Sinclair ZX80 / ZX81 / Z88 Forums

As the title says, I'm attempting to build a new ZX Spectrum, but I'm having some trouble locating all of the parts.

Thus far, I've got all of the resisters, diodes, transistors, and most of the capacitors. So I'm pretty much good on those. Also, I have sources for most of the ICs as well (including the ULA!).

However, the coil and crystals are another story.
I've found a source for the 14.000000MHz (X1), but they don't carry the 4.433619MHz (X2). I should mention at this point that I'm in the US, so the timing on these isn't exactly standard over here.
As for the coil... The parts list that I've been working with isn't that informative. It just says "SPECTRUM". I mean... Yeah. But, could we be a little more specific?

The last part I'm trying to find is the ROM. I probably need two of those, as I have another original Spectrum that isn't booting (Black border with thick black and white vertical bars). I've practically replaced all the ICs, with the exception of the ROM and IC14, and for the life of me, I can't think of what else could be wrong with it?
I might post about that later, but for now, I'm focusing on building the new board in hopes that it might lead me to the problem with the old.

Here's the parts list that I've been working with: https://www.1000bit.it/support/manuali/ ... html#note2

For the most part, it's been pretty good, though I've noticed some inaccuracies when compared to my original 3B board that I've been trying to repair. Generally, when such a discrepancy shows up, I tend to go with what's on the board.

In any case, any help would be appreciated. Thanks!

Here's an image of the progress I've made so far:

Crossposting? https://spectrumcomputing.co.uk/forums/ ... php?t=6743

I thought I recognized your avatar from somewhere!

Also, I think my soldering skills are improving? Just figured I'd throw as wide a net as I can. I also have a similar post at World of Spectrum (https://worldofspectrum.org/forums/disc ... rts#latest)

Sometimes you get different recommendations/responses from people who know different things. I try to share what I find.

Here is a link for your ROM question (you could find more with "ZX ROM to EPROM' search in www)
https://spectrumforeveryone.com/technic ... -spectrum/

Update: Thanks to the advice I've gotten so far, the crystals and ROM are on their way! I got the crystals from Mouser and ordered one ROM from Retrolium. Initially, I was holding off on that, as I wasn't familiar with any of the alternative ROMs, but Looking Glass seemed the most interesting/familiar to work with. I also ordered a speaker while I was at it. In any case, that accounts for most of the difficult-to-find components but still leaves the coil.

I took another look at the parts list I have and noticed the number 1703, looked that up on Mouser and came across these: https://www.mouser.com/ProductDetail/KE ... B33bvQY%3D
https://www.mouser.com/ProductDetail/Wu ... rG1aTiI%3D
https://www.mouser.com/ProductDetail/KE ... pKlC7eI%3D

Could any of these be equivalent to the original?

Hi DistantStar,
I was wondering whether you ever resolved your coil query, as I’ve been doing a similar build, and was wondering about alternatives to the original coils….

The coils were custom made for Sinclair… they were based on an available base/former, but the copper windings were to Sinclair’s specifications.

It is possible to carefully remove the existing windings, making sure you note the start and finish, direction and number of turns for each. Then obtain some enamelled transformer wire that is the exact same diameter. Then wind on the new windings so that they are the same as the original.

Other than that, the only sources are other ZX Spectrum boards, or occasionally someone rewinds some old ones and sells them on eBay…

In regards to differences with the parts fitted to an issue 3B ZX Spectrum 16K/48K/+ board, Sinclair was continuously ‘fine tuning’ the performance. See the service manual and the various different issue schematic diagrams to see the various changes.

In relation to the changes in the DC/DC converter circuitry, I give the final circuit design on my blog here. This is the recommended version of this circuit.

Mark