Most liked posts in thread: Voltages wondering about the Oric-1 - Just to be sure before I toast it!

Putting 15v into an Oric is not in itself a disaster as long as it didn’t go beyond the 7905. The electrolytic capacitor at C8 should have exploded as they are normally quite a low voltage ( 10v or 12v ) so it wouldn’t be able to cope with more volts for long. The 7905 can take up to 30v input but it would get insanely hot trying to get the surplus power dissipated as heat.
All that being said, if you found 8.8v ( 9v in reality ) and 3.8v elsewhere something has gone very wrong. 9v on a Oric will kill everything.
So quick and dirty check on the resistance on some of the logic IC’s which should be around 270 Ohms if it’s low like 160 Ohms then desolder a couple and check them in your EPROM programmer.
Also check the RAM and see if they heat up when the Oric is powered on.
Finally bud if you want it fixed and don’t have the spares then you are welcome to send it to my workshop. I have a couple of ULA’s and 6502’s and 6522’s and an AY chip. I have a 65c02P4 as well that I use for testing so I have all the bits bar the PROM for the RF output.

 

I have tested the resistance from all the chips including the 6502, 6522, AY, ROM, RAM etc.
They all give 180ish Ohms. It would mean they are all fried? I don't think so, since I have a good looking activity between some of them with my scope, at least for the Address bus.

There is no overheating, I have tested all the chips with an IR thermometer gun.

So, for the moment I have no hints of who the culprit could be. I'll focus on the ROM chip since it cannot be read with the programmer. Can it be?

Thanks for you help Rich, I already have ordered (from what appears to be a good source here in France, not from China) a 6502, a 6522 and a 27C512 to program a test ROM and/or BASIC ROM, and to do some swapping with the main chips.

I'll keep you updated.

 

Well the Ohms test isn’t 100% it was just something I picked up on the Acorn Stardot forums. If you have a logic analyser or scope and can see activity it would be handy if you could check the video output and see what is presented on screen.
I have a couple of Oric test PCB’s left if you wanted one to build one.

Plus, just a gentle reminder you need the 2Mhz version of the 6502 and 6522 so that’s a 6502A and 6522A in case you weren’t aware.

 

There is a guy in Bulgaria selling the ULA's ( most Oric spare chips come from there now ) They are NOS from when they made the Pravetz 8D clone of the Atmos. I have bought one from there previously and they are genuine chips. I have a couple spare but it might be easier to get one from Bulgaria now we are outside the EU and Customs Union. All the other chips ( save for the PROM used to generate the RF output ) are standard and easy to find. The PROM is impossible to find unless you strip one from another Oric. They are less important really as most people use the RGB now. In fact you can live without all the Chips in the top quarter of the PCB under the Modulator as they and the second crystal are all to generate the RF signal.

 

I hear from Richie, Klyde, that a certain Oric-1 object has already arrived at chez Richie!

I do hope sincerely that your parcel still arrives safely, mom ami, as no-one likes to hear of retro goodies parcels going missing or being damaged in the post... they're way way too precious.

Bonne chance.

 

I didn't have a lot of time to look after the Oric these days, too much work! But it is cooling down in July (not the weather), so I'll let you know when I have something new!

 

Thanks, Baz for the news about the Oric orphans, now shipped to good homes (I'm sure) and making some good guys happy. Much happier I am because the income of that huge sale went for a very good cause, your wedding! Amazing! So happy for you and Bev, once again the Oric computers have shown their real usefulness, set aside becoming great and colorful doorstops. ;-) I am joking, I learnt to love the Orics!

 

Cheers, Daz.

Without those Oric sales I fear I would have been sent up chimneys cleaning the buggers!



Baz contemplating how many more chimneys he needs to clean before being let back into the marital maison.

 

Now that the RAM chips are replaced with new ones, I have white still rectangles on a black screen display. You guess it, it is not fixed yet.

After a quick look at the oscilloscope, the RAM signals seems ok, excepted the Write signal (floating high), the 6502 have some signal pins stuck high, the 6522 chip appears to have almost all its signals stuck high.

Next time I'll focus on the 6522, and maybe replace it too.

To be continued...

 

Good idea, I will.

 

Here we go guys, I nailed it!

First, the white rectangles I was having before, the Oric used to be stuck on that screen:


And the culprit was... a bad solder joint on the ROM socket pin 12!
I found out by first taking the ROM chip out, then checking all the connections with the oscilloscope and multimeter.

Once the socket was replaced with a good quality one... Result!


I can now ZAP, PING, SHOOT and EXPLODE the Oric!


Last thing, I have a quite loud and constant humming from the speaker. I'll try to have a look at the sound circuit, maybe a bad capacitor? Any idea?

Next step will be to hook up a tape recorder and try to load some games, and replace the ROM with a 1.1 BASIC version, like @Vyper68 suggested.

Many thanks to all of you guys who helped and supported me with the fixing attempt, especialy Andy for the example pictures above, and @Vyper68 who sent me a ULA after the one I ordered from Bulgary was lost during its journey through the Carpathians?!

ZAP!

 

Thank you Andy, I know that you particularly like this machine, I hope I will appreciate it as much as you do.

Cheers!

 

Richie will give you all the correct voltage readings at the various points, Manu.
I've no idea if those 15V applied will have fried anything - and of course it may have been damaged before if it has arrived untested. I wish I had known about you having this and I would have sent you a RGB/Peritel cable I had for the past 2months or so - I sold it last week!
As I say, Richie will help and all I can confirm is the correct voltage to be supplied is 9v centre positive, mate.
I do hope we soon have this little beauty up and running real soon.
I have some notes on the voltage regulator somewhere and if I find them before Richie replies, I will post them, buddy.
BON CHANCE, MON AMI!

 

This is so much in Richie's territory it hurts!

Sorry to hear that despite all your best efforts so far you have a dead Oric-1 there, Manu.

Here's hoping Rich can kickstart the recovery, mate.

He's always performed miracles with my micros in the past so hopes are high.

Keep the faith, buddy.

 

The resistances are consistent, I guess it is ok.

I don't have a logic analyser, but various multimeters, logic probes, and a medium quality but handy 25Mhz 100Msa scope.
About the video output, the 64uS sync signal is present on the ULA but no RGB signal. Do you want me to test the RF out?

Yes, I'd like to have a test PCB please. I'll send you my details.

I have ordered Rockwell 6502AP & 6522AP, basically the same as in the Oric.

 

If you are getting no signal on the RGB outputs of the ULA that might mean it’s toast.

So if you have 5v all around the PCB...
So can you check you are getting a 12Mhz clock from the crystal from Pin 2 of IC21 to pin 7 of the ULA
1 MHz from pin 14 of ULA to pin 37 of 6502,
1 MHz from pin 3 of 6502 to pin 15 of AY chip
1 MHz from pin 39 of 6502 to pin 25 of 6522 and pin 5 IC21
1 MHz from pin 6 IC21 to pin 6 of IC09 and IC10

A missing clock from one of these might help narrow down where the problem is.

 

@Klyde here is a link for the service manual with the waveforms you should see.

http://www.48katmos.freeuk.com/servman.pdf

 

Thank you richie! I printed it!

 

I forgot to say, I'll be posting the Oric Test & Joystick PCB's via Royal Mail Airmail tonight or tomorrow morning so you should have them by middle of next week
If you are waiting for the chips to arrive have you spent any time looking at the rear of the PCB yet? sometimes there are track breaks and deterioration on these PCB's down by the AY and 6522A and the RAM. If all your tests on your chips prove inconclusive then it would seem like you will need to check all the tracks one by one

 

Yes I was already watching it. Thank you for confirmation of genuinity! I am going to tackle this Oric thanks to you.

 

@Klyde PCB’s are on their way mate. You can fit a 64KB EEPROM in this so you can have V1.0, V1.1 and V1.22 BASIC as well as the test ROM. Where you can only fit a 16KB ROM inside unless you make some modifications.
Have you managed to connect it to a display yet? I have been thinking about this Oric for a while and if you have all the clocks where they should be but it won’t start then I think the RAM might be the problem as the ROM does a dirty RAM initialisation before it boots to BASIC.
The last couple I’ve fixed that had IC faults were the RAM and none were getting hot and the resistance check didn’t flag any, so I replaced all the 4164’s. You can normally pick up 8 for £8/€9 on feeBay. Don’t forget to check for the service modification on the AY chip. The ROM basically kills the AY chip over time on Oric-1’s and it needs a service mod to fix this or fit a V1.1 ( Atmos ) ROM which fixed,the problem. The details are in the service manual.

 

Thank you Richie, you are really helpful!

I found an Oric-1 SCART cable for sale on leboncoin for 15.00€, but the seller never replied, so I built one myself. I only have a black screen (the ULA outputs a sync signal but no R, G or B).

I have ordered the full Oric chips set (CPU, 6522, ULA, RAM) except the AY one. The ULA and the RAM are still on their way. I also have a 28C512 EEPROM.

I'll do some chip swapping as soon as I receive them all, and I'll let you know what I find. Very interesting info about the RAM being faulty with no obvious signs... Thank you for sharing your experience.

 

Richie, I don't have received your parcel yet, but it should arrive in a couple of days now.

I either don't have the ULA and RAM chips yet, although the ULA is announced as "delivered" by the tracking system I hope the parcel was not lost...

I wanted to thank you again for helping me so kindly, that's why you will receive a gift from me in a few days. You'll know when you see it, hopefully it doesn't break during transportation.

Of course I'll let you know as soon as I have some news with the Oric.

Cheerio!

 

If your ULA has gone AWOL then I will send you one FOC ASAP hopefully then I won’t use so many abbreviations LOL ROFL LMAO

 

Not a big deal Andy, but yes it is a shame they delivered somewhere else, maybe the seller did a mistake with my address? I'll try to find that out...