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Re: Dead oric 1

Posted: Tue Feb 26, 2019 11:18 am
by Traindriver69
So is what you are saying I need to make a lead up one end plugged into the power supply the other end plugged into the oric with a terminal spliced into the + wire so I can connect the multimeter to get a reading.

Re: Dead oric 1

Posted: Tue Feb 26, 2019 3:48 pm
by Traindriver69
An update
The new voltage regulators came today but I have had an issue removing the old one pin 3 nearest the dc power socket has lifted and taken a bit of the top side of the board with it.but no damage to the underside.
I don't think there are any tracks on the top to damage there but maybe someone knows different.
But after putting the new one in still dead and for some reason the regulator is showing an output of 7v which is not right so don't know if it's the damage to the board or the regulator causing that.
IMG_20190226_144546[1].jpg

Re: Dead oric 1

Posted: Tue Feb 26, 2019 9:06 pm
by Badger
Might be a silly suggesteion but have you tested the multimeter to check that it isnt showing eratic values. New batteries perhaps.

I'm not sure how it would be possible to get 7v from the 7905 otherwise.

Maybe if you have a spare and a breadboard, rig up a simple 7905 , resistor, LED and the 12v supply and test the voltage across that. Not forgetting the 7905 is a negative supply so will need to reverse the LED fom normal.

Just run it long enough to text the voltage seperate from the Oric and then you can eliminate the regulator for the possible issues.

Re: Dead oric 1

Posted: Tue Feb 26, 2019 9:11 pm
by Badger
Just looked at the circuit digram for the motherboard and it shows that C8 is connected the input voltage before the regulator. It is possible that this has failed and is causing the problem. Might be worth replacing this too.

Re: Dead oric 1

Posted: Tue Feb 26, 2019 10:07 pm
by iss
1.jpg
On picture above frames 1 and 2 (yellow numbers) are reference to easy follow the tracks around the 7905 regulator.
Frame #3 shows how you need to restore the broken track. Did you restore it properly?
On frame #4 are two possible places (easy to reach) to measure the supplied voltage after the regulator.
What are the readings with your Voltmeter on (one of) this places?

Re: Dead oric 1

Posted: Wed Feb 27, 2019 11:02 am
by Traindriver69
Hi
Just checking does that pin 3 of the regulator go to the leg of C13 as looks like in pic 3 and that's what needs repairing.
Many thanks

Re: Dead oric 1

Posted: Wed Feb 27, 2019 6:12 pm
by mikeb
Badger wrote:
Tue Feb 26, 2019 9:06 pm
Might be a silly suggesteion but have you tested the multimeter to check that it isnt showing eratic values. New batteries perhaps.

I'm not sure how it would be possible to get 7v from the 7905 otherwise.
I did mention to check the multimeter in my first post. Previously it was reading 4.2v on 5v rail -- now it's gone the other way.

If the regulator is putting out 7V I would say the board is now scrap, instead of just faulty. TTL is hugely intolerant of overvoltage.

It is perfectly possible to get 7V out if the regulator fails, or if the common leg is disconnected (e.g. damaged PCB traces, failure to solder).

Re: Dead oric 1

Posted: Thu Feb 28, 2019 11:28 am
by Traindriver69
Hi
Leg three of the regulator was not going through C13 so would the voltage been carried through the board to do any damage could you let me know.
Anyway today I have replaced the regulator again and repaired the board so leg 3 is know going through C13 and I have replaced C8 just incase plugged it in and seem back to square one voltage regulator showing 4.1v and buzzing coming through the speaker again.
many thanks

Re: Dead oric 1

Posted: Thu Feb 28, 2019 11:53 am
by Voyageur
Hi Traindriver69,

good to see that the 7905 is good.
But there is still something on the mother board that drains a "lot" of current.
4.1 V are not sufficient ! And you said that the speaker is making noise... Not good !
Is your Oric plugged to a tv or a monitor ? Unplug everything. Just keep the Oric and the power supply. Did you make a measurement as Iss showed on different points of the board ?
No sign of heat ? Test with your finger on the chips. You could find some of them warm : the 6502 processor, the 6522, and so on...
And if you could solder a piece of cable/jumper with two Jack plugs (5.5 mm / 2.1 mm, one male and one female) to perform a test with your ammeter, that will be useful...
It is really difficult to tell you which chip (or any other component) is faulty...
And you can't replace all of them, one by one, unless you have time and money to do that ! :D

Did you separate the mother board from the keyboard ? No sign of burnt or bad solder on her back ?

We'll try to help you. Courage !

A+

Re: Dead oric 1

Posted: Thu Feb 28, 2019 1:07 pm
by Traindriver69
Just checked the points on the board that iss said to check and
IC10 the red arrow point is measuring 9.6v
IC10 the black arrow point is measuring 4,4v
IC11 point is showing 8.93v

Re: Dead oric 1

Posted: Thu Feb 28, 2019 1:20 pm
by Traindriver69
6502 and 6522 get warm but nothing else

Re: Dead oric 1

Posted: Thu Feb 28, 2019 2:40 pm
by iss
Traindriver69 wrote:
Thu Feb 28, 2019 1:07 pm
Just checked the points on the board that iss said to check and
IC10 the red arrow point is measuring 9.6v
IC10 the black arrow point is measuring 4,4v
IC11 point is showing 8.93v
Sorry if I mislead you - to measure the voltage in above picture put the black test probe where the black arrow points near IC10 and put the red probe where the red arrow points near IC10 than read the voltage. You can measure the same voltage on both arrows near IC11. There should be no difference (or just very little).

From your readings I think you put the black probe somewhere before the 7905 - and then the real voltage between the two IC10 arrows is: 9.6-4.4=5.2V - and this is very good!

Re: Dead oric 1

Posted: Thu Feb 28, 2019 2:55 pm
by Traindriver69
hi
both ic10 and 11 reading 5.10v

Re: Dead oric 1

Posted: Thu Feb 28, 2019 3:42 pm
by Traindriver69
I have made a lead up and tested the amps it is drawing and it says zero the lead is all good any ideas?
IMG_20190228_144029[1].jpg
I put the block connector in for somewhere to place the multimeter probes.

Re: Dead oric 1

Posted: Thu Feb 28, 2019 4:01 pm
by iss
Traindriver69 wrote:
Thu Feb 28, 2019 2:55 pm
both ic10 and 11 reading 5.10v
Cool! 7905 is working fine and the board is powered OK.

To measure the drawn current use:
amper.jpg
Be careful: set the multimeter to 2A (or 2000mA).