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Computer Terminal Corp DataPoint 3300


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  Computer Terminal Corp DataPoint 3300 by Bill Degnan - 12/29/2011 15:51
The Computer Terminal Corp. DataPoint 3300 after cosmetic restoration work completed. This is the first glass terminal first produced by CTC in 1969 (after being announced in 1967). The 3300 was a play on the ASR 33, which is what this machine was designed to replace. The serial number sticker says 1030. Click image for larger view.

System after cleaning. The terminal was in pretty bad shape (evidence of rodents on the keyboard), but fortunately there was no rodent nests inside. First, the cover was removed and disassembled. The dust therein was blown out on the porch outside. Each key and the underside of the keyboard was cleaned thoroughly. Click image for larger view.

Here is a picture of the terminal with the front bezel removed. Click image for larger view.

Rear ports of the DataPoint 3300 terminal. This was a very early glass terminal, most terminals in the late 1960's were paper. The max baud rate is 2400, but there are a lot of choices - this terminal emulated the teletype speeds. Click image for larger view.

More pictures

Operational Status:
1) The fuse was missing so I installed a new one.
2) The keys all work (!), but when a key is pressed the key repeats until BREAK is pressed.
3) The screen prompt is not always visible, but the CRT itself is OK. There is a logic problem or an A/D problem preventing the characters to be written to the screen. If you flip on and off a few times, you can get the characters to be visible.
4) The baud rate select is loose, I had to use a plyers to turn the post with the knob removed.
5) The REM/LOC switch works.

I was able to determine the 2400 baud rate setting by the speed in which characters were written to the screen when printing repeatedly.

I need to disassemble the four logic boards from the chassis and clean them. I need to also remove and clean the keyboard logic board. Perhaps a good cleaning will restore the system to proper function?? Hey, we can hope!

I need to test the caps and the power supply.

  1969 CTC Datapoint 3300 Ad by Bill Degnan - 05/06/2013 12:26
1969 CTC Datapoint 3300 Ad

  Repair Update by Bill Degnan - 07/09/2022 20:19
Bob Grieb took a stab at the repairs of this terminal. First he used the technical documentation he has to ID the correct power supply component. He found a replacement for sale and ordered it.
The machine has power again.

"I cut new rubber washers for the keyboard (75 of them)
out of a tractor tire inner tube. Today the assortment of reed
switches arrived from Digikey. They are really cheap, so I
bought 3 kinds, 5 each. The magnetic field strength required
to close the switch was different for the three types, since I
didn't know what part was originally used. One of the three
seemed fairly close to the old switches, so I installed four of
them to replace ones that were broken.

The power cord arrived today.

The connectors used for the 5 pc boards require an uncomfortable
amount of force to plug them in. Hope I didn't break anything.
I don't like pushing that hard on anything that old...

I have not applied full line voltage to the power supply yet.
Will probably do that tomorrow."


I figured out how the CRT got the burn mark in the very center.
When you turn off the terminal, the deflection stops right away,
but the beam is still on, so it's very bright right in the center.
Over time that burnt the phosphor. I will see if turning down the
intensity first prevents that.

If I press a key, it repeats until I hit Rub Out or Backspace, or a
few others. Unfortunately, I am currently thinking this is not a problem
with the keyboard, but rather with the screen buffer control circuitry.
But I am not sure.

When I first powered it up, the intensity control was not set to
show a beam.
I played with it a little. Turned it back and forth to clean it, as
it's a sealed pot.
Anyway, I have not noticed the issue you mentioned about characters not
being visible sometimes. More testing needed.

The G and J characters were repeats when I pressed those keys.


Fixed the repeating character issue.

I was able to power up the Interface 1 board by itself,
and found a couple of bad 7474 chips.

Luckily I had two of them from a long time ago.

  Restoration Completed. by Bill Degnan - 11/13/2022 19:18
Character output.
Click image for larger view.

The power supply that made this whole project possible. Click image for larger view.

Re-assembled, attached to Kennett Classic Wifi @ 300b 7-E-1. Pictured is the Level 29 telnet BBS. Click image for larger view.

As a footnote to Bob's great work I created a simple WIFI modem that works at 300 baud 7-E-1



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