Sinclair ZX80 / ZX81 / Z88 Forums

mrtinb wrote: ↑Tue Apr 03, 2018 9:29 pm Lambda 8300 with ZX81 ROM (I think).

I inserted a ZX81 ROM, but that does not work. Maybe the Lambda insists on a modified ZX81 ROM.

https://youtu.be/Eyz3EM5ADJY

I believe what you have in the video is the original 4K rom for the ZX80

EDIT:
(which I just now saw is also in the comments

There is a solution to ZX81s that don’t produce a ‘back porch’. In fact, there are a number of different solutions, both DIY, ready build modules and professional fitting services. These should work with a Lambda, if the problem is in fact a missing ‘back porch’. One of the popular modules is PokeM...

I've managed to source around a handful of original tapes for the Lambda / Power - and have started to do preservation, which means - Preservation of tape to TZX format - High-res scan of inlay - Photo of cassette - Register in ZXDB / Upload to spectrumcomputing.co.uk (SC) (for long term preservatio...

Update: kind of solved... and it points to the worst case scenario, a dying ULA I managed to source a working Lambda with a working ULA - loaded a few games without any problems. Switched the ULAs and now the "working" got unstable, and the machine in discussion got stable... With working ULA, both ...

I don’t think I’ve asked this, but apart from a multimeter, what test gear do you have? Also, excluding the keyboard connections, did you do any soldering or desoldering work on this board? Mark Only have a multimeter- but strongly considering an osciliscope. I have replaced the 7805 and added a ZX...

Will the internal 2kb RAM be disabled if you attach external 16K Ram - as with the ZX81?

/Thomas

The ULA runs at around 9V IIRC. So, if the DC supplies are okay, it’s got to be either a poor/intermittent connection/contact somewhere, or a problem with the ROM/EPROM. Or the Z80 is loosing its clock input. I’m assuming you don’t see any screen corruption, which is why you think the ULA is okay. ...

. Mark what do you think? Maybe it's one of the ICs that stops working after beeing warmed up. At least it looks like the ULA is working :-) What happens after resetting when it goes to black screen? Does it then work again? Does it only stop working when you use it, or will it go black, when you j...

Yeah, need more information. It does sound heat related. Is the +5V rail stable and in spec? The ULA runs off a separate supply derived from the input, not the +5V supply. So test the positive supply pin to the ULA. Are all the socketed chips firmly pushed into their sockets? Have all the pins been...

I might have misunderstood the info on 2kb.dk - he mentions tapes preserved as a83 files, but looks like they were never available for download anyway