forum.defence-force.org

Posted: **Tue Apr 17, 2018 6:10 pm**

Hi ,

my atmos is out of order .

it stays stuck at the test pattern AA with a black case bottom right

I've allready replaced the via 6522 "A" with a new one

but still the same result...

i could hear some noize at startup then the "click" from relay, then nothing ... else that desesperate screen

any ideas ?

seb

Posted: **Tue Apr 17, 2018 6:59 pm**

To me that looks as when the memory is filled for testing just before booting, but I am not sure.

Did you check the memories to see if any chip gets too hot?

The noise and ""click" from relay" when starting is something strange... that does not happen in my Oric.

Posted: **Tue Apr 17, 2018 7:50 pm**

Hi,

rams aren't hot at all
so far i've changed rom , 6522A is new one
now i'm thinking about changing capacitors
and testing with diagnostic eeprom asap

here is the sound i speak about tape relay during via init after the memory is filled with 0xAA then 0x55

oric atmos boot sound.wav.tap: (236.28 KiB) Downloaded 350 times

remove .tap extension, file is .wav !!!

thanks for any support, any help grantly appreciated
seb

Posted: **Tue Apr 17, 2018 10:15 pm**

+1 for diagnostic ROM else the usual suspects are RAM chips - btw, very interesting rare chips Inmos Ims2600.
Do you have any modifications on back of the PCB? And one easy thing: check if the NMI button works i.e. its contacts are not permanently connected.

Posted: **Wed Apr 18, 2018 5:40 am**

It could simply be a bad contact on the pins of some socketed chips.

Try removing and reseating all socketed chips, giving a light brush on the pins with an isopropyl alcohol soaked Q-tip if they are slightly tarnished or dirty,

Sometimes that is all you need.

Posted: **Wed Apr 18, 2018 9:12 am**

hi,

thanks for the answers & clues

dram isn't hot
6522 is little hot (but not so much, i can touch it without burning)

i've forgotten to solder 1 pin on 6522, but no changes after soldered

every chip is soldered on board !
except the 6502 and also now the 6522

i'm waiting for another 6522 to test
also some 4164 dram...

so wait & see now....
sebastien

Posted: **Thu Apr 19, 2018 3:20 pm**

Hello,

some good news at last ,

the oric atmos is back on the tracks !

just a power problem ???

i just swap alim and it booted ! (no easily but yes)

Posted: **Thu Apr 19, 2018 8:07 pm**

seb wrote: ↑Wed Apr 18, 2018 9:12 am i just swap alim ...

You swapped what??? What da hell is "alim"?

Posted: **Thu Apr 19, 2018 8:46 pm**

alim = alimentation in french, power supply unit in english

Posted: **Fri Apr 20, 2018 4:41 am**

Yeah, I guess this is where we should have started. Verifying that the power supply is providing correct voltages should be the basic step in any troubleshooting.

What value of voltage did you read with the previous power supply?
I would guess that this is a classic linear one and you most likely would be fine simply replacing the capacitors.

In passing I gave a look at the Oric service manual and found the trouble shooting section interesting:

"Powering up (initialization) faults
If after powering up, the screen is covered with black horizontal bars or random patterns, this indicates that the contents of the ROM (language interpreter and operating system) have not been correctly loaded into DRAM."

This seems to match your symptoms however it does not list power supply issues as a possible cause but that does not mean this is not what is happening with your machine. The manual is alas severely lacking as far verifying that the power supply is functional.

Still might be worth a look, (cf http://www.le-grenier-informatique.fr/p ... .html#oric ).

Posted: **Fri Apr 20, 2018 1:13 pm**

NekoNoNiaow wrote: ↑Fri Apr 20, 2018 4:41 am "Powering up (initialization) faults
If after powering up, the screen is covered with black horizontal bars or random patterns, this indicates that the contents of the ROM (language interpreter and operating system) have not been correctly loaded into DRAM."

I would really want more details on this (I recall having read that sentence too). Which contents are copied into which RAM? The upper 16K of the address space are masked by the ROM chip contents (you cannot poke a value there), but the RAM is still there and usable if you have an external device which could drive the ROMDIS signal. That is what we do in games and demos to have access to the 64K of RAM.

The only case in which I know the Basic interpreter is copied into the high RAM is when selecting the corresponding option in Sedoric's boot menu!

So I am totally confused here

BTW if your Atmos is a bit picky when booting (you need to plug in and out several times or it takes too long) maybe it is worth to check if all the Service modifications have been applied. One was exactly for that. They are also in the Service Manual.
http://www.48katmos.freeuk.com/servman.pdf

Posted: **Fri Apr 20, 2018 4:20 pm**

Hello,

power supply is strange problem maybe hazard or short circuit, i've measured both psu, voltages seems ok
even with the new psu i've got the screen with vertical bars as in first
so i've replaced 3 capactitors (1uF,10uF & 220uF)
and boot is a little better now, not always good but better than before

i will take a look at service mods , thx chema

Posted: **Sat Apr 21, 2018 11:57 am**

hello !

Oric Atmos is booting fine now

but , not the first time is powered only white screen with CAPS
after 1st time , every boot is ok except a random character appears after ready prompt (very often)
as this oric has always do ...

things went really better after i changed the capacitors !

as my solder iron was hot, and me too

i do also the twin rom & composite mods

twin rom mod link :
http://oric.signal11.org.uk/html/twinrom.htm

video output is not as pretty as i wished but it s a test , based on this schematic for atari 2600 :
https://www.thefuturewas8bit.com/index. ... 0_comp_mod

as i dont kwow what is the value of R0* in this post
viewtopic.php?f=8&t=1130&p=11369&hilit=rgb#p11375
so i tried the atari 2600 mod ( they sell a small mounted pcb too)

i didn't do any service modification , especially the 63b to improve boot process
as in this oric , there is an undocumented modification on 6522 with a small green ceramic capacitor & resitor in parallel between pins 1 & 3 (pcb side) i forgot to take a picture

, i must re open again the oric for this...

is there something to do to avoid high temperature on 7905 regulator, i think it is really hot for nothing as in all orics ...
a psu modification maybe ???

thanks for help & clues
sébastien

Posted: **Sat Apr 21, 2018 1:07 pm**

Nice work, seb!
About the R0* in my old post - it depends on amplification of the particular chosen transistor - it should be in range 200 Ohms ... 2kOhms,
or maybe even more. It's not danger to experiment with any R value, the best is to use 10k trimmer and adjust the picture. I think you can get better image.
The hot in 7905 can be reduced with lowering of the input voltage, but it's matter of tests - I have Orics which work with 6V adapters and such which doesn't. IMO the optimal is ~7.5V.

Posted: **Sat Apr 21, 2018 11:22 pm**

seb wrote: ↑Sat Apr 21, 2018 11:57 am Oric Atmos is booting fine now

but , not the first time is powered only white screen with CAPS
after 1st time , every boot is ok except a random character appears after ready prompt (very often)
as this oric has always do ...

things went really better after i changed the capacitors !

Good news!
And yup, changing capacitors is almost mandatory if only to make sure the they do not leak and damage the circuit board, it is in my opinion the first thing to do to any old machine.

Still, this weird boot behavior is not normal. But I guess that to figure out what is going out you would need at least an oscilloscope.
If you do, then I would advise going through the Oric Service Manual as it lists the expected waveforms at many points on the board, that might help you figuring out what still needs fixing on your machine.

iss wrote: ↑Sat Apr 21, 2018 1:07 pm The hot in 7905 can be reduced with lowering of the input voltage, but it's matter of tests - I have Orics which work with 6V adapters and such which doesn't. IMO the optimal is ~7.5V.

Yup, the Texas Instruments datasheet confirms that the regulator expects a minimum of 7V, which by the way contradicts the Oric service manual which states that the regulator needs at least one volt above the supplied +5V voltage:

An unregulated +9 volt supply is fed into the computer from the plug-in external power unit. Regulation to +5 volts is provided by IC1 and associated components. IC1 is a negative regulator, however this does not matter as the dc supply in the computer is 'floating'. IC1 which is a 7905 requires 1 volt headroom.

But according to the datasheet (https://www.ti.com/lit/ds/symlink/ua79.pdf):

Code: Select all

Recommended Operating Conditions
Vl Input voltage  μA7905   –7 –25    (Unit: V)

So yup, 7.5V is likely the safest.

forum.defence-force.org

oric atmos boot stuck at AA pattern

oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern

Re: oric atmos boot stuck at AA pattern