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by 1024MAK
Mon Feb 26, 2024 8:33 pm
Forum: Hardware
Topic: ZX spectrum spider mod
Replies: 6
Views: 125

Re: ZX spectrum spider mod

That looks like a problem with the 'lower' DRAM, or a problem with the busses that means the ULA is having trouble getting screen data. In your photo, the border is white. Does it go white at every power up (NOT reset)? Try six to ten times. If it always goes white, this indicates that the Z80 is ab...
by 1024MAK
Mon Feb 26, 2024 7:12 pm
Forum: Hardware
Topic: ZX spectrum spider mod
Replies: 6
Views: 125

Re: ZX spectrum spider mod

Okay, have a look at my flickr photos here ;-)

Mark
by 1024MAK
Mon Feb 26, 2024 7:01 pm
Forum: Hardware
Topic: ZX spectrum spider mod
Replies: 6
Views: 125

Re: ZX spectrum spider mod

Yes, it will work in BASIC without the spider transistor. It's machine code programs (games) that access I/O ports (the ULA or joystick interface) that would experience problems. And yes, there are alternative positions for this transistor. I'll try to find a photo showing a better position. Mark
by 1024MAK
Mon Feb 26, 2024 6:21 pm
Forum: Hardware
Topic: I've borked it
Replies: 116
Views: 3210

Re: I've borked it

Reading the diagrams on a datasheet is an art :lol: Keep in mind that the diagram itself can be misleading if taken literally. In the real world, the "width" of the various features on the diagram depends on a number of variables, including the clock/bus access speed of the system. Which in the ZX81...
by 1024MAK
Mon Feb 26, 2024 1:28 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 31
Views: 634

Re: 16k Sinclair issue 1 pack

msknight wrote: Mon Feb 26, 2024 11:07 am Unless someone says different, I'm going to go for ....
BAT85 30V 200mA Small Signal Schottky Diode
They should be fine ;-)

Mark
by 1024MAK
Mon Feb 26, 2024 1:24 pm
Forum: Welcome Area
Topic: Hello from Poulette73
Replies: 10
Views: 489

Re: Hello from Poulette73

Yes, as this avoids the effects of any extra video circuitry that may be fitted depending on the country that the board was manufactured for. The wiring to the modulator and any extra components connected to it should also be disconnected.

Mark
by 1024MAK
Sun Feb 25, 2024 10:47 pm
Forum: Welcome Area
Topic: Hello from Poulette73
Replies: 10
Views: 489

Re: Hello from Poulette73

Issue one board
Issue one board
Issue one board
Issue 3 board
Issue 3 board
Issue 3 board
Click on the pictures for the full size version.

Pin 16 shown. An alternative is on the connection for diode D9 indicated.

Mark
by 1024MAK
Sun Feb 25, 2024 5:26 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 31
Views: 634

Re: 16k Sinclair issue 1 pack

msknight wrote: Sun Feb 25, 2024 5:01 pm This is messy, but it's "open" so you can see what I've done. - probably something stupid, knowing me.
I think I will need to open those pics on a PC rather than my 'phone while crawling around in the loft :lol:

Mark
by 1024MAK
Sun Feb 25, 2024 5:23 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 31
Views: 634

Re: 16k Sinclair issue 1 pack

msknight wrote: Sun Feb 25, 2024 4:49 pm I have some N4007 - should I use those instead?
No. They are designed for low frequency use.

Mark
by 1024MAK
Sun Feb 25, 2024 4:41 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 31
Views: 634

Re: 16k Sinclair issue 1 pack

Not having a RAM pack in front of me, I can't answer your question directly. Both the black band on both diodes on both diodes indicates the cathode, and should be connected to the circuit that goes to the relevant edge-connector socket pins. The other end of each diode should form a connection with...