Closed Commodore 64 Repair WANTED

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mancity12

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Hi guys,

I'm looking for somebody who can repair my C64 please?

The images are all garbled up probably due to it being in the loft the past 15 years.

Images here - http://imageshack.us/g/1/9953513/

If you could let me know I would really appreciated and a possible total cost too.


Regards,
 
rom defect or ram, have cartridge for test?
more cartridge exclude internal rom
 
rom defect or ram, have cartridge for test?
more cartridge exclude internal rom

I have one cartridge game and that loads, but the image is all scrambled. The scrambled black image is hat cartridge trying to load. Music comes on, but the image is broken.

Hope that helps. Let me know if anybody can help.
 
It could be that the PLA or RAM is on it's way out. Is this a 'Breadbin' early C64 or a later C64C?

I have a donor board for the early C64 and could desolder the PLA or RAM from that for you; whereabouts are you in Lancashire?
 
It could be that the PLA or RAM is on it's way out. Is this a 'Breadbin' early C64 or a later C64C?

I have a donor board for the early C64 and could desolder the PLA or RAM from that for you; whereabouts are you in Lancashire?

I have the earlier Amiga looking one Mate. I'm in Oldham if that's any good?

I'm happy to pay for parts, work, p&p etc etc. I just want this baby working again :)
 
I think is PLA.

I have used with success an EPROM 27C512 as replacement of original chip. You can Google EPROM PLA :)
 
It could be that the PLA or RAM is on it's way out. Is this a 'Breadbin' early C64 or a later C64C?

I have a donor board for the early C64 and could desolder the PLA or RAM from that for you; whereabouts are you in Lancashire?

I have the earlier Amiga looking one Mate. I'm in Oldham if that's any good?

I'm happy to pay for parts, work, p&p etc etc. I just want this baby working again :)

The 'Amiga' looking one is the C64C model and it's the later one. The old C64 was a sort of grey/brown colour and was nicknamed the 'Breadbin' because of it's shape, like the old breadbins.

@ Gennyflick / anyone

My first thought was PLA as well. Do you know if the earlier PLA will fit the later model, as a direct swap-out?

@Mancity12

The PLA (chip U5) in the board I've got is version 901225-01 - what version is the one on your board?

My board still has the RAM chips, if any need to be swapped out.
 
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I have see PCB image now: this is one of the last versions, in this case isn't possible PLA replacement using an EPROM because PLA chip is not present. Try change RAM chip and electrolitic capacitors.

---------- Post added at 23:01 ---------- Previous post was at 22:56 ----------

@ Gennyflick / anyone

My first thought was PLA as well. Do you know if the earlier PLA will fit the later model, as a direct swap-out?

In this version there isn't PLA chip, however in older versions you can use same PLA.
 
@ Genny_flick

Is this the version with the 906114-01 PLA in it?

@Mancity12

If it's the RAM chips, you need to source some 64k x4 DRAM chips. A certain auction site *cough* may be able to assist you.
 
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problem is ram 2114 or 41464
the pla not exist, there are 251715-01 in the c64c
 
@ Genny_flick

Is this the version with the 906114-01 PLA in it?


Hi mate,

901225-01 is character rom;

906114-01 is PLA (still same in all PCB having 8 x 4164 chips (64K x 1bit)

C64C version have a glue logic chip to reduce more of TTL chip of previous version and PLA. This is an all in one solution ;)
 
So, basically we need to know which RAM chips are on his board, either 2114 or 41464 DRAMs? Are these interchangeable, as they both appear to be 18-pin devices? I realise it may be an 'either one or the other' situation and that you can't mix them.

@ Genny_flick

The early board I have (250407) dating from 1983 still has all of the 4164 RAM chips on it. I'll remove them over the next few days and keep them to one side for this repair.
 
No, the 2 types of RAM have a different job in C64:

4164 or 41464, classic RAM for programs and datas;
2114 is the COLOR RAM, used to generate video image.
 
This version I have is all 4164 RAM chips, 15 nanosecond versions, unless I'm missing something; I am tired though so the grey slush isn't 100%.

The version I have is definitely 250407, Artwork No. 251137 Rev C. It's an older version than the C64C that Mancity12 has.
 
@ Genny_flick

The early board I have (250407) dating from 1983 still has all of the 4164 RAM chips on it. I'll remove them over the next few days and keep them to one side for this repair.


4164 RAM is very easy to find and his cost is very low.

To summarize:

2114 have 1Kb x 4 bit and is COLOR RAM;
4164 have 64Kb x 1 bit, so 8 chips required to make a BYTE;
41464 have 64Kb x 4 bit, so 2 chips required to make a BYTE :)
 
2114 is a sram
41464 is a dram
not are pin to pin

mn2114n-3l = lc3514a-15

m41464-15 = lh2464-12
 
OK, I understand all of that, but I don't remember seeing any 2114 SRAM chips on the old C64 board I was looking at last night, unless I missed something.
 
OK, I understand all of that, but I don't remember seeing any 2114 SRAM chips on the old C64 board I was looking at last night, unless I missed something.

Would it at all help if I listed all the Chips on my C64 tonight Merlin?

Also, dont know if it helps, but this is the one I have here http://scacom.bplaced.net/Collection/64/6419.jpg and it was bought in 1990. It has a test date inside of 1990 too.
 
Hi,

If you could take a couple of hi-res photos of the board and stick them up on Photobucket or similar, we can probably work out what chips are present from those.

There were several revisions of C64C motherboards and it's best if we work on your actual board; Commodore weren't averse to 'mix and match' when it came to chips at times.

Edit: It's chips U10 and U11 we are interested in, as these are the RAM chips. They should be 41464 -150 DRAMs, according to the schematics. These are the ones that are likely to need replacing.

We are also interested in chip U19 (the 2114 video SRAM chip). If replacing the RAM chips makes no difference, this chip is next on the list for a swap-out.

Schematics are here:-
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/index.html

A good night's sleep and some coffee and I'm back on the case.
 
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