464+ Failure

[jockavelli]

Hi All


After 30+yrs my trusty 464+ has developed a problem, i'm hoping its not terminal as i will be devastated if it is.


The issue is that now when the system is turned on with the Burnin' Rubber/OS cart inserted i get a screen with a kind of pink background with blue matrix type lines through it & black banner.


Yet with any other standard game cart i get a screen with a pure black background & blue banner.


So by my logic that says to me the system can tell the difference between the carts but just cant process them correctly.
By reading through the forums here i'm guessing its either the ASIC or RAM that is the issue?


What should i do to start of trying to sort this out, bearing in mind i am not electronically minded so bear with me if i ask dumb-ass questions.


Thanks in advance.

[Bryce]

More likely a RAM issue. Open it up and see if either of the RAM ICs are getting hot. As for repairs, if you don't think you can fix it yourself, you can send it (just the PCB) to me for repair.

Bryce.

[jockavelli]

I think i should be able to do a RAM swap, i have done a little soldering in the past, but i may take you up on that.


Are RAM chips easy enough to get hold of nowadays?

[Bryce]

Yes, those chips are easy to find. Make sure to cut the pins and de-solder them seperately to ensure you don't damage the PCB and order sockets for the new chips to make things easier.

Bryce.

[jockavelli]

Well while i'm doing that are there any other upgrades or mods you'd recommend doing, might as well just do them at the same time.

[jockavelli]

Ok.... so what chips should i be checking on this?

[jockavelli]

Ok I have found that IC12 (KM41464AP-12) is getting burning hot, so I presume that's the likely culprit I need to replace, would that be correct?

[gerald]

DRAM are IC10 and IC12 on the right side of the ASIC
If you're changing them you also might just also add the missing 64K and go to 128K.To do so, just add IC11, IC13 (same pars as IC10/12) and R128 (10K) to enable 128K.
For a full conversion to 6128Plus : https://www.cpcwiki.eu/index.php/464Plus_Conversion

[gerald]

Ok I have found that IC12 (KM41464AP-12) is getting burning hot, so I presume that's the likely culprit I need to replace, would that be correct?

Yes. These are not supposed to be burning hot 

[jockavelli]

Yes. These are not supposed to be burning hot [/size] [/size]

It was a bit of a surprise how hot it got, so yeah no wonder it ain't working.


On the IC is the 939 relevant or would one with a 909 be ok to use?


As for adding the 64k i'll need to have a look over that (several times) or find a video (to watch, several times) just to be sure i want to risk it.

[1024MAK]

On the IC is the 939 relevant or would one with a 909 be ok to use?

That's either a batch number, or a date code. No need to worry about that number being different.

The important thing, is that the part code is the same (KM41464AP-12) or use an equivalent from a different manufacturer, but with the same or faster access timing (speed).

Mark

[jockavelli]

Brilliant, I thought it may be something like that but just wanted to be sure.


Now to source the chips & the correct socket!

[Bryce]

It was a bit of a surprise how hot it got, so yeah no wonder it ain't working.


On the IC is the 939 relevant or would one with a 909 be ok to use?


As for adding the 64k i'll need to have a look over that (several times) or find a video (to watch, several times) just to be sure i want to risk it.

939 = Manufactured in the 9th week of 1993
909 = Manufactured in the 9th week of 1990

Bryce.

[jockavelli]

939 = Manufactured in the 9th week of 1993
909 = Manufactured in the 9th week of 1990

Bryce.

Thant makes sense, also makes the system younger than i had thought.


I have found a few chips but i'm not sure of the correct socket to use, surely it can't be that hard to solder directly back on without the socket?
OR....
should i step away now LOL

[Bryce]

The socket helps to make the soldering safer, but the main reason to use sockets is because ALL of these chips, even the new ones will be relatively old and prone to fail at any time. Using a socket means that the next replacement only involves pulling a chip from the socket and inserting a new one, with no soldering involved.


Bryce.

[1024MAK]

I have found a few chips but i'm not sure of the correct socket to use, surely it can't be that hard to solder directly back on without the socket?
OR....
should i step away now LOL

You want a DIL socket with the same number of pins as the chip. And the same width.
Stamped pin sockets are cheaper, but some prefer turned pin sockets.
Modern quality 'dual wipe' stamped pin sockets (where the IC chip pin goes in between a receptacle such that there is a metal contact on two sides so the chip pin is in the middle) are more reliable than the older cheaper sockets (which only had metal on one side).
Turned pin sockets more reliable still, especially if subjected to multiple insertions/removals.

Mark

[jockavelli]

You want a DIL socket with the same number of pins as the chip. And the same width.
Stamped pin sockets are cheaper, but some prefer turned pin sockets.
Modern quality 'dual wipe' stamped pin sockets (where the IC chip pin goes in between a receptacle such that there is a metal contact on two sides so the chip pin is in the middle) are more reliable than the older cheaper sockets (which only had metal on one side).
Turned pin sockets more reliable still, especially if subjected to multiple insertions/removals.

Mark

I'm hoping to find what i'm looking for and get it all ordered next week, then take it from there.
Pretty sure i'll find somewhere doing the right sockets once i actually look properly.

[jockavelli]

Would a socket with these dimensions be the correct ones to get?

18 Pin - 22.86mm, 10.16mm, 4.80mm

[1024MAK]

Would a socket with these dimensions be the correct ones to get?

18 Pin - 22.86mm, 10.16mm, 4.80mm

Yes

Stamped pin socket datasheet here
Turned pin socket datasheet here
[Note that the above links are to a U.K. supplier that I use. Other brands/makes/suppliers are available...]

Mark

[jockavelli]

We'll seeing as i'm UK based too i think i'll stick with what you have used before.


on another note i managed to pick up a 6128 today for £5 with a Multiface Two still boxed...... no idea what it does yet, will read up on it later.
No screen or cables to connect to a TV so no idea if it works but it was £5 so would be silly to pass it up.

[Skunkfish]

on another note i managed to pick up a 6128 today for £5 with a Multiface Two still boxed......

Woah, what a bargain! How did you come across that one?

[jockavelli]

Woah, what a bargain! How did you come across that one?

Saw it at a car boot sale, no monitor for it so the guy couldn't say if it worked, don't think he knew what he had.

[jockavelli]

Okay, some small progress


So the sockets arrived, i started the repair and noticed some black residue joining 3 pins together, no idea what it was.


I now have clean board with the socket in place, while i wait on the RAM arriving , which sadly i have just been told could now be sometime in February .


So if anyone has a spare RAM chip they are willing to sell me now or send me & i will replace it when mine arrive it would be appreciated [size=78%].[/size]

[jockavelli]

Good news the RAM arrived


Bad news, it appears both RAM chips have failed.


I only noticed this after replacing the first one, which i admit i found harder to do than i expected that is probably through lack of experience & confidence.
As such i cannot do the second one, i don't see an easy way for me to do it without messing something else out.


So.... is there anyone willing to help me out by doing the repair?
Bryce i know you said you could but i don't want to assume you are still willing to do so.


I have plenty of RAM as i bought 10 just in case as well as a few sockets.

[Bryce]

No problem. Send it over (send me a PM for details).

Bryce.