New Member and New Oric Atmos Owner

If you want to ask questions about how the machine works, peculiar details, the differences between models, here it is !
How to program the oric hardware (VIA, FDC, ...) is also welcome.
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mikeb
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Re: New Member and New Oric Atmos Owner

Post by mikeb »

SpaceFlightOrange wrote:
Mon Dec 02, 2019 12:25 am
Hopefully some replacements will turn up this week.
If it's still no go, then I think we're back to first principles -- get out the continuity tester, checking all 8 "row/col" addresses from the ULA are correctly connected to the correct pins on the multiplexer, that the other 8 address lines from the CPU into the multiplexer are connected correctly, that they then connect to each and every DRAM chip, that each DRAM chip's data IN and OUT pins are tied to each other and to the buss, that the R/W line on each and every DRAM is being driven ... same with the RAS and CAS lines. You've changed almost every chip in this path, and it still isn't working ...

It's always possible to exchange a faulty chip in a working board, for a working chip in a now-faulty board :(

SpaceFlightOrange
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Re: New Member and New Oric Atmos Owner

Post by SpaceFlightOrange »

Thanks mike. I’ll get on that while I’m waiting.

I did check the dram lines when I socketed them but I didn’t check from the multiplexer to the ULA. But I’ll go back over everything.

omelette
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Re: New Member and New Oric Atmos Owner

Post by omelette »

Fascinating read, this thread. Not much to add except to say that I bought 2 8912 chips from China recently, for use in resurrecting some Oric-1's. They came well packaged in an anti-static tube. Removed one from tube, plugged it into Oric, powered it on and was treated to a constant tone, with no keys working. Plug the second one into the Oric and it worked perfectly! Imo, there seems to be little or no quality-control in operation from most of these cheap Chinese component manufacturers. So has Phil used to say on HSB, "let's be careful out there."

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Re: New Member and New Oric Atmos Owner

Post by SpaceFlightOrange »

omelette wrote:
Thu Dec 05, 2019 3:01 am
Imo, there seems to be little or no quality-control in operation from most of these cheap Chinese component manufacturers. So has Phil used to say on HSB, "let's be careful out there."
I think you’re right. Best guess the ram I have is because they all appear to work they can’t be managing the advertised speed.

I’ve just bought a NOS 8912 from a UK Supplier so hopefully it’s ok. I can’t test it unfortunately as I haven’t socketed this yet and I don’t want to go down that road unless I have to.

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Re: New Member and New Oric Atmos Owner

Post by SpaceFlightOrange »

signal-2019-12-08-085024.jpeg
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Thank You, and, Goodnight :D

RAM arrived from Bulgaria (Finally) NOS Fujitsu MB8264-15. It's been sitting there for a few days to be honest, but I was trying to get the Spectrum refurb done, but the keyboard was giving me some grief (its in a Lo>>Profile Keyboard case, and the tails had been badly repaired resulting in some solder tabs being destroyed, and when reassembling it, I struggled to get even pressure and the odd key didn't work).

I pulled the dodgy Chinese ram out and continuity tested all the address lines between the ULA and the Multiplexers, from the multiplexers to the ram, the address lines between the ULA and the CPU, the RAM and the CPU and the RAM and the VIA. all were ok

I then individually tested the new chips using DRAMArduino and fitted them. I booted using Mike's diagnostic ROM. on first startup I get nice straight vertical black and white bars. All tests up to the printer one passed. I stopped there because I haven't yet made the loopback connectors so that's the next thing.

Swapped the original ROM back in and started up fine, and "ping" and "explode" work! happy days.

So I now have a bunch of spares available (ULA, ROM, CPU, VIA, AY, and more RAM thats due to arrive). Unfortunately I have no way of testing the spare AY and I'm not desoldering the one from the Oric if I can help it. I am able to test the rest (CPU and VIA in the Beeb)

The original RAM was clearly bad from the beginning, evidenced by the dodgy $ being displayed randomly around the screen and the available memory only being 315 bytes free. Me shorting the regulator cured its headache for good, but how I never killed anything else (apart from the multiplexers, possibly? I'll re-test the originals), I have no idea!!

Thank you all so much for your support. Couldn't have done it without you.
Last edited by SpaceFlightOrange on Sun Dec 08, 2019 1:01 pm, edited 1 time in total.

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Vyper68
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Re: New Member and New Oric Atmos Owner

Post by Vyper68 »

Great result!

I bought my DRAM and spare ULA as well as a 8912 from Bulgaria. Does this mean someone has a load of Pravetz spares?
Bazinga!

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iss
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Re: New Member and New Oric Atmos Owner

Post by iss »

@SpaceFlightOrange: Great picture! Congrats for the result and happy time with your Oric.
Vyper68 wrote:
Sun Dec 08, 2019 12:30 pm
I bought my DRAM and spare ULA as well as a 8912 from Bulgaria. Does this mean someone has a load of Pravetz spares?
Yes, there should be lot. As I already said all chips on eBay with sellers from Bulgaria are fine. They are remains after Pravetz 8D production was stopped and someone was clever to get them for cents (or maybe for free?). I don't know personally the seller but it seams he is honest enough and reliable as source for Oric parts. IMO the prices are bit high but this is how the monopoly works. :(

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Chema
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Re: New Member and New Oric Atmos Owner

Post by Chema »

Great news! Congratulations. Enjoy your machine!

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mikeb
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Re: New Member and New Oric Atmos Owner

Post by mikeb »

Excellent news -- another one rescued :)

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Re: New Member and New Oric Atmos Owner

Post by SpaceFlightOrange »

Hi. Further update.

I made up some loopback connectors to run the full suite of tests from the diagnostic ROM. TL;DR They all passed but I observed some odd behaviour.

The loopbacks I made for the printer and keyboard were not using the standard connectors as I didn't have those available, so I used 2 5-way Dupont connectors for the printer and a 5- and a 3-way for the keyboard. Used a standard 7-pin din plug for the cassette port loopback
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Keyboard loopback on the left, printer on the right

I pulled the board out and swapped the ROM over, and when I powered up, I got the vertical bars as always, but nothing else. I swapped the ROM for ISS's diagnostic ROM and that worked fine. swapping Mike's ROM back in had the same effect, but on second try it started up ok.

All tests passed up to the point where I needed to fit the loopback connectors (printer and cassette) I fitted these but Test 8 (Port A loopback) failed. my first guess was that it failed because I installed the printer loopback by fitting each of the 2 connectors separately. a retry and successful fitting of both connectors simultaneously, and test 8 passed. the result from here from all tests passed. Great news.
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IMG_0599.JPG
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next thing was to swap out the RAM and replace it with the other batch of NoS TI 4164's that turned up in the week. These had all tested ok with the DRAMArduino. These gave a more common pattern on startup but got the Atmos got stuck again. another try and it started. I only did the RAM tests but they passed.

I then tried my spare ULA. I couldn't get the machine to start up at all this time. put the original ULA back in and got exactly the same result!! a very corrupt screen. I swapped out the ROM and eventually it started up. I then replaced the original RAM and again it was fine.

Any thoughts? my initial guess its a reset issue.

also, I'm now 100% certain that the RF output is not working, so I'd like to diagnose that. all I get is a change in the noise parttern when the machine is turned on.

Thanks

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mikeb
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Re: New Member and New Oric Atmos Owner

Post by mikeb »

SpaceFlightOrange wrote:
Sun Dec 15, 2019 11:30 am
... but on second try it started up ok.
You may indeed have a reset issue, check/replace the capacitor C21 (1uF/10V) -- or next time it "hangs", manually short CPU/6502 Pin 40 to Ground (CPU Pin 1 or 21) with a short wire -- just dab on and let go, if it then resets, the reset is definitely not holding in the reset state long enough for power to stabilize.
SpaceFlightOrange wrote:
Sun Dec 15, 2019 11:30 am
that it failed because I installed the printer loopback by fitting each of the 2 connectors separately. a retry and successful fitting of both connectors simultaneously, and test 8 passed
Yes, the prompts are there for a reason, only fit stuff when prompted, and then fit everything it asks for :)

I am slightly disturbed by the "HRIC Diagnostic ROM" status line, do you always see that, or just sometimes (bad EPROM burn or still a lurking problem?)
SpaceFlightOrange wrote:
Sun Dec 15, 2019 11:30 am
I'm now 100% certain that the RF output is not working, so I'd like to diagnose that. all I get is a change in the noise parttern when the machine is turned on.
On the official circuit, all the 74LS chips from the ULA's RGB output, heading right across -- they could also have been damaged in the overvoltage incident. Also, there is a PROM in there, which is not easily replacable/programmable (it's a high speed PROM used to generate the colour signal for PAL). I don't know if anyone has a stash of new spares for these (like the ULAs from Bulgaria).

Apart from people with old TV equipment, the UHF output isn't much use anyway -- and the quality is nowhere near as good as your lovely crisp RGB SCART picture, so you'd be repairing that purely for completeness, rather than utility? :)

EDIT to add: Divide the faultfinding in two here -- can you check to see if there is a composite video signal going INTO the modulator. If you look on a scope, it's quite a distinctive video signal. Or, if you have a monitor with a composite in (RCA/Phono style socket) you could connect a temporary lead -- the picture quality may not be great, as it's not intended to drive a monitor -- but should show if there's something. You'll need a ground, too, off the modulator body (or 0v on the board).

This should tell you if it's the modulator not modulating, or that has no input to work with.

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Re: New Member and New Oric Atmos Owner

Post by SpaceFlightOrange »

mikeb wrote:
Sun Dec 15, 2019 6:05 pm
[You may indeed have a reset issue, check/replace the capacitor C21 (1uF/10V) -- or next time it "hangs", manually short CPU/6502 Pin 40 to Ground (CPU Pin 1 or 21) with a short wire -- just dab on and let go, if it then resets, the reset is definitely not holding in the reset state long enough for power to stabilize.
I replaced C21 at the beginning when I did the regulator, I know the original seems fine (im using it in another circuit :lol: ) and the replacement tested fine on my little tester, but I'll have a look see if I have another replacement.

For some reason it never occurred to me short pin 1 and 40 at the time, because we went through that during diagnosis earlier in this thread :oops: I'll do that.
mikeb wrote:
Sun Dec 15, 2019 6:05 pm
SpaceFlightOrange wrote:
Sun Dec 15, 2019 11:30 am
that it failed because I installed the printer loopback by fitting each of the 2 connectors separately. a retry and successful fitting of both connectors simultaneously, and test 8 passed
Yes, the prompts are there for a reason, only fit stuff when prompted, and then fit everything it asks for :)
Sorry, I wasn't being clear, I meant the two connectors on my printer loopback, its split into two lots of 5 pins. second time round I got all 10 pins connected simultaneously. I did fit everything at the right time (printer and cassette loopbacks, for example)
mikeb wrote:
Sun Dec 15, 2019 6:05 pm
I am slightly disturbed by the "HRIC Diagnostic ROM" status line, do you always see that, or just sometimes (bad EPROM burn or still a lurking problem?)
I never noticed that! I've just verified the ROM and yup, its on there!! not sure whats happened, It auto verifies after a burn. I've compared the rest of the ROM and its just that byte that's different.
Screen Shot 2019-12-15 at 19.02.41.png
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The image taken from the ROM is on the right.
mikeb wrote:
Sun Dec 15, 2019 6:05 pm
Apart from people with old TV equipment, the UHF output isn't much use anyway -- and the quality is nowhere near as good as your lovely crisp RGB SCART picture, so you'd be repairing that purely for completeness, rather than utility? :)
To be honest, it is just for completeness :D
The RF was faulty when I got it so I just used RGB until everything else was sorted; but yes, the over voltage could have made things worse. I'll verify the composite output and take it from there!

Thanks Mike!!

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Re: New Member and New Oric Atmos Owner

Post by mikeb »

I never noticed that! I've just verified the ROM and yup, its on there!! not sure whats happened, It auto verifies after a burn. I've compared the rest of the ROM and its just that byte that's different.
Well, I'd suggest your EPROM burner/verifier is next on the list of things to fix ;)

Seriously though, I have had this happen accidentally while reading an EPROM -- the programmer's microcontroller crashed, and somehow managed to zap (program) the first byte of the chip.

Not happy.

I was reading the firmware of a device to back it up! Fortunately, this was in the verify phase, so I'd read it correctly, and knew what value it SHOULD have been before destruction. Needless to say, I didn't realise until I put the chip back in the device and got an error on the display. Had to make a new chip from the backup rather sooner than expected.

I know: If it ain't broke ... but the device was open for other repairs at the time, so it was an opportune moment to clone the chip.

It really shouldn't verify back with one byte different though. That's another level of wrong ....

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