Model 1 - RS232 Expansion board query

[1980s_john]

Hi,

I have a Model 1 Expansion unit with an RS232 board, as per:

http://akhara.com/trs-80/docs/model1/RS-232-C (1978)(Tandy)(pdf).zip

My board is missing the DC converter, which takes 5V input and provides dual +/-12V outputs. The above manual shows the part number is Astec AA4890. Can someone with an RS232 board please verify this part number, as I can't find a datasheet for it. There are many replacement DC converters available today (starting with the slightly newer Astec AD1D12A10).

Hopefully someone can dig out a datasheet for the Astec AA4890 or even its maximum current output, my Google skills could only find the one for the AD1 series.

Regards,
John

 

[Tibs]

That looks right, however, I would urge you to reach out to Ian Maveric, he had an article showing the difference between the two revisions. He also has a board replica.

I can't remember but there was something you can do to make it more reliable. Pretty sure it was related to that very thing you're talking about.

http://ianmav.customer.netspace.net.au/trs80/model1s_files/image022.jpg

I think this was the issue (taken from his website):

So look for TRS8BIT March 2013 and it could help you out.

March 2013: I talk about how to set up your hard drive partitions using RSHARDx, and I talk about fixing Model I RS232 boards.

 

[ldkraemer]

Yes, that is it.




Larry