on Mods. 1,3,100,Coco etc. but nada
> on this beast. Any sites I might have missed ? Merch , Cord ?
> What I have is a TRS Model II with 1 internal 8' fdd and 1 external
> fdd , 3 humungous 5Meg hdd ( about the size of a large XT) , K-B ,
> TRS model 7 modem , and a box of 8" disks with CP/M 2.2 , TRSOS,
> Scripsit and a bunch of other prgms.
> When I boot up with or without an OS disk I get a "boot error ht'
> msg. The dd spins up and sounds like its loading. Could it have been
> set up to boot off one of the hard drives ? I'm really a novice with
> TRS-80s but have Coco 1 and 2 in my collection and a Scriptsit cart.
> Is there something I'm not doing ?
> ciao larry

Great... that you got such a fine part.

I've a TRS80 MII too but without a harddiskdrive.
For other use I add an extern DSDD 8" diskdrive.
The internal diskdrive is singlesided I believe it's a shugart 801.

I got several errormessages during bootup every time I tried to do
so which was every 2-4 months.

My problem was the dispositioned head of the diskdrive.

 (1) --------------------\
      ---------------+ !
 (2) +-----+__ 1_2_3_____...77+----------
 (3) -------------- /====\

There I trie to show the disk with head and the part against the head
for the singlesided drive.

If you put in the disk between part (1) and (3) must be place enough to
the fleydisk into the drive. If there isn't enough place the disk will
contact with part (1) or (2) and you throw the head backwards. If you
don't recocnise it and after some triese are able to get the fleyxdisk
the drive you change the correct position of the head against track

Normaly the head must find track oneduring bootup. If the system boots
the diskdrive will reset the position of the head(s) and a indicator
now the head is in Track 0 position. The the stepper stepps backwards
from track
to track.

 Dispositioned head:
 (1) --------------------\
      ---------------+ !
 (2) +-----+__ 1_2_3_____...77+----------
 (3) -------------- /====\

Here you see that the head can't stepp backwards during the poweron /
reset time
because during inserting the flexydisk I dispositioned the head.
The distance between (1) and (3) was to small because part (1) fall down
the metallplate which make the headload.
Now during boot I got a DC error.

It's a nice mechanical problem in my case and maybe you have the same.
Even the indicator for Track 0 maybee dusty or inoperable.


Fritz Chwolka / collecting old computers just for fun.
Received on Wed Feb 18 1998 - 18:43:04 GMT

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