sourcing voltage regulator (IC1)

nobbysnuts · Post by **nobbysnuts** » Sat Jan 13, 2007 8:39 pm

Hi bought another oric 1 (could not resist as it has a different colour badge to mine and makes my set almost complete)with the seller saying he had killed it with overvoltage (trying wrong power supply) opened it up and can see IC1 blown tried it it works but make a horrible noise ,so im hoping its just the regulator but im not sure what spec to source and where I can source an equivalent any ideas anyone Thanks Ian

nobbysnuts · Post by **nobbysnuts** » Mon Jan 15, 2007 8:45 pm

Tried a voltage regulator that I picked up at maplins electronics today not life out of the oric at all ( but soldered a power supply board from a scrap acorn to main board and its working fine apart from interferance on screen when oric outputs sound ,guy in shop says this is the only type of regulator stocked its a +5v output with pin connections in ,ground ,out
am I right in thinking the oric layout is(from by reset )out,in , ground and could i cross these connections on new unit(dont want to blow oric up)

Womble · Post by **Womble** » Tue Jan 16, 2007 12:12 pm

Popped the lid on my Oric 1 and took a look - my IC1 labelled
X =304
LM7905CT

X is the National Semiconductor double squiggle insignia - not sure what the =304" means - if anything spec related.

But

this chap will sell you 1 for £1.50 plus shipping - might be worth asking for the full specs he offers by request only.

http://cgi.ebay.com/LM7905CT_W0QQitemZ1 ... dZViewItem

According to the datasheet here http://www.national.com/pf/LM/LM7905.html

the pins from beside reset are ground, input, output, with output the closest pin to the reat of the oric. This makes sense when looking at the underside of the board. The fat rail running round the outside of the upper face of the board looks like the 5v rail, the fat rail on underside looks like ground. Dont want to power mine up to test that as it has no RAM in it at the moment, am waiting for an ebay parcel myself

nobbysnuts · Post by **nobbysnuts** » Tue Jan 16, 2007 5:40 pm

Thanks
second time youve sorted it out for me ,the service manual said it was ti but your description of the chip is same as mine ive bought a couple off the guy in the link you gave (I trawled the net looking for that model thinking it was ti (how dull am I) I will post once Ive sorted it thanks again Ian

nobbysnuts · Post by **nobbysnuts** » Fri Jan 19, 2007 7:30 pm

fitted regulator chip today works perfectly chip sent was ti 7509c same chip different make.

Womble · Post by **Womble** » Mon Jan 22, 2007 5:27 am

Excellent - well the repair manuals tended to state their prefered supplier at the time of writing. I have a repair doc that doesnt mention the suppier at all - just the chip number, perhaps its an earlier or later edition.

In other news my new RAM chips have arrived so I should be able to resurect 2 perfectly working Orics tonight. Before 1 gave odd free RAM figures and the other failed to boot due to a dead chip 2nd in the rank - ie within the 1st 16k that shadows the rom.

Time will tell but hopefully I can load some games now - the ram was randomly shot on the Atmos so no large programs would load at all.

What are you running on your Orics - any recomendations?

Post by **Dbug** » Mon Jan 22, 2007 11:15 am

Womble wrote:What are you running on your Orics - any recomendations?

You can probably ask this question again on the game section of the forum, because most probably people that would reply to you are not the one that read the tech section