Search found 76 matches

by mikeb
Wed Jun 19, 2019 5:04 pm
Forum: Technical questions
Topic: Telestrat failure?
Replies: 14
Views: 508

Re: Telestrat failure?

Depends. Mask ROMs are extremely reliable Very true, and the clue is in the name. Unlike UVEPROMS, Flash-ROMS (analogue storage, see above), Mask ROMS are not programmed as such, but the data is put there at time of manufacturer by including, or not including, metal/silicon bits of the chip design ...
by mikeb
Sun Jun 16, 2019 7:38 pm
Forum: Technical questions
Topic: Telestrat failure?
Replies: 14
Views: 508

Re: Telestrat failure?

Also UV-EPROMS (the ones with windows on) have varying voltage requirements. Not all programmers meet the spec and so the chip may not be fully programmed, which can lead to early failure. The data stored isn't digital/binary after all, but a level of analogue charge. It's only rendered binary by a ...
by mikeb
Wed Jun 05, 2019 5:11 pm
Forum: Hardware hacks and extensions
Topic: Composite video mod?
Replies: 12
Views: 363

Re: Composite video mod?

and a 'conversion table' with 4-bit accuracy (the PROM). The "conversion table" has small snippets of a sine-wave (very rough) in it, indexed by the two-bit counter from IC24, and also depending on the 3-bit value of colour (from 0 0 0=black to 1 1 1=white) produces the same 4.43MHz sine wave, but ...
by mikeb
Sat Jun 01, 2019 8:36 pm
Forum: Hardware hacks and extensions
Topic: Atmos with a Slice of Raspberry Pi
Replies: 7
Views: 318

Re: Atmos with a Slice of Raspberry Pi

I was thinking the use of the DPDT switch along with using diodes on the 14 way y cable I'll have to make would help isolate the Oric from the Teensy. I don't have a working rig yet so what I'm not sure about is if I mechanically isolate the 5v and 0v lines would the 4051 signal pins still have a c...
by mikeb
Tue May 28, 2019 4:59 pm
Forum: Hardware hacks and extensions
Topic: Atmos with a Slice of Raspberry Pi
Replies: 7
Views: 318

Re: Atmos with a Slice of Raspberry Pi

... wire a DPDT switch to a decent 2A 5V PSU and bypass/remove the regulator altogether and simply wire the switched 0v/5v lines to both the Pi and Oric - any thoughts on if this presents any concerns? That's a better approach, IMO, once you are on the "inside" of the regulator, supplying ground an...
by mikeb
Mon May 27, 2019 5:22 pm
Forum: Technical questions
Topic: 65c22
Replies: 15
Views: 488

Re: 65c22

I see, thanks for the link/context The above diode suggestion by @iss will solve the problem (make sure it's in line with only the 65C22 leg, as per my caution on physical layout issues) -- the 65C22 having "totem pole" output means it will try and drive the line both HIGH (when idle) and LOW (when ...
by mikeb
Sun May 26, 2019 4:48 pm
Forum: Technical questions
Topic: 65c22
Replies: 15
Views: 488

Re: 65c22

The pull up resistor also connects to the 6502 IRQ input, and any external peripherals. Removing it may well have unintended effects. What is the source of this knowledge that the resistor should be removed? The only other thing to check is the physical order/routing of the track, you may find that ...
by mikeb
Sun May 26, 2019 4:41 pm
Forum: Hardware hacks and extensions
Topic: Atmos with a Slice of Raspberry Pi
Replies: 7
Views: 318

Re: Atmos with a Slice of Raspberry Pi

Voyageur wrote:
Sun May 26, 2019 12:04 am
There is not much room inside the case of the Oric.
I didn't address this most obvious point :oops: It would take some serious crowbarring to get it in.

I do think the suggestion for building it into an Oric/Atmos case (minus the original motherboard) is the best idea.
by mikeb
Sat May 25, 2019 6:26 pm
Forum: Hardware hacks and extensions
Topic: Atmos with a Slice of Raspberry Pi
Replies: 7
Views: 318

Re: Atmos with a Slice of Raspberry Pi

Can I/Should I pull 5V for the Pi directly from the Oric's regulator I would say no -- a fully working PI may peak higher than that 140ma, and then you've got your USB peripherals etc. which need power. If the power sags, the PI will start to misbehave, if you're lucky you'll get a "rainbow patch" ...
by mikeb
Tue May 21, 2019 6:14 pm
Forum: Technical questions
Topic: Oric-1 Repair
Replies: 36
Views: 1762

Re: Oric-1 Repair

Here is the matrix and the keys are on the same row: They're not in the same row, hence my puzzled comment. Original posting 7 failed keys: Right: "8 0 - =" and Left: " , . / " By your picture (which is in a different (more logical order) compared to the service manual) :- "8,0,/ and =" are in one ...
by mikeb
Mon May 20, 2019 6:08 pm
Forum: Technical questions
Topic: Oric-1 Repair
Replies: 36
Views: 1762

Re: Oric-1 Repair

An odd combination of characters, they seem to be grouped physically (by proximity) rather than by organization in the row-column matrix (see the Service Manual .pdf).

Wait, you got a 10 key? What advanced model of Oric is this? :)
by mikeb
Sun May 19, 2019 8:05 pm
Forum: Technical questions
Topic: Oric-1 Repair
Replies: 36
Views: 1762

Re: Oric-1 Repair

although the left and right shift keys do not work on all keys I can get by using alternate shift keys to cover the entire keyboard. That is a pretty odd symptom. The shift keys (and FUNC, CTRL) are on a common "column" of the keyboard matrix, with nothing else. So are you seeing any problem with C...
by mikeb
Sat May 18, 2019 5:32 pm
Forum: Technical questions
Topic: Oric-1 Repair
Replies: 36
Views: 1762

Re: Oric-1 Repair

After powering it up (at the wall, and plugging in), if you get nothing beyond the black-white bars, try briefly shorting pin 40 of the CPU (Reset) to any ground point (e.g. Pin 1 or 21 of the original CPU or pin 1 of 6522 -- I don't know the significance of the pin-1-cutting comment you posted, but...
by mikeb
Sat May 18, 2019 5:25 pm
Forum: Technical questions
Topic: Up to date Oric-1/Atmos Schematic
Replies: 4
Views: 200

Re: Up to date Oric-1/Atmos Schematic

And there's Oric Owner, Issue 05 (Page 44-45, centre pages), which is quite readable.

http://www.defence-force.org/computing/ ... ner_05.pdf
by mikeb
Fri May 17, 2019 4:45 pm
Forum: Demos
Topic: OricExos - making the impossible
Replies: 143
Views: 17034

Re: OricExos - making the impossible

... buy four Orics, which was not especially cheap, as well as design and print PCBs manually because there were no PCB design tools available on the Oric. Oh yes, at about £149-£169 (and those are 1980's pounds, not the current ones!) it would be a bit crazy, financially. However, PCB design tools...