On 7/31/2018 10:32 PM, systems_glitch via vcf-midatlantic wrote:
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:
http://www.glitchwrks.com/2018/07/31/tdl-smb
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 invisible.
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.
Thanks, Jonathan As usual, awesome job there, Jonathan!