exxos's Atari, Amiga & retro forum

Nice to hear the SEC runs fine with the others

TT PSU Recap


Well I got my hands on another TT and wanted really to give it a service, update it and then offer it up for a good home once completed.

My first job is to recap the PSU and thought I would also document to see if there were any differences based on discussions around the A1 and A2 boards on this thread - https://www.exxosforum.co.uk/forum/viewt ... psu#p39560

First observation the PSU has an odd fan controller stuck on the side. Now to crack open the PSU and see what version is inside. For reference the TT is an early version with the 68030 daughter board. Need to check the exact revision using @Atarian Computing revision guide - https://www.exxosforum.co.uk/forum/viewt ... 1025#p7684

Somehow, the fan controller doesn't exactly look "factory original" to me. Maybe the previous owner found the fan to be too loud and installed something to drop/regulate the voltage?

BTW: After this discussion I think the TT's PSU needs to always have a reasonable airflow.

Well the fan board turned out to be plugged into the fan connector with a thermistor wrapped to the inside of the case.


The PSU is a REV O2 with the PC111. @mikro you may be interested as its different rev to our A1 and A2's the O looks like an O as opposed to a zero if you compare the text to the line above.

With all the boards we are making smaller and cramming as much as we can into footprints we are finding that the JTAG is starting to dominate and be a rather large part of the board. This is space that can be used elsewhere including all the peripheral pull-up / pull-down resistors around the JTAG.

@exxos and I have been discussing a small micro JTAG adaptor board that allows us to remove these bulky components and have a small 2.0mm plug / socket to connect to our boards enabling us to update firmware.

Continuing with the TT PSU work. Have just braided the floppy and HDD power wires. Now onto the re-capping.

Just checking out the voltages prior to the recap. It always makes me smile and have a bit of nostalgia when using those resistors.

The CGS Resistance Co. Ltd in Lymington who produced the one on the right was a child company of the electronics firm I worked at in the late 90's.

I forgot to mention anyone re-capping a MegaSTE / TT PSU please follow this greatt guide by @Pacman - https://www.exxosforum.co.uk/forum/viewt ... ?f=9&t=300

Original voltages before re-cap:

+12V (yellow) = 11.76V
-12V (blue) = -12.53V
+5V (red) = 5.17V
-5V (white) = -4.98V
+5V PG "Power good" (orange) = 5.16V

- Looks like the caps have been glued to the board and the epoxy is as stubborn as hell.