Spectrum 128k Toastrack issue

[n8mfafie]

Hi all,

I've acquired a Spectrum 128k toastrack + a bundle of games and accessories.

It appears original and I don't think it has been used since the early 90's but apart from a duff enter key, it fired up ok and once the membrane was replaced, I was back in the 80s in Jetpac heaven.

Been reading and watching vids of the various mods and have ordered a few bits from ebay and retroleum, namely a PSU lead in-line switch, various capacitors (general re-cap bundle, jailbar and the beep level fix) and 5v regulator but am undecided whether to apply or leave as original as possible.

Transformer is a bit noisy once the plates warm up but the only real issue is the signal to the tv (using rf) occasionally blips for a second - drops to snow then black - then recovers and the program is still running ok. Is this a known issue?

Finally any other must-do mods for this unit?

Thanks

[1024MAK]

Hello and welcome

... the only real issue is the signal to the tv (using rf) occasionally blips for a second - drops to snow then black - then recovers and the program is still running ok. Is this a known issue?

Not that I am aware of. The RF/UHF output doesn’t fully meet the normal TV standard, so it could be your TV not being happy with the slightly non-standard signal. The RF/UHF output also suffers due to the crude way that the audio signal is mixed into the video signal.

Personally I would say getting a DIN to SCART RGB cable (assuming your TV/monitor/converter has a RGB compatible SCART input socket) is the highest priority. It produces a much higher quality image compared to RF/UHF or composite video.

As for keeping it original, only you can really answer that. Some of the electrolytic capacitors may need renewing due to them ageing. But unlike the earlier models, none of them are critical parts. Hence it’s safe to run them to failure.

However, if carrying out modifications means that you are more likely to use it, rather than sitting in a cupboard, go ahead with the modifications.

By “5v regulator” do you mean replacing the existing 78 series voltage regulator with a DC/DC converter / switching regulator? If you do mean this, yes, this is something that I recommend. It does significantly improve its energy efficiency and the computer runs cooler. Although that’s a disadvantage if you were intending to use it as a hand warmer

If you can’t use the RGB SCART method, then the modification to improve the composite video signal by changing how the audio is mixed into the video signal is recommended. Then the composite video signal is slightly better quality.

The other thing that most people want is a SD card reader and a joystick interface. Lucky that various modern interfaces / expansions are available that do both of these things.

Mark

[n8mfafie]

Thank you.

so it could be your TV

Possibly, it's a modern tv and they don't do partially tuned or interference as I remember from my portable 14". Any signal issues it goes black.

Personally I would say getting a DIN to SCART RGB cable

This is a great idea and negates the composite mod? I have a scart socket. Think I need the variant with the mono 3.5mm lead along with the DIN?

The computer will be used so I likely will replace the components - gives me an excuse to play with the de-soldering gun

By “5v regulator” do you mean replacing the existing 78 series voltage regulator with a DC/DC converter / switching regulator?

I think so - it's listed as 'MuRata OKI Switch Mode 5v Regulator for Spectrum 128 "Toast Rack'

I will research the sd card option. Two old tape drives were included but both have belt issues so I'm loading via an Android app for now.

[n8mfafie]

I did the re-cap yesterday along with the regulator, beep level and jail bar fix. The new scart cable has arrived and the picture quality is very good. I've ordered new ear / mic sockets as they're loose and don't always connect.

One issue has become apparent after the unit has been powered on for a while and only seems to affect the loading screen and 48/128 BASIC screens. The display starts to jitter or wobble badly with lots of black dashes appearing. Weirdly disappears if a game is loaded; the picture then looks clear and stable. I've attached a short low res video which shows the problem.

InShot_20241221_152253755.mp4

(1.5 MiB) Downloaded 132 times

I presume some other component is on its way out but no idea where to begin so grateful for any pointers

Thanks.

[1024MAK]

I think so - it's listed as 'MuRata OKI Switch Mode 5v Regulator for Spectrum 128 "Toast Rack'

Yes, that's a DC/DC converter / switching regulator.

I'll watch your video later.

Mark