What have I done wrong?
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- Posts: 2173
- Joined: Sat Nov 26, 2016 2:42 am
Re: What have I done wrong?
I put the ceramic cap here:
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Re: What have I done wrong?
That looks like a tantilum bead. I have a small round circle.
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: What have I done wrong?
I had high hopes, but that didn't solve it.
All that I've learned - https://msknight.com/bbc/index.html#zx81
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- Posts: 2173
- Joined: Sat Nov 26, 2016 2:42 am
Re: What have I done wrong?
It is just a normal ceramic cap. Not sure why it arrived in a shiny case!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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- Posts: 2173
- Joined: Sat Nov 26, 2016 2:42 am
Re: What have I done wrong?
I had to mess around with different values to get it to work.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
-
- Posts: 2173
- Joined: Sat Nov 26, 2016 2:42 am
Re: What have I done wrong?
I think Manic Miner is pseudo hires rather than true hires.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Re: What have I done wrong?
That does match with me. Manic Miner worked, JB Racing didn't.
After many muttered words, desoldering the 100pF and fitting a socket, I had a 220pF and that works.
It is throwing up calibration issues with the RGBtoHDMI with the wespi either in or out, but I'll work that out.
Thanks for the help!
After many muttered words, desoldering the 100pF and fitting a socket, I had a 220pF and that works.
It is throwing up calibration issues with the RGBtoHDMI with the wespi either in or out, but I'll work that out.
Thanks for the help!
All that I've learned - https://msknight.com/bbc/index.html#zx81
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- Posts: 2173
- Joined: Sat Nov 26, 2016 2:42 am
Re: What have I done wrong?
Excellent!
It’s likely the RAM in your mod is faster than the stuff I use therefore needing the higher value cap. I think it works that way round anyway!
It’s likely the RAM in your mod is faster than the stuff I use therefore needing the higher value cap. I think it works that way round anyway!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: What have I done wrong?
Pin 27 may have a 10kΩ connected to +5V (pin 28) because this design copies a schematic on the web. None of that affects hi-res.
No need for tantalum capacitors, ceramic types are suitable. Some multilayer ceramic types may look like tantalum types.
Yes, we can't tell you what value will work because it depends on how quickly the RAM chip switches it's outputs. Too low or too high a value of capacitor and it won't work correctly.
QuiteLardo Boffin wrote: ↑Mon Jan 15, 2024 11:27 am It’s likely the RAM in your mod is faster than the stuff I use therefore needing the higher value cap. I think it works that way round anyway!
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.