Search results

The "proper" way to do the fix is tie the Gate of Q1 to 3.3V so Q1 buffers the SD card from the PIC. The "hack" of removing R15 & Q1 & installing the jumper is certainly simpler. I still haven't modded my FreHD to keep Q1 in the circuit. :) Tom

The TRS-80 4P has half-height drives with half-height face plates, the 4D has the half-height drives with full-height face plates.

The FreHD ROM allows you to select what image you boot from the FreHD using a menu. I think you would need separate boot floppy images for the Gotek, one for each HD image you want to run.

Newprint 80 may fit your needs.

Check out Mike Brutman's mTCP.

https://www.minuszerodegrees.net/5161/misc/5161_reproductions.htm & https://www.minuszerodegrees.net/5161/cable/5161_cable.htm

The 4P doesn't have Basic in ROM.

The anti-static cases are nice. I got a pair at a previous job years ago. I was told they were from the Series/1 computer systems.

DOS for Workgroups

You could send a message to the user "Glitch", he has an ACI-2. He may be able to help. Tom

They may not be the main switching transistors. They could be regulators on secondary outputs like the +12v line.

Could possibly be a version of the LM1086 3 terminal regulator IC.

Digikey carries the Keystone parts.

Ian's site is at http://www.trs-80.com.au/trs80/index.htm

I thought the original 1000 didn't search for add on ROMs like the 1000A does. You need to load some kind of driver to access the HD with those machines.

Looks like a drop in replacement for the TI SN75185. Their are other manufacturers of compatible chips. It looks like the Holtek chip only comes in SOP-20 package. Digikey sells the TI SN75185DW for $1.44/ea. If you can solder SMT ICs, it should be relatively easy to replace.

According to the datasheet, Holtek HT6751 chips are motor driver chips intended for camera zoom/focus, etc. functions. They can't be kludged to function as RS232 driver/receivers.

You may have blown one or more of the RS232 driver/receiver chips on the m/b.

According to here, it is a DS1216B or C. that suggests that the many webpages showing how to replace batteries on those modules should apply to these modules also.

Measure the resistance between the 2 front leads. That should tell you what the value is.