Don’t bother with the 10kΩ resistor, as this is only required if you are fitting a battery back-up system [see http://www.zx81.de/english/32k-rame.htm ].
Without a battery, it serves no purpose.
With modern faster SRAM chips, sometimes a control line to the SRAM chip may need a low value capacitor (47pF to 100pF) to delay the timing. Connect between pin 20 and 0V/GND.
However, if BASIC runs okay, the first thing when having display problems is always to try different TVs/monitors. The normal SLOW mode from BASIC is not a standard broadcast video signal, and the various hi-res schemes will also not be generating a standard broadcast video signal. Hence some TVs/monitors may not like it.
Mark
16k internal RAM and graphics issue (I think).
- 1024MAK
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Re: 16k internal RAM and graphics issue (I think).
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: 16k internal RAM and graphics issue (I think).
Many thanks for the information Mark1024MAK wrote: ↑Mon Jul 08, 2019 9:14 am Don’t bother with the 10kΩ resistor, as this is only required if you are fitting a battery back-up system [see http://www.zx81.de/english/32k-rame.htm ].
Without a battery, it serves no purpose.
With modern faster SRAM chips, sometimes a control line to the SRAM chip may need a low value capacitor (47pF to 100pF) to delay the timing. Connect between pin 20 and 0V/GND.
However, if BASIC runs okay, the first thing when having display problems is always to try different TVs/monitors. The normal SLOW mode from BASIC is not a standard broadcast video signal, and the various hi-res schemes will also not be generating a standard broadcast video signal. Hence some TVs/monitors may not like it.
Mark