Spectrum Computing

Thanks Mark, Apparently the issue was this: So why the Recall? Some units were produced where the mains 240V could potentially become live on the outer metal positively charged part of the barrel connector – despite this supposedly being the low voltage DC connector. Taken from here: https://popeymo...

I see some posts dotted around various pages about the recall of certain PSUs.

My question is does anyone have information of the differences between a pre and post recall PSU, and if so are the differences something that can be implemented if they are missing?

Thanks

H

Thanks for the replies good to know what options I have. Of course if it only turns out to be 1 or 2 of the existing ram chips it probably makes more sense just to swap those rather than re-solder all 8 to change the chip type. I did the or gate mods and got the DiagRom in. It seems to be running th...

I have a poorly 48k Spectrum Issue 4B, it seems like a lower ram issue, I'm just waiting for some BAT85 diodes so I can do the OR gate mod. I intend to try the DiagRom written to a 27128 chip to verify this is the case. Doing the resistance check between pins 1 & 16 comes in at about 2.7kR acros...

Morkin wrote: ↑Wed Jan 31, 2024 3:10 pm Wow, that's one hell of a collection

And I thought my collection was getting a bit excessive! Wow that's very nice an impressive haul

Hi I'm H,

I'm from the UK, I'm really an Acorn enthusiast at heart but I was given a Tandy TRS80 model 100 and from there I have branched out into fixing many different retro computers and it just so happens that the ZX Spectrum is one of them.

Cheers

H

It looks like all the DRAM was originally soldered. And all the original DRAM has been removed. The ‘lower’ DRAM chips been replaced with 64K bit DRAM chips that only need a single +5V supply. That may explain the changes near to capacitor C44. Has the +12V supply to pin 8 of the ‘lower’ DRAM been ...