Re: PET 2001 fix Part 3 - RAM/ROM board etc.

From: Philip Lord <random6000_at_mac.com>
Date: Sat, 14 May 2011 13:40:06 +0900
Message-id: <ACEFD297-FB3C-4891-B381-480CCCC5B8C2@mac.com>
Hi Mike,
I read the thread on VCF. Here are the voltages I'm getting off the CPU:

Ready pin 2:   5.06 VDC
Sync Pin 7:    0.98 VDC
Reset Pin 40:  4.71 VDC
clock (phase 2) pin 39: 1.8 VDC

I tried moving the ROM's around as you suggested but that didn't change anything, I'll try putting the ROM in a socket with pin 18 lifted and try reading them again.

Phil


On May 14, 2011, at 4:21 AM, MikeS wrote:

> If you have a spare 24pin IC socket, bend out pin 18 to isolate it and put
> it between the 2316 and your programmer socket, and you might be able to
> read the H5 - H7 ROMs that way; if not, try connecting that 2K resistor
> between the bent-out pin 18 and pin 24.
> 
> Pleasant dreams ;-)
> 
> m
> 
> ----- Original Message ----- From: "MikeS" <dm561@torfree.net>
> To: <cbm-hackers@musoftware.de>
> Sent: Friday, May 13, 2011 3:06 PM
> Subject: Re: PET 2001 fix Part 3 - RAM/ROM board etc.
> 
> 
>> The ROM numbers and locations look good, but I would expect H1 to H4 to
>> all
>> read OK. Why not try putting your respective 2716 equivalents into H1 and
>> H3, leaving the originals in H2, 4, 5, 6 and 7.
>> 
>> BTW, can you program 2532s and do you have any?
>> 
>> m
>> 
>> *******************
>> 
>> ----- Original Message ----- From: "Philip Lord" <random6000@mac.com>
>> To: <cbm-hackers@musoftware.de>
>> Sent: Friday, May 13, 2011 2:39 PM
>> Subject: Re: PET 2001 fix Part 3 - RAM/ROM board etc.
>> 
>> 
>> Don't worry, I'm not insulted at all.
>> 
>> I believe I have the following ROM set (I'll double check in the morning):
>> 
>> Location  Part Number
>> ------------------------------
>> H1  901447-09
>> H2  901447-03
>> H3  901447-05
>> H4  901447-06
>> H5  901447-02
>> H6  901447-04
>> H7  901447-07
>> 
>> And I have followed the above convention for placement. 09, 03, 05, 06,
>> 02,
>> 04 and 07 in that order.
>> 
>> When I read the original ROMs in my burner I got the following:
>> 
>> H1 - full of 00's
>> H2 - good
>> H3 - full of FF's
>> H4 - good
>> H5 - full of FF's
>> H6 - full of FF's
>> H7 - full of FF's
>> 
>> so is it possible that H5, H6, ad H7 were not read correctly by my
>> programmer. H3 also shows full FF's, but H1 read as full 00's...Could it
>> be
>> that H1 is the only one that is indeed dead?
>> 
>> I'll remove the two 6520 PIAs, and I'll take a look on VCF for the
>> voltages
>> thread.
>> 
>> Thanks again for your time.
>> 
>> Phil
>> 
>> On May 14, 2011, at 3:17 AM, MikeS wrote:
>> 
>>> Sorry, emails crossed and you answered my question before I asked it ;-)
>>> 
>>> A crude way would be to measure the voltage on the various 6502 pins,
>>> especially the Reset, Sync and Ready pins.
>>> 
>>> There's a thread on VCF right now that might be relevant.
>>> 
>>> m
>>> 
>>> ----- Original Message ----- From: "Philip Lord" <random6000@mac.com>
>>> To: <cbm-hackers@musoftware.de>
>>> Sent: Friday, May 13, 2011 1:55 PM
>>> Subject: Re: PET 2001 fix Part 3 - RAM/ROM board etc.
>>> 
>>> 
>>> Thanks André,
>>> I only have limited tools. Logic probe, eprom burner and multimeter.
>>> 
>>> I'll have to snag the keyboard out of my working pet to try the 'LOAD'
>>> test.
>>> What other ways can I test if the CPU is working?
>>> 
>>> Phil
>>> 
>>> 
>>> On May 14, 2011, at 2:39 AM, André Fachat wrote:
>>> 
>>>> 
>>>> 
>>>> Looking at the further discussion, you are concentrating on the video
>>>> part, but is the CPU actually running ok? I didn't see that, may be I
>>>> overlooked it. But you mentioned burning new ROMs as the original ones
>>>> were dead.
>>>> 
>>>> If the cpu is not running ok, this could explain the random characters
>>>> on
>>>> one side and also the "snow", as some random code would not wait for the
>>>> vertical retrace when writing to the screen memory.
>>>> 
>>>> Did you try checking for example with a tape and typing LOAD and
>>>> pressing
>>>> the Play button that the tape starts turning?
>>>> 
>>>> I'd concentrate finding why the CPU isn't working and looking at the
>>>> video later.
>>>> 
>>>> André
>>>> 
>>>> 
>>>> -------- Original-Nachricht --------
>>>>> Datum: Fri, 13 May 2011 19:27:34 +0200
>>>>> Von: "André Fachat" <afachat@gmx.de>
>>>>> An: cbm-hackers@musoftware.de
>>>>> Betreff: Re: PET 2001 fix Part 3 - RAM/ROM board etc.
>>>> 
>>>>> 
>>>>> -------- Original-Nachricht --------
>>>>> 
>>>>>> So now I have a screen of random and slightly deformed characters
>>>>>> (seems
>>>>>> like the same or similar character layout on each start up though),
>>>>>> with
>>>>> a
>>>>>> pixel flicker through them. I've put pics and a short video up on the
>>>>> same
>>>>>> page here:
>>>>> 
>>>>> Sorry to chime in so late only. The pixel flicker might be from the
>>>>> fact
>>>>> that the CPU accesses the video RAM. The oldest PETs had video RAM with
>>>>> max
>>>>> 1MHz operation only, so when the CPU accesses the video RAM the video
>>>>> display presented "snow". The CPU controlled access to the video RAM by
>>>>> sampling
>>>>> the vertical retrace on a VIA pin (VIA Port B ($e840, 59456), bit 5).
>>>>> This
>>>>> could relate to the fact that characters seem stable when the machine
>>>>> resets (switching off?)
>>>>> 
>>>>> Maybe the VIA has a problem here?
>>>>> 
>>>>> On a side note: the fact that switching this vertical retrace off
>>>>> resulted
>>>>> snow, but also faster screen output - no wait anymore - a certain POKE
>>>>> was
>>>>> found to make that VIA input pin an output - accidentally destroying
>>>>> some
>>>>> newer models, the "killer poke".
>>>>> 
>>>>> André
>>>>> 
>>>>> -- 
>>>>> NEU: FreePhone - kostenlos mobil telefonieren und surfen!
>>>>> Jetzt informieren: http://www.gmx.net/de/go/freephone
>>>>> 
>>>>>    Message was sent through the cbm-hackers mailing list
>>>> 
>>>> -- 
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>>>> belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de
>>>> 
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>>> 
>>> 
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Received on 2011-05-14 05:00:08

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