Re: Pet64 DOA

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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