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Oric 1 computers. Appear to work but no RF display....???

M

mubase

Experienced Member
Joined
Feb 20, 2016
Messages
70
Location
Peckham, London,UK
Hi everyone. I was hoping someone might be able to help me with a couple of ORIC 1 computers I have. I have replaced the 7905 regulators in them after seeing that the originals were destroyed and they now seem to come to life. I hear key click sounds and when I enter the ZAP or PING basic commands I hear the respective sound effects however, when I plug in via the RF socket to my TV all I see is a wavery screen with the usual static and no real picture. The ATMOS I also have seems to work fine. With the Oric 1s, it looks like a picture is trying to get through but it can't....any help appreciated,
thanks,
Steve.S
 
The repair/maintenance/troubleshooting manual is over here http://www.48katmos.freeuk.com/projects.htm.
Click to expand...

Thanks Dave. This is an invaluable source!!
I've noew repaired both ORIC 1's. The problem with the display turned out to be not a chip fault fortunately but a simple case of RV1 which is a composite bias trimmer needing to be adjusted. I also replaced both regulators in both machines as they were running HOT HOT.

I wonder why the original voltage regulators died?
Click to expand...

This was/is a common fault with the ORIC machines. Even with a small heat sink the regulators heat up massively so its not surprising that over time and with prolonged use they would explode/corrode/deteriorate.

The two ORIC 1's have a major difference in their ROMS. One has both ROM slots filled with a High ROM and a LOW ROM and the other has just one of the ROM slots filled.
They both run the original ORIC 1.0 ROM which I understand was full of bugs....

Both working nicely though... I'll get to the RGB socket and tape soon. Now to get onto those ZX Microdrives and cassettes!! :)
 
>>> Thanks Dave. This is an invaluable source!!

No problem, glad to help out.

I saw the potentiometer on the video signal and was going to mention it in my post - but I couldn't decipher the circuit reference as I was on my mobile device and (when I blew up the schematic) I couldn't read it...

I assume that things have aged a bit and the pot. needed a little 'tweak' to bring the signal back into specification.

Glad you are now operational.

Dave
 
I don't know anything about Oric-1s, but if your regulators fail in the future, you might consider replacing them with one of the drop-in switching regulator modules. It would reduce both the heating and the power supply load.
 
Chuck(G) said:
I don't know anything about Oric-1s, but if your regulators fail in the future, you might consider replacing them with one of the drop-in switching regulator modules. It would reduce both the heating and the power supply load.
Click to expand...

This is common on old S-100 boards (and new designs from s100computers.com ), some of them just can't be adequately cooled with specific power supply and chassis combinations. They work well, but some of the modules I've seen have been of lesser quality than others.
 
Chuck(G) said:
I don't know anything about Oric-1s, but if your regulators fail in the future, you might consider replacing them with one of the drop-in switching regulator modules. It would reduce both the heating and the power supply load.
Click to expand...

Yeah thanks Chuck I've seen these switching regulators. Excellent idea as these ORICS run BLOODY HOT!!!
 
mubase said:
Now to get onto those ZX Microdrives and cassettes!! :)
Click to expand...

With both Microdrive cartridges and cassettes, watch out for the foam head pressure pads which by now will sometimes have turned into something like melted toffee. If you find this problem on any of your cassettes you can buy some new or NOS cassettes and rob the spring loaded head pressure pads from the new tapes to put in the old cassettes, assuming the old ones have something important on them which you don't want to lose.

If you have the same problem on Microdrive cartridges I don't know what to suggest, as the pads are physically much smaller with a slippy surface layer on the side nearest the tape - not easy to conjure replacements for if the original pads have turned to brown liquid.

Don't even attempt to run a Microdrive cartridge or cassette with a sticky head pad, the goo will end up inside the tape as well as all over the head and pinch roller.
 
Good Morning Sirius. :) Thanks for the info. I've got around 8 cartridges. 5 are in black sinclair cases, One of the cases is the Introductory case and it has 2 carts one with "Introduction" label on it and the other "Games". The other 3 are blank. There's also a nice "Taking care of you Microdrive cartridges" leaflet and a small lined pad with the sinclair logo at the top. The other carts aren't labelled but I've run a CAT1 successfully on 2 of them and they showed "Scrabble". Most of the carts' pads have just disintegrated altogether. I have managed to "fix" one using a pad from an old audio cassette and some padded double sided tape. I got one of the drives to format it and then saved a simple BASIC program to it. That all seemed to go well but I can't get it to load using the LOAD*"m";1;"Test1" command. So I don't know whats going on there. I've got plenty of old audio cassettes I can sacrifice for the other carts. I've also got a couple of Microdrive oriented interfaces. I've got 3 ZX Interface 1's, a Draysoft Doubler interface and another interface to do with saving from tape to Microdrive.
 
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