Help - issue 2

[Aiden]

Hi all, any ideas what’s happened to my issue 2?
Thanks
Aiden

[Waldroid]

Looks like several of your lower RAM chips are broken.

Probably the Z80 is fine because it's managed to run some of the startup code and turn the border white.

Was you Spectrum working fine and then this suddenly happened, or is this one you got off ebay or somewhere?

[Aiden]

Hi Waldroid.
It’s my test board, it was working fine when I was testing 4116s, just swapping out. Plus I swapped out the Rom chip. I turn it on this morning and see this.
Thanks

[Waldroid]

Blimey, dunno then. Accidentally put a faulty 4116 back in? Little bit of resistor lead off-cut bridging a couple of address lines?

I'm sure 1024MAK will be along shortly with some more helpful advice.

[Aiden]

Swapped out all the 4116s and now got this

[cj7hawk]

Voltages to the RAM chips?

You should never change the rams before you check the voltages, or you may break the replacements.

Make sure -5v and 12v are present and reasonably accurate on the chips ( within 10% )

[Aiden]

Thanks everyone
It turns out it was a bad Rom and ULA together.
Oh well we live and learn on to the next one now

[Waldroid]

Oof!

Ah well, glad you got it sorted anyway.

[1024MAK]

I was going to say, that first screen is not typical of a single DRAM fault.

Surprised it was both ROM and ULA.

Mark