exxos's Atari, Amiga & retro forum

stephen_usher wrote: 05 Sep 2023 19:20

rubber_jonnie wrote: 05 Sep 2023 17:34

Yeah, I was prepared to use a cap, but the pic was fine as it was, though the article I linked to does mention the cap too.

The picture will be fine, until the DC offset kills the ULA! The cap is there to decouple the circuits electrically.

Yeah, did some thinking last night and you're right, the ULA is clearly good, so I'll fit a cap when I pull it apart to do the keyboard membrane. I almost certainly have a suitable cap, and for want of protecting the ULA it's not worth leaving it out.

@alexh

I had a Spectrum+, so the keyboard was that one (even if the design seems to have slightly changed):

https://www.ginger-electronic.com/en/re ... _soldering

Ok, so I got round to fitting the 100uF cap in place of a straight wire and the image quality is just as good:


And the legs were long enough that I could just fit it in as is and snip off the excess :)

I also removed the faceplate and cleaned the case in readiness for the new keyboard membrane:


I've splashed out and ordered a new faceplate too as although the old one came off ok with a little application of heat, it's looking a bit beaten up on closer inspection.

Hopefully both will arrive in the next few days.

The new membrane arrived today, seen here with the old, which is incredibly brittle:


I installed it quickly and tested, then did a game load test and it all went perfectly:


The faceplate is still the old one, but will do fine for now and has just enough stick left to stay in place.

I then decided to composite mod the Spectrum +, which took just a few minutes and the output was great:


However, 10 minutes down the line, the display suddenly changed to this:


I thought at first the ULA had died, but I tested it in the rubber keyed machine and it all worked just fine, so now off to find a Spectrum 4S schematic to see what could have gone wrong. I am grateful it's not a dead ULA though.

I have tried blind typing Load "" but nothing is loading, which is a bind.

So, time to try and figure out why it just died on me. Ho Hum...

Have you checked the -5V and 12V rails? Could be the transistors generating those voltages (T4 and T5 from memory) as they often go. (Most often T4)

stephen_usher wrote: 07 Sep 2023 15:19 Have you checked the -5V and 12V rails? Could be the transistors generating those voltages (T4 and T5 from memory) as they often go. (Most often T4)

I just pulled them and ran them through the tester. T4 looks like this:


So I've ordered replacements for both, even though T5 comes back as ok.

So good call sir :)

If you like playing with spectrums that don't have HDD/FDD I can recommend the android app that finds the tape images online and then can playback via headphone jack. Some apps have incorporated OTLA+ which can accelerate game loading to just 15-30 seconds instead of minutes due to better snr.

alexh wrote: 07 Sep 2023 17:20 If you like playing with spectrums that don't have HDD/FDD I can recommend the android app that finds the tape images online and then can playback via headphone jack. Some apps have incorporated OTLA+ which can accelerate game loading to just 15-30 seconds instead of minutes due to better snr.

My current Android doesn't have a headphone socket, and I can't recall if it came with a USB C to audio adapter. I do have an nVidia Shield tablet that does though and I may have the app already installed. I do have an Arduino based tape emulator too. Need to check my tablet.

I've loaded games from my PC headphone socket before (using an emulator with real tape sounds) - you just have to make it mono (accessibility settings in Windows) and crank up the volume. Cumbersome though :D

I can heartily recommend the DivMMC Future from The Future Was 8 Bit

rubber_jonnie wrote: 07 Sep 2023 17:30 My current Android doesn't have a headphone socket, and I can't recall if it came with a USB C to audio adapter. I do have an nVidia Shield tablet that does though and I may have the app already installed. I do have an Arduino based tape emulator too. Need to check my tablet.

A cheap £5 MP3 player works too. You can batch convert from TAP/TZX to accelerated WAV using OTLA+