New project: An ACT Apricot F1 "barn find"

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stephen_usher
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Re: New project: An ACT Apricot F1 "barn find"

Post by stephen_usher »

Reflowing the solder made no difference so I pulled the SRAM daughter board and soldered an SRAM chip (plus the required capacitor) onto the board and it worked first time.

It looks like PCBWay either fitted a faulty chip or it was damaged by the soldering process. *sigh*

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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: New project: An ACT Apricot F1 "barn find"

Post by stephen_usher »

Note: NO BODGE WIRES!!!!!!!

HOW IS THIS POSSIBLE?!

Hehe
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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Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
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Re: New project: An ACT Apricot F1 "barn find"

Post by stephen_usher »

It's been running GEM for two hours now without issue. Looks like it may be working OK.
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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PhilC
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Re: New project: An ACT Apricot F1 "barn find"

Post by PhilC »

:cheer: :cheer: :cheer: :cheer:
If it ain't broke, test it to Destruction.
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stephen_usher
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Re: New project: An ACT Apricot F1 "barn find"

Post by stephen_usher »

Tonight I thought I'd had a cunning plan to stop the external floppy drive running all the time and have it only run when the disk was accessed (as the MOTOR-ON signal is always asserted), I'd use the HEAD-LOAD signal, as that should be asserted when data is required and "modern" drives spin up quickly enough.

I was thwarted, however. I didn't notice that it only asserted the HDLD signal when drive A was accessed. Bother!
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
Posts: 5580
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
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Re: New project: An ACT Apricot F1 "barn find"

Post by stephen_usher »

I'm slowly getting back into designing the hard disk interface emulation again.

I purchased a number of CD4020BE chips as they were advertised as 14 stage ripple counter chips and I need 13 bits of address to sequentially access 8K of SRAM. It wasn't until I started doing a schematic that I discovered that bits 2 and 3 actually don't come out on pins on the chip, only 1,4-14, so they're useless.

Instead I'm going to have to build something out of a 12 bit counter, the CD4040BE and a 74LS112 dual flip-flop (negative edge triggered). Those should be arriving today and I can prototype a circuit on a breadboard over the weekend. I've just got to work out a quick and dirty way of driving LEDs from the outputs so I can see that it's counting correctly. I can then use the signal generator on the new hand-held oscilloscope to clock the counter. I can use the top bit of the counter as an input to the first flip-flop, and the output of that into the second one. The output of this flip-flop can be inverted and passed into the reset, so both chips get reset when the top bit gets set.
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.
User avatar
stephen_usher
Posts: 5580
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: New project: An ACT Apricot F1 "barn find"

Post by stephen_usher »

Could someone advise me if for a temporary test just sticking an LED + 220 ohm resistor onto a TTL chip pin would work?
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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