Need help to get My pet 4016 work !

[techtatan]

hi again

After a long night of switching RAM chips running PET RAM TEST program and so on, It turned out to be a another defective RAM chip in UA16.
This faulty chip did not prevent the pet from startup but having issus runing certain bigger programs for exemple space invaders works fine with the bad RAM chip.

I replaced the bad RAM chip and it seems to have no more errors i will let run the test till cycle 99999 but this will take a lot of time. Anyway it has passed the bad point several times.
I contacted Bo Zimmerman about the U1 return, he never run the program but suggest a bad ram chip and says the program need to be run on the right computer. But the only information i was able to obtain is that the program is for the pet, but witch edtion i can not tell.

Any way it helped me catching another issue on my long way to get this pet back to life

Regarding the memory dump with the petvet it still returns garbage in BYPASS mode. I'm still waiting on mike replying to my mails

Regarding the modifications (brown wires) on the motherboard still need help to indentify them on shematics.

Kind regards, techtatan

 

[techtatan]

hi everybody

here is a little up

So finally the pet does the whole RAM test 99999cycles (paranoid mode). So there should be no more memory issues

Regarding the memory dump in bypass mode mike told me that this is simply not possible with the petvet. due to that the whole petvet is bypassed (not just memory like i miss understood).
So this memorydump problem solved it selfs, but brought me to check the whole RAM of the pet and finally catched another bad ram chip.

Regarding the board modification (my last point) i'm on my way to catch them on shematics.

I provide feedback soon

still if there are some PET gurus out here with some litle time to spend ? YOU ARE WELCOME !

Kind regards

 

[techtatan]

Hi everybody

I had reseached the (brown wires) on shematics and it seems that they should be on the board !
As i have annother PET4032 without them and as the 4016 was upgrades to 32 i thought they where modofications !

So the first one runs from UC3/6 to UB1/3 regarding shema and data sheets its connects SN74L2138N G1(input) to SN74LS74AN CLK
The SN74L2138N decoder/demultiplexer (UC3)
The SN74LS74AN DUAL D TYPE POSITIVE EDGE TRIGGERED FLIPFLOPS WITH RESET & CLEAR (UB1)



This seems to accord the shema !

The second one runs from UE6/8 to UB13/21

The SN74177N 35-MHz PRESETTABLE DECADE AND BINARY COUNTERS/LATCHES (UE6)
The MOS MPS 6545 1481 CRT CONTROLLER (UB13)

FROM CLOCK2(INPUT) TO 6545 CCLK

I was able to found ue6 on shema :


and we have the CRT chip on page 10


Regarding shema on page 10 UB13/21 shoud be connected to CLK1
regarding datasheet of the SN74177N PIN 8 is CLK1
I was not able to clearly follow it on the shemas due to my lack of knowledge in the electronic field

but this seems to be ok !

also after a long time of searching arround on shemas i came over the partslist and have found a see sheet of the whole board where the wires a clearly identifyed !
why didn't i start there ?


As i said i did not think that wires must be on a original PCB ?

My question is :

As is disconnected the wires and reconnect the pins to mother board the computer works perfectly !
so why these connections ?
Can someone help me to understand it from the electronic point of view (if i can say so)

So finnaly this means that the pet is fully repared i feel like an idiot for the last part but at least after years the the PET IS BACK TO LIFE !

But just to not die stupid, please can someone explain to me this connections ? this would be very nice please !

Kind regards, techtatan

 

[JonB]

Can't help with the wires but I would like to say congratulations on fixing your PET!

:D

 

[techtatan]

hi

here is a little up, hoping to find some pet guru on the forum.
I past below the questions i asked on MAY 22 hope to be lucky this time..
Thanks for any help, kind regards

Hi everybody

I had reseached the (brown wires) on shematics and it seems that they should be on the board !
As i have annother PET4032 without them and as the 4016 was upgrades to 32 i thought they where modofications !

So the first one runs from UC3/6 to UB1/3 regarding shema and data sheets its connects SN74L2138N G1(input) to SN74LS74AN CLK
The SN74L2138N decoder/demultiplexer (UC3)
The SN74LS74AN DUAL D TYPE POSITIVE EDGE TRIGGERED FLIPFLOPS WITH RESET & CLEAR (UB1)

Click image for larger version. Name: 8032081-08.jpg Views: 1 Size: 16.3 KB ID: 18782

This seems to accord the shema !

The second one runs from UE6/8 to UB13/21

The SN74177N 35-MHz PRESETTABLE DECADE AND BINARY COUNTERS/LATCHES (UE6)
The MOS MPS 6545 1481 CRT CONTROLLER (UB13)

FROM CLOCK2(INPUT) TO 6545 CCLK

I was able to found ue6 on shema :
Click image for larger version. Name: 8032081-06.jpg Views: 0 Size: 14.8 KB ID: 18783

and we have the CRT chip on page 10
Click image for larger version. Name: 8032081-10.jpg Views: 1 Size: 10.6 KB ID: 18784

Regarding shema on page 10 UB13/21 shoud be connected to CLK1
regarding datasheet of the SN74177N PIN 8 is CLK1
I was not able to clearly follow it on the shemas due to my lack of knowledge in the electronic field

but this seems to be ok !

also after a long time of searching arround on shemas i came over the partslist and have found a see sheet of the whole board where the wires a clearly identifyed !
why didn't i start there ?
Click image for larger version. Name: 8032080-7.jpg Views: 2 Size: 18.0 KB ID: 18785

As i said i did not think that wires must be on a original PCB ?

My question is :

As is disconnected the wires and reconnect the pins to mother board the computer works perfectly !
so why these connections ?
Can someone help me to understand it from the electronic point of view (if i can say so)

So finnaly this means that the pet is fully repared i feel like an idiot for the last part but at least after years the the PET IS BACK TO LIFE !

But just to not die stupid, please can someone explain to me this connections ? this would be very nice please !

Kind regards, techtatan