ZX spectrum spider mod

[1024MAK]

ZX Spectrum Spider Modification

Alternative location in between the ‘upper’ DRAM chips.

On the schematic this is shown as transistor TR6, a ZTX313 or a ZTX312.

All references to the leads of the transistor are with the leads pointing downwards and the rounded side with marking facing towards you.

The collector (left hand lead) is connected to a +5V point. Where you see it fitted near capacitor C57 (in between the ‘upper’ DRAM chips), there is a convenient plated through hole used to route the +5V supply between the tracks on the top and bottom of the board. A plated through hole that doesn’t normally have a component fitted is typically referred as a ‘via’.

The base (middle lead) is connected by using a insulated wire to address line A0. Either to IC2 (Z80A / D780C-1) processor) pin 30 or any other point that is connected to address line A0 of the main address bus).

The emitter (right hand lead) is connected to the left wire of resistor R27 (470Ω or 680Ω depending on which build version the board is) which is connected to the /IOREQ signal to ULA pin 33.

Mark

[Distinct0983]

thanks so much, that's a huge help. I'll give this a go as soon as I get a chance

[Distinct0983]

Just had a go, thank you for the super clear instructions, once I had it open in front of me I could see it exactly as you described. It was a bit fiddly and I've left some ugly solder lumps but as far as I can tell it's worked, or I least haven't destroyed it as it still turns on, a victory in itself.