Dead oric 1

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Traindriver69
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Dead oric 1

Post by Traindriver69 » Fri Feb 22, 2019 10:23 am

Hi all
I have just received a oric 1 which came with no power supply but I have already got a working oric 1 so plugged my power supply into it and nothing.
I have took the back off and notice that when I plug the power in there is a low hum from the speaker but nothing else.
I have put a multimeter on the power regulator and one side is showing 9v and the other about 4.2v.
Intresting there is a sticker on the side of the oric saying 12v plus showing which way the connector should be
The attachment IMG_20190221_124304[1].jpg is no longer available
I know the oric power supply is 9v but mine says 12v when I tested it with a multimeter so I don't know if this would have caused any damage I have included some pics of the board any help on what to try next would be appreciated.
The attachment IMG_20190221_124407[1].jpg is no longer available
IMG_20190221_124304[1].jpg

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Voyageur
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Re: Dead oric 1

Post by Voyageur » Fri Feb 22, 2019 11:17 am

9V or 12V are the same for testing purpose. No damage to expect.
But the value of 4.2V seems to be not enough for the Oric... Around 5V is perfect.
The schematics on the sticker is good.
I propose to put the multimeter in ammeter option in your power line positive. It should read around 700-800 mA (less than 1 Amp).
You could also replace the regulator 7905 with a new one, maybe it didn't appreciate working a long time with 12V instead of 9... More power and heat to evacuate ! :evil:

And you posted only one picture, I cannot see the mother board. :?:
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Traindriver69
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Re: Dead oric 1

Post by Traindriver69 » Fri Feb 22, 2019 3:09 pm

Hi
The pictures showed up on the preview so don't know where they went.
IMG_20190221_124407.jpg

Traindriver69
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Re: Dead oric 1

Post by Traindriver69 » Fri Feb 22, 2019 3:10 pm

IMG_20190221_124445.jpg

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mikeb
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Re: Dead oric 1

Post by mikeb » Fri Feb 22, 2019 6:31 pm

I can confirm that your 4.2v is too low -- make sure your multimeter has a fresh battery though, as a lot of handheld DMMs read funny when the battery is going off! It is possible that something is holding the 5v rail down (have you checked to see if any of the 8 DRAM chips (4164) get warm when it's been powered on for a minute or so. Really warm ...)

The power supply of 12v is too high, first: The input smoothing capacitor C8 (100uf, 10V) won't like that, and second: the 7905 will have to shed more heat (9-5v = 4v drop, 12-5v = 7v drop, so almost twice as much dissipation!). A normal Oric gets toasty enough, no need to try and go full Spectrum mode and cook eggs :)

An easy way to kill an Oric is to miss your aim with the DC jack, and go straight into the expansion port. This may have happened before you got it :(

You might pick up some more hints from :- http://oric.signal11.org.uk/html/repairguide.htm

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Re: Dead oric 1

Post by Traindriver69 » Sat Feb 23, 2019 12:36 pm

Hi
Dram chips are stone cold after a couple of mins plugged in I have ordered some power regulators for a start.

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Re: Dead oric 1

Post by mikeb » Sat Feb 23, 2019 7:33 pm

Oh well, sometimes you get really lucky and find one DRAM chip is toasting!

The question (further above) asking you to check the current drawn -- that's useful information, so let us know when you measure it!

If you do unbolt and unsolder the regulator, make sure to fold the legs correctly to hit the holes, then bolt it down, and finally solder it.

If you solder-then-bolt, it puts strain into the joints and could fail later (mechanically).

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Re: Dead oric 1

Post by Traindriver69 » Sun Feb 24, 2019 11:19 am

Hi
The power supply I am using is a proper oric one which is working on my other oric 1 so should be no problem with that and the regulators are pre bent so I am hoping they are right.

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Re: Dead oric 1

Post by mikeb » Sun Feb 24, 2019 9:33 pm

It's not about whether the PSU works on your other Oric (although that's good to know!) -- it's about how much current is drawn by the faulty Oric when connected to a power supply. If excessive current is being drawn, that could well be the reason your 5v line is low, and changing the regulator wouldn't help that.

Pre-bent legs is good, if they are correct, but definitely mount it, then solder it. Not the other way.

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Re: Dead oric 1

Post by Traindriver69 » Mon Feb 25, 2019 11:19 am

Hi mikeb
sorry how do I go about testing if excessive current is being drawn on the oric.
many thanks

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ibisum
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Re: Dead oric 1

Post by ibisum » Mon Feb 25, 2019 11:41 am

>I propose to put the multimeter in ammeter option in your power line positive. It should read around 700-800 mA (less than 1 Amp).

Follow this advice from Voyageur!

FWIW, I've had a few Oric's that I thought were dead, only to find out that I wasn't giving them enough amps in the power supply... its really a key factor in whether or not the Oric can boot.

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Re: Dead oric 1

Post by mikeb » Mon Feb 25, 2019 5:53 pm

@ibisum -- you don't "give things amps". You give things volts. They draw whatever amps they feel like, up to the point the power supply expires or shuts down under overload.

It's an original Oric power supply, so it should be capable of powering an Oric. No wait, it is capable, as it powers another working Oric ok.

The (unanswered) question is -- what current is this Oric drawing? The regulators in Oric are only good for a max of 1 Amp (1000mA), correct answer was posted up-thread.

Of course, sometimes it's easier to just change components at random and hope, instead of making measurements. If Oric is drawing too much current, a new 7905 probably won't fix anything. Nor will trying a power supply "with more amps" (other than the wisp of smoke somewhere showing where the fault used to be. It's a valid last-resort technique!)

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ibisum
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Re: Dead oric 1

Post by ibisum » Mon Feb 25, 2019 6:31 pm

>give things amps

Yeah, I clearly meant "give the Oric a power supply that doesn't cry over how many amps it draws", but .. whatever.

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Re: Dead oric 1

Post by Traindriver69 » Mon Feb 25, 2019 10:03 pm

Thanks for the answers I am just a little unclear what point I need to measure when it is said get a reading from the plus power line is that the end of the power adaptor on its own which would not show what the oric was using or do you mean a point somewhere on the oric board sorry if I sound a bit thick.

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Voyageur
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Re: Dead oric 1

Post by Voyageur » Tue Feb 26, 2019 3:40 am

The measure has to be done outside the Oric, between the power supply and the computer.
If you make it with the Plus Power line (usually in red on the schematics), you could try something like that :
schema2.jpg
and tell us what you read in DC amperemeter position (settings on 2 Amp or more in a first shot), that would be fine !

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