Apple 2 europlus , characters on screen help

[Offscreen6]

Re: Apple 2 europlus , characters on screen help

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

The more I read about these testers, the more interesting they seem. Pretty cool that this kind of thing even exists, and it will probably make motherboard repair easier for beginners in the future.

[zen]

Re: Apple 2 europlus , characters on screen help

Will do , thanks .

[stj]

Re: Apple 2 europlus , characters on screen help

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

[zens electronics]

Re: Apple 2 europlus , characters on screen help

Yes sorry , meant vertical .

Will check out suggestions .

[RJARRRPCGP]

Re: Apple 2 europlus , characters on screen help

Issue now is that there are horizontal lines on display .

I see vertical lines.

[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?

[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 ?

[zen]

Re: Apple 2 europlus , characters on screen help

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

[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

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

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

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 .

[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 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 .

[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 additional info.

Will carry out checks & report back .

[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

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

[zen]

Re: Apple 2 europlus , characters on screen help

Thanks , will do

[stj]

Re: Apple 2 europlus , characters on screen help

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