Of all the retro channels on KZfaq, this is my favorite. I love how there's no "big theme", it's just a normal man in a a basement fixing some old computers. I love it.

Glen, different types of capacitors suit different frequency bands. It's a vast topic and I would be happy to go through it with you but for this comment let's just say - no capacitor is ideal, they all have parasitic properties (resistance, inductance) - parasitic inductance makes their behaviour transition from 'capacitive' (= impedance decreasing with frequency) to 'inductive' (= impedance increasing with frequency) and there's a frequency which marks this change of behaviour - if you take different capacitors with the same nominal capacitance but different parasitic inductance you'll get different frequencies at which the behaviour changes. The parasitic inductance is linked to the physical structure of the component so wider/larger is associated with lower inductance, longer terminals/legs (through-hole vs SMD) with higher inductance. - placing components in parallel gives you the sum of the capacitance and the 1/Lp = 1/L1 + 1/L2 of the inductance (kind of like for resistors) - as technologies, electrolytic generally offer the highest capacitance for component but ceramic offer the lowest parasitic inductance per nominal capacitance. This means that at "high" frequencies electrolytic cap are likely to have a significant higher inductance than at lower frequencies while ceramic ones keep decreasing (so to speak). At 10s of MHz the nominal capacitance value of electrolytic does not give you a good guide of their actual behaviour while ceramic capacitors are typically characterised for such frequencies and, even if their nominal capacitance is lower, the effective impedance is lower than the one of electrolytic. - knowing the frequency band at which you want the component to show low impedance can guide you in the choice of technology and different capacitors in parallel work together to give you the desired impedance in each band of interest I hope not to have confused you!

Hi Glen, good to see this , as I just bought a 48k Plus as spares/repair, and re-capped it and got it working. Then I done the 5v regulator mod, and the jailbar mod also. I didn't find the jailbar mod made a lot of difference though. Also the composite mod, but used a capacitor across the output. Very interested to see if the 1uf axial caps would improve my one too... I'll drop it round to you :)

Great work! Only thing I might have done differently is to replace the regulator with a new 78S05 rather than a switch mode regulator. That Traco may be the reason you were seeing 10-30khz noise with the oscope, and could potentially contribute to the jailbars.

The music on Dizzy is actually coming from the ULA/beeper... Yes it is possible to emulate multi-channel sound on the 48 (kind of!)

I don’t think we were hearing the AY chip there. I’m not 100% sure but I think the AY chip was only really used on 128k games. The AY has a much “fuller” sound than what we heard there. Pretty impressive of the coders to get what sounded like multi voice audio out of the old beeper. Some of the later Dizzy games used the AY chip, like Fantasy World Dizzy for example.

good video..glenn ...i thoght you did a good job!..those jailbars seem to be somewhat of a pain to eliminate!

Adding that many 1uF caps could cause the regulator to take longer to start up. a modern switcher with "soft start" would help.

Those little rotary resistors are notorious for breaking once they get old. Trash 80/Dragon computer use the same parts and they break all the time.

The 128 +2 has the voltage regulator on a heatsink and connected to the board with a plug and wires like the toastrack.

Nice.

Thumbs up from me - nothing Amiga related

The music in the game was not coming from the AY chip. You switched to 48K mode which does not access the AY chip. That was all pure Spectrum 48K buzzer. You can also very easily tell when the music is AY as it's a lot clearer.

The audio cable holding you did; was that shorting both channels to make a mono type mode?

I made the sound mod to my toast rack now I don't get any sound at all :(

That Traco regulator is 1A rated, it is a bit borderline for the Toastrack, better to use the 1.5A version, or even better, 2A unit from Recom.

Nice job with spectrum image quality finetuning. But, is it just me, or is there a slight postprocessing blur forgotten througout most of the video? E. g. 3:33 around G, V, B Keys.