Re: Pet64 DOA

From: Philip Lord <random6000_at_mac.com>
Date: Sun, 12 Dec 2010 20:19:52 +0900
Message-id: <7DD4C0E1-09BC-48E2-A4F6-1059CBAC2A69@mac.com>
I put some pics of the machine in question here:

http://web.mac.com/lord_philip/other_computers/Commodore_PET_64.html


On Dec 10, 2010, at 6:19 PM, matt wrote:

> can i see some pix.
> is it a pet or c64???
> 
> ----- Original Message ----- From: "Philip Lord" <random6000@mac.com>
> To: <cbm-hackers@musoftware.de>
> Sent: Friday, December 10, 2010 7:08 PM
> Subject: Re: Pet64 DOA
> 
> 
>> Thanks Richard,
>> It's the PLL version as far as I know, as It's the original 326298-01  REV A board.
>> 
>> Well, I'm not sure I have any equipment that can test the clock  circuit, and I haven't the first idea how to approach it actually.
>> 
>> I think trying to acquire a second c64 motherboard would be a good  idea, but certainly not a cheap one as I'd probably have to buy a c64  from ebay and have it shipped from the US to Japan!!!
>> 
>> There is a C64 on Japan Yahoo auction at the moment, but it's like US $100+ !!!!
>> 
>> :-(
>> 
>> 
>> On Dec 10, 2010, at 1:29 PM, Richard Atkinson wrote:
>> 
>>> Is it a MOS 8701 based clock circuit or a discrete PLL version?  Probably the latter if it's an early C64 board. That's quite a  complex circuit with lots to go wrong. You should be looking for a  14.31818MHz crystal and a working circuit for that for the colour  clock, a divide by 14 circuit producing a 1.02MHz clock and an 8MHz  voltage controlled oscillator producing the dot clock, which gets  divided down by 8 by the VIC-II chip to produce another 1.02MHz  clock. These two 1.02MHz clocks should be kept phase locked by the  circuit controlling the 8MHz VCO.
>>> 
>>> Have you also tried the standard C64 chips trick of finding another  C64 board of the same era that's known to work, and swapping out all  the socketed chips in the Pet 64 board for the ones in the other  board?
>>> 
>>> Richard
>>> 
>>> 
>>> On Dec 10 2010, Philip Lord wrote:
>>> 
>>>> Thanks Richard,
>>>> Maybe I should have checked there first...
>>>> The reset pin 40 on the 6510 seems to get the correct reset signal,  It starts low then goes high. Can I assume that the reset is  working?
>>>> 
>>>> Maybe next I should look at the clock circuit as it doesn't look  like I'm getting any pulsing. Does anyone know what I should check  next?
>>>> 
>>>> Cheers..again
>>>> Phil
>>>> 
>>>> On Dec 10, 2010, at 11:42 AM, Richard Atkinson wrote:
>>>> 
>>>>> Start from the 6510 RESET# line and work backwards. What is that connected to?
>>>>> 
>>>>> 
>>>>> On Dec 10 2010, Philip Lord wrote:
>>>>> 
>>>>>> Ok this morning I printed out the schematic and theory of   operation for the C64.
>>>>>> 
>>>>>> The theory of operation states that the reset signal is  originally produced at pin 9 of the 556 time (MC3456p in my  case). The output is  active high. I have tested this pin with  my probe, and it does indeed  switch from low to high on power- up. The theory of  operation then says  that this signal is sent  to pin 13 of a 7406  hex inverter (U8) and the  output from the  7406 is active low from  pin 12...this is the reset  signal.
>>>>>> 
>>>>>> However, on my machine pin 9 of the 556 is tied to pin 13 (on  the same  556) with some wire, and I have tested the continuity  from  pin 9 of  the 556 to pin 13 of the 7604, and I can't see  any  physical connection  between these pins which in contrary to  the  schematic and the theory  manual. Maybe I'll pull the board  out and  have a look at the bottom  side for any damage or cut  traces.
>>>>>> 
>>>>>> I probed pins 12 and 13 of the 7406 and pin 12 is always low and   pin 13 is always high.
>>>>>> 
>>>>>> So I'm a little confused...this doesn't seem right. Maybe I can  I briefly apply 5v to pin 12 of the 7604 to see what happens?
>>>>>> 
>>>>>> Maybe I have the wrong schematic, but I don't think so. I'll  look for  others anyway.
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> On Dec 10, 2010, at 12:43 AM, MikeS wrote:
>>>>>> 
>>>>>>> The supply voltages to the ICs are all correct?
>>>>>>> 
>>>>>>> Reset line is being released?
>>>>>>> 
>>>>>>> 
>>>>>>> ----- Original Message ----- From: "Philip Lord"  <random6000@mac.com
>>>>>>> >
>>>>>>> To: <cbm-hackers@musoftware.de>
>>>>>>> Sent: Thursday, December 09, 2010 3:23 AM
>>>>>>> Subject: Re: Pet64 DOA
>>>>>>> 
>>>>>>> 
>>>>>>>> Well, it seems like the power might be ok after all, so I  broke out  my  logic probe...it's a cheap one but has helped  me fix  many simple  issues over the years.
>>>>>>>> The first think I noticed after probing around is that I'm  not getting  any pulsing (or at least that what the probe   indicates), lines are  either high, or low, or nothing, but   there doesn't seem to be any  pulsing at all!
>>>>>>>> So I guess I should look at the timing circuit or Xtal?  Anywhere else?  Not sure how to test is a Xtal is working as  I don't  think my probe  can do that.
>>>>>>>> Cheers
>>>>>>>> Phil
>>>>>>>> On Dec 9, 2010, at 2:10 PM, Philip Lord wrote:
>>>>>>>>> Great...so then maybe my power voltages are all good? Should  I find  some test point on the C64 motherboard and get some voltages  there?  Any idea what I should check next?
>>>>>>>>> 
>>>>>>>>> Re-PET board. Ethan has been working very hard, and he  believes he  has fixed both boards now (but can not test  loading as his C2N  data  cassette deck is in need of a new  drive belt). Last I heard   everything is almost packed up  and ready to ship. It would be  great  to get the boards back  before years end, as I have been  building a  number of add- ons in anticipation for their arrival  and I'm excited  to  try everything out.
>>>>>>>>> I have built one of Nicolas Welte's Ram/Rom boards which  will hopefully take my ram to 32k and allow me to use  various basics (V1  through V4) and not have to worry about  failing RAM in the future. I  have also built a number of  adaptor boards to  replace the video ram  and character ROM.  Finally I got myself  a C2N232 as  I don't know how  reliable  the original cassette  drive is. I'm  hoping to 'fail proof'   this machine for at least  another 30 years ;-)
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> On Dec 9, 2010, at 1:44 PM, MikeS wrote:
>>>>>>>>> 
>>>>>>>>>> 5V DC and 9V AC - sounds OK.
>>>>>>>>>> 
>>>>>>>>>> Did you finally get your PET boards back and working?
>>>>>>>>>> 
>>>>>>>>>> m
>>>>>>>>>> 
>>>>>>>>>> ----- Original Message ----- From: "Philip Lord" <random6000@mac.com
>>>>>>>>>> >
>>>>>>>>>> To: <cbm-hackers@musoftware.de>
>>>>>>>>>> Sent: Wednesday, December 08, 2010 10:41 PM
>>>>>>>>>> Subject: Re: Pet64 DOA
>>>>>>>>>> 
>>>>>>>>>> 
>>>>>>>>>>> 8.91 vac
>>>>>>>>>>> On Dec 9, 2010, at 12:31 PM, MikeS wrote:
>>>>>>>>>>>> Hi Philip!
>>>>>>>>>>>> 
>>>>>>>>>>>> What AC voltage do you get between the two white wires?
>>>>>>>>>>>> 
>>>>>>>>>>>> mike
>>>>>>>>>>>> 
>>>>>>>>>>>> ----- Original Message ----- From: "Philip Lord" <random6000@mac.com
>>>>>>>>>>>> >
>>>>>>>>>>>> To: <cbm-hackers@musoftware.de>
>>>>>>>>>>>> Sent: Wednesday, December 08, 2010 10:07 PM
>>>>>>>>>>>> Subject: Re: Pet64 DOA
>>>>>>>>>>>> 
>>>>>>>>>>>> 
>>>>>>>>>>>>> Sorry maybe I should have tested the some lines using AC  not DC.
>>>>>>>>>>>>> So here again is what I believe I have (suing the black   line as  GND):
>>>>>>>>>>>>> White: - 5.8 vac
>>>>>>>>>>>>> (KEY)
>>>>>>>>>>>>> White - 0.5 vac
>>>>>>>>>>>>> Black (I'm guessing this is ground)
>>>>>>>>>>>>> Red - 4.98 vdc
>>>>>>>>>>>>> Of course I could just be confused as I've never owned a   C64 before.
>>>>>>>>>>>>> Looking at schematics seems maybe the two white lines   could/ should  be  9vac, and maybe the red line should be  5  vdc???
>>>>>>>>>>>>> Phil
>>>>>>>>>>>>> On Dec 9, 2010, at 11:16 AM, Philip Lord wrote:
>>>>>>>>>>>>>> I just got myself a PET64 from Yahoo Auction Japan.  Quite  a rare   machine I hear, so I'm not sure how one  ended up  in Japan. I got  if  for a decent price as I  don't think  the Japanese knew exactly  what  it was.
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> Anyway, It arrived the other day, after a quick  internal inspection,  I powered it on. I can hear the  transformer buzzing(!), but no  action at all on the  screen at all,  and it   doesn't seem like the  chips  are getting warm at  all Maybe need  to  leave it on a  little  longer to make  sure, but I didn't  want to do   that incase bad  voltages  kill anything more).
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> There are 4 wires leading from the small PCB which is attached  to   the transformer to the C64 motherboard,  and  I have  measured the   voltage from the black wire  (GND?)  to the 3  others. Here are the   reading i get:
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> White: - 100mv
>>>>>>>>>>>>>> (KEY)
>>>>>>>>>>>>>> White - 100mv
>>>>>>>>>>>>>> Black (I'm guessing this is ground)
>>>>>>>>>>>>>> Red - 4.98v
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> That's as far as I have gotten. Next I will remove  the motherboard  and see where exactly these 4 wires  go.
>>>>>>>>>>>>>> Anyway, I was just wondering if anyone had any insights   or thoughts.
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> Cheers
>>>>>>>>>>>>>> Phil
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Received on 2010-12-12 12:00:04

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