Okay, I've run into a snag with this machine.
I did four modifications at once before testing, always a no-no when testing/troubleshooting - two on the main board and two on the core board. I'm confident the main board is fine (RS232 improvements) as they look similar to a Series 2 and it also "works" with a Series 2 core board (beeps and has video output, but doesn't work properly because it's 2MHz but BASIC 5.22 on the core board I assume).
The modifications on the core board were:
[1] I modified the NET IC34 as per the HWNB from 2532 to 2732 but it didn't work - and the instructions didn't make much sense in hindsight so I did something else. I drilled out the holes, cut tracks, soldered in a socket and C31.
The HWNB (section B, chapter 6) details how to modify the socket to accept a 2732 - it says to connect pin 21 (A11) to pin 18 of IC25 - simple enough. It then says to connect pin 18 (enable) to pin 1 of IC26 (A12 line).
This confused me - shouldn't the 2732 ENABLE connect to the ROMSEL line - the 2532 pin 20 connects to IC26 pin 9 ... not pin 1. So I moved pin 18 to pin 9.
Summary: the NET ROM (IC34) now has pin 21 (was PD/PGM, now A11) connected to A11, and pin 18 (was A11, now ENABLE) connected to ROMSEL, and not A12.
[2] I added the missing components for the battery backup according to the schematic: R5, R6, R9, R12, TR1, LED.
I'm feeling that the NET ROM is causing the issue - voltages look fine, will hook up a logic analyser next. I'm assuming it should still work without the BB connected?
But in case someone has an idea where I went wrong
I did four modifications at once before testing, always a no-no when testing/troubleshooting - two on the main board and two on the core board. I'm confident the main board is fine (RS232 improvements) as they look similar to a Series 2 and it also "works" with a Series 2 core board (beeps and has video output, but doesn't work properly because it's 2MHz but BASIC 5.22 on the core board I assume).
The modifications on the core board were:
[1] I modified the NET IC34 as per the HWNB from 2532 to 2732 but it didn't work - and the instructions didn't make much sense in hindsight so I did something else. I drilled out the holes, cut tracks, soldered in a socket and C31.
The HWNB (section B, chapter 6) details how to modify the socket to accept a 2732 - it says to connect pin 21 (A11) to pin 18 of IC25 - simple enough. It then says to connect pin 18 (enable) to pin 1 of IC26 (A12 line).
This confused me - shouldn't the 2732 ENABLE connect to the ROMSEL line - the 2532 pin 20 connects to IC26 pin 9 ... not pin 1. So I moved pin 18 to pin 9.
Summary: the NET ROM (IC34) now has pin 21 (was PD/PGM, now A11) connected to A11, and pin 18 (was A11, now ENABLE) connected to ROMSEL, and not A12.
[2] I added the missing components for the battery backup according to the schematic: R5, R6, R9, R12, TR1, LED.
I'm feeling that the NET ROM is causing the issue - voltages look fine, will hook up a logic analyser next. I'm assuming it should still work without the BB connected?
But in case someone has an idea where I went wrong