Welcome, Guest. Please login or register.
Forums
« previous next »
Pages: [1]   Go Down

Author Topic: Whats going on with this A500?  (Read 4300 times)

Description:

0 Members and 1 Guest are viewing this topic.

Offline gunniTopic starter

  • Jr. Member
  • **
  • Join Date: Jun 2011
  • Posts: 83
  • Country: scotland
  • Gender: Male
    • Show only replies by gunni
Whats going on with this A500?
« on: August 23, 2011, 04:15:25 PM »
Since my girlfriend managed to acquire a box of various commodore goodies a while back I haven't had much time to really investigate other than getting one A500 up and running and doing a bit of gaming and testing out the 3 C64s (2 dead one working but I'll get back to that later).
Today I decided to get the (hideously yellowed) other A500 out of its box to see if it was working and came across a curious switch next to the joystick 1 port. I popped in a workbench disk and switched on, all went well so I decided I would try to boot up after flicking the switch to see what happened. Nothing happened... the insert disk screen was there and the floppy drive was doing nothing.
Even more curious I opened it up and even through the shielding I could see there were "extra bits".
Anyway... can anyone give me a clue to what is going on with this frankenstein A500?






Sorry about the pic quality by the way... any suggestions to the wiring on this memory expansion? The yellow wire has no wire exposed so I don't think its been connected anywhere and the other 2 have been connected together...



Also, with regard to the C64's - the 2 non functioning ones seem to have chips missing although I can't tell if it would be the same chip or not as one is a 64C. Can anyone point me to someplace that might help me identify the missing chips?
Thanks!
Logged
 

Offline Franko

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 5707
    • Show only replies by Franko
Re: Whats going on with this A500?
« Reply #1 on: August 23, 2011, 05:00:45 PM »
Quote from: gunni;655868
Also, with regard to the C64's - the 2 non functioning ones seem to have chips missing although I can't tell if it would be the same chip or not as one is a 64C. Can anyone point me to someplace that might help me identify the missing chips?
Thanks!


Can't help with that weird setup on the A500 but if you could post some pics or open up the C64's and tell me what chips are missing by identifying them from their component reference numbers printed on the motherboard, I'll be able to tell you which chips are missing as I have the Commodore C64 service manuals and all the different models of the C64 myself... :)
Logged
 

Offline RobertB

  • VIP / Donor - Lifetime Member
  • Hero Member
  • *****
  • Join Date: Jun 2005
  • Posts: 2026
  • Thanked: 31 times
    • Show only replies by RobertB
    • http://www.dickestel.com/fcug.htm
Re: Whats going on with this A500?
« Reply #2 on: August 23, 2011, 05:24:17 PM »
Quote from: gunni;655868
Can anyone point me to someplace that might help me identify the [C64] missing chips?

Try http://www.commodore.ca/products/c64/commodore_64_motherboard_1982_1992.jpg

Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
Logged
 

Offline gunniTopic starter

  • Jr. Member
  • **
  • Join Date: Jun 2011
  • Posts: 83
  • Country: scotland
  • Gender: Male
    • Show only replies by gunni
Re: Whats going on with this A500?
« Reply #3 on: August 23, 2011, 06:18:03 PM »
thanks guys, I'll open them up again a bit later and have a look :)

the mystery components in the A500 are a Roctec RM2MC 2Mbyte Expansion board and daughterboards, although I'm pretty damn sure the wires on the expansion card itself should not be loose like that
Logged
 

Offline psxphill

Re: Whats going on with this A500?
« Reply #4 on: August 23, 2011, 06:39:25 PM »
Quote from: gunni;655879
thanks guys, I'll open them up again a bit later and have a look :)
 
the mystery components in the A500 are a Roctec RM2MC 2Mbyte Expansion board and daughterboards, although I'm pretty damn sure the wires on the expansion card itself should not be loose like that

From the position of the wires I'd say they were an enable/disable switch for the clock or ram. Probably fine for them to be like that.
 
The processor looks like a 14mhz one.
Logged
 

Offline gunniTopic starter

  • Jr. Member
  • **
  • Join Date: Jun 2011
  • Posts: 83
  • Country: scotland
  • Gender: Male
    • Show only replies by gunni
Re: Whats going on with this A500?
« Reply #5 on: August 23, 2011, 07:15:28 PM »
missing C64 chips: from C64C - U9, from breadbin C64 - U18
Logged
 

Offline Franko

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 5707
    • Show only replies by Franko
Re: Whats going on with this A500?
« Reply #6 on: August 23, 2011, 08:30:54 PM »
Quote from: gunni;655885
missing C64 chips: from C64C - U9, from breadbin C64 - U18


U18 = 6581 SID Chip : Commodore Part Number "C 906112-01"

U9 is a bit more difficult to tell you what that is as the service manual covers 3 different motherboard revisions and of the four C64c's that I have unfortunately none of them are covered in the service manual... :(

All I can tell you about U9 is the following...

According to the service manual for the following motherboard revisions U9=

MB REV 326106 / 251138 & 251469 then U9 = 4164 (200 ns) (RAM CHIP) Commodore Part No "901505-01"

On My own physical C64c's...

MB REV 252311 then U9 = 8580RS

So apart from U18 being the SID Chip, U9 can be any of the above until you check which motherboard revision you have by opening it up... ;)

Hope this helps... :)
Logged
 

Offline RobertB

  • VIP / Donor - Lifetime Member
  • Hero Member
  • *****
  • Join Date: Jun 2005
  • Posts: 2026
  • Thanked: 31 times
    • Show only replies by RobertB
    • http://www.dickestel.com/fcug.htm
Re: Whats going on with this A500?
« Reply #7 on: August 23, 2011, 08:31:27 PM »
Quote from: gunni;655885
missing C64 chips: from C64C - U9...

8580 SID chip
Quote
...from breadbin C64 - U18

6581 SID chip

Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
Logged
 

Offline Franko

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 5707
    • Show only replies by Franko
Re: Whats going on with this A500?
« Reply #8 on: August 23, 2011, 08:41:51 PM »
I've used the photo from the link RobertB supplied to point out where U9 is on my C64c's as the photo is of the REV 252311 board and if yours is this version the U9= 8580RS

Logged
 

Offline gunniTopic starter

  • Jr. Member
  • **
  • Join Date: Jun 2011
  • Posts: 83
  • Country: scotland
  • Gender: Male
    • Show only replies by gunni
Re: Whats going on with this A500?
« Reply #9 on: August 23, 2011, 09:29:44 PM »
yup, that one exactly Franko
thanks for your help :)
Logged
 

Offline Rob

Re: Whats going on with this A500?
« Reply #10 on: August 23, 2011, 10:03:53 PM »
The SID chips may have been removed to use on dual SID boards.  Have you looked inside the working one yet?
Logged
 

Offline gunniTopic starter

  • Jr. Member
  • **
  • Join Date: Jun 2011
  • Posts: 83
  • Country: scotland
  • Gender: Male
    • Show only replies by gunni
Re: Whats going on with this A500?
« Reply #11 on: August 24, 2011, 05:29:41 PM »
Quote from: Rob;655921
The SID chips may have been removed to use on dual SID boards.  Have you looked inside the working one yet?

I opened up the working one today... and its missing the SID chip too!
I assumed the missing chips were the reason for the others not working, apparently not!

Further investigation with the A500 reveals the switch previously mentioned is wired to the "EVEN CIA" chip. With the switch in one position the Amiga boots up fine but appears to have only 512K RAM, in the other position the floppy drive refuses to operate. Any ideas anyone?
Logged
 

Offline tone007

Re: Whats going on with this A500?
« Reply #12 on: August 24, 2011, 09:51:25 PM »
Quote from: Franko;655899


I can't stand these newer C64C boards, all raster dots and SID incompatibilities...
Logged
3 Commodore file cabinets, 2 Commodore USB turntables, 1 AmigaWorld beer mug
Alienware M14x i7 laptop running AmigaForever
 
Pages: [1]   Go Up
« previous next »