+9v on -12v line? Expansion pin 23B

[Calab]

[edit] Excuse posting to the wrong forum... Should have gone to the Spectrum Hardware forum [/edit]

Hey all!

On my Issue 3 48k Spectrum ZX I had a Z80 with a bad M1 line. I pulled it and installed a socket and new 10Mhz Z80 (https://www.digikey.ca/en/products/deta ... PEG/929206). Upon power up, the Spectrum did not work. I've checked my work and I have continuity to everything I should, and no shorts that I can find.

Checking the voltages, I discovered that on pin 23B on the expansion port I have +9v. According to the schematics I find online, this should be -12v.

Any ideas what could be causing my issues?

Attached is a photo of the new Z80, and a video of my Spectrums display.

New Z80

20220415_003131_Trim.mp4

Video of display

(943.82 KiB) Downloaded 64 times

[Calab]

Hey all! Reposting this message to the correct board...

On my Issue 3 48k Spectrum ZX I had a Z80 with a bad M1 line. I pulled it and installed a socket and new 10Mhz Z80 (https://www.digikey.ca/en/products/deta ... PEG/929206). Upon power up, the Spectrum did not work. I've checked my work and I have continuity to everything I should, and no shorts that I can find.

Checking the voltages, I discovered that on pin 23B on the expansion port I have +9v. According to the schematics I find online, this should be -12v.

Any ideas what could be causing my issues?

Attached is a photo of the new Z80, a video of my Spectrums display, and the power schematic that I'm looking at.

20220415_003131_Trim.mp4

(943.82 KiB) Downloaded 73 times