Topic: Wanted : Memory Chips for C64  (Read 4938 times)

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Offline Panther

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Wanted : Memory Chips for C64
« on: June 04, 2009, 03:42:44 PM »
I'd like to repair a C64 (original version), that shows a memory error on boot up, but I'm struggling to find suitable ram chips, can anyone help out ?

Offline AndyRCM

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Re: Wanted : Memory Chips for C64
« Reply #1 on: June 04, 2009, 04:01:29 PM »
Yeah - we have a c64 in bits  . . .  you can certainly steal some chips from that if you want?

Andy
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Offline Panther

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Re: Wanted : Memory Chips for C64
« Reply #2 on: June 04, 2009, 04:13:02 PM »
Cheers for the offer Andy,

I think the problem with taking chips from the existing board is not frying them in the process with all the heat  :-\ I've got sockets to put on my board, so I can plug the new ones in, anyone any good at removing RAM chips  :P

Offline AndyT

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Re: Wanted : Memory Chips for C64
« Reply #3 on: June 04, 2009, 04:34:12 PM »
If you know that the chip is dead (and you dont mind damaging the old chip), the best way to remove the chip is to cut the legs off and remove each pin one by one using a soldering iron, tweezers, solder sucker and some solder braid.

You are less likely to damage the pcb then.
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1200xl

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Re: Wanted : Memory Chips for C64
« Reply #4 on: June 04, 2009, 11:32:31 PM »
never had a c64, what chips does it require?

Offline Panther

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Re: Wanted : Memory Chips for C64
« Reply #5 on: June 05, 2009, 12:22:55 AM »
Got this off Google  ::)

Early C64 computers have eight 4164 TTL RAM chips installed

1200xl

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Re: Wanted : Memory Chips for C64
« Reply #6 on: June 05, 2009, 12:48:49 AM »
not sure if these will work, but they do with 8bit Ataris, even though they are 41256
http://www.grandata.co.uk/4125612-p-5579.html

Offline Akastaff

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Re: Wanted : Memory Chips for C64
« Reply #7 on: June 05, 2009, 08:38:43 AM »
Salvage from an old board though be warned that the RAM is the biggest culprit for killing 64's in the first place. Heat shouldnt be to much of an issue, watch the solder go molten and soon as you can move the leg with the tip use a solder sucker to remove. Check all legs are free then lift chip slowely from board. If it puts up a fight, repeat process on any pins that are still tacked to the board, usually the ground is the pig being lot thickier trace. Modern chips are more prone to heat damage and static damage due to being much more complex devices.

Always put in a socket, checking the correct orientation (notch is same way to id pin 1). 4164 chips where common place at the time and used in numerous systems and electronics. Good way to detect a bad one is let the board warm up, get some freeze spray and freeze the RAM bank and the culrpits will often be hotter than there counterparts. If no freeze spray then use your top lip (dont slobber in machine) and run it accross the chips... you look a bit daft but your top lip is very heat sensetive and you can determine a warmer chip quiet easily. Was common practice for speed repairs otherwise after that its logic probes and scopes.

Chances are you only have 1 or 2 bad RAMS, not all will be faulty, if they are then chances are the PSU is bad.


If your stuck feel free to PM me, I repaired 1000's of the damn things for commodore  ;D

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Re: Wanted : Memory Chips for C64
« Reply #8 on: June 05, 2009, 09:41:16 AM »
I have got 5 un-tested 4264-15 that you can have if they will work on the C=,

Offline Blackpanther

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Re: Wanted : Memory Chips for C64
« Reply #9 on: June 07, 2009, 12:21:03 AM »
Give these a go. They don't have any in stock but maybe if you contact them, they mite be able to help you.

http://stores.shop.ebay.co.uk/The-Commodore-Store
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Offline Womble

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Re: Wanted : Memory Chips for C64
« Reply #10 on: June 07, 2009, 10:00:48 AM »
4164s are very common chips of the era and often pop up on ebay.

The problem you will face is you have no way to know which chip is the faulty one (or more than one) on the C64. These are 64 Kbit chips but they are 1 bit wide, by that I mean that at each of the 65536 memory address locations the chip only holds 1 bit, so the C64 (and most machines of the era) use 8 of them, each chip providing 1 bit for every byte. The address lines are common so every chip reads the same address at the same time as all the others, and their outputs are carried separately on the Data bus. So, any chip could be the culprit, as every chip has the ability to bugger up every byte in the RAM stack. Finding out which chip is dead without a scope is going to be almost impossible. You might get lucky if the output pin is stuck high or low, but memory chips rarely die in that way, usually the output is flapping about but not being useful, so a logic probe is useless.

The second problem is that it is very hard to get a chip off the board without a proper desolder station, solder pumps and solder braid are next to useless I have found for clearing solder from around chip legs. You will probably do more damage to the board with multiple attempts at getting the solder out. The chip will probably survive but its not certain.

Not the news you were hoping for I imagine, also piggy backing RAM chips on the old ones has about 50/50 chance of showing anything useful.

I would happily fix it up for you, but I guess the postage would be a bit steep for such a common machine.
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1200xl

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Re: Wanted : Memory Chips for C64
« Reply #11 on: June 07, 2009, 10:40:57 AM »
I have had good success with the snip the legs off the chip and use de-soldering wick method.
Make sure you get some descent wick though, I use Rosin Chem-wick and buy it from Grandata, the stuff from Craplins is utter garbage and will do more harm than good

Offline Womble

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Re: Wanted : Memory Chips for C64
« Reply #12 on: June 07, 2009, 11:17:34 AM »
I have had good success with the snip the legs off the chip and use de-soldering wick method.

If you snip the legs off then you can removed them one by one with pliers and a soldering iron, then use a solder sucker to clear the holes from beneath. It does mean that you risk chopping off perfectly good chips and you have to be prepared to replace all 8.
Sic Transit Gloria Atari

Offline Blackpanther

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Re: Wanted : Memory Chips for C64
« Reply #13 on: June 07, 2009, 02:17:10 PM »
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Offline AndyT

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Re: Wanted : Memory Chips for C64
« Reply #14 on: June 07, 2009, 03:12:30 PM »
I have a breadbox C64 you can have when you pop over. Will check its condition later.
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