C-64 diagnostic checks the zeropage, stackpage, colour ram, etc... It found 
the bad memory U21 on 64K ram. I was checking the mainboard, there is no U21 
printed on the board. I dont know if the board is different. The board was 
made in 1986 and Hong Kong. Other printed is W-18 94HB. Anyone help me where 
I find the memory chip?

JT 

"Jack Tseng" <tseng4@hotmail.com> wrote in message 
news:s7Gin.9733$mn6.7678@newsfe07.iad...
> C-64 diagnostic checks the zeropage, stackpage, colour ram, etc... It 
> found the bad memory U21 on 64K ram. I was checking the mainboard, there 
> is no U21 printed on the board. I dont know if the board is different. The 
> board was made in 1986 and Hong Kong. Other printed is W-18 94HB. Anyone 
> help me where I find the memory chip?
>


http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg

If that looks like your board, there are two DRAMs directly above where it 
says PCB ASSY on the mainboard.

DRAM failure is common for that board, especially if the power supply has 
ripple so you best check that too. 

"Clocky" <notgonn@happen.com> wrote in message 
news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>
> "Jack Tseng" <tseng4@hotmail.com> wrote in message 
> news:s7Gin.9733$mn6.7678@newsfe07.iad...
>> C-64 diagnostic checks the zeropage, stackpage, colour ram, etc... It 
>> found the bad memory U21 on 64K ram. I was checking the mainboard, there 
>> is no U21 printed on the board. I dont know if the board is different. 
>> The board was made in 1986 and Hong Kong. Other printed is W-18 94HB. 
>> Anyone help me where I find the memory chip?
>>
>
>
> http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>
> If that looks like your board, there are two DRAMs directly above where it 
> says PCB ASSY on the mainboard.
>
> DRAM failure is common for that board, especially if the power supply has 
> ripple so you best check that too.
>

I think I found C64 PSB ASSY #250466, it looks exactly one as mine.

http://www.auctiva.com/hostedimages/showimage.aspx?gid=45129&ppid=1122&image=300723127&images=300723127&formats=0&format=0

"Jack Tseng" <tseng4@hotmail.com> wrote in message 
news:Uj_in.215862$OX4.209979@newsfe25.iad...
>
> "Clocky" <notgonn@happen.com> wrote in message 
> news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>>
>> "Jack Tseng" <tseng4@hotmail.com> wrote in message 
>> news:s7Gin.9733$mn6.7678@newsfe07.iad...
>>> C-64 diagnostic checks the zeropage, stackpage, colour ram, etc... It 
>>> found the bad memory U21 on 64K ram. I was checking the mainboard, there 
>>> is no U21 printed on the board. I dont know if the board is different. 
>>> The board was made in 1986 and Hong Kong. Other printed is W-18 94HB. 
>>> Anyone help me where I find the memory chip?
>>>
>>
>>
>> http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>>
>> If that looks like your board, there are two DRAMs directly above where 
>> it says PCB ASSY on the mainboard.
>>
>> DRAM failure is common for that board, especially if the power supply has 
>> ripple so you best check that too.
>>
>
> I think I found C64 PSB ASSY #250466, it looks exactly one as mine.
>
> http://www.auctiva.com/hostedimages/showimage.aspx?gid=45129&ppid=1122&image=300723127&images=300723127&formats=0&format=0
>
>

What are the numbers on the two chips in the left corner of the board above 
the bare section to the left of the empty solderpads? Those two 18 pin chips 
look like the DRAM's. 

Hello Jack,

This is the rare version motherboard and used in the C64C. The serial
number ends with B3...
And Clocky is right: the two 18 pins are the DRAM's !

Here you can find the different C64 motherboards:
http://www.cbmhardware.de/c64/c64board.php?Lang=E

SAM

"Sam" <siemappelman@quicknet.nl> wrote in message 
news:7f0cabbe-d77a-4a2d-aa41-73f8e0a7e034@q15g2000yqj.googlegroups.com...

>
> Here you can find the different C64 motherboards:
> http://www.cbmhardware.de/c64/c64board.php?Lang=E
>
> SAM
>


Good link Sam, thanks for posting! 

"Clocky" <notgonn@happen.com> wrote in message 
news:4b8c73bd$0$8841$c3e8da3@news.astraweb.com...
>
> "Jack Tseng" <tseng4@hotmail.com> wrote in message 
> news:Uj_in.215862$OX4.209979@newsfe25.iad...
>>
>> "Clocky" <notgonn@happen.com> wrote in message 
>> news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>>>
>>> "Jack Tseng" <tseng4@hotmail.com> wrote in message 
>>> news:s7Gin.9733$mn6.7678@newsfe07.iad...
>>>> C-64 diagnostic checks the zeropage, stackpage, colour ram, etc... It 
>>>> found the bad memory U21 on 64K ram. I was checking the mainboard, 
>>>> there is no U21 printed on the board. I dont know if the board is 
>>>> different. The board was made in 1986 and Hong Kong. Other printed is 
>>>> W-18 94HB. Anyone help me where I find the memory chip?
>>>>
>>>
>>>
>>> http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>>>
>>> If that looks like your board, there are two DRAMs directly above where 
>>> it says PCB ASSY on the mainboard.
>>>
>>> DRAM failure is common for that board, especially if the power supply 
>>> has ripple so you best check that too.
>>>
>>
>> I think I found C64 PSB ASSY #250466, it looks exactly one as mine.
>>
>> http://www.auctiva.com/hostedimages/showimage.aspx?gid=45129&ppid=1122&image=300723127&images=300723127&formats=0&format=0
>>
>>
>
> What are the numbers on the two chips in the left corner of the board 
> above the bare section to the left of the empty solderpads? Those two 18 
> pin chips look like the DRAM's.
>

it is MN41464-15 Japan 64432 on the U9 and U10 sockets. 

Jack Tseng wrote:
> "Clocky" <notgonn@happen.com> wrote in message
> news:4b8c73bd$0$8841$c3e8da3@news.astraweb.com...
>>
>> "Jack Tseng" <tseng4@hotmail.com> wrote in message
>> news:Uj_in.215862$OX4.209979@newsfe25.iad...
>>>
>>> "Clocky" <notgonn@happen.com> wrote in message
>>> news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>>>>
>>>> "Jack Tseng" <tseng4@hotmail.com> wrote in message
>>>> news:s7Gin.9733$mn6.7678@newsfe07.iad...
>>>>> C-64 diagnostic checks the zeropage, stackpage, colour ram,
>>>>> etc... It found the bad memory U21 on 64K ram. I was checking the
>>>>> mainboard, there is no U21 printed on the board. I dont know if
>>>>> the board is different. The board was made in 1986 and Hong Kong.
>>>>> Other printed is W-18 94HB. Anyone help me where I find the
>>>>> memory chip?
>>>>
>>>>
>>>> http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>>>>
>>>> If that looks like your board, there are two DRAMs directly above
>>>> where it says PCB ASSY on the mainboard.
>>>>
>>>> DRAM failure is common for that board, especially if the power
>>>> supply has ripple so you best check that too.
>>>>
>>>
>>> I think I found C64 PSB ASSY #250466, it looks exactly one as mine.
>>>
>>> http://www.auctiva.com/hostedimages/showimage.aspx?gid=45129&ppid=1122&image=300723127&images=300723127&formats=0&format=0
>>>
>>>
>>
>> What are the numbers on the two chips in the left corner of the board
>> above the bare section to the left of the empty solderpads? Those
>> two 18 pin chips look like the DRAM's.
>>
>
> it is MN41464-15 Japan 64432 on the U9 and U10 sockets.

That's them. You can replace them with virtually any xx464 memory chip, I 
would recommend removing both DRAMs and replacing them with sockets.

"Clocky" <notgonn@happen.com> wrote in message 
news:4b8ee8bc$0$8757$c3e8da3@news.astraweb.com...
> Jack Tseng wrote:
>> "Clocky" <notgonn@happen.com> wrote in message
>> news:4b8c73bd$0$8841$c3e8da3@news.astraweb.com...
>>>
>>> "Jack Tseng" <tseng4@hotmail.com> wrote in message
>>> news:Uj_in.215862$OX4.209979@newsfe25.iad...
>>>>
>>>> "Clocky" <notgonn@happen.com> wrote in message
>>>> news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>>>>>
>>>>> "Jack Tseng" <tseng4@hotmail.com> wrote in message
>>>>> news:s7Gin.9733$mn6.7678@newsfe07.iad...
>>>>>> C-64 diagnostic checks the zeropage, stackpage, colour ram,
>>>>>> etc... It found the bad memory U21 on 64K ram. I was checking the
>>>>>> mainboard, there is no U21 printed on the board. I dont know if
>>>>>> the board is different. The board was made in 1986 and Hong Kong.
>>>>>> Other printed is W-18 94HB. Anyone help me where I find the
>>>>>> memory chip?
>>>>>
>>>>>
>>>>> http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>>>>>
>>>>> If that looks like your board, there are two DRAMs directly above
>>>>> where it says PCB ASSY on the mainboard.
>>>>>
>>>>> DRAM failure is common for that board, especially if the power
>>>>> supply has ripple so you best check that too.
>>>>>
>>>>
>>>> I think I found C64 PSB ASSY #250466, it looks exactly one as mine.
>>>>
>>>> http://www.auctiva.com/hostedimages/showimage.aspx?gid=45129&ppid=1122&image=300723127&images=300723127&formats=0&format=0
>>>>
>>>>
>>>
>>> What are the numbers on the two chips in the left corner of the board
>>> above the bare section to the left of the empty solderpads? Those
>>> two 18 pin chips look like the DRAM's.
>>>
>>
>> it is MN41464-15 Japan 64432 on the U9 and U10 sockets.
>
> That's them. You can replace them with virtually any xx464 memory chip, I 
> would recommend removing both DRAMs and replacing them with sockets.
>
>

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=41574&productId=41574&cid=findchips

how s about it? 

Jack Tseng wrote:
> "Clocky" <notgonn@happen.com> wrote in message
> news:4b8ee8bc$0$8757$c3e8da3@news.astraweb.com...
>> Jack Tseng wrote:
>>> "Clocky" <notgonn@happen.com> wrote in message
>>> news:4b8c73bd$0$8841$c3e8da3@news.astraweb.com...
>>>>
>>>> "Jack Tseng" <tseng4@hotmail.com> wrote in message
>>>> news:Uj_in.215862$OX4.209979@newsfe25.iad...
>>>>>
>>>>> "Clocky" <notgonn@happen.com> wrote in message
>>>>> news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>>>>>>
>>>>>> "Jack Tseng" <tseng4@hotmail.com> wrote in message
>>>>>> news:s7Gin.9733$mn6.7678@newsfe07.iad...
>>>>>>> C-64 diagnostic checks the zeropage, stackpage, colour ram,
>>>>>>> etc... It found the bad memory U21 on 64K ram. I was checking
>>>>>>> the mainboard, there is no U21 printed on the board. I dont
>>>>>>> know if the board is different. The board was made in 1986 and
>>>>>>> Hong Kong. Other printed is W-18 94HB. Anyone help me where I
>>>>>>> find the memory chip?
>>>>>>
>>>>>>
>>>>>> http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>>>>>>
>>>>>> If that looks like your board, there are two DRAMs directly above
>>>>>> where it says PCB ASSY on the mainboard.
>>>>>>
>>>>>> DRAM failure is common for that board, especially if the power
>>>>>> supply has ripple so you best check that too.
>>>>>>
>>>>>
>>>>> I think I found C64 PSB ASSY #250466, it looks exactly one as
>>>>> mine. 
>>>>> http://www.auctiva.com/hostedimages/showimage.aspx?gid=45129&ppid=1122&image=300723127&images=300723127&formats=0&format=0
>>>>>
>>>>>
>>>>
>>>> What are the numbers on the two chips in the left corner of the
>>>> board above the bare section to the left of the empty solderpads?
>>>> Those two 18 pin chips look like the DRAM's.
>>>>
>>>
>>> it is MN41464-15 Japan 64432 on the U9 and U10 sockets.
>>
>> That's them. You can replace them with virtually any xx464 memory
>> chip, I would recommend removing both DRAMs and replacing them with
>> sockets.
>
> http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=41574&productId=41574&cid=findchips
>
> how s about it?

Perfect! 

On Mar 4, 12:23=A0am, "Clocky" <notg...@happen.com> wrote:
> Jack Tseng wrote:
> > "Clocky" <notg...@happen.com> wrote in message
> >news:4b8ee8bc$0$8757$c3e8da3@news.astraweb.com...
> >> Jack Tseng wrote:
> >>> "Clocky" <notg...@happen.com> wrote in message
> >>>news:4b8c73bd$0$8841$c3e8da3@news.astraweb.com...
>
> >>>> "Jack Tseng" <tse...@hotmail.com> wrote in message
> >>>>news:Uj_in.215862$OX4.209979@newsfe25.iad...
>
> >>>>> "Clocky" <notg...@happen.com> wrote in message
> >>>>>news:4b8b4dbb$0$8789$c3e8da3@news.astraweb.com...
>
> >>>>>> "Jack Tseng" <tse...@hotmail.com> wrote in message
> >>>>>>news:s7Gin.9733$mn6.7678@newsfe07.iad...
> >>>>>>> C-64 diagnostic checks the zeropage, stackpage, colour ram,
> >>>>>>> etc... It found the bad memory U21 on 64K ram. I was checking
> >>>>>>> the mainboard, there is no U21 printed on the board. I dont
> >>>>>>> know if the board is different. The board was made in 1986 and
> >>>>>>> Hong Kong. Other printed is W-18 94HB. Anyone help me where I
> >>>>>>> find the memory chip?
>
> >>>>>>http://www.c64-wiki.com/index.php/Image:C64Cmotherboard.jpg
>
> >>>>>> If that looks like your board, there are two DRAMs directly above
> >>>>>> where it says PCB ASSY on the mainboard.
>
> >>>>>> DRAM failure is common for that board, especially if the power
> >>>>>> supply has ripple so you best check that too.
>
> >>>>> I think I found C64 PSB ASSY #250466, it looks exactly one as
> >>>>> mine.
> >>>>>http://www.auctiva.com/hostedimages/showimage.aspx?gid=3D45129&ppid=
=3D112...
>
> >>>> What are the numbers on the two chips in the left corner of the
> >>>> board above the bare section to the left of the empty solderpads?
> >>>> Those two 18 pin chips look like the DRAM's.
>
> >>> it is MN41464-15 Japan 64432 on the U9 and U10 sockets.
>
> >> That's them. You can replace them with virtually any xx464 memory
> >> chip, I would recommend removing both DRAMs and replacing them with
> >> sockets.
>
> >http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId...
>
> > how s about it?
>
> Perfect!

U21 in the test equals U10 on your 2 DRAM board... It helps when you
have the manual that goes with it and the  DEAD-TEST Manual the
updates for later PCB revisions.... replace that one.  And check the
output of your power supply.. anytime ram is found to be bad....