Search Posts:

MITS Altair 8800b T with Dual Drives

SHARE

Return to Threads

  MITS Altair 8800b T with Dual Drives by Bill Degnan - 09/22/2013 18:37
Two MITS model 88-DCDD Single 8" disk drives. These are the older design made to match the 8800a system faceplate. Serial numbers DD 2100 and DD 3216


I have initiated work on MITS Altair 8800b Turnkey System with Dual 8" disk drives. It's a complete system with cables, cards, and a custom MITS desk to hold everything. The 8800b turnkey was first produced during the takeover of MITS by Pertec corporation. At some point, Pertec started calling an 8800b turnkey with dual drives the "300/25" system, but this particular system was sold before that. The serial number plate for the 8800b is still MITS, later versions' s/n plate read Pertec.

8800b T System Photos

NEXT: List of the components replaced, and a video of the system in action.



Reply
  New Altair Disk Images Uploaded by Bill Degnan - 09/26/2013 00:14
I have uploaded 5 new Altair disk images that are new to the web you may have to right-click on them to download. Please tell me if they work in an emulator and/or actual disk drive.

LB-CPM-141.dsk: Original Lifeboat CP/M 1.41 disk - does not boot on my Turnkey system using port 10, but the disk is readable. See also Durbin CPM below.

E-BASIC_300-5-C.dsk: MITS Extended BASIC 300-5 rev C

WS.dsk: A disk that has WordStar on it for LearSiegler. It did not image correctly. I will try in a different drive asap.

DURBIN-CPM.dsk: CP/M on MITS 62K Version 1.41 probably a gen for the turnkey of the original LP-CPM-141 image. This version was used with a GE Terminet 1200 printer, 300b modem, and 9600b terminal. The printer and modem were operated through a separate 2SIO card.

CBASIC_206A.dsk: Lifeboat CBASIC v 2.06A

Reply
  Log from Altair BASIC Disk Session by Bill Degnan - 12/11/2013 12:28
MEMORY SIZE? 48K
SYNTAX ERROR}C
MEMORY SIZE? 48
ILLEGAL FUNCTION CALL}C
MEMORY SIZE? C B 
LINEPRINTER? N
LINEPRINTER? C
HIGHEST DISK NUMBER? 0
HOW MANY FILES? 1
HOW MANY RANDOM FILES? 1

41080 BYTES FREE

ALTAIR DISK EXTENDED BASIC
VERSION 300-5-C [01NOV78]
COPYRIGHT 1978 BY MITS INC.

OK
10 FOR K=1 TO 1000
20 PRINT K;
30 NEXT K
40 END
RUN
SYNTAX ERROR IN 10
OK
10 FOR K=1 TO 1000


Reply
  MITS Power Supply Bd Repair by Bill Degnan - 12/27/2013 11:10
MITS disk drive power supply
Pictured is the drive 1's disk power supply board after I removed most of the caps and regulators for servicing. MITS used Pertec FD400 drives in this unit. Click on image for larger view.


More photos


I have assembled the Altair desk and I am up and running with one drive (Drive 0). I am using TeraTerm as a terminal.

Drive 1 blows fuses and needs service. I decided if I was going undertake the tricky task of digging into the bowels of the drive to get to the power componentry I should replace everything that might deteriorate over time.

I consulted the straight-forward drive assembly manual. Compared to the schematics I noticed that a few ICs were non-standard and that this drive appears to have been disassembled at least once before. I do not know why the work was done, it almost seems like the previous owner did not have the exact parts on hand and improvised to get the drive working.

I could not find any good reason not to return drive to match drive 0 config which is working and has stock ICs installed.

As you can see the board is a little fried by the original owner.

Parts on order...

Reply
  MITS Power Supply Board - Update by Bill Degnan - 01/23/2014 11:18
MITS 8in drive power supply board
Replacement parts installed but not yet soldered. Note all of the trace connection issues. Click image for larger view.


I still need to replace the transformer, It was very difficult to work with this board.

For now I have this drive installed into the desk as the 0/A drive.

Reply
  Serial Settings for Altair Disk BASIC by Bill Degnan - 03/08/2014 16:09
On my system, in order to avoid weird syntax errors, I needed to set the serial terminal settings to 9600b, 7/N/2


Reply

Resources:


Buy a Commodore Computer Poster

Popular Topics and FAQs


Past Issues:


vcfmw ECCC 2011 ZenithLaptop8086

This image was selected at random from the archive. Click image for more photos and files from this set.