SX repair help ~ pic link included
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From: polishedball on 17 Feb 2010 16:56 I have socketed and swapped every chip on the CPU board with known good chips. Thats why I am leaning to a clocking perhaps crystal issue right now. Or that out sourced piggy back board on the cpu that has the crystals. my handy work http://home.comcast.net/~polishedball/socket.jpg Every chip that came out of the SX went back into the donor c-64 and it works fine. john On Feb 17, 2:59 pm, Michael <mister...(a)gmail.com> wrote: > On Feb 16, 1:44 pm, polishedball <polishedb...(a)gmail.com> wrote: > > > > > > > Well my search for an SX-64 brought me to a broken one, I was > > thinking no problem plenty of repair guides and I was a bench tech for > > 10 years until board swaps became the norm. I haven't dug in far yet > > but was surprised that the suggested chip swaps did nothing. I am > > suspecting a logic chip and am curious if anyone has any guesses as > > this unit isn't friendly to work on in it design while hot. Gonna > > download the schematics now. > > > 1) Have garbage screen with border (maybe the check-board i have read > > about) > > 2) Cartridge slot doesn't appear to work. > > 3) Swapped Vic Chip with known good Same problem > > 4) Swapped PLA with known Good Same problem > > 5) Swapped character rom Same problem > > > Screen pics > > >http://home.comcast.net/~polishedball/screen.jpghttp://home.comcast.n... > > > Thanks for any thoughts > > > John > > Look at Ray Carlton's sheets, the SX-64 has a lot missing compaired to > the 64 on. Basically the same issue with chips would affect either. > > Since you appear not to have any problem on that document (besides the > PLA) I checked the 64 one. The U numbers might be different but should > be the same chip. > > U6 2114 SRAM (COLOR RAM) > Startup screen shows flickering characters with shimmering > colors. check also PLA U17. > > U16 CD4066 (generic CMOS quad bilateral switch) > Color problems such as random color "checkerboard" pattern on > screen or no color. > > Check by removing SID and seeing if works. > U18 906112-01 (6581) SID > Normal screen. No sound or garbled sound. Mouse or graphics > tablet > pointer stuck or jitters. If shorted, can cause blank or "garbage" > screen. > NOTE: computer will work without a SID plugged in (unplug to check). > This > chip normally runs hot. > > U26 74LS373 LOGIC > Startup screen has normal border, but characters are scrambled.. > > U27 74LS08 (or MOS7712) LOGIC > Normal startup border, but screen full of "garbage" characters.. > > I would say Yank the SID first and try. Then, if you have access to > another 64, swap the 74LS08 chip. That really looks like what you got. > Where it is in the SX is another story.
From: polishedball on 17 Feb 2010 18:57 Fixed it actually turned out to be a CIA chip error on the I/O board. Thanks everyone.
From: Michael on 18 Feb 2010 07:53 On Feb 17, 6:57 pm, polishedball <polishedb...(a)gmail.com> wrote: > Fixed it actually turned out to be a CIA chip error on the I/O board. > Thanks everyone. Good to here. BTW, this is the second one that was found bad in a few months. Here is a post in regards to another one that was found: http://www.lemon64.com/forum/viewtopic.php?t=32578&highlight=cia
From: none on 18 Feb 2010 11:13 "polishedball" <polishedball(a)gmail.com> wrote in message news:03346688-0330-48ad-8f79-baf08c8f8309(a)j31g2000yqa.googlegroups.com... > On Feb 17, 10:29 am, bluebirdpod <bluebird...(a)gmail.com> wrote: >> Have you checked your power supply voltages, The SX-64's MSPS has been >> known to cause all kinds of >> problems. And does not have much spare capacity, as I know of a SX-64 >> that had an additional drive installed >> along with its controller board to make a artificial DX-64. Its now >> located in Bo Zimmers collection and came >> from Colorado. > > Yep 5v 12v and 9vac are all good on meter will scope them tonight for > ripple. > Sorry John For pointing you at a lemon. It looks like it`s been passed from ebayer<> ebayer! Well, at least you`ve got the foremost C64`ers on the planet under your nose to help. Just don`t be rude to them, and be patient for a reply.
From: polishedball on 18 Feb 2010 13:44
This was a different unit, bought it actually for just the case as it was really nice. I had located a working one with a smashed top, bent handle and was going to combine them into one unit. I then decided to work on this one out of habit (I can fix that ;)). So thanks everyone for the lead to a box and your help with this one. It is now working. > > Sorry John > > For pointing you at a lemon. > > It looks like it`s been passed from > ebayer<> ebayer! > > Well, at least you`ve got the > foremost C64`ers on the planet > under your nose to help. > Just don`t be rude to them, > and be patient for a reply. |