[vcf-midatlantic] TDL SMB Repair Writeup

systems_glitch systems.glitch at gmail.com
Tue Jul 31 22:32:55 EDT 2018

Last October, I traded Herb Johnson for two TDL SMB boards that had been
stripped of all socketed parts, and even some of the soldered-down ones!
Here's my writeup on the repair process:


Both boards had an etch error that shorted the +5V rail to ground! This is
presumably why they ended up in the TDL boneyard. Herb had acquired them
stripped of all parts from a former TDL employee, presumably someone
plugged it in, noticed the power draw, and moved on to the next board. I
found the short by stripping one board of its sockets and bisecting the +5V
rail with trace cuts. The short was hidden under silkscreen, making it

In the process, I did two things that will probably be useful to other
people here: I designed a replacement board for the SEMI 4804 SRAMs, which
are unobtainium, and I reproduced the Interface One and Interface 2 I/O
breakout boards. All will be available through my Tindie store as I get
time to photograph and list them, but if you're in need of them now, send
me an email!

The writeup also covers the cuts and jumps necessary to use 2716 EPROMs
instead of the mask ROM that TDL originally supplied with the SMB. There
are pictures of my modifications, with the cut areas circled for clarity.


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