Apple 2 europlus , characters on screen help

[zen]

Hi all

No experience whatsoever on computers .

Hoping someone can advise .

[stj]

Re: Apple 2 europlus , characters on screen help

try with all the cards removed,
that is often video ram failure

[zen]

Re: Apple 2 europlus , characters on screen help

Thanks , will do

[zen]

Re: Apple 2 europlus , characters on screen help

Suspecting RAM issue , as you suggested .

Pulled out all the RAM chips , cleaned pins & re-seated .

Still characters on screen , but altered .

Anyone know a trusted source for RAM chips ?

Type MK4116N-3 GP

[stj]

Re: Apple 2 europlus , characters on screen help

4116 needs 5v, 12v and -5v
before you replace any - check those voltages.
if any are missing, it can kill the chip.
also touch each chip while it's on - bad chips often get VERY hot.

https://cdn.badcaps-static.com/pdfs/...447c7c4eff.pdf

[zen]

Re: Apple 2 europlus , characters on screen help

Thanks for the additional info.

Will carry out checks & report back .

[momaka]

Re: Apple 2 europlus , characters on screen help

I see a lot of ICs in a lot of sockets... so that's a lot of failure points, especially in this age. Might be a bit tedious, but probably worthwhile to remove every IC and make sure the contacts in the sockets are clean and tight, then re-insert the IC. These aren't machined sockets, so they tend to not be as good.

[zen]

Re: Apple 2 europlus , characters on screen help

Thanks for the info .

Have tried already with all the RAM chips , cleaning pins , plus spraying out sockets using switch cleaner .

Will update once i have the opportunity to work on it again .

[mon2]

Re: Apple 2 europlus , characters on screen help

OMG. Brings me back to high school days. The schematic was published for these at the back of the apple 2+ manual. Tons of clones were made of the same in Asia.

https://downloads.reactivemicro.com/...IIe/Schematic/

[zen]

Re: Apple 2 europlus , characters on screen help

Thanks

printed out pin out of RAM chip .

PIN 1 ( VBB ) MINUS 5 VOLTS

PIN 8 ( VDD ) PLUS 12 VOLTS

PIN 9 ( VCC ) PLUS 5 VOLTS

I assume supplies are common to all the RAM chips .

Customer ordered 4 RAM chip for me , therefore will have a play .

[stj]

Re: Apple 2 europlus , characters on screen help

check the voltages first,
if any are missing - specially the -5v then it can trash the chips.

[zen]

Re: Apple 2 europlus , characters on screen help

Thanks , voltage seem fine .

On a recommendation from a colleague , i bought a RAM chip tester .

Will update once it arrives .

Here's the link .

https://www.ebay.co.uk/itm/4116-DRAM....c101197.m1850

[stj]

Re: Apple 2 europlus , characters on screen help

interesting,
i know the designs for those type of things are on github but didnt know you could buy them ready built.

[zen]

Re: Apple 2 europlus , characters on screen help

No , nor did i , until a colleague made me aware of tester.

[zen]

Re: Apple 2 europlus , characters on screen help

Tester arrived & seems to work quite well .

Detected 4 faulty chips , which i replaced using ones ordered by customer without the GP at the end .

Repaired a further 2 working chip , by adding pins , where the legs fell off .

No strange characters on display now & Apple logo present .

Issue now is that there are horizontal lines on display .

Any advice ?

[stj]

Re: Apple 2 europlus , characters on screen help

that still looks like a vram problem - or the associated circuits.
got any multiplexers like 74ls157, 158, 257 or 258 on the board?

[RJARRRPCGP]

Re: Apple 2 europlus , characters on screen help

Issue now is that there are horizontal lines on display .

I see vertical lines.

[zens electronics]

Re: Apple 2 europlus , characters on screen help

Yes sorry , meant vertical .

Will check out suggestions .

[stj]

Re: Apple 2 europlus , characters on screen help

btw, check inside the psu for bad caps.
and RIFA's

[zen]

Re: Apple 2 europlus , characters on screen help

Will do , thanks .