Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss

41464 ram equivalent chips ?

1,308 views
Skip to first unread message

Reini

unread,
Apr 24, 2002, 9:33:40 PM4/24/02
to
Hi group,

I have one C64-C which produces a black screen.
Since both 41464 rams are getting very hot some seconds after power-up,
while all other chips stay cool, I suspect them being shorted.

But I cannot find any new 41464 rams in my area :(

Does anyone know of some other chips which are equivalent to the 41464 or
some others which could replace them ?
I think I once read that it is possible to use bigger rams which are still
available ( or easier to get ) and then connect some pins to ground or
something like that.

If anyone knows more about this, please help me.

Thanks,

Reini

A E

unread,
Apr 24, 2002, 9:54:34 PM4/24/02
to
Reini wrote:
>
> Hi group,
>
> I have one C64-C which produces a black screen.
> Since both 41464 rams are getting very hot some seconds after power-up,
> while all other chips stay cool, I suspect them being shorted.

Sounds reasonable. I have several 128D's that did that. All the DRAMs
(464) were toast. They usually run cool when OK.

>
> But I cannot find any new 41464 rams in my area :(

Do you have any used computer/scrap dealers? Pick up an old PC
motherboard or video card. Standard VGA video cards from late 80s-early
90s have a good chance of having some (sometimes on sockets even!).
That's how I got 16 of the chips, all good, for 5$ Can!

>
> Does anyone know of some other chips which are equivalent to the 41464 or
> some others which could replace them ?

Usually the '464' is buried somehwere in the part number, like the Intel
P21464, or the Hyundai 53CY464.

> I think I once read that it is possible to use bigger rams which are still
> available ( or easier to get ) and then connect some pins to ground or
> something like that.

I've heard the 44256 can be used, but I've never had to since 464s are
so easy to find, at least for me. :)


>
> If anyone knows more about this, please help me.
>

Email me your snail mail and I can send you two if you can't find any.

> Thanks,
>
> Reini

Raymond Carlsen

unread,
Apr 24, 2002, 11:37:54 PM4/24/02
to Reini
> I have one C64-C which produces a black screen. Since both 41464 rams are
> getting very hot some seconds after power-up, while all other chips stay
> cool, I suspect them being shorted.

Reini,
Yep, hot RAM chips are shorted. Someone answered your other questions
about sourcing replacement chips, but I must add that your power supply may
have killed that RAM. If only one chip had failed, I might say it just went
bad on it's own. Two chips? Nope. One nasty failure mode of the black brick
is overvoltage, and TTL RAM chips are most vulnerable to that. The supply
may check OK when cold but the regulator can fail (leaky or shorted) and
put out too much voltage after warmup. I torched two C64s with one bad
supply before I realized what was happening.

Ray

Reini

unread,
Apr 25, 2002, 5:14:49 AM4/25/02
to

Raymond Carlsen schrieb in Nachricht ...

> Yep, hot RAM chips are shorted. Someone answered your other questions
>about sourcing replacement chips, but I must add that your power supply may
>have killed that RAM. If only one chip had failed, I might say it just went
>bad on it's own. Two chips? Nope.

Well, I don't know anything about the former 'life' of this C64 because I
got it donated without psu. So I cannot tell if it was fried due to a bad
psu.
But the psu I now use to test it is 100% ok.

But thanks for this info !
If the rams got fried due to a bad psu then I hope the other chips still
work and haven't been fried as well....

Reini

Reini

unread,
Apr 25, 2002, 5:29:45 AM4/25/02
to

A E schrieb in Nachricht <3CC761DA...@videotron.ca>...

>Sounds reasonable. I have several 128D's that did that. All the DRAMs
>(464) were toast. They usually run cool when OK.
>


Yes, they get hot when shorted. But they can also fail by going open and
then they stay cool and cannot be identified as fried so easy. But it my
case I am pretty sure it is

>Do you have any used computer/scrap dealers? Pick up an old PC
>motherboard or video card. Standard VGA video cards from late 80s-early
>90s have a good chance of having some (sometimes on sockets even!).
>That's how I got 16 of the chips, all good, for 5$ Can!

>Usually the '464' is buried somehwere in the part number, like the Intel
>P21464, or the Hyundai 53CY464.
>


Thanks !
I will have a look on the fleamarket next time :)

>I've heard the 44256 can be used, but I've never had to since 464s are
>so easy to find, at least for me. :)
>>


Oh, great ! I have an old PC grafic card here that has lots of 44256 rams
which I once saved to upgrade ram in an A-500.

>Email me your snail mail and I can send you two if you can't find any.
>


Thanks for your kind offer, but I hope I will find some here in Austria as I
suppose you are from the US ( shipping and money transaction will get too
expensive, I think )

Reini

A E

unread,
Apr 25, 2002, 1:40:57 PM4/25/02
to
>
> Thanks for your kind offer, but I hope I will find some here in Austria as I
> suppose you are from the US ( shipping and money transaction will get too
> expensive, I think )
>
Nah, free... If you can't find any, then email me...

A E

unread,
Apr 25, 2002, 1:53:12 PM4/25/02
to
Raymond Carlsen wrote:

> Yep, hot RAM chips are shorted. Someone answered your other questions
> about sourcing replacement chips, but I must add that your power supply may
> have killed that RAM. If only one chip had failed, I might say it just went
> bad on it's own. Two chips? Nope. One nasty failure mode of the black brick

How about 128DCRs? Are there any known PS weaknesses? I can't figure out
why all three 128DCRs motherboards I got all had toasted DRAMs. Then I
got a dead 128DCR with casing from eBay, I tested the supply with a
dummy load and it works fine, although the MB in that one ALSO had
toasty DRAMs..... Thank (your deity) for PC video cards. :)

Circus

unread,
May 6, 2002, 2:15:39 AM5/6/02
to
44256 chips are pin compatible with 464 chips. I think you just bend the two
most signifigint address lines out or something similar.

circus

A E <aeis...@videotron.ca> wrote in message
news:3CC761DA...@videotron.ca...

Ville Jouppi

unread,
May 6, 2002, 2:57:00 PM5/6/02
to
On Sun, 5 May 2002 23:15:39 -0700, "Circus" <circ...@splam.hotmail.com>
wrote:

>44256 chips are pin compatible with 464 chips. I think you just bend the two
>most signifigint address lines out or something similar.

I'd say tie them to ground. You'll probably get interesting results if you
just leave them floating.
--
CBM, Amiga and PEZ-nut, Scout, Glider pilot, Administrator
Email: vjo...@sci.fi, URL: http://www.sci.fi/~vjouppi/
GSM: +358-40-5679999, IRCNet: Jope
**** COMMODORE BASIC V2 ****

Sergio Aguayo

unread,
May 8, 2002, 4:43:49 PM5/8/02
to
I own a C64 with a strnge assy number: 2550425. Can someone give me a
downloadable of it's schematics?


Louis Mazzei

unread,
May 9, 2002, 5:34:08 AM5/9/02
to
Good luck to you in this... in my experience with bad PSUs on 64s is
that SID is often among the first to be slagged as well, so be sure and
check your sound really well, too. Try it with a SID player so you can
check all three voices, though when mine have fried it's always been no
sound whatsoever.

Louis


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

AxiMaxi

unread,
May 13, 2002, 2:33:07 PM5/13/02
to

What's so strange about it?

~AxiMaxi

Sam Gillett

unread,
May 13, 2002, 11:58:59 PM5/13/02
to

Sergio Aguayo ...

>I own a C64 with a strnge assy number: 2550425. Can someone give me a
>downloadable of it's schematics?

Look on funet for the schematics (don't have the URL handy...) or on Ray
Carlseon's site:

http://landru.myhome.net/rcarlsen

Best regards,

Sam Gillett aka Mars Probe @ Starship Intrepid 1-972-221-4088
Last 8-bit BBS in the Dallas area. Commodore lives!


0 new messages