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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

It's really frustrating waiting for components.

The 555s and 556 chips are sitting in Stansted Airport and have been for nearly a day.

I've pretty well proved that it's the first timer in the 556. The Threshold input is pulling the Discharge line down to ~2.5V. Lift the pin and the D line will bounce up to the correct 5V. The Threshold just goes to a comparitor and hence shouldn't draw much power at all.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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derkom
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Re: General Stuff(tm)

Post by derkom »

stephen_usher wrote: Sun Dec 19, 2021 10:16 pm The 555s and 556 chips are sitting in Stanstead Airport and have been for nearly a day.
Sounds quite similar to my most recent experience at Stansted.
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rubber_jonnie
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Re: General Stuff(tm)

Post by rubber_jonnie »

stephen_usher wrote: Sun Dec 19, 2021 10:16 pm It's really frustrating waiting for components.

The 555s and 556 chips are sitting in Stansted Airport and have been for nearly a day.

I've pretty well proved that it's the first timer in the 556. The Threshold input is pulling the Discharge line down to ~2.5V. Lift the pin and the D line will bounce up to the correct 5V. The Threshold just goes to a comparitor and hence shouldn't draw much power at all.
Before we were bought out, our office was at Stansted, we had a grandstand view when Trump arrived!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

Good news: The chips have arrived at the delivery depot.
Bad news: They're not going out for delivery until tomorrow.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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rubber_jonnie
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Re: General Stuff(tm)

Post by rubber_jonnie »

stephen_usher wrote: Mon Dec 20, 2021 7:33 am Good news: The chips have arrived at the delivery depot.
Bad news: They're not going out for delivery until tomorrow.
How very annoying!

Don't they know that some of us are looking forward to the next stage of this story!!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

:lol:
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

Oh, looks like the e-mail lied! :-)
Screenshot_20211220_094607.jpeg
Screenshot_20211220_094607.jpeg (13.07 KiB) Viewed 2127 times
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
Top
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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

I haz chips!
:cheer: :cheer: :cheer: :cheer:
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
Top
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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

Well, the new chip hasn't fixed things. I do at least have a serial clock now but for some reason the drain on the first 555 is constantly triggered and CV is a weird voltage. *sigh*

P.S. OK, this means that it's not being triggered, even though the signal coming in does seem to be going below 1/3rd Vcc. Going down to 1.2V with Vcc 4.72V)
P.P.S. Looking at the TI data sheet, the V-Trig voltage for the NE556N at 5V Vcc is typically 1.62V... *BUT* can be as low as 1.1V. So, with a Vcc of 4.72V this could be even lower with certain batches of chips.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
Top
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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher »

OK, theory confirmed. Putting a 10K resistor between GND and the data in pin (pulling the mean voltage of the data line to 2.5V, balancing the 10K pull-up allows the data pulses to go low enough to trigger the 555. So, I'm going to have to fit that on the back of the board.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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