Sinclair ZX80 / ZX81 / Z88 Forums

Hi. Would it be advisable to use an external LM7807 or LM7808 to feed the internal LM7805 jut to avoid the extra heating inside the case? I know that some rampacks need the 9v line but I am planning to use a 4164 modified rampack or a custom made SRAM one.. My min xon er is about a ZX80 .. I have tw...

1024MAK wrote: ↑

Wed May 27, 2020 10:14 am

Maybe the colour encoder circuit has a problem, for example the crystal frequency has drifted badly.

You may have more luck if you post on World of Spectrum forums

Mark

thank you !! I'll check crystal and go to work..

I think your TS2068 provides good colours for NTSC standard. Do not expect anything similar to PAL, in NTSC all colours are washed out. There a solution, a mini board with PAL encoder like AD724 that could be connected to the edge connector. R, G, B & video signals are available there. When using a...

Hi, I know this is a mainly Sinclair forum but I just Got this TS 2068 to discover how Ugly its video output is. It has an RF modulated output and a "monitor" composite output.. This is an NTSC computer but is not a problem as all my LCD TV support both PAL and NTSC.. but colours are not OK.. it loo...

Hi, I've built the 555 based circuit By Ziggurat http://zx.zigg.net/misc-projects/ I plan to use it on a ZX80 but meanwhile tested it with my CZ1000.. with a Ferranti 2C210E ULA which grates an appropriate back porch. 20200521_211818.jpg What I've noticed is a really crisp, steady and noiseless K cu...

Also read this topic ;) Mark Thanks.. I am about to receive one ZX80 US soon so I am quite anxious :D I've already made my own video back porch composite mod from http://zx.zigg.net/misc-projects/ while waiting.. (Should this be moved to the hardware forum?) Are there any known software incompatibi...

What would be the differences between the ZX80 US vs UK versions? Do both have ISS 1 and 2? Having owned both US and UK types the only difference I could detect was the television standard between the two countries ie the modulator. Mine was a later ABS cased model suggesting issue 2 as per my UK o...

What would be the differences between the ZX80 US vs UK versions? Do both have ISS 1 and 2?

Please confirm that the Z80 has power. Test between any 0V/GND point and pin 11 on the Z80. Test from any +5V point and pin 29 on the Z80. On the Z80, test the actual pins of the chip. Done If you still have access to a ‘scope, and it is a dual channel type, use one channel to monitor pin 26 on the...

Hang on a minute! That photo of the ‘scope screen showing the clock on pin 6 is showing a 6.4MHz signal :shock: . The NMOS Z80 is only rated for a maximum of 4MHz and in a ZX81/TS1000 should be 3.25MHz. Are you using a modern ULA module rather than an original Ferranti ULA? The waveform on ULA pin ...