Oric Atmos power supply - UK Vintage Radio Repair and Restoration Discussion Forum

paul.brett · 14th Mar 2007, 12:48 pm

I have recently acquired what was claimed to be a working Oric Atmos.

I am having a problem with the power supply, and hope somebody reading this forum can help me. As far as I know, it is the second model of power supply produced, rated at 9v 5.4va, but I think it is dead.

My question to you is, can I use a variable power supply, rated at 9v 3.6va (max)? Will the Oric try to draw too much and blow-up the power supply?

Can anybody tell me the correct polarity. I assume it is positive tip (centre). The sticker says:

Output 9v
___
...
5.4VA

My computer collecting efforts to date: http://www.pbrett.com/cm (the Atmos is not listed yet, as I only list working stuff.)

Thank-you all for your time.

Paul.

Denis G4DWC · 14th Mar 2007, 1:54 pm

I'm not an expert on the Atmos....
If the Power supply you have was rated at 5.4VA and has died it could be that there was a fault in the Atmos causing it to draw too much current and hence causing the PSU to fail. I would not advise using a lower rating supply until you have ascertained what the Atmos is actually drawing. If the Power supply comes apart and is not stuck together you could easily check polarity with an ohm-meter. The only failures in small Power supplies I have had is that the Thermal fuse has tripped although this is often diificult to get at to replace.

If it were me I would probably take the lid off the Atmos and look for the ground connections on the ICs (Usually Pin 7 for 14 pin ICs and Pin 8 for 16 Pin ICs) You could also locate the negative connection of any large electrolytic capacitors. Then check continuity to the power input socket on the Atmos. That will tell you the -Ve connection.

It would be wise to run the computer up on a stabilised Bench power supply and monitor the current. If the Power supply was only rated at 5.4VA I would expect the unit to draw 400-500mA. HTH

Like the Web site by the way. Where is the Microtan Tangerine?

Denis

Dave Moll · 14th Mar 2007, 3:53 pm

Quote:

Originally Posted by G4DWC

Like the Web site by the way.

Yes, and the collection which it represents

14th Mar 2007, 12:48 pm	#1
paul.brett Tetrode Join Date: Dec 2005 Location: Wisbech, Cambridgeshire, UK. Posts: 97	Oric Atmos power supply I have recently acquired what was claimed to be a working Oric Atmos. I am having a problem with the power supply, and hope somebody reading this forum can help me. As far as I know, it is the second model of power supply produced, rated at 9v 5.4va, but I think it is dead. My question to you is, can I use a variable power supply, rated at 9v 3.6va (max)? Will the Oric try to draw too much and blow-up the power supply? Can anybody tell me the correct polarity. I assume it is positive tip (centre). The sticker says: Output 9v ___ ... 5.4VA My computer collecting efforts to date: http://www.pbrett.com/cm (the Atmos is not listed yet, as I only list working stuff.) Thank-you all for your time. Paul.

14th Mar 2007, 1:54 pm	#2
Denis G4DWC Pentode Join Date: Oct 2006 Location: Brackley Northamptonshire, UK. Posts: 240	Re: Oric Atmos power supply I'm not an expert on the Atmos.... If the Power supply you have was rated at 5.4VA and has died it could be that there was a fault in the Atmos causing it to draw too much current and hence causing the PSU to fail. I would not advise using a lower rating supply until you have ascertained what the Atmos is actually drawing. If the Power supply comes apart and is not stuck together you could easily check polarity with an ohm-meter. The only failures in small Power supplies I have had is that the Thermal fuse has tripped although this is often diificult to get at to replace. If it were me I would probably take the lid off the Atmos and look for the ground connections on the ICs (Usually Pin 7 for 14 pin ICs and Pin 8 for 16 Pin ICs) You could also locate the negative connection of any large electrolytic capacitors. Then check continuity to the power input socket on the Atmos. That will tell you the -Ve connection. It would be wise to run the computer up on a stabilised Bench power supply and monitor the current. If the Power supply was only rated at 5.4VA I would expect the unit to draw 400-500mA. HTH Like the Web site by the way. Where is the Microtan Tangerine? Denis __________________ If you take something apart often enough, eventually you'll have two of them....