๐Ÿ‡ฌ๐Ÿ‡ง Sinclair ZX Spectrum: Part 6 (Troubleshooting in circles?) [TCE #0520]

Channel:
Australia The Clueless Engineer
Subscribers:
2,950
Published on ● Video Link: https://www.youtube.com/watch?v=I3ixrDaoIeo


Duration: 0:00
257 views
24

Still replacing parts, as indicated, but not making any progress. I would like to replace the Z80 but its soldered in ...

Phil at Retroleum in the UK makes some neat RAM replacement boards, so I got one of each. Have replaced the whole lower 16KByte of RAM (eight 4116) as one was flagged as faulty (despite passing the initial lower RAM test ... ?)

I am also using the Retroleum diagnostic ROM installed on the Speccy board in place of the Sinclair ZX Spectrum ROM. And ... the text is readable now! Well, after a cold boot. Once the machine has warmed up a little it starts misbehaving.

http://blog.retroleum.co.uk/electroni...

--------------------------------
From Part 3:
Ivan very kindly donated one of his 128KByte RAM expansion boards so I am looking forward to trying that out - my first package from ๐Ÿ‡ท๐Ÿ‡ธ Serbia! In order for it to work you need to disable the upper 32KBytes of internal RAM, which I've done by adding a switch to inhibit the !CAS signal for that bank of RAM (make one OR gate input on IC23 always HIGH by connecting to +5V thus forcing the output HIGH, thus disabling !CAS).

I've verified the switch works by executing "PRINT PEEK 23732 + 256 * PEEK 23733" : I get 65535 (full 48KBytes), or 32767 (upper 32KBytes disabled).

However, after this it seems things started to go awry (nothing to do with Ivan's board).
--------------------------------
Check out my Patreon for regular blog-type updates between videos - there is a free membership tier and two paid tiers (US$2 and US$5). There is also a one-week trial for the paid tiers so if you don't think it's worth it, then cancel ... no hard feelings ... I appreciate any support, even if it's just subscribing to my YouTube channel!

ย ย /ย thecluelessengineerย ย 
--------------------------------

Music by Karl Casey @ White Bat Audio
https://karlcasey.bandcamp.com
ย ย ย /ย @whitebataudioย ย 



Other Videos By The Clueless Engineer


2024-10-12๐Ÿ‡ฏ๐Ÿ‡ต Casio PB-770 & FA-11: Part 4 (Closer Look at FA-11 Cassette Mechanism) [TCE #0529]
2024-10-11๐Ÿ‡ฏ๐Ÿ‡ต Casio PB-770 & FA-11: Part 3 (Dismantling the FA-11 Data Recorder) [TCE #0528]
2024-10-10๐Ÿ‡ฌ๐Ÿ‡ง Psion Organiser: Part 2 (Comparing the Organiser I & Organiser II) [TCE #0527]
2024-10-09๐Ÿ‡บ๐Ÿ‡ธ Tandy Colour Computer 2: Part 1 (US NTSC model in Australia) [TCE #0526]
2024-10-08Quick (promise!) Patreon update/plug [TCE #0525]
2024-09-30๐Ÿ‡ฏ๐Ÿ‡ต Sega Saturn Audio CD Visualiser [TCE #0524]
2024-09-29๐Ÿ‡น๐Ÿ‡ผ Princess PBW-121 (Adding Video Input to RF-only TV): Part 2 [TCE #0523]
2024-09-25๐Ÿ‡บ๐Ÿ‡ธ Neo Geo X (NGX): Part 1 [TCE #0522]
2024-09-24๐Ÿ‡ญ๐Ÿ‡ฐ COMX-35 (1983) using the CDP1802 processor #8bitcomputer #retrogaming #c64 #boulderdash
2024-09-22๐Ÿ‡บ๐Ÿ‡ธ Osborne 1: Part 6 (OZROM Memory Tester) [TCE #0521]
2024-09-21๐Ÿ‡ฌ๐Ÿ‡ง Sinclair ZX Spectrum: Part 6 (Troubleshooting in circles?) [TCE #0520]
2024-09-20๐Ÿ‡ฆ๐Ÿ‡บ Amstrad CPC PicoROM: Part 1 (Building & flashing) [TCE #0518]
2024-09-19๐Ÿ‡ญ๐Ÿ‡ฐ COMiX-35: Part 11 (PAL key auto-repeat issue)
2024-09-17๐Ÿ‡ญ๐Ÿ‡ฐ COMX-35/COMiX-35: Part 10 (Audio causing video glitches) [TCE #0517]
2024-09-17๐Ÿ‡ญ๐Ÿ‡ฐ COMX-35/COMiX-35: Part 9 (Loading software via high speed serial) [TCE #0516]
2024-09-15๐Ÿ‡ธ๐Ÿ‡ฐ SMEP PP 01: Part 8 (Small Progress) [TCE #0515]
2024-09-14๐Ÿ‡บ๐Ÿ‡ธ Osborne 1: Part 5 (Mouting the Gotek in the drive bay) [TCE #0514]
2024-09-11๐Ÿ‡จ๐Ÿ‡ณ Creality Ender-3 V3: Part 1 (It doesn't work) [TCE #0513]
2024-08-29๐Ÿ‡บ๐Ÿ‡ธ Osborne 1: Part 4 (Dual BIOS ROM Installation) [TCE #0512]
2024-08-26๐Ÿ‡ฌ๐Ÿ‡ง Sinclair ZX Spectrum: Part 5 (RGB cable & more diagnostics) [TCE #0511]
2024-08-24๐Ÿ‡ฌ๐Ÿ‡ง Psion Organiser II: Part 1 (Quick Look) [TCE #0510]