Sinclair ZX80 / ZX81 / Z88 Forums

As I understand it, the AY chip and its associated parts were an 'optional extra' - yes, there are blank holes on the board ready for the parts,but maybe some were ready-fitted with it? Mine doesn't have it. There was a website showing the details of how to fit it but it doesn't exist anymore.

What about spraying the inside of the case of the rampack with conductive nickel(or copper) paint(expensive stuff,though!)? It is designed especially for RF screening? Or even sticking aluminium foil in it? (and connecting it to the 0v line , of course!!) The American versions of the rampack( TS1016...

Obviously the RAMPACK is generating noise - you will probably need to replace or add extra capacitors in the power supply part of it. I've had trouble with zener diodes self-oscillating in the past - that could also cause it!

I have a copy of the TS1500 circuit - albeit a poor quality one - and none of the ULA pins are listed as 60Hz or 50Hz - and as far as I know it was only sold in the US, so it would only be for 60Hz anyway... this ULA is totally different to the Zx81/TS1000 one, it is a square/four sided surface moun...

This was an idea a had a while back for a 'patcher' to force a TS1000/TS1500 to run at 50Hz , note that I haven't yet tried it, so no guarantees...

As far as I know, that should work.. but no good for a TS1500 as it doesn't use the sinclair ULA..:-( I did have an idea for an external unit to fit on the expansion socket which would make either the TS1000 or TS1500 run at 50Hz, by 'patching' 2 ROM addresses , haven't yet got round to building one...

Just to warn about using 'small' screen LCD tv's with 'vintage' computers - you may find that some horizontal lines are 'missing' - that's what happened to me when I tried a 7 inch colour LCD tv with a VIC20 when testing it(the VIC, that is) - it worked ok with a larger (17 inch) LCD tv and a normal...

I have seen these filters in SFE and CDA types - my ZX81 I've just peeked at has a CDA6.5 in it - as far as I understand it , the SFE type is for selectivity and filtering, such as the amplifying part of a TV sound IF strip or notch filter, and the CDA for the quadrature demodulator at the end.... w...

Does all other zx functions work ok, eg. what happens if you get an error , does it work with both fast and slow modes, does it need 'reactivating' under certain circumstances..are there any occasions when it won't work or even cause a crash......(haven't yet tried it but it sounds interesting)!! Ba...

What about making a modified ROM, moving the '£' to the spare/missing function on the 'V' and then its ok having shift+space as break, as in the spectrum!