Spectrum + 128K with no toroid

Post Reply
Lardo Boffin
Posts: 1078
Joined: Sat Nov 26, 2016 2:42 am

Spectrum + 128K with no toroid

Post by Lardo Boffin » Mon Dec 02, 2019 11:36 pm

Hi all

I recently bought a toastrack spectrum and after opening it was surprised to see no toroid. I have only seen the insides of 4 or 5 of these so not sure if this is a common thing?

33895214-8136-4F6A-AAA5-DDB517D19AE1.jpeg

It does not obviously look like it has been removed. Although there was a repair / warranty sticker on it (not details though).

It works fine apart from a slightly jumpy video on RGB SCART on one of my TVs (most are fine). Research suggests it may be a similar issue to the ghosting on the +3 (https://spectrumforeveryone.com/technic ... compliant/)

I have seen a few photos of them minus toroid on Spanish websites.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

User avatar
1024MAK
Posts: 2565
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Spectrum + 128K with no toroid

Post by 1024MAK » Tue Dec 03, 2019 1:34 am

The toroid is actually part of a filter circuit to suppress noise escaping on the power supply input. The toroid would have had two windings on it. Only fitted where deemed to be needed...

The 128k, +2, +2A, +2B, +3 etc were never designed to control the SCART signalling pins...

They work fine if your telly can be manually controlled by a remote control or menu option (like one of mine 8-) ).

Otherwise you need to provide a proper +12V and a higher current 1.5V to 3V (to feed 75Ω input impedance). Either from an external supply or by making changes to the computer and the DIN to SCART lead or both.

Mark

Post Reply