Search found 623 matches

by Lardo Boffin
Sun Nov 19, 2017 11:08 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

PokeMon wrote:
Sun Nov 19, 2017 9:14 pm
Yes - I think this product have been upgraded with a fourth leg in the last 30 years. ;)
Cut it with a side cutter.
:D
by Lardo Boffin
Sun Nov 19, 2017 2:50 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

I got new sockets from Sell My retro:-

https://www.sellmyretro.com/offer/details/3473

They have four legs rather than the three in use on the zeddy. Do i just fold the unwanted one under or do i need to remove it? Currently I have reused an old one.
by Lardo Boffin
Sun Nov 19, 2017 1:59 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

I wimped out and bought one :( - I would have had to buy some bits in order to make my own.
by Lardo Boffin
Sat Nov 18, 2017 6:41 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

I would check for shorts near the data pins of the cpu, the track clearances are quite close around there, also the diodes near the keyboard connector some.of the traces run very close to the diode pads. Other than it not working it looks very nice, good job so far. Regards Andy Cheers Andy. I will...
by Lardo Boffin
Sat Nov 18, 2017 6:40 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

It's not polarised, any way is fine. Except upside down :lol: If you have a 'scope or logic probe, check Z80 address lines A14 and A15. Also is you have a 'scope, test the video/TV output pin to see if it is switching between the three levels (high = white, "mid-way" = black and low= low part of th...
by Lardo Boffin
Sat Nov 18, 2017 4:42 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

I got the 6.5mhz resonator from sell my retro:- https://www.sellmyretro.com/offer/details/ceramic-filter-~~-resonator-6.5-mhz-for-zx81-%28new-stock%29-3469 What is the correct alignment for this? Does it matter? I went with the same as an installed one (lettering facing the ULA). The zeddy assembly ...
by Lardo Boffin
Sat Nov 18, 2017 12:50 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

Thanks sirmorris. Although not sure how to test that... I need to make sure the ZX8-CCB is correctly tuned. Although it works fine / reasonably on all the zeddies i have tried it with. My plan is to double check what i ordered and how I labelled the bags and then triple check the soldering and for s...
by Lardo Boffin
Fri Nov 17, 2017 10:41 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

Switched it on and sadly nothing. Well, nearly - after a couple of seconds i get a brief flash of white and then it goes black again. :cry: :cry: The time delay between switch on and flash and death roughly corresponds to how long it takes to work out that it has 16k of RAM. 0D32F08F-AEC4-47F5-B9C6-...
by Lardo Boffin
Fri Nov 17, 2017 10:31 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

Some big bits added.

93A0A507-6923-4E83-B1B4-BA50DA8EB61B.jpeg
93A0A507-6923-4E83-B1B4-BA50DA8EB61B.jpeg (935.92 KiB) Viewed 92 times
by Lardo Boffin
Fri Nov 17, 2017 9:54 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1283

Re: ZX81 rebuild

Diodes and transistors.

503CDB09-BE8B-4092-8263-1CFE73108DBB.jpeg
503CDB09-BE8B-4092-8263-1CFE73108DBB.jpeg (952.42 KiB) Viewed 103 times